Fig. 7: Optical absorptance spectra of as-deposited and annealed SnGe samples.

The as-deposited sample and the samples annealed at 300 and 500 °C have no or little α-Sn, while those annealed at 350 and 375 °C have substantial amount of α-Sn, leading to characteristic optical absorption at 1250–1750 nm wavelength range.