Lead author Dr. Kannan Udaya Mohanan, a postdoctoral fellow in Professor Chang-Hyun Kim’s research group at the University of Ottawa, said the materials and architectures represent a fundamentally different way of processing information. By operating more like a human brain than a traditional processor, the emerging technologies are expected to produce physical devices that are dramatically more energy-efficient, faster and adaptive. These are projections from the review, not demonstrated performance results for commercial data-centre systems.

The review addresses a limitation of conventional computing known as the “memory wall,” in which data transfer between memory and processors causes major delays and energy loss. According to the research team, the most promising post-CMOS materials and device architectures identified in the review can act as artificial neurons, with next-generation circuits designed to process information faster and with less energy than current mainstream chips. The authors mapped the broader hardware landscape to connect progress in materials science with pathways for developing scalable, brain-like systems.

Energy efficiency is only one of the potential advantages of these brain-inspired technologies. Post-CMOS refers to materials and architectures that move beyond traditional chips, and some of the emerging materials may be lower-cost, highly scalable and compatible with ultra-thin, lightweight and flexible form factors. The review therefore considers possible applications beyond greener AI data centres, including smarter, low-power wearable technology, personalised healthcare and human-machine interfaces.

These proposed uses extend the hardware roadmap into areas in which compactness, adaptability and reduced power consumption could be valuable. Taken together, the review presents hardware neurons as a possible response to the energy demands associated with AI data centres and the bottlenecks created by conventional processor-memory communication. Its central conclusion is that emerging post-CMOS materials, artificial-neuron devices and system integration offer a credible research direction for computing that is more energy-efficient, fast and adaptive.

Because the publication is a systematic review and forward-looking roadmap, its role is to identify promising technologies and integration pathways rather than to establish finished products or measured data-centre savings.

Subject of Research: A systematic review of post-CMOS hardware neurons for energy-efficient, brain-inspired computing systems

Article Title: Building brain-inspired semiconductor chips for smarter, greener data centres

Article References: Building brain-inspired semiconductor chips for smarter, greener data centres. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: neuromorphic computing, hardware neurons, post-CMOS devices, artificial intelligence, data centres, energy efficiency, semiconductors, artificial neurons, wearable electronics, human-machine interfaces, Building, brain-inspired

Zirconium and hafnium occupy adjacent positions in the periodic table, and their outer electron shells are so similar that they behave almost identically in most chemical reactions. That resemblance is more than a curiosity for chemists; it has real industrial consequences. Natural zirconium silicate, the mineral zircon, almost always carries trace amounts of hafnium, and zircon mining is the principal economic source of both elements. Yet for microelectronics and nuclear reactors, the two must be separated to very high purity, because their nearly identical chemistry conceals dramatically different nuclear behavior.

In a nuclear reactor, zirconium is prized for its transparency to neutrons, making it ideal for fuel cladding, while hafnium absorbs neutrons so strongly that it is used in control rods. If hafnium contaminates zirconium cladding, the material’s neutron economy is compromised. In semiconductor manufacturing, hafnium compounds serve as high-k dielectric gate materials in modern transistors, demanding exceptional purity. Only two facilities in the United States, ATI Specialty Alloys & Components in Albany, Oregon, and Westinghouse Electric in Ogden, Utah, are equipped to perform the separation on an industrial scale, and each consumes millions of pounds of flammable organic solvent annually.

The current state-of-the-art technique, liquid-liquid extraction, is energy intensive and also loses roughly four percent of the solvent to the air as noxious pollution. The Oregon State team, led by graduate research assistant Alex Roseborough and Terence Bradshaw Chemistry Professor May Nyman, set out to demonstrate that precipitation-based separations can compete with solvent extraction. Precipitation relies on a simple principle: dissolved ions with opposite charges attract each other and form an insoluble solid that can be filtered out of solution.

The patented process combines an aqueous solution of natural zirconium, which contains a few percentage points of hafnium impurity, with thiocyanate ligands that bind to both the hafnium and zirconium ions, and choline, an inexpensive, nontoxic chemical commonly used as a food additive. The result is a low-energy process involving no organic solvent, producing a precipitation of hafnium-rich species with a separation factor much higher than the industry standard.

Separation factor measures a process’s ability to divide two components in a mixture. A value greater than one means separation is possible, and the higher the number, the better. The industry standard for zirconium-hafnium separation sits between six and seven; the Oregon State process produced a top score of 33. The team also captured the separation in atomic-level detail, showing how the different nuclearity, or the number of metal atoms clustered together in the aqueous thiocyanate molecules, controls which species precipitate. Crystals in the precipitates take on distinct shapes depending on their hafnium concentration, providing visual evidence of the molecular selectivity at work.

We describe in atomic-level detail how the separation works and how precipitation-based separations can compete with solvent extraction, Nyman said. We still have questions to answer and milestones to achieve, but these findings are really exciting and impactful, especially as society must move toward more carbon-free and high-density electricity generation, including nuclear energy.

The study, published on 7 September 2026 under the title Emergent Hf-Selective Precipitation of Aqueous (Zr,Hf) Thiocyanate Molecules through Nuclearity Control, also included contributions from OSU researchers Doctor Stephen, Jack McLaughlin, Lev Zakharov, George Donkor-Gyami and Pere Miró. The U.S. Department of Energy and the Murdock Charitable Trust supported the research, and Roseborough is now a metallurgist with the department’s National Energy Technology Laboratory.

The implications reach well beyond the laboratory bench. As demand grows for both advanced microelectronics and carbon-free nuclear power, a greener, cheaper and more selective separation chemistry could ease a supply chain bottleneck that has persisted for decades. By eliminating millions of pounds of organic solvent each year and cutting the energy cost of one of chemistry’s most stubborn separations, the Oregon State process offers the semiconductor and nuclear industries a path toward cleaner production of two metals on which modern technology quietly depends.

The difficulty of the zirconium-hafnium separation stems from a phenomenon chemists call the lanthanide contraction. Because hafnium sits directly below zirconium in the periodic table, the added electrons in hafnium are balanced by the contraction of its atomic radius, leaving the two elements with nearly identical ionic sizes and charge densities. This means that reagents designed to grab one metal almost invariably grab the other, which is why conventional separation schemes have relied on brute-force methods that cycle enormous volumes of material through many extraction stages. Any chemistry that can discriminate between the two elements in a single, simple step therefore represents a meaningful departure from decades of practice.

Precipitation itself is one of the oldest tools in the chemist’s repertoire, but its use in high-precision metal refining has been limited by a lack of selectivity. The Oregon State team’s insight was that selectivity could emerge not from a specially engineered synthetic ligand but from the way the metals organize themselves in solution. In the presence of thiocyanate, the zirconium and hafnium ions assemble into clusters of different nuclearity, meaning different numbers of metal atoms are joined into a single molecular unit. Because hafnium-rich clusters adopt structures that fall out of solution preferentially, the separation arises from the self-assembly behavior of the mixture rather than from a one-to-one binding event. This emergent selectivity, as the study’s title suggests, is what allows a simple precipitation to rival a multi-stage solvent extraction plant.

The choice of choline as the counter-ion is also notable from a sustainability standpoint. Choline is produced on an industrial scale, is recognized as safe in food applications, and is readily biodegradable, which stands in sharp contrast to the organic diluents and extractants used in conventional liquid-liquid extraction. Those solvents, typically flammable hydrocarbon mixtures, pose fire hazards in addition to the volatile emissions already noted, and their disposal adds cost and regulatory burden. A process whose main reagents are water, thiocyanate salt, and choline would be far easier to permit and operate, particularly if the thiocyanate and choline can be recovered and recycled from the mother liquor after the hafnium-rich solid is removed.

The separation factor of 33 deserves some context. In industrial separations, each incremental improvement in this metric translates into fewer processing stages, smaller equipment, and lower energy consumption, because the amount of material that must be recycled or reprocessed shrinks. A fivefold improvement over the standard value of six to seven could, in principle, compress a separation train that currently requires many repeated extraction and scrubbing cycles into a much shorter sequence. The researchers caution, however, that laboratory-scale separation factors do not translate directly into plant performance; questions of crystal handling, throughput, reagent recovery, and the behavior of real zircon feedstocks with their full complement of trace impurities remain to be resolved.

