Hydrogenated nonstoichiometric germanium materials have been produced by x-ray-activated chemical vapour deposition from germane, GeH4. The optical gap, Tauc slope and Urbach energy have been obtained from UV–Vis spectra and correlated with structural parameters, considered as a measure of short and intermediate order, calculated by Raman spectra.The results show that the structural disorder increases with the irradiation time. Investigation of the hydrogen local bonding configuration demonstrates a correlation between the variation of the relative abundances of GeH, GeH2 and GeH3 groups and both structural parameters and Eopt value. Moreover, evidence of the crucial role played by the increase in the GeH3 group abundance in the determination of the Eopt value was revealed.

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.

Articles you may be interested inCharacterization of hydrogenated amorphous germanium compounds obtained by x-ray chemical vapor deposition of germane: Effect of the irradiation dose on optical parameters and structural order

Amorphous germanium carbides have been prepared by X-ray activated CVD from germane/ethyne systems containing from 10 % to 80 % of ethyne. The effects of the dosage on the composition, characteristics, and properties of the solids obtained have been investigated. The composition of the material is found to change depending on both the ethyne percentage in the mixture and the irradiation time. Electron paramagnetic resonance (EPR), X-ray diffraction (XRD) analysis, and infrared spectroscopy (IRS) results indicate that the solids are formed by a randomly bound network of carbon and germanium atoms with hydrogen atoms terminating all the dangling bonds. Optical gap values higher than 3.0 eV, and increasing with the carbon molar fraction of the solid, have been found.

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