NSF grant will help Evans study how disordered materials become crystals

Some of the most important materials in modern technology, from the memory chips in a laptop to the superconductors envisioned for future quantum computers, depend on thin layers of crystals grown with near-perfect precision. Making those layers is especially challenging when the starting point is amorphous, meaning its atoms are arranged with no repeating pattern at all.

Paul Evans, a professor in the Department of Materials Science and Engineering, has received a three-year, $540,000 grant from the Ceramics Program in the Division of Materials Research of the National Science Foundation to study this transition in metal oxides.

The process, known as solid-phase epitaxy (SPE), takes an amorphous material and turns it into an ordered crystal by using a neighboring crystal as a structural template. To do this, the amorphous material is vaporized under high heat and pressure and then deposited on the template layer, which guides the formation of its crystalline structure. For complex oxides, which are the ceramic-like compounds at the center of many advanced electronic and quantum devices, the atomic-scale mechanics can be improved by better understanding and designing this process.

Part of the problem is that the transformation is hard to see. The volume of material involved is very small, the rearrangement of atoms happens quickly and the structural signatures of the process are subtle.

 “Catching the process of crystallization is a real challenge,” says Evans.“The changes happen in the top atomic few layers of the materials we’re studying. It’s like we’re trying to tell the difference between the ordered stack of oranges you see at the supermarket and the disordered arrangement in a bag full of oranges – but with atoms. It takes great new tools and clever experiments.”

Evans and his research group will use precise, in situ growth and synchrotron X-ray techniques to watch the crystallization happen in real time, tracking how atoms rearrange at the moving boundary between the amorphous and crystalline material. 

The insights could extend well beyond the materials being studied. Improving the fundamental understanding of SPE also has direct applications in microelectronics, digital memory devices, optics and the superconducting materials used in emerging quantum technologies. The scientific concepts involved could also be generalized to other classes of materials, including biomaterials and emerging semiconductors.

Evans is excited about the potential to create new materials that are not yet available, saying “It’s exciting to think about making crystals that haven’t been possible in the past and to have our creativity in using them go in new directions.”

The grant will also support the training of early-career scientists and engineers, giving them hands-on experience with advanced X-ray characterization techniques and the chance to work directly with researchers at Argonne National Laboratory’s user facility. The project will additionally produce instructional materials and public demonstrations to share the underlying science with wider audiences.