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Demystifying the Art of Novel Material Crystal Growth with Diffraction

byZEISS Microscopy 26 October 2022 2 min read

Introduction

Researchers use a non-destructive CT technique to study a flux-grown layered semiconductor crystal KBiS_2.

You may be surprised to know that the computing processors you use in a phone or computer are built on super-perfect arrangements of atoms, all lined up across a chip. Single crystals are the ticking hearts of these devices and consist of some of the most perfect arrangements of materials in the universe, and we carry them around without a second thought. Yet today, we only use very simple crystals like silicon for this purpose. For the next generation of devices, taking advantage of more complex materials for new functions and energy efficiency is exciting and inevitable.

Dr. Daniel Shoemaker, Associate Professor at the University of Illinois Urbana-Champaign, USA, directs research to create materials with new electronic and magnetic functions. In his recent publication, his lab uses diffraction contrast tomography with ZEISS Xradia Versa to understand the morphology and growth habits of a novel flux-grown layered semiconductor crystal, KBiS₂.

The 3D-rendered structure of the KBiS2 sample still intact within the reaction vessel obtained using a combination of absorption and diffraction contrast tomography.

Non-destructive CT Reveals Crystal Morphology and Growth

Dr. Shoemaker's lab grows a lot of large, single crystals in their effots to create materials with new electronic and magnetic functions. He describes it as a very mysterious process. These crystals form in an opaque liquid at high temperatures, so they are not easily observed during or after their formation. Opening the vessels they grow in would cause them to react with the oxygen in air.

In their publication, a non-destructive CT technique with ZEISS Xradia Versa is used to probe not just the shape of the crystals of a novel flux-grown layered semiconductor crystal, KBiS₂, but also to investigate how the atomic planes in the crystals are oriented in three dimensions.

K. Qu et al., Morphology and Growth Habit of the New Flux-Grown Layered Semiconductor KBiS2 Revealed by Diffraction Contrast Tomography

I was really shocked that we could look inside such a “messy” system and get such rich information. It was an unexpected bonus when we discovered a new type of crystalline material in the process.

Dr. Daniel Shoemaker University of Illinois Urbana-Champaign, USA

Diffraction Contrast Tomography Reveals Needle-Shaped Crystals

Left: 3D rendering of absorption contrast tomography data of a KBiS2 sample, with a portion cut to show the needle-shaped crystals. The central volume in color was used for a diffraction tomography study. Right: reconstructed slice view from the absorption tomography data reveals microstructural details of the rods and needle shaped crystals. Data acquired with ZEISS Xradia Versa. — Left: 3D rendering of absorption contrast tomography data of a KBiS₂ sample, with a portion cut to show the needle-shaped crystals. The central volume in color was used for a diffraction tomography study. Right: reconstructed slice view from the absorption tomography data reveals microstructural details of the rods and needle shaped crystals. Data acquired with ZEISS Xradia Versa.

The Benefits of Diffraction Contrast Tomography

Dr. Shoemaker explains that many might be more familiar with traditional computed tomography (CT) methods, which basically record a series of projections and reproduce the 3D shapes of things. Here they did a diffraction CT measurement, which also analyzes the orderly rays of X-rays that arise from specific atomic arrangements in crystals. Merging the diffraction data and CT data tells them the full information about not only the crystal size and shape, but also the atomic arrangements inside them.

Laue Diffraction Patterns Collected Using Lab-based Diffraction Contrast Tomography (LabDCT)

Laue diffraction patterns collected from a selected region of interest within the KBiS2 sample using Lab-based Diffraction Contrast Tomography (LabDCT) with ZEISS Xradia Versa. For the sake of clarity, only three prominent grains and their corresponding Laue reflections are highlighted. The outlined reflections within selected Laue diffraction patterns correspond to the three grains with the colors assigned as unique identifiers. — Laue diffraction patterns collected from a selected region of interest within the KBiS₂ sample using Lab-based Diffraction Contrast Tomography (LabDCT) with ZEISS Xradia Versa. For the sake of clarity, only three prominent grains and their corresponding Laue reflections are highlighted. The outlined reflections within selected Laue diffraction patterns correspond to the three grains with the colors assigned as unique identifiers.

Dr. Daniel Shoemaker (left) with lab members: Kejian Qu, Juneau Park, Zachary Riedel, and André Schleife — Dr. Daniel Shoemaker (left) with coauthors: Kejian Qu, Juneau Park, Zachary Riedel, and André Schleife

Using Diffraction for Future Studies

These experiments were conducted as a challenge to discover if a non-destructive CT technique with ZEISS Xradia Versa could reveal more information about crystal morphology and growth patterns.

Now that they have discovered it is possible, Dr. Shoemaker and his team are exploring how this technique can grow improved materials with novel functions. Topological materials and spintronic compounds are often grown from melts, but their crystallization behavior has not been imaged directly. By watching these processes unfold, they hope to identify new materials, as was accomplished for KBiS₂.