The demand backdrop strengthens the case for such advances. Zirconium alloys have long been the material of choice for nuclear fuel cladding because of their combination of neutron transparency, corrosion resistance, and mechanical strength, and a renewed interest in nuclear energy as a low-carbon power source is expected to sustain or grow that demand. On the semiconductor side, hafnium-based dielectrics became standard in advanced logic transistors after the industry transitioned away from silicon dioxide gate insulators, and hafnium consumption has grown with each generation of chip manufacturing. Both supply chains currently funnel through the same narrow refining bottleneck, which is why a chemistry that could be adopted more broadly, without the scale and hazard of solvent extraction plants, would be strategically significant.

The atomic-level characterization reported in the study also carries methodological weight. By determining the structures of the precipitated species and correlating crystal morphology with hafnium content, the researchers provided a mechanistic account of why the separation works, rather than merely demonstrating that it does. That kind of understanding is what allows a laboratory discovery to be optimized rationally, since future work can target the specific cluster geometries and solution conditions that favor hafnium enrichment. The team’s acknowledgment that questions remain suggests they view the current result as a foundation rather than a finished technology, with the path forward involving refinement of the precipitation conditions and demonstration at larger scales.

Funding from the U.S. Department of Energy reflects the national-security and energy dimensions of the work, since domestic production of reactor-grade zirconium has long been considered a strategic capability. With only two industrial separation facilities in the country, the supply chain for both nuclear fuel and semiconductor-grade hafnium is unusually concentrated, and any disruption at either site would ripple through both industries. A precipitation-based alternative that could be implemented at smaller scale, with lower capital intensity and without flammable solvents, would add resilience to that chain while reducing the environmental footprint of a process that has remained essentially unchanged in principle for many decades.

Subject of Research: Green chemistry separation of zirconium and hafnium for semiconductor and nuclear industries

Article Title: Semiconductor, nuclear industries poised for green boost thanks to chemistry breakthrough

Article References: Semiconductor, nuclear industries poised for green boost thanks to chemistry breakthrough. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: zirconium, hafnium, green chemistry, semiconductors, nuclear energy, precipitation, Oregon State University, separation factor, thiocyanate, materials science, Semiconductor, nuclear

What distinguishes the work from most previous theoretical models is its scope. Earlier density functional theory calculations on ZnO typically examined one dopant at a time, substituting a single impurity atom into the lattice to tune the band gap, electron density, or defect chemistry. Those models clarified individual dopant behavior but ignored the intricacies that arise when two or more dopants share the same crystal. The new study breaks with that tradition by investigating multiple and mixed-dopant cases under equivalent computational conditions, enabling a direct, apples-to-apples comparison of doping strategies that the literature, with its inconsistent methods across studies, has never provided.

The computational framework is rigorous. All calculations were performed with the DMol³ package in Materials Studio, based on the all-electron numerical atomic orbital method. A pristine wurtzite ZnO structure from the Materials Project was expanded into a 2 × 2 × 1 supercell, large enough to represent realistic doping concentrations while avoiding spurious interactions between periodic dopant images. Geometry optimizations used the generalized gradient approximation with Perdew–Burke–Ernzerhof exchange-correlation, a Fermi-level smearing of 0.5 electron volts, and stringent convergence criteria: total energy within 1 × 10⁻⁵ Hartree and forces below 0.002 Hartree per angstrom. Because conventional GGA-PBE methods systematically underpredict semiconductor band gaps, electronic and optical properties were additionally evaluated with a hybrid functional that includes exact Hartree–Fock exchange, eliminating the self-interaction error and producing band-gap predictions in far better agreement with experimental measurements. All reported band gaps in the study rest on these hybrid-functional results.

Dopants were introduced by substituting zinc atoms in the supercell with aluminum, gallium, indium, magnesium, or silver. The Zn site was chosen deliberately: in wurtzite ZnO, cation substitution is energetically favorable, and comparisons of ionic radii and oxidation states with Zn²⁺ confirm that Zn-site incorporation carries lower energy than interstitial or oxygen-site modes. Spin-polarized calculations were included for doped systems to capture possible localized magnetic moments or unpaired electronic states, while pristine ZnO remained non-magnetic. Brillouin-zone sampling used a Monkhorst–Pack k-point mesh verified through convergence testing, and the same converged sampling was applied to every model to maintain consistency. The pseudopotential treatment paid special attention to the Zn 3d and 4s states together with the O 2p states, the orbitals that dominate the valence-band maximum, conduction-band minimum, and overall band-gap behavior.

The single-doping results are striking. Pristine ZnO shows a calculated band gap of 3.21 electron volts, matching experimental values of 3.37 to 3.44 electron volts. Every dopant narrows the gap: aluminum reduces it to 2.46 electron volts, gallium to 2.41, indium to 2.61, magnesium to 2.71, and silver to 2.75. Gallium produces the largest narrowing, aluminum the second largest. Mechanistically, aluminum and gallium form donor-like couplings to the conduction band, indium’s extended 5s orbitals interact with the s-type conduction band of ZnO, magnesium modifies local Zn–O bonds, and silver’s 4d states hybridize with O 2p states near the valence band, potentially shifting the valence-band edge upward and extending absorption into the visible range.

Increasing the concentration of a single dopant produces far more dramatic narrowing. With two dopant atoms in the supercell, the gaps fall below 2 electron volts across the board: 1.61 electron volts for ZnO–2Al, 1.52 for ZnO–2Ga, 1.72 for ZnO–2In, 1.81 for ZnO–2Mg, and 1.91 for ZnO–2Ag. These values reflect a transition from isolated donor levels to broadened conduction-edge or impurity-band levels as dopant wavefunctions begin to overlap. Such gaps would permit solar photon absorption across a much broader range, but the same high density of electronically active centers can increase scattering and non-radiative loss, so the predicted optical benefit must be tested against carrier lifetime and mobility before any efficiency claim is made.

The mixed co-doping results reveal that band-gap engineering in ZnO is neither additive nor monotonic. At 1:1 ratios, gaps range from 2.1 to 2.7 electron volts; at 2:2 ratios, from 1.6 to 2.6. The final gap emerges from local lattice relaxation, orbital hybridisation, charge redistribution, dopant–dopant separation, and the position of dopant-derived states relative to the ZnO band edges. Some pairs show strong narrowing as concentration increases—Al–Mg falls from 2.2 to 1.6 electron volts, In–Mg from 2.3 to 1.6, In–Ag from 2.7 to 1.7—while Ga–In remains constant at 2.1 and Al–Ga actually rises slightly from 2.4 to 2.6. These deviations prove that the relaxed electronic structure, not merely dopant content, governs the outcome. When dopants occupy nearby or electronically connected positions, relaxation around one site changes the bonding environment of the other through shared oxygen neighbors and overlapping strain fields, altering metal–oxygen distances, bond angles, local electrostatic potential, and orbital overlap.

The density of states analysis explains why. In pristine ZnO, deep Zn 3d states appear at low energy, O 2p states dominate the valence band, and the conduction band is formed primarily from Zn 4s states, confirming the wide gap and limited visible-light absorption. Aluminum, gallium, and indium form s donor-like states that overlap with the Zn 4s orbitals at the conduction-band minimum, with indium producing broader and more delocalized conduction-band features that enhance electronic mobility. Magnesium modifies the conduction band while maintaining a clean gap, improving band alignment without creating deep defects. Silver adds density of states near the valence-band edge through Ag 4d and O 2p hybridization, which may improve hole participation but also raises the possibility of deep state formation and greater recombination.

