Colloquium: Dr. Baishakhi Mazumder, University of Buffalo

Atom probe tomography is an advanced characterization tool that offers three-dimensional chemical imaging of material structures at the sub-nanometer scale. This lensless point-projection microscopy technique resolves individual atoms from a nano-dimensional tip with magnifications up to 106. The continuous removal of atoms provides the ability for 3D elemental characterization of the solid along with chemical distributions, grain boundary segregation, nature of interfaces, dopant distributions, etc. It can be used to resolve particular problems in material science related to advanced alloys, radiation damage, electronic device design, and fabrication, etc. (AlxGa1-x)2O3 being a new class of ultra-wide band gap (UWBG) semiconductors is a potential candidate for high power electronics application. The performance and quality of UWBG heterojunction device structures rely on the interfacial integrity, alloy homogeneity, dopant distributions, and composition of the active layers. APT was employed to obtain the atomic scale structure-chemistry information and establish a processing-structure-chemistry relationship. Various complex and diversified physical phenomena (e.g., phase segregation varying alloy composition, dopant-defect interaction, etc.) were observed and elucidated during this study. Machine learning modeling was integrated on rich data sets from APT to extract latent features such as local phase transition, point defects, vacancies, etc. In this presentation, I will focus on the atomistic understanding of the complex structure and chemistry of (AlxGa1-x) 2O3 and the contribution of APT to its design and development for power electronics application.

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