Structural Study of Amorphous Ge Using Extended X-Ray Absorption Fine Structure

Extended X-ray absorption fine structure measurements were made on amorphous germanium, a-Ge, and hydrogenated amorphous germanium, a-Ge:H, both prepared at the substrate temperature of 50°C by sputtering. The first nearest neighbor distances of a-Ge and a-Ge:H are longer than that of crystalline germanium, c-Ge, by 0.016 Å and 0.011 Å, respectively. The Debye-Waller factor, Δ σ, and the third moment of the first nearest neighbor distribution, < Δ r 3 >, were also determined. The relationships among the first nearest neighbor distance, Δ σ and < Δ r 3 > are in agreement with theoretical results derived from thermodynamics. These results suggest the existence of states corresponding to several hundred degrees quenched in a-Ge and a-Ge:H. Furthermore, the state of a-Ge is estimated to be about one hundred degrees higher than that of a-Ge:H.