From a solar-cell perspective, the study is careful to note that the smallest calculated gap is not automatically the best material. A wider spectral response can raise the photogeneration rate and short-circuit current density when the absorption coefficient is sufficiently high, but strong narrowing may enhance current while reducing the maximum open-circuit voltage, and deep impurity states can trap carriers and support non-radiative recombination. Band-edge positions must remain compatible with adjacent transport layers, electrodes, dyes, or redox couples in heterojunction or sensitized devices. The most promising candidates identified are ZnO–2Al–2Mg and ZnO–2In–2Mg at 1.6 electron volts, followed by ZnO–2Ga–2Mg and ZnO–2In–2Ag at 1.7 and ZnO–2Al–2Ag at 2.0, compositions that provide substantial visible-light gap reduction while remaining within the approximate 1 to 2 electron volt photovoltaic design window, unlike ultra-narrow sub-1 electron volt systems that would suffer from reduced photovoltage and stronger defect-assisted recombination.

The study also proposes experimental pathways to validate the computational predictions. Photoluminescence spectroscopy can determine defect emissions and doping-induced energy levels within the gap; Hall effect tests give direct indications of carrier concentration and mobility; ultraviolet-visible spectroscopy can measure the optical absorption edge and band-gap energies. Synthesis routes such as sol–gel, hydrothermal, pulsed laser deposition, and magnetron sputtering are already established for ZnO thin films and nanostructures, while X-ray diffraction and scanning electron microscopy can verify phase purity and crystallinity. Formation-energy calculations under Zn-rich and O-rich limits, together with spectroscopy and lifetime measurements, are needed to distinguish useful dopant states from harmful trap states. The work establishes a mechanistic framework showing why some co-dopant combinations are substantially more effective than others, demonstrating that successful optimisation of ZnO requires deliberate control of dopant chemistry, concentration, and atomic configuration rather than indiscriminate increases in dopant loading or pursuit of the smallest possible gap.

Subject of Research: Density functional theory comparison of single, mixed, and multi-doping strategies in ZnO for enhanced solar energy conversion

Article Title: Computational investigation of single, multi and mixed doping strategies in ZnO for enhanced solar energy conversion

Article References: Nyangiwe, N. N. (2026). Computational investigation of single, multi and mixed doping strategies in ZnO for enhanced solar energy conversion. Results in Physics, Article 108769. https://doi.org/10.1016/j.rinp.2026.108769

Image Credits: AI Generated

DOI: 10.1016/j.rinp.2026.108769

Keywords: solar energy, zinc oxide, density functional theory, doping, photovoltaics, band gap engineering, semiconductors, co-doping, visible light absorption, materials science, Computational, investigation

The new technique hinges on a counterintuitive insight about how perovskites crystallize. By adding a mixture of zinc bromide and methyl ammonium chloride early in the fabrication process, the researchers discovered they could dramatically reduce the number of defects that form in the crystal structure as the material solidifies. The consequences of that seemingly small intervention are striking. In defect-free perovskites produced this way, electrons retain the excess energy they absorb from sunlight roughly ten times longer than in untreated material. According to Dane deQuilettes, assistant professor at Princeton and a senior author on the paper, the improvement could translate into a one percent gain in power generation even for the most cutting-edge perovskite solar cells already in existence — a meaningful margin in a field where incremental gains are fiercely contested.

To understand why those microseconds matter, it helps to grasp what actually happens inside a working solar cell. When sunlight strikes a semiconductor, photons transfer their energy to electrons, lifting them into an excited state. The whole point of a photovoltaic device is to harvest that excess energy as electricity before the electrons relax back down and release it as heat. Defects in the crystal lattice act like traps along this pathway, snaring excited electrons and squandering their energy before it can be collected. The longer electrons can hold onto their excess energy — a property measured in microseconds in these experiments — the more opportunities there are to extract useful power. In deQuilettes’ measurements, electrons in the treated perovskites retained their energy for up to 300 microseconds, roughly a hundred thousand times longer than in many other semiconductors.

The discovery itself was born of serendipity. A few years ago, Jason Yoo, a first author on the paper who was then a researcher at the Korea Research Institute of Chemical Technology, noticed that his samples were behaving in ways he could not explain. He reached out to deQuilettes, whose laboratory specializes in developing tools to probe how electrons behave and interact inside perovskites. “He told me the samples were behaving like nothing he had seen before,” deQuilettes recalled. “He asked if I could help study them.” What deQuilettes found when he examined the samples amazed him: the extraordinary carrier lifetimes that would eventually form the basis of the Science paper.

The chemistry behind the breakthrough is as subtle as it is effective. The key, deQuilettes explained, is that the two added chemicals — zinc bromide and methyl ammonium chloride — must have a lower melting point when combined than either does alone, much as adding salt to ice lowers its freezing point. Such mixtures are known as eutectics, and the paper’s title, “Volatile eutectics to tailor crystallization for perovskite optoelectronics,” reflects this principle. By introducing a volatile eutectic during the early stages of fabrication, the researchers changed the way the perovskite crystal grows, steering it toward a more ordered lattice with fewer of the atomic-scale imperfections that plague conventionally processed films. “We opened up this new class of chemical mixtures that improve the performance of perovskites,” deQuilettes said.

The broader context makes the advance especially significant. Most solar cells installed around the world today are made of silicon, a material prized for its durability but constrained by its physics and its energy-intensive manufacturing. Perovskites, by contrast, can be prepared from liquid precursors and printed in sheets, like ink on newsprint, potentially making them cheaper and more sustainable to produce at scale. Increasingly, the two technologies are being combined rather than competing: a thin coat of perovskite layered over a silicon solar cell forms a tandem device that generates about 40 percent more power than a cell made from either material alone. The catch has always been that the printing and layering process tends to introduce those damaging atomic-level defects, blunting the perovskite layer’s contribution. Fewer defects mean a more efficient perovskite layer, which in turn means more efficient tandem modules rolling off future production lines.

The timing could hardly be more pointed. Global electricity demand is climbing rapidly, driven in no small part by the explosive growth of artificial intelligence and the datacenter infrastructure that underpins it. “The whole solar industry has been asking, what are the next set of technologies that are going to contribute to energy production?” deQuilettes noted. A one percent improvement in power conversion may sound modest, but in the economics of utility-scale solar — where installations span thousands of acres and margins are measured in fractions of a cent per kilowatt-hour — even single-digit percentage gains compound into substantial additional generating capacity. And because the improvement is achieved through chemistry during fabrication rather than through expensive post-processing, it is the kind of change that manufacturers could in principle adopt without redesigning their entire production workflow.

Perhaps the most intriguing implications reach beyond photovoltaics altogether. Because electrons in the treated perovskite persist in their excited state for hundreds of microseconds — an eternity by semiconductor standards — the material opens possibilities that conventional semiconductors simply cannot offer. “Energy is living in the material for so long, it broadens what’s actually possible with a semiconductor,” deQuilettes said. Long carrier lifetimes are coveted not only in solar cells but in a range of optoelectronic applications, from light-emitting devices to photodetectors and potentially quantum technologies, where the ability of a material to hold onto excitation energy determines what device architectures are feasible. The researchers emphasize that the discovery has raised more questions than it has answered. “It’s been really eye-opening,” deQuilettes added, suggesting that the eutectic approach may be only the first entry in what could become a broad family of defect-mitigating chemical mixtures.

The study was a genuinely international effort. In addition to deQuilettes at Princeton and Yoo and Bong Joo Kang at the Korea Research Institute of Chemical Technology, the author list spans Connor J. Dolan, Zhewen J.D. Deng, Jack R. Palmer, Kelly X. Vences and David P. Fenning at the University of California-San Diego; Seongsik Nam, Jinho Lee, Kyu Min Kang, Daesoo Kim, Jang Hee Cho, Donghyuk Chung and Seong Sik Shin at Sungkyunkwan University in Korea; Rushik Desai and Arun Mannodi-Kanakkithodi at Purdue University; Niranjana Mohan Kumar, Mariana I. Bertoni and Arkita Chakrabarti at Arizona State University; Yanqi Luo, Barry Lai, Zhonghou Cai, Martin V. Holt and Tao Zhou at Argonne National Laboratory; Andrew M. Kiss at Brookhaven National Laboratory; and In Sun Cho at Ajou University and Dong Hyun Kim and Jun Hong Noh at Korea University. That breadth of expertise — spanning synthesis, ultrafast spectroscopy, synchrotron characterization and computational modeling — reflects the multidisciplinary challenge of understanding and controlling defects at the atomic scale.

