Micro-trenches, tiny grooves etched into materials, play a critical role in various high-tech applications. Their precise three-dimensional morphology dictates key properties such as electronic performance, mechanical strength, and fluid dynamics on microscale devices. Yet, traditional imaging methods have struggled to achieve comprehensive, high-resolution measurements of structures with high aspect ratios—those with depths significantly larger than their width—due to limitations in focus depth and resolution.

The newly developed FPCSI technique addresses these challenges by combining the power of Fourier ptychography with coherence scanning interferometry. Fourier ptychography itself is a computational imaging method that synergistically uses multiple low-resolution images captured under varying illumination angles to synthesize high-resolution images free of the limitations imposed by conventional optics. Meanwhile, coherence scanning interferometry is a well-established optical technique for measuring surface topography with nanometric precision.

By fusing these two approaches, the research team has effectively created a hybrid system capable of resolving complex micro-trench geometries with unprecedented clarity. The method exploits the coherent nature of light and computational reconstruction algorithms to extract phase information, which, when analyzed across different focal positions, renders a high-fidelity 3D image. This allows for the meticulous profiling of microstructures, including deep trenches and composite formations that were previously inaccessible.

In demonstrating the efficacy of FPCSI, the researchers meticulously investigated micro-trenches with aspect ratios far exceeding those measurable by existing solutions. Their approach yielded precise depth maps and surface profiles, revealing subtle features within the trenches that conventional microscopy would miss. This opens doors to better quality control and design optimization in semiconductor fabrication, where such trench structures are ubiquitous.

Furthermore, the technique’s non-destructive nature stands out as particularly advantageous. Unlike methods requiring physical sectioning or those employing harsh probing tools, FPCSI operates purely through optical means, preserving the integrity of delicate samples. This characteristic is crucial in research and industry where every sample holds significant value and must remain unaltered for subsequent analysis or functional use.

The ability to characterize composite micro-trenches—those composed of multiple materials or layers—adds another dimension to the method’s versatility. Different materials often exhibit unique refractive indices and scattering properties, complicating optical measurements. FPCSI leverages its coherent scanning framework to differentiate between these layers, providing a detailed morphological map that elucidates structural composition as well as geometry.

Technically, the process involves scanning a sample through multiple focus positions while illuminating it under varying incident angles. The resulting dataset, rich in both amplitude and phase information, is then processed through iterative algorithms rooted in Fourier ptychography principles. These algorithms reconstruct high-resolution images and precise depth profiles from what would otherwise be fragmented or blurred data, overcoming classical optical trade-offs between resolution and depth of field.

The impact of this innovation stretches beyond just micro-trenches. The researchers envision applications in microfluidics, biomedical devices, and nanofabrication, where accurate morphological characterization is essential. For instance, in microfluidics, the precise dimensions of channels and reservoirs influence fluid flow dynamics and reaction rates; FPCSI could provide a powerful tool for designing and validating such devices with greater efficiency.

Another promising avenue lies in the realm of materials science, particularly in the inspection of composite materials and layered structures. FPCSI’s sensitivity to phase variations makes it an excellent candidate for evaluating internal morphologies and detecting sub-surface defects that traditional imaging struggles to resolve.

While the technique is computationally intensive, advances in processing power and algorithm optimization have made it increasingly accessible. The researchers have implemented efficient codebases and integrated machine learning strategies to accelerate image reconstruction, envisioning real-time or near-real-time imaging capabilities in future iterations.

Despite the successes, the team acknowledges certain limitations. The requirement for controlled illumination angles and precise scanning mechanisms can pose experimental challenges. Furthermore, complex surface reflections and multiple scattering in highly irregular structures might still introduce artifacts. However, ongoing refinements in hardware and software are expected to mitigate these issues.

The paper detailing the development and validation of FPCSI represents a significant contribution to optical microscopy and metrology. By cleverly integrating established methods into a cohesive and powerful imaging tool, the researchers have carved out a new pathway for detailed, non-invasive exploration of microscale features that were, until now, elusive.

Ultimately, the innovation not only fills a technical gap but also paves the way for enhanced quality assurance, novel device design, and deeper scientific understanding across multiple disciplines. As the digital and physical worlds continue to converge at micro- and nano-scales, tools like Fourier ptychographic coherence scanning interferometry will become instrumental in shaping the next wave of technological advancement.

The versatility and precision of FPCSI underscore the increasing importance of interdisciplinary approaches, combining optics, computational imaging, and materials science. This convergence reflects a broader trend toward harnessing light’s coherent properties alongside algorithmic ingenuity, positioning this technique at the forefront of imaging science innovation.

In an era where micro- and nano-fabrication is integral to numerous industries, the ability to fully characterize complex internal structures without destruction or compromise is invaluable. FPCSI fulfills this need with elegance and efficiency, promising to become a standard in advanced optical metrology.

Continued research and development will likely enhance the technique’s robustness, reduce its dependence on idealized sample preparation, and expand its applicability to a wider array of materials and geometries. The vision of capturing intricate 3D micro-morphologies in real time is now closer than ever, thanks to this breakthrough.

By unlocking new dimensions of imaging capacity, Fourier ptychographic coherence scanning interferometry stands to accelerate innovation in microelectronics, photonics, and beyond, echoing the ever-growing demand for precision and detail at the smallest scales of technology and nature.

Subject of Research:
Three-dimensional morphological characterization of high aspect ratio and composite micro-trenches.

Article Title:
Fourier ptychographic coherence scanning interferometry for 3D morphology of high aspect ratio and composite micro-trenches.

