Imaging of Coupled Film-Substrate Elastodynamics During an Insulator-to-Metal Transition (Penn State, et al.)

A new technical paper titled “In-Operando Spatiotemporal Imaging of Coupled Film-Substrate Elastodynamics During an Insulator-to-Metal Transition” was published by researchers at Pennsylvania State University, Cornell University, Argonne National Lab, Georgia Tech and Forschungsverbund Berlin.

Abstract
“The drive toward non-von Neumann device architectures has led to an intense focus on insulator-to-metal (IMT) and the converse metal-to-insulator (MIT) transitions. Studies of electric field-driven IMT in the prototypical TiO₂  thin-film channel devices are largely focused on the electrical and elastic responses of the films, but the response of the corresponding TiO2 substrate is often overlooked, since it is nominally expected to be electrically passive and elastically rigid. Here, in-operando spatiotemporal imaging of the coupled elastodynamics using X-ray diffraction microscopy of a TiO₂  film channel device on TiO₂  substrate reveals two new surprises. First, the film channel bulges during the IMT, the opposite of the expected shrinking in the film undergoing IMT. Second, a microns thick proximal layer in the substrate also coherently bulges accompanying the IMT in the film, which is completely unexpected. Phase-field simulations of coupled IMT, oxygen vacancy electronic dynamics, and electronic carrier diffusion incorporating thermal and strain effects suggest that the observed elastodynamics can be explained by the known naturally occurring oxygen vacancies that rapidly ionize (and deionize) in concert with the IMT (MIT). Fast electrical-triggering of the IMT via ionizing defects and an active “IMT-like” substrate layer are critical aspects to consider in device applications.”

Find the technical paper here. Published March 2024. Find the university’s news release here.

G. Stone, Y. Shi, M. Jerry, V. Stoica, H. Paik, Z. Cai, D. G. Schlom, R. Engel-Herbert, S. Datta, H. Wen, L.-Q. Chen, V. Gopalan, In-Operando Spatiotemporal Imaging of Coupled Film-Substrate Elastodynamics During an Insulator-to-Metal Transition. Adv. Mater. 2024, 2312673. https://doi.org/10.1002/adma.202312673.