For a field that has weathered its share of hype and hard lessons, the new result offers something refreshingly concrete: a reproducible chemical strategy, published in a peer-reviewed journal, that measurably extends carrier lifetimes by an order of magnitude and points toward real gains in device performance. Perovskites have always been crystals of extraordinary promise; the challenge has been coaxing that promise out of an imperfect lattice. With volatile eutectics now shown to tailor crystallization in a way that suppresses defects at their source, researchers have a new tool — and a new class of chemistry to explore — in the long effort to build better solar technology, one crystal at a time.

Subject of Research: Defect mitigation in perovskite solar cells using volatile eutectic chemical additives during fabrication

Article Title: Building better solar tech, a crystal at a time

Article References: Building better solar tech, a crystal at a time. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: perovskite, solar cells, crystal defects, eutectics, photovoltaics, tandem solar cells, semiconductors, carrier lifetime, zinc bromide, methyl ammonium chloride, Princeton University, Science journal

The challenge the researchers set out to solve is one of the most stubborn in condensed matter physics and device engineering. A conventional transistor is not made of one material but of several fundamentally different ones working in intimate contact. A semiconductor carries the current, a dielectric insulator controls it through an applied gate voltage, and metallic or semimetallic contacts allow charge to enter and exit. As silicon devices shrink toward their physical scaling limits, atomically thin two-dimensional semiconductors have been heralded as natural successors. Yet for more than two decades, the obstacle to practical 2D electronics has rarely been the performance of the semiconductor itself. It has been the integration problem: how to attach the other components without destroying the delicate atomic sheet they must sit upon.

The surfaces of two-dimensional semiconductors are chemically inert in a troublesome way. They contain few dangling bonds or reactive sites where other materials can anchor, which makes it extraordinarily difficult to deposit a gate dielectric uniformly across them. Conventional dielectric deposition tends to produce patchy, leaky films on such surfaces. Direct metal deposition is equally problematic, since the energetic process can damage the atomically thin semiconductor or create large contact barriers that choke off the flow of charge. Mechanical transfer methods, in which separate 2D materials are peeled, aligned, and stacked one by one, offer an alternative, but they are slow, difficult to scale uniformly over large areas, and poorly suited to the demands of mass production.

The IBS team’s answer was to stop thinking of the crystal as just the semiconductor and start treating it as the raw material for everything. They began with multilayer tungsten diselenide, a two-dimensional semiconductor whose electrical character can be altered by replacing the atoms surrounding the tungsten layer. By preserving the tungsten framework while selectively swapping those surrounding atoms, the researchers changed the electronic identity of individual regions without rebuilding the crystal from scratch. The upper layers were first oxidized into insulating tungsten oxide, and that oxide could then be further converted through vapor-phase reactions into either tungsten disulfide, an n-type semiconductor, or tungsten ditelluride, a semimetal. Regions left untouched retained the original tungsten diselenide semiconductor behavior. In this way, semiconducting, insulating, and semimetallic functions were created directly within different layers and locations of the same parent crystal.

The precision of the method rests on a remarkably elegant physical principle: the tiny gaps between neighboring atomic layers act as natural barriers that confine the chemical reaction. By tuning the reaction temperature and gas pressure, the researchers could halt the conversion after a chosen number of layers, achieving depth control of roughly 0.7 nanometers per tungsten diselenide monolayer. That is the thickness of a single atomic sheet, meaning the process can be steered with a resolution measured in individual atomic planes. This layer-by-layer chalcogen substitution, as the technique is known, effectively turns a crystal-growth problem into a controllable chemical editing problem, one atomic layer at a time.

The most consequential demonstration involved converting the upper layers of tungsten diselenide into tungsten oxide directly above the semiconductor channel. The resulting oxide served as the gate dielectric without any need to deposit a separate high-permittivity material, forming an insulating layer with an effective thickness below one nanometer while maintaining strong insulating performance. This is a significant achievement, because the gate dielectric is where many would-be 2D devices fail. A dielectric that is too thick or too leaky wastes voltage and allows current to slip through when the transistor should be off. A dielectric grown from the channel material itself, atom-for-atom matched to the surface beneath it, sidesteps the interface problems that have plagued conventional deposition.

The electrical performance of the resulting devices came astonishingly close to theoretical ideals. Using this self-grown oxide, the researchers fabricated tungsten diselenide transistors in which a change of only 61.3 millivolts in gate voltage increased the current tenfold. That figure sits very near the theoretical room-temperature limit of about 60 millivolts per decade, the so-called Boltzmann limit that defines the most efficient switching any conventional transistor can achieve. The devices also achieved an on/off current ratio exceeding ten million, meaning the difference between the transistor’s conducting and blocking states spans more than seven orders of magnitude. For low-power electronics, where every wasted millivolt translates into wasted energy, these numbers represent the kind of switching efficiency that device engineers spend careers pursuing.

The contact side of the problem was addressed with equal precision. When the upper layers were converted into tungsten ditelluride, a semimetal, the resulting contacts reduced the barrier for charge injection to about one-third of what was observed with direct platinum contacts. Lower injection barriers mean charge carriers can enter the semiconductor more freely, cutting the parasitic resistance that has historically limited the performance of 2D transistors. The semimetal-to-semiconductor junction created by chemical conversion is also atomically clean by construction, since it forms within the same crystal lattice rather than across the boundary between two separately grown materials.

To show that the method extends beyond individual devices, the team fabricated n-type molybdenum disulfide transistors using the same tungsten oxide dielectric, and then stacked p-type and n-type transistors vertically to construct a complementary van der Waals inverter, a basic building block of digital logic. The successful voltage inversion demonstrated that the technique is not merely a laboratory curiosity for single transistors but a plausible foundation for more highly integrated circuitry. Vertical stacking of complementary devices is particularly attractive for future electronics, because it multiplies functional density without shrinking lateral dimensions further, a direction the industry finds increasingly costly.

The implications reach well beyond one material system. The study combines fundamental materials science based on atomic-scale manipulation with modern semiconductor technology, addressing what Jo Moon-Ho described as the central integration challenge in two-dimensional semiconductor research: not simply finding better semiconductors, but securing equally suitable dielectrics and electrical contacts. By directly converting selected regions of a two-dimensional crystal into different electronic functions, the approach could provide a new route toward ultralow-power, ultrascaled, and vertically integrated semiconductor devices. If the method can be scaled to wafer dimensions with the same layer-by-layer precision demonstrated here, the era in which a complete transistor is grown rather than assembled may be closer than the industry dared expect.

Subject of Research: Layer-by-layer chemical conversion of a single 2D crystal into semiconducting, insulating, and semimetallic regions for integrated transistors

Article Title: Turning single 2D crystal into a complete high-performance transistor

Article References: Turning single 2D crystal into a complete high-performance transistor. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: two-dimensional materials, tungsten diselenide, transistors, gate dielectric, chalcogen substitution, van der Waals heterostructures, semiconductors, tungsten ditelluride, low-power electronics, integrated circuits, Institute for Basic Science, atomic-scale fabrication

The team synthesized three compositions of silver-doped zinc oxide, written chemically as Zn(1-x)Ag(x)O with silver fractions x of 0.00, 0.02, and 0.04, using a straightforward co-precipitation route. Zinc acetate dissolved in distilled water was mixed with carefully measured amounts of silver acetate, then sodium hydroxide was added dropwise at a controlled rate while the solution was stirred at 60 degrees Celsius. After washing, drying, and annealing at 450 degrees Celsius, the powders were pressed into pellets and interrogated with X-ray diffraction, high-resolution transmission electron microscopy, infrared spectroscopy, and broadband dielectric spectroscopy spanning frequencies from 0.1 hertz to 20 megahertz and temperatures from 30 to 150 degrees Celsius.

