Sputtered SnTe Thin Films on Si and Ge as a Plasmonic Material

We demonstrate the potential of SnTe films as a mid-infrared plasmonic material, harnessing its innate ability to be degenerately p-type doped above 10(20)/cm(3). SnTe, a narrow bandgap rocksalt semiconductor, is deposited on CMOS-compatible substrates of Si(001) and Ge(001) using sputtering as a scalable deposition method. We identify a growth window for sputtering SnTe films and find that films on Ge substrates have grains with defined epitaxial relationships to the substrate and lower surface roughness compared to largely polycrystalline grains on Si. Despite differences in crystallinity in SnTe across these two substrates, we find similar scattering losses at optical wavelengths that are comparable to other high-quality semiconductors, and this is mirrored in our finding that electrical transport in our polycrystalline films is as much as half that of high-quality bulk crystals. Finally, we show that changing the growth temperature tunes the plasma wavelength of our material across 3.9-5.3 mu m, likely by altering the Sn/Te stoichiometry, and provides supplementary methods to extrinsic dopants.