Characterization 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

Abstract

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.

Investigation of stress and structural damage in H and He implanted Ge using micro‐Raman mapping technique on bevelled samples

“…the band around ~2050 cm −1 is observed for the unannealed Ge samples implanted with H. As is shown in the insert in Fig. , this band can be fitted with four peaks at around 1980, 2010, 2050 and 2080 cm −1 . These features correspond to the stretching modes of Ge–H bonds in GeH n ( n = 1–3) and vacancy‐hydrogen defects.…”

Relationship between structural changes, hydrogen content and annealing in stacks of ultrathin Si/Ge amorphous layers

“…Hydrogenated a-Si and a-Ge layers are key materials for employment in (nano) structures used, e.g., in the technology of multi-junction solar cells as a-Ge acts as the low-band gap absorber while a-Si acts as the high-band gap one, thus allowing a better exploitation of the solar spectrum and the achievement of higher efficiencies [1]. However, the a-SiGe alloy is now the material of choice as the low-band gap absorber [2-4].…”

“…It allows a higher degree of freedom as regards the choice of the band gap, as the latter one can be tailored over some range by changing the Si/Ge ratio [2,4]. The a-SiGe alloy can be realized from a sequence of thin a-Si and a-Ge layers by intermixing them [1,5,6], which is obtained by heat treatments. The latter treatments are often also used for activating dopants.…”

A catalyst-free synthesis of germanium nanowires obtained by combined X-ray chemical vapour deposition of GeH4 and low-temperature thermal treatment techniques

“…Lengths of NWs up to 20 μm and over were screened (with an aspect ratio of about 100 : 1, figure 1a-d). Among these NWs, there is a substantial lack of different by-product morphologies, like aggregated spheroids of amorphous hydrogenated germanium which can be obtained with X-ray CVD activation of Ge gaseous reactants [32,33]. Herein, the presented high aspect ratio morphologies resulting from the reported synthetic experimental set-up, although featured with large NW diameters, are appropriate standard results in the germanium NW scenario [6,10,11,[13][14][15]36].…”

“…In this study, an innovative catalyst-free synthesis in quantitative extents of Ge-NWs featured with high purity and quality, obtained by a combined application of CVD activated by X-ray irradiation (X-ray CVD) [32,33] and of thermal treatment technique of the deposition substrate, is reported. The X-ray radiolytic CVD technique, which has never been applied since so far to Ge-NW synthesis, provides an high amount of energy, to promote the chemical dissociation of gaseous precursors and the formation of highly reactive species (i.e., ions and radicals) [34] that enhance the deposition process on thermal-activated surfaces [35].…”