X-ray diffraction confirmed that every sample retained the hexagonal wurtzite crystal structure of zinc oxide, with no detectable secondary phases even at the highest silver loading. Rietveld refinement of the diffraction data revealed a subtle but telling non-monotonic trend: at 2 percent silver the lattice parameters expanded slightly, consistent with larger silver ions replacing zinc ions in the crystal lattice, but at 4 percent the lattice parameters snapped back to nearly the undoped values. The researchers attribute this reversal to competing effects, including silver segregation at grain boundaries and defect clustering that counteracts the simple ionic-size substitution picture at higher concentrations.

Perhaps the most striking structural finding is that crystallite size and particle size move in opposite directions as silver content rises. The coherent crystalline domains grew from 22.83 to 25.91 nanometers, while the overall particle size measured by transmission electron microscopy shrank dramatically from about 122 nanometers for pure zinc oxide to roughly 47 nanometers at 4 percent doping. The explanation involves two competing mechanisms: silver incorporated at zinc sites promotes atomic rearrangement and reduces defects during annealing, allowing larger crystalline domains to form, while silver that segregates to particle surfaces acts as a barrier that prevents particles from clumping together. Dislocation density, micro-strain, specific surface area, and porosity all fell with increasing silver content, confirming that the dopant cleans up the crystal lattice even as it keeps the particles dispersed.

From the infrared spectra, the team extracted a battery of mechanical parameters that are rarely measured alongside electrical properties. The Debye temperature, a measure of the stiffness of atomic bonding, climbed from 610.87 to 632.47 kelvin with increasing silver content. Young’s modulus, shear modulus, bulk modulus, and hardness all rose in parallel, as did the longitudinal, shear, and mean elastic wave velocities. The researchers attribute these gains to the increased density, reduced porosity, and shortened metal-oxygen bond lengths that accompany silver substitution. All samples remained brittle in character, and the residual stress stayed tensile at roughly 0.195 to 0.198 gigapascals, essentially unchanged by doping.

On the electrical side, the dielectric constant and dielectric loss both increased with temperature and silver content, while the alternating-current conductivity climbed across the entire frequency range. The team identified the underlying conduction mechanism as correlated barrier hopping, in which charge carriers leap over energy barriers between localized defect sites in a correlated fashion. The frequency exponent extracted from the conductivity data fell between 0.05 and 0.55 and decreased with rising temperature, a signature that distinguishes correlated barrier hopping from competing models such as quantum mechanical tunneling. The binding energy associated with this hopping process ranged from 0.163 to 0.345 electronvolts and shrank as temperature or silver content increased.

Activation energy measurements told a similar story. Using the Arrhenius relation, the team found that the energy barrier for charge carriers dropped from as high as 0.68 electronvolts in pure zinc oxide down to 0.187 electronvolts in the most heavily doped sample, with the lowest values occurring at the highest frequencies. The interpretation is that silver introduces shallow impurity levels within the zinc oxide bandgap, raising the free carrier concentration and lowering the energy needed for electrons to hop between neighboring grains. At high frequencies, carriers are already oscillating with the applied field and require less additional energy to respond, further reducing the effective barrier.

Impedance spectroscopy, analyzed through Cole-Cole plots, revealed single semicircular arcs corresponding to parallel resistor-capacitor circuits for all samples. The impedance of grains, grain boundaries, and the total series resistance all decreased with increasing silver content or temperature, falling from as high as 100 million ohms down to roughly 2,000 ohms, while the effective capacitance rose from 0.005 to a remarkable 38.73 microfarads at 150 degrees Celsius for the 4 percent doped sample. That capacitance is about 28 times higher than what pure zinc oxide achieves at the same temperature, a combination of low series resistance and high capacitance that the researchers identify as ideal for supercapacitor electrodes, where energy dissipated in internal resistance must be minimized.

The most novel contribution of the study is the quantitative correlation analysis linking mechanical and electrical properties measured on the same batch of samples. Young’s modulus correlated strongly with the dielectric constant, with a coefficient of determination of 0.82, indicating that stronger interatomic bonding goes hand in hand with a stronger polarizable response. Hardness and alternating-current conductivity showed a moderate correlation of 0.66, while the relationship between porosity and effective capacitance was essentially perfect at 1.00, confirming that squeezing out pores is the dominant mechanism behind the capacitance boost. Particle size and activation energy correlated moderately at 0.50, reflecting the fact that smaller particles facilitate charge hopping.

Taken together, the results establish that the same microstructural features that make silver-doped zinc oxide mechanically robust, namely denser packing, fewer defects, and stronger bonds, also make it a better dielectric and conductor. The researchers suggest that the simultaneous enhancement of elastic moduli, hardness, dielectric constant, conductivity, and capacitance opens a path toward multifunctional oxide nanomaterials for advanced electronics, energy storage, and solar energy applications. While questions remain about the exact distribution of silver between substitutional sites, grain boundaries, and possible minor silver-rich clusters at higher doping levels, the work provides a comprehensive framework that other groups can now apply to related doped oxide systems, and it demonstrates that mechanical toughness and electrical performance need not be traded off against each other in nanoscale semiconducting oxides.

Subject of Research: Correlation between mechanical and dielectric properties of pure and silver-doped zinc oxide nanoparticles

Article Title: On the correlation between mechanical and electrical properties of pure and Ag doped ZnO nanoparticles

Article References: Mohamed, M., Ismail, Y. A. M., Bouzidi, M., Khan, Z. R., & Sedky, A. (2026). On the correlation between mechanical and electrical properties of pure and Ag doped ZnO nanoparticles. Scientific Reports, 16(1), Article 28493. https://doi.org/10.1038/s41598-026-67220-7

Image Credits: AI Generated

DOI: 10.1038/s41598-026-67220-7

Keywords: zinc oxide, silver doping, nanoparticles, dielectric properties, mechanical properties, correlated barrier hopping, impedance spectroscopy, elastic moduli, supercapacitors, wurtzite structure, activation energy, semiconductors

The central difficulty in studying hydrogen-induced platelets has always been one of scale. Density functional theory, the workhorse of first-principles materials simulation, can compute the energies and forces on atoms with high accuracy, but only for systems containing a few hundred atoms at most. A realistic platelet embedded in a silicon crystal, complete with edges, surrounding strain fields and a population of trapped hydrogen molecules, demands hundreds of thousands of atoms. Earlier theoretical pictures of platelet structure therefore relied on idealized, infinitely periodic models, in which the platelet extends endlessly in two dimensions and has no boundary. Such models capture the chemistry of the platelet interior but miss the physics of the edges, where the platelet meets pristine silicon and where much of the interesting hydrogen chemistry is expected to occur. The Nagoya team set out to close that gap.

Their approach centered on developing a neural-network potential, a class of interatomic potential in which a machine-learning model is trained on a large database of quantum-mechanical calculations and then learns to predict the energy and forces of any atomic configuration with near-DFT accuracy at a tiny fraction of the computational cost. The concept traces back to the high-dimensional neural-network framework introduced by Behler and Parrinello in 2007, and has since matured into a family of machine-learning potentials that are transforming computational materials science. The potential developed in this work was specifically constructed to be transferable to simulations involving hydrogen atoms in silicon, meaning that it remains accurate not just for one fixed bonding environment but across the wide variety of configurations hydrogen can adopt: bonded to silicon atoms at the platelet surfaces, sitting interstitially in the lattice, or existing as free H2 molecules within the platelet cavity.

A critical validation of the new potential was its ability to reproduce the relative stability of different hydrogen configurations in silicon. Hydrogen in crystalline silicon is famously versatile, occupying bond-centered and antibonding sites, forming Si-H bonds that passivate dangling bonds, pairing into molecules, and clustering into extended complexes. Previous experimental work, notably Raman scattering and infrared absorption studies dating back to the early 1990s, had identified the vibrational fingerprints of hydrogen molecules trapped inside {111}-oriented platelets, and theoretical studies had catalogued the energies of various hydrogen configurations. The neural-network potential was shown to predict these relative energies accurately, giving the researchers confidence that the large-scale simulations built on top of it would rest on a trustworthy quantum-mechanical foundation.

