Today, Peter gave a great defense of his PhD dissertation, titled “Disorder-Engineering of Ferroic Properties“. Congratulations Peter! The Ferroelectronics Lab wishes you the very best luck in your future work!
Sieun gave a virtual talk at the American Physical Society (APS) March Meeting last week. Congratulations! Her abstract is included below.
Epitaxial stabilization of rutile germanium oxide thin film by molecular beam epitaxy
Ultrawide-band-gap (UWBG) semiconductors have tantalizing advantages for power electronics. Materials such as AlN/AlGaN, β-Ga2O3, and diamond have been developed for UWBG semiconducting devices, however, they are still facing challenges, such as doping asymmetry and/or inefficient thermal conduction. Rutile GeO2 (r-GeO2) has been theoretically established to have an UWBG (4.68 eV), high electron and hole mobility (289 cm2 V-1s-1 and 28 cm2 V-1s-1), high thermal conductivity (51 W m–1 K–1) and ambipolar dopability. The synthesis of r-GeO2 thin films has not been reported but is critical to enable microelectronics applications. Here, we report the growth of single-crystalline r-GeO2 thin films on R-plane sapphire substrates using molecular beam epitaxy. We control the competing reactions between the deeply metastable glass phase formation and rutile phase formation as well as absorption and desorption by utilizing (1) a buffer layer with reduced lattice misfit, and (2) the growth condition that allows the condensation of the preoxidized molecular precursor yet provides sufficient adatom mobility. The findings advance the synthesis of single-crystalline films of materials prone to glass formation and provide opportunities to realize promising UWBG semiconductors.
The award recognizes the outstanding graduate student in each degree program. Prize criteria include a student’s active participation in research, leadership and academic performance (GPA).
The Rackham Predoctoral Fellowship supports outstanding doctoral students who are actively working on dissertation research and writing. It seeks to support students working on dissertations that are unusually creative, ambitious and impactful.
Abstract: Rashba spin current generation emerges in heterostructures of ferromagnets and transition metal dichalcogenides (TMDs) due to an interface polarization and associated inversion symmetry breaking. Recent work exploring the synthesis and transfer of epitaxial films on the top of low layer count 2D materials reveals that atomic potentials from the underlying substrate interface are not completely screened. The extension of this transparency effect to other interfacial phenomena, such as the Rashba effect and associated spin torques, has not yet been demonstrated. Here, we report enhanced spin transfer torques from the Rashba spin current in heterostructures of permalloy (Py) and WSe2. We show that insertion of up to two monolayers of WSe2 enhances the spin transfer torques in a Rashba system by up to 3×, without changing the fieldlike Rashba spin−orbit torque (SOT), a measure of interface polarization. Our results indicate that low layer count TMD films can be used as an interfacial “scattering promoter” in heterostructure interfaces without quenching the original polarization.
Full text available from ACS Publications