Characterization of a-Ge:H compounds obtained by X-Ray Chemical Vapor Deposition of Germane: effect of the irradiation dose on optical parameters and structural order

Hydrogenated nonstoichiometric germanium materials have been produced by x-ray activated-chemical vapor deposition from germane. The reactions pattern leading to the solid products has been investigated. The dose effect on the composition, the local bonding configuration, and structural characteristics of the deposited solids has been studied using infrared absorption and Raman spectroscopy and has been discussed. Optical parameters have been also determined from ultraviolet-visible spectrophotometry data. The results show that the solids are formed by a random bound network of germanium and hydrogen atoms with a-Ge zones dispersed in the matrix. The Raman results and optical parameters indicate that the structural order, both short-range and intermediate-range, decreases with increasing irradiation time. This behavior suggests that the solid is involved in the reactions leading to the final product and indicates that the formation of amorphous germanium zones is stimulated by postdeposition irradiation, which induces compositional and structural modifications.