Article References:
Li, Y., Yuan, Q., Huo, X. et al. Fourier ptychographic coherence scanning interferometry for 3D morphology of high aspect ratio and composite micro-trenches. Light Sci Appl 15, 93 (2026). https://doi.org/10.1038/s41377-026-02189-6

Image Credits: AI Generated

DOI: 29 January 2026

Chirality in inorganic materials manifests distinctively, influencing electron transport behaviors under magnetic fields in ways previously observed primarily at molecular or nanoscale levels. For instance, chiral carbon nanotubes exhibit anisotropic electrical conductivity responsive to magnetic field orientation, a phenomenon highlighting how structural asymmetry guides electron dynamics. Extending this concept to oxides with intrinsic magnetic properties presents unique challenges and opportunities, particularly when considering the interplay of electron correlations, spin exchange interactions, and, crucially, spin-orbit coupling effects.

Magnetic oxides such as SrRuO₃ are known for their complex balance of electron correlation and spin exchange interactions, which shape their magnetic ordering and transport properties. Introducing strong spin-orbit coupling in these materials further diversifies their physical behaviors, giving rise to emergent phenomena like Rashba-type spin splitting and Dzyaloshinskii-Moriya interactions (DMI). While the Rashba interaction has been extensively studied in oxide interface two-dimensional electron gases—producing measurable electromagnetic chiral effects—the in-depth exploration of DMI’s contribution to magneto-chiral behavior remains a formidable experimental and theoretical frontier due to its subtle and direction-dependent nature.

The researchers at ShanghaiTech innovatively fabricated superlattices comprising SrRuO₃, SrRu₁₋ₓTiₓO₃, and SrTiO₃ layers arranged in a novel A-B-C-C stacking sequence. Utilizing laser molecular beam epitaxy, a technique allowing atomic-layer precision in constructing heterostructures, they engineered a deliberate breaking of inversion symmetry essential for realizing pronounced chiral responses. This architectural control endowed the material with a finely tunable Dzyaloshinskii-Moriya interaction, acting as a microscopic source of asymmetric spin interactions that influence the macroscopic electromagnetic behavior.

Their experimental approach involved rotating these carefully constructed superlattice samples within an external magnetic field while performing precise electrical resistance measurements. Intriguingly, the direction corresponding to the minimum resistance—indicative of the magnetic easy axis orientation—exhibited distinct left-handed and right-handed rotational modes. This handedness-dependent rotational symmetry demonstrates a direct link between the engineered chiral atomic stacking and the emergent macroscopic magneto-chiral phenomena, a signature that had remained elusive in oxide heterostructures.

One of the most compelling aspects of their discovery is the magnitude of the angular rotation; the maximum rotation angle of the magnetic easy axis reached up to 45 degrees, a remarkably large value uncommon in similar systems. This provides unequivocal evidence for the effective control of spin textures via interfacial DMI and magnetic anisotropy engineering. The ability to induce such a semi-self-controlled rotation opens avenues for precise manipulation of spin configurations, crucial for future spintronic devices aimed at higher efficiency and lower power consumption.

Unlike traditional magneto-chiral effects that are typically constrained to configurations where currents flow strictly parallel or antiparallel to the applied magnetic field, the effect demonstrated here transcends these limitations. The observed ‘semi-self-controlled’ rotational behavior suggests that the superlattice can discern not only the directional vector of an external magnetic field but also resolve its intensity. This dual sensitivity enhances the functional versatility of these materials, positioning them as potential candidates for novel magnetic sensors and advanced information processing technologies.

Fundamentally, the study illuminates how engineered Dzyaloshinskii-Moriya interactions within oxide superlattices provide a rich platform for exploring non-trivial spin-dependent transport phenomena. As inversion symmetry is locally broken at interfaces, and spin-orbit coupling intertwines with magnetic exchange, emergent chiral behaviors can be induced and manipulated at will. This contrasts with bulk materials, where such subtle effects are often averaged out or suppressed by higher symmetries.

The implications of this research extend beyond fundamental physics into the rapidly evolving field of spintronics, where the electron spin degree of freedom is harnessed for next-generation electronic devices. The demonstrated angle-resolved magneto-chiral effect could enable devices capable of operating based on magnetic field angle detection, offering prospects for ultra-sensitive magnetic memory elements, tunable spin filters, and logic devices with integrated directional control.

Moreover, the methodology employed—layer-by-layer atomic precision growth paired with detailed transport measurements under variable magnetic fields—establishes a robust experimental framework for investigating other exotic phases where chirality and spin-orbit coupling interplay. The findings encourage further exploration into related transition metal oxides and engineered heterostructures to tailor magneto-electric coupling phenomena, potentially unveiling new quantum states and functionalities.

In conclusion, the angle-resolved electrical magneto-chiral effect realized within SrRuO₃-SrRu₁₋ₓTiₓO₃-SrTiO₃ superlattices represents a significant advancement in the manipulation of chiral spin interactions via artificial symmetry breaking. By harnessing the Dzyaloshinskii-Moriya interaction and precise layer stacking, this research unlocks unprecedented control over magnetic anisotropy and electron transport in oxide materials. This breakthrough not only broadens the fundamental understanding of magneto-chiral phenomena but also paves the way for transformative applications in spintronics and magnetic sensor technologies.

Subject of Research: Angle-resolved electrical magneto-chiral effect in oxide superlattices; Dzyaloshinskii-Moriya interaction engineering; spintronics.

Article Title: Angle-resolved Electrical Magneto-Chiral Effect Demonstrated in SrRuO₃-SrRu₁₋ₓTiₓO₃-SrTiO₃ Superlattices with Broken Inversion Symmetry.

Web References: DOI:10.1016/j.scib.2025.03.021

Image Credits: ©Science China Press

Keywords

Chirality, Magnetic fields, Oxides, Discovery research, Atomic structure, Spintronics, Electronic devices, Electrical conductivity, Electron spin