With the potential in hand, the team constructed simulation cells containing on the order of one hundred thousand atoms, large enough to embed a finite-sized platelet, with real edges, inside an otherwise perfect silicon lattice. This is the decisive methodological step. Because the platelet is finite, the simulation does not impose any artificial constraint on what happens inside it: the internal pressure exerted by hydrogen on the two facing platelet surfaces, and the resulting displacement of silicon atoms around the defect, emerge spontaneously from the molecular dynamics rather than being prescribed. The platelet can relax, its surfaces can separate or compress, and hydrogen atoms and molecules can migrate to whatever sites they find most favorable. In effect, the simulation lets the crystal solve its own structural problem.

The headline finding concerns hydrogen molecules. In the finite-sized platelets with low formation energies, the number of H2 molecules turned out to be two to three times greater than previous studies based on infinite-sized platelet models had predicted. This is not a small correction to a niche quantity. The population of molecular hydrogen inside a platelet is directly tied to the internal pressure that drives platelet growth, blistering and ultimately the exfoliation of thin silicon layers, the process exploited in silicon-on-insulator fabrication and layer-transfer technologies. If earlier periodic models systematically underestimated the molecular hydrogen content, then the quantitative picture of how platelets pressurize and crack open the crystal needs revision, and this study supplies the computational evidence for that revision.

Equally significant is where the molecules sit. The simulations revealed that H2 molecules reside at specific sites between the two platelet surfaces, rather than being distributed randomly through the cavity, and that this preferential placement contributes to lowering the formation energy of platelets that contain molecular hydrogen. In other words, the molecules are not passive passengers pumped up like a tire; they are structural participants whose positioning stabilizes the defect. This finding resonates with long-standing experimental observations of trapped molecular hydrogen in platelets, including Raman studies that detected the characteristic vibrational signature of H2 confined within {111}-oriented platelets, and it gives those spectroscopic observations a concrete atomistic interpretation.

The broader significance of the work lies in what it demonstrates about methodology. By directly modeling realistic finite-sized platelets with edges, the large-scale molecular simulations capture physics that periodic models structurally cannot: the elastic interaction between the platelet and the surrounding lattice, the role of the platelet periphery as a sink or source for hydrogen, and the spontaneous development of internal pressure. The authors argue that this capability provides deeper insight into hydrogen configurations and their energetics than was previously attainable. Given the growing family of machine-learning potentials, including Gaussian approximation potentials, moment tensor potentials and deep potential models, now being applied to hydrogenated silicon systems ranging from amorphous Si:H to heterointerfaces, the study positions neural-network potentials as the natural tool for revisiting other extended defects whose structures were frozen decades ago by the limits of first-principles cell sizes.

There is also a technological payoff. Hydrogen implantation and subsequent thermal treatment are used industrially to cleave off atomically thin silicon films, and the efficiency of that exfoliation depends sensitively on how quickly platelets nucleate, accumulate molecular hydrogen and coalesce into blisters. A corrected atomistic model of the platelet interior, one that accounts for the true H2 population and the stabilizing role of molecular hydrogen at specific inter-surface sites, feeds directly into more reliable predictions of blistering kinetics and layer-splitting conditions. The work, supported by the Japan Society for the Promotion of Science, the JST FOREST program and the Mitsubishi Foundation, with density functional calculations performed on the SQUID supercomputer at the University of Osaka, thus closes a loop that opened more than thirty years ago when transmission electron microscopists first imaged these tiny hydrogen-filled cracks. The smallest atom, it turns out, required one of the largest simulations, and a neural network, to finally show its hand.

Subject of Research: Atomic structure and energetics of hydrogen-induced {111} platelets in silicon modeled with a neural-network potential

Article Title: Revisiting atomic structures at hydrogen-induced platelets in silicon

Article References: Yokoi, T., Hasegawa, T., Ogura, Y., & Matsunaga, K. (2026). Revisiting atomic structures at hydrogen-induced platelets in silicon. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13902-6

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13902-6

Keywords: silicon, hydrogen platelets, neural-network potential, molecular dynamics, H2 molecules, density functional theory, machine learning, defects, exfoliation, semiconductors, layer transfer, computational materials science

The initiative, known as the Integrated Diamond and Carbon Research in Space Applications, or IDiCaRS, represents an unusual approach to a stubborn problem. Today, the development, manufacturing and severe-environment testing of radiation-hardened electronics typically occur at separate facilities, often in separate locations, forcing researchers to shuttle prototypes between sites and stretching development timelines considerably. IDiCaRS aims to collapse that fragmented pipeline by bringing an end-to-end research infrastructure under one roof: the growth and processing of diamond and related carbon materials, the fabrication of electronic devices from those materials, and radiation-effects testing using high-energy heavy-ion beams at the Facility for Rare Isotope Beams, or FRIB, located on the MSU campus.

The choice of diamond as the flagship material is not accidental. Diamond possesses a unique combination of physical properties that make it exceptionally promising for space electronics. It conducts heat better than nearly any other material, which allows devices to dissipate the thermal loads that accumulate during operation. It resists high temperatures, tolerates intense radiation and withstands significant electrical stress, all qualities that conventional silicon struggles to match in harsh conditions. By establishing what project leaders describe as a first-of-its-kind diamond foundry, the facility will allow researchers to investigate these materials and devices in depth and generate systematic data about how they respond to extreme radiation and temperature regimes, data that is currently difficult and slow to obtain.

Wen Li, an MSU Research Foundation Distinguished Professor in the College of Engineering and executive director of Fraunhofer USA Center Midwest, is leading the effort. According to Li, the goal is to give researchers in space and automotive electronics a place to move more quickly from developing a material or device to testing how it performs under the harsh environmental conditions that can damage electronics in space. That speed matters. In the current landscape, a promising new radiation-tolerant material may take years to progress from laboratory synthesis to qualified flight hardware, in part because each stage of validation happens at a different institution with different equipment and protocols. By co-locating the full workflow, IDiCaRS intends to shorten development cycles and establish shared testing methodologies and qualification approaches for electronics intended for extreme environments.

The facility will not be built from scratch. It leverages existing MSU capabilities and partnerships, most notably FRIB, a DOE Office of Science user facility that accelerates heavy ions to energies capable of simulating decades of space radiation exposure in a matter of hours. It also draws on the MSU Space Electronics Initiative and the Fraunhofer USA Center Midwest, which has collaborated with the university on advanced diamond and carbon materials science for decades. Thomas Glasmacher, director of the FRIB Laboratory, said the laboratory is excited to bring its heavy-ion beam infrastructure to the IDiCaRS initiative to help expand MSU’s reach of cutting-edge research for extreme environments, adding that joining forces in advanced material science positions the partners to make a lasting impact on space exploration and semiconductor innovation while preparing the next generation of STEM leaders.

Industry and government leaders have framed the project as strategically significant well beyond the university. Thomas Schuelke, president of Fraunhofer USA and a professor in the College of Engineering, described the grant as the culmination of decades of collaborative research between MSU and Fraunhofer USA in advanced diamond and carbon materials science. What began as fundamental research partnerships, he noted, has evolved into a shared-use facility intended to accelerate the translation of next-generation semiconductor materials from the laboratory to the marketplace, strengthening America’s position in critical materials innovation. John Papapolymerou, dean of the College of Engineering and director of the MSU Space Electronics Initiative, emphasized that IDiCaRS will strengthen the university’s ability to bring together researchers, industry partners and advanced research capabilities to tackle some of the most important challenges facing space electronics and semiconductors.

The technical payoff could be transformative for spacecraft design. More radiation-resistant and thermally capable semiconductor technologies could reduce the need for the heavy shielding and redundant systems that current spacecraft must carry to protect conventional silicon electronics. Every kilogram of shielding is a kilogram that cannot be devoted to scientific instruments, fuel or payload capacity, so electronics that survive radiation natively could enable future missions to fly smaller, lighter and more efficient systems with advanced capabilities. The implications extend beyond space exploration as well. Research conducted at IDiCaRS could contribute to high-power electronics and next-generation communications technologies used on Earth and in orbit, from electric-vehicle power systems that already demand extreme-environment semiconductors to the growing constellation of satellites that form the backbone of global connectivity.

