Composition-dependent structural transition in epitaxial Bi_{1−x}Sb_{x} thin films on Si(111)

dc.creatorWalker, Emily S.
dc.creatorMuschinske, Sarah
dc.creatorBrennan, Christopher J.
dc.creatorNa, Seung Ryul
dc.creatorTrivedi, Tanuj
dc.creatorMarch, Stephen D.
dc.creatorSun, Yukun
dc.creatorYang, Tianhao
dc.creatorYau, Alice
dc.creatorJung, Daehwan
dc.creatorBriggs, Andrew F.
dc.creatorKrivoy, Erica M.
dc.creatorLee, Minjoo L.
dc.creatorLiechti, Kenneth M.
dc.creatorYu, Edward T.
dc.creatorAkinwande, Deji
dc.creatorBank, Seth R.
dc.description.abstractBismuth-Antimony alloys (Bi1-xSbx) are topological insulators between 7-22% Sb in bulk crystals, with an unusually high conductivity suitable for spin-orbit torque applications. Reducing the thickness of epitaxial Bi1-xSbx films is expected to increase the maximum bandgap through quantum confinement, which may improve isolation of topological surface state transport. Like Bi(001) on Si(111), Bi1-xSbx has been predicted to form a black phosphorus-like allotrope with unique electronic properties in nanoscale films; however, the impact of Sb alloying on both the bulk-like and nanoscale crystal structures on Si(111) is currently unknown. Here we demonstrate that the allotropic transition in ultrathin epitaxial Bi1-xSbx films on Si(111) is suppressed above 8-9% Sb, resulting in an unexpected (012) orientation within the topologically insulating regime. The metallic temperature-dependent conductivity associated with surface states in Bi(001) was not observed in the Bi1-xSbx(012) films, suggesting that the (012) orientation may significantly reduce surface state transport. Growth on a Bi(001) buffer layer may prevent this orientation transition. Finally, we demonstrate that Sb alloying improves the continuity and quality of nanoscale Bi1-xSbx(012) films in the thickness regime expected for the black phosphorus allotrope, suggesting a promising route to large-area growth of puckered-layer 2-D Bi1-xSbx, which will be necessary to harness its unique electronic properties in practical applications.
dc.description.departmentCenter for Dynamics and Control of Materials
dc.description.sponsorshipThis work was primarily supported by both the Texas Instruments Semiconductor Research Corporation Graduate Fellowship Program and the National Science Foundation through the Center for Dynamics and Control of Materials; an NSF MRSEC under Cooperative Agreement No. DMR-1720595.
dc.relation.ispartofCenter for Dynamics and Control of Materials Publications
dc.subjectBismuth-Antimony alloys
dc.titleComposition-dependent structural transition in epitaxial Bi_{1−x}Sb_{x} thin films on Si(111)

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