Bridging Thin Films Growth and Advanced Electron Microscopy to Uncover Structure-Property Correlations in Oxide Electronics

Reactive Molecular Beam Epitaxy (RMBE), among other Physical Vapor Deposition (PVD) techniques, can precisely fabricate high-quality semiconductor heterostructures necessary for complex oxide electronics [1]. Their composition and crystallinity can be engineered through careful selection of growth parameters [2], [3], however are subject to the underlying layer. Here, miscut, composition and lattice mismatch impact texture transfer and thus the resulting microstructure [4].<br/>Typically, RMBE is used to grow epitaxial thin films, yet textured thin films with defects might be more promising in oxide electronics applications like superconductors or emerging memories like resistive random access memory (RRAM). In our study, we investigated the texture relationship of TiN grown on c-cut sapphire by combining ion channeling contrast imaging (ICCI) with pole figure mapping. In addition, textured HfO₂ has been in situ grown on optimized TiN layers to investigate the impact of extended defects on RRAM performance by using atom probe tomography (APT) and operando electron microscopy. Our results indicate that a certain miscut of c-cut sapphire promotes distinct types of extended defects, which, as confirmed by elemental composition investigations using APT, are essential for RRAM operations.<br/>Combining synthesis, macroscopic and microscopic investigation, and device characterization can bridge the information gaps required to further oxide electronics.<br/>References:<br/>[1] <i>Beam Technologies for Integrated Processing</i>. Washington, D.C.: National Academies Press, 1992. doi: 10.17226/2006.<br/>[2] R. Winkler <i>et al.</i>, ‘Controlling the Formation of Conductive Pathways in Memristive Devices’, <i>Advanced Science</i>, vol. n/a, no. n/a, p. 2201806, doi: 10.1002/advs.202201806.<br/>[3] S. U. Sharath <i>et al.</i>, ‘Control of Switching Modes and Conductance Quantization in Oxygen Engineered HfOx based Memristive Devices’, <i>Advanced Functional Materials</i>, vol. 27, no. 32, p. 1700432, 2017, doi: 10.1002/adfm.201700432.<br/>[4] A. Zintler <i>et al.</i>, ‘Enhanced Conductivity and Microstructure in Highly Textured TiN1–x/c-Al2O3 Thin Films’, <i>ACS Omega</i>, vol. 7, no. 2, pp. 2041–2048, Jan. 2022, doi: 10.1021/acsomega.1c05505.