The project also carries an explicit workforce mission, one that Michigan’s elected officials have highlighted as central to the state’s economic future. IDiCaRS will create hands-on education and training opportunities for students, including access to advanced research facilities and specialized equipment used in semiconductor manufacturing and radiation testing. Plans include updated undergraduate and graduate coursework, a graduate certificate and an undergraduate minor related to the facility’s research areas, along with space electronics programs for middle and high school students and opportunities for community college students. U.S. Sen. Gary Peters noted that semiconductors power many of the products Michigan excels at making and that the federal investment will help MSU bring key university, government and industry partners together to accelerate deployment of cutting-edge semiconductor technologies. U.S. Rep. Haley Stevens added that Michigan students will have opportunities to learn and work with technologies pushing the boundaries of space exploration, quantum technologies and semiconductor manufacturing.

The broader context is a national push to shore up the domestic semiconductor ecosystem at a moment when chips have become as strategically important as energy or food. Advanced wide-bandgap materials such as diamond sit at the frontier of that effort, promising devices that operate at higher voltages, higher temperatures and higher frequencies than silicon allows. By pairing materials discovery with device fabrication and world-class radiation testing in a single shared facility, IDiCaRS is designed to serve researchers from academia, industry and government, creating a common resource for advancing technologies built to operate where ordinary electronics fail. Ultimately, the initiative is intended to accelerate the development and testing of electronics that can withstand extreme environments while strengthening the infrastructure, technologies and workforce needed for the future of space exploration and advanced manufacturing, a bet that the next generation of machines, whether bound for the outer planets or the factory floor, will be built on carbon.

Subject of Research: A $20 million NSF-funded shared-use facility at Michigan State University for developing and radiation-testing diamond and carbon-based semiconductor electronics for space applications

Article Title: Building for the future of space and semiconductors

Article References: Building for the future of space and semiconductors. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: space electronics, semiconductors, diamond materials, radiation testing, Michigan State University, National Science Foundation, Facility for Rare Isotope Beams, Fraunhofer USA, extreme environments, workforce development, advanced manufacturing, spacecraft technology

The case for diamond begins with physics. Diamond possesses the highest thermal conductivity of any bulk material, reaching values far beyond copper or silicon, while simultaneously acting as an excellent electrical insulator. That combination is almost paradoxical: the material can pull enormous amounts of heat away from a transistor junction without conducting a single stray electron. Add outstanding thermo-mechanical stability and a coefficient of thermal expansion that can be managed through engineering, and diamond becomes uniquely suited to sit directly against the hottest, most power-hungry regions of a chip. In an era when three-dimensional integrated systems stack multiple dies on top of one another, trapping heat in layers where conventional cooling cannot reach, this near-junction heat extraction capability is precisely what the industry needs.

But the review is candid about the central obstacle: the thermal boundary resistance that arises wherever diamond meets another material. When heat flows across an interface between two solids, phonons—the quantum packets of vibrational energy that carry heat in insulators—scatter at the boundary due to differences in vibrational spectra, bonding, and crystal structure. This interfacial resistance can dominate the entire thermal budget of a device, sometimes negating the benefit of diamond’s extraordinary bulk conductivity. The authors trace the theoretical framework, rooted in the classic acoustic mismatch and diffuse mismatch models, and show how modern interface engineering—ultrathin interlayers, carbide-forming adhesion layers, and controlled amorphous transition regions—can dramatically reduce this resistance. Recent molecular dynamics studies, including work using machine-learned interatomic potentials, are now revealing how phonon bridge mechanisms and nanoscale structural transitions govern heat flow across these heterogeneous junctions.

The most mature application is the GaN-on-diamond platform. Gallium nitride high-electron-mobility transistors are the workhorses of radio-frequency and power electronics, but their performance is throttled by self-heating in a thin channel near the surface. Growing polycrystalline diamond directly onto GaN wafers, or bonding single-crystal diamond membranes to processed devices, moves the heat sink within micrometers of the hot spot. The review documents remarkable progress: room-temperature surface-activated bonding of GaN to diamond, carbide interlayers that achieve low thermal boundary resistance, and even all-around diamond integration of nanoscale gate-length devices. Record-low interfacial resistance has been reported at bonded GaN-diamond interfaces by controlling an ultrathin heterogeneous amorphous layer, and top-side diamond integration into AlGaN/GaN transistors demonstrates that diamond can now be placed on both sides of the active region.

Silicon, silicon carbide, and the emerging ultrawide-bandgap semiconductor beta-gallium oxide each present distinct integration challenges that the review addresses in turn. For silicon, the mismatch in thermal expansion and the chemical incompatibility of diamond growth conditions with silicon processing demand careful strategies, including ion-beam-activated hydrophilic bonding with aluminum nitride interlayers and atomic-level transition engineering to boost thermal boundary conductance. Silicon carbide, with its own high thermal conductivity, benefits from diamond-SiC engineered substrates that have already demonstrated enhanced heat dissipation in GaN transistors, though non-equilibrium molecular dynamics simulations continue to pinpoint the sources of residual interfacial resistance. Beta-gallium oxide, a material with enormous promise for power devices but notoriously poor thermal conductivity, may benefit most of all: researchers have grown polycrystalline diamond directly on it, demonstrated van der Waals thin-film integration, and even shown wafer-level transfer printing of beta-gallium oxide films and MOSFETs onto diamond substrates at the IEEE International Electron Devices Meeting.

Achieving these device-level wins requires a reliable supply of diamond itself, and the review devotes substantial attention to manufacturing. Chemical vapor deposition, particularly microwave plasma CVD, is the dominant route, and reactor design has become a science of its own, with multiphysics modeling and electromagnetic mode engineering now enabling four-inch deposition areas. Single-crystal diamond wafers, historically limited to a few millimeters, have grown to inch sizes through mosaic growth techniques that stitch together multiple seeds with precisely controlled crystallographic orientations, and heteroepitaxial growth on iridium buffer layers offers a scalable path to larger wafers. Perhaps most striking is the recent demonstration of scalable production of ultraflat, ultraflexible diamond membranes published in Nature, which opens the door to transferring thin diamond layers onto arbitrary substrates—the same logic that transformed silicon-on-insulator technology decades ago.

Beyond the chip, the review surveys a full arsenal of diamond-based packaging technologies. Diamond heat spreaders, long used in laser diodes and RF amplifiers, are now being combined with copper-diamond composites whose metal matrices are engineered with carbide coatings to maximize thermal conductivity. Diamond microchannel heat sinks represent the most aggressive approach: by etching or laser-machining channels directly into diamond and flowing coolant through them, researchers have demonstrated cooling of heat fluxes approaching the kilowatt-per-square-centimeter regime, with designs including zigzag double-layer channels, rhombus pin fins, and hybrid single-crystal-polycrystalline structures that direct heat away from hot spots. Two-phase flow boiling in diamond microchannels and in-chip microfluidic cooling on diamond substrates have both pushed wide-bandgap electronics to record-high heat fluxes, echoing the microfluidic cooling concepts first proposed for VLSI circuits in the 1980s but now realized in a far superior material.

For three-dimensional integration, the review highlights through-diamond vias and diamond interposers as the packaging equivalents of through-silicon vias, but with thermal performance that silicon cannot match. Bottom-up copper filling of high-aspect-ratio diamond through holes enables vertical electrical interconnection while the surrounding diamond conducts heat laterally and vertically. Diamond interposers have been demonstrated for 2.5D chiplet packaging in supercomputing applications, diamond-on-chip-on-glass architectures have shown efficient thermal management, and diamond-copper composite interposers are being explored for electric vehicle power modules. Warpage mitigation, a persistent headache in wafer-to-wafer bonding, is being tackled through heterogeneous integration of diamond heat spreaders, while hybrid copper-diamond microbump bonding points toward fully three-dimensional heterogeneous systems in which the thermal and electrical pathways are co-designed from the outset.

