Growth and characterization of α -Sn thin films on In- and Sb-rich reconstructions of InSb(001)

\ensuremath{\alpha}-Sn, the inversion symmetric analogue of HgTe, can be tuned through various topologically non-trivial phases by a combination of strain and/or confinement effects. In addition, thin films of \ensuremath{\alpha}-Sn have demonstrated very efficient spin-charge conversion. However, \ensuremath{\alpha}-Sn thin films grown on InSb have been plagued by heavy incorporation of the p-type dopant indium. To better study and make use of the topological phases in \ensuremath{\alpha}-Sn, this indium doping must be minimized. The authors realize this reduction by tuning the surface reconstruction of InSb(001) on which molecular beam epitaxy growth of \ensuremath{\alpha}-Sn is initiated. The low indium doping is verified by both photoemission and magnetotransport measurements. The accessibility of the surface Dirac node in angle-resolved photoemission spectroscopy---made possible by the substrate preparation procedure---allows direct measurements of the effect of confinement and epitaxial strain on the topological phase in this system.