Epitaxial growth of (100)-oriented SmN directly on (100)Si substrates

Abstract

We demonstrate growth of epitaxial (100)SmN thin films directly on (100)Si surfaces. By using physical vapor deposition of Sm metal in an ${\mathrm{N}}_{2}$ atmosphere we show that careful control of substrate temperature, ${\mathrm{N}}_{2}$ pressure, and postannealing steps leads to epitaxial SmN without the formation of samarium silicide impurity phases. While rare-earth silicide formation competes with and is favored over nitride formation at high growth temperatures, we find that low-temperature grown SmN seed layers are stable against high-temperature annealing, and thus allow for subsequent high-temperature growth of SmN with a clear epitaxial relationship to the Si substrate. The relatively low lattice mismatch of SmN with (100)Si, compared to other commonly available substrates, coupled with the low cost and maturity of Si processing technology provide a promising route for further studies of the fundamental properties of SmN and other isostructural members of the rare-earth nitride series. Because SmN is a ferromagnetic semiconductor, which also becomes superconducting close to 4 K under sufficient doping, integration with Si technology presents new opportunities for spin-transport devices.