The review closes with a forward-looking agenda: wafer-scale diamond manufacturing that can feed standard semiconductor fabrication lines, advanced packaging flows that treat diamond as a first-class structural and thermal material rather than an afterthought, and system-level thermal design that co-optimizes materials, devices, and packaging from the transistor to the heat sink. The authors also note emerging applications beyond conventional electronics, including three-dimensional integration of diamond spin qubits for quantum computing and heterogeneous integration of spin-photon interfaces with CMOS platforms, where diamond’s role is not merely thermal but functional. If the integration challenges documented in this review can be overcome at scale, the industry may find that the oldest gemstone becomes the defining material of the hottest new technology of the century.

Subject of Research: Diamond heterogeneous integration and advanced packaging for thermal management of semiconductor devices

Article Title: Review: diamond heterogeneous integration for thermal management—integration strategies and advanced packaging

Article References: Wu, S., Wu, F., Zhang, J., Ji, J., Zhang, W., Luo, W., Shao, W., & Chen, Y. (2026). Review: diamond heterogeneous integration for thermal management—integration strategies and advanced packaging. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13776-8

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13776-8

Keywords: diamond, thermal management, heterogeneous integration, GaN, advanced packaging, thermal boundary resistance, microchannel heat sink, CVD diamond, power electronics, 3D integration, semiconductors, heat spreaders

The appeal of plant-mediated synthesis lies in the chemistry hidden inside leaf tissue. Extracts of Rumex nepalensis are rich in polyphenols, flavonoids, tannins, and organic acids, and these phytochemicals perform two roles simultaneously: they reduce zinc ions to form the oxide, and they cap the growing crystal surfaces, preventing the particles from clumping into larger aggregates. In effect, the plant acts as both a reducing agent and a stabilizing surfactant. This dual function eliminates the need for reagents such as sodium borohydride or hydrazine, and it also leaves a benign organic coating on the particle surface, which is often associated with improved biocompatibility in downstream applications.

Once the nanoparticles were formed, the team subjected them to a battery of analytical techniques to confirm what they had actually made. X-ray diffraction revealed sharp, well-defined peaks corresponding to the hexagonal wurtzite crystal structure, the thermodynamically stable form of zinc oxide under ordinary conditions. The absence of extra peaks indicated that no contaminating phases, such as zinc hydroxide or unreacted precursor salts, had survived the synthesis. Crystallite sizes estimated from diffraction data were consistent with the particle dimensions later observed by electron microscopy, suggesting that each particle was essentially a single crystallite rather than a polycrystalline aggregate.

Spectroscopic evidence filled in the chemical picture. Fourier-transform infrared spectroscopy detected absorption bands attributable to Zn–O stretching vibrations, along with features associated with the organic molecules from the plant extract adsorbed onto the particle surfaces, which is exactly what a capping layer should look like. Energy-dispersive X-ray spectroscopy showed strong signals for zinc and oxygen with minimal extraneous elements, indicating a high degree of elemental purity. Optical measurements using UV–Visible spectroscopy yielded a band gap energy of 3.26 electron volts, squarely in the expected range for zinc oxide and a confirmation that the material retains the semiconducting behaviour that makes ZnO useful in sensors, photocatalysts, and optoelectronic devices.

Electron microscopy provided the most striking visual confirmation. Scanning electron microscopy showed clusters of roughly spherical particles, while transmission electron microscopy resolved individual nanoparticles and allowed direct measurement of their diameters. The narrow size distribution, approximately 11 to 13 nanometres, is notable for a room-temperature biological route, where size control is often the hardest parameter to tune. Particles in this size range have an enormous surface-to-volume ratio, which matters because the antibacterial and antioxidant effects of zinc oxide depend heavily on surface area and on how much zinc can interact with biological membranes and generate reactive oxygen species at the particle surface.

That surface activity translated into real biological performance. The nanoparticles showed significant antibacterial activity against human pathogenic bacteria, positioning them as candidate antimicrobial agents at a moment when antibiotic resistance is spreading and demand for non-traditional antimicrobials is intense. Zinc oxide nanoparticles are thought to attack bacteria through several mechanisms at once: they generate reactive oxygen species that damage DNA, proteins, and lipids; they release zinc ions that disrupt metabolic enzymes; and their physical contact with cell membranes can compromise membrane integrity. Because these mechanisms differ fundamentally from those of conventional antibiotics, researchers view ZnO nanomaterials as a promising avenue against pathogens that have evolved resistance to standard drugs.

The team also documented strong antioxidant activity, meaning the particles could scavenge free radicals and mitigate oxidative stress in test systems. This property opens a different set of doors. In cosmetics, antioxidant nanomaterials are sought for skin-care formulations, and zinc oxide already has a long safety track record as a physical sunscreen agent. In food nanotechnology, antioxidant packaging additives could slow the oxidation that spoils fats and vitamins. The combination of antimicrobial and antioxidant activity in a single biogenic particle is what the authors point to when they describe the material as suitable for biomedical, cosmetic, and industrial applications.

The broader context is the rise of green nanotechnology as a sustainability strategy. Conventional nanoparticle synthesis typically requires high temperatures, strong reducing agents, and organic solvents, all of which carry environmental and energy costs. Plant-mediated routes operate in water, at ambient or mild conditions, and use renewable biological feedstock. The Rumex nepalensis used in this work is widespread and easy to propagate, making the process potentially cheap to scale. The authors, who include collaborators from institutions in India, Indonesia, and across Maharashtra, frame the result as part of a growing body of evidence that nature-inspired synthesis can match chemical synthesis on quality while dramatically reducing its environmental footprint.

Caveats remain before such particles reach pharmacies or factories. The study reports characterization and in vitro biological activity, so efficacy in clinical settings, toxicity profiles in animal models, and the long-term environmental fate of the nanoparticles all require further investigation. The paper’s data availability statement notes that no datasets were generated or analysed during the study beyond those presented in the article, and the work received no specific external funding. Still, the complete analytical record, from wurtzite diffraction patterns to a measured band gap of 3.26 electron volts, gives other laboratories a solid benchmark to reproduce and improve upon the synthesis.

What makes the result resonate beyond the laboratory is its simplicity. A leaf extract, a zinc salt, and standard benchtop equipment produced semiconductor nanoparticles with defined crystal structure, narrow size distribution, and measurable antimicrobial and antioxidant power. As drug-resistant infections accelerate and industries search for greener raw materials, the idea that a mountain weed long used in traditional medicine can serve as a nanofactory is the kind of cross-disciplinary surprise that keeps green chemistry moving forward. The researchers suggest their biogenic ZnO nanoparticles could serve as a foundation for sustainable nanomaterials in biomedicine, cosmetics, and industry, and on the evidence presented, the leaf’s chemistry is more than capable of carrying that ambition.

Subject of Research: Green synthesis of zinc oxide nanoparticles using Rumex nepalensis leaf extract with physicochemical characterization and antibacterial and antioxidant evaluation

Article Title: Plant-mediated synthesis of ZnO nanoparticles using Rumex nepalensis extract and physicochemical characterization and biological applications

Article References: Pawar, A., Naktode, K., Mungole, A., Gaikwad, S., Parshuramkar, D. M., Pandhurnekar, C. P., Gulzar, J., Mammen, M. V., & Rasool, A. (2026). Plant-mediated synthesis of ZnO nanoparticles using Rumex nepalensis extract and physicochemical characterization and biological applications. The Science of Nature, 113(5), Article 108. https://doi.org/10.1007/s00114-026-02161-9

Image Credits: AI Generated

DOI: 10.1007/s00114-026-02161-9

Keywords: zinc oxide nanoparticles, green synthesis, Rumex nepalensis, nanotechnology, antibacterial activity, antioxidant, wurtzite structure, phytochemicals, sustainable materials, biomedical applications, cosmetics, semiconductors