Evidence for A Sharp Absorption Edge in Amorphous Ge

TLDR: A sharp optical absorption edge has been found at about 0.5 eV for amorphous Ge on a quartz substrate as discussed by the authors, which is comparable in sharpness with the direct edge of crystalline Ge.

Abstract: A sharp optical absorption edge has been found at about 0.5 eV for amorphous Ge on a quartz substrate. The edge is comparable in sharpness with the direct edge of crystalline Ge. No evidence for tailing of the band edges into the forbidden band or for a high density of states in the forbidden band is found by these optical measurements. A new density determination gives a value of 4.54\ifmmode\pm\else\textpm\fi{} 0.14 g/${\mathrm{cm}}^{3}$.