ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Thin films of hydrogenated amorphous silicon-germanium (a-Si1−xGex@B:H) alloys have been prepared by reactive ion beam sputtering of a composite target of silicon and germanium. The dependence of the deposition rate, conductivity-temperature variation, optical absorption coefficient, refractive index, imaginary part of the dielectric constant, hydrogen content, and infrared (IR) absorption spectra on germanium content (x) are reported and analyzed. For a typical composition—a-Si28Ge72:H (x=0.72), the effect of beam voltage, H2:Ar flow ratio, and substrate temperature on the material properties have also been investigated. For the films prepared with increasing x, the expected behavior of a decrease in both hydrogen content and band gap and an increase in the electrical conductivity have been observed. The films prepared at x〉0.80 are found to be more homogeneous than the films deposited at 0.0〈x〈0.80, due to the compositional disorder introduced by the random mixing of Si and Ge atoms in the a-Si1−xGex@B:H network in the latter case. The a-Si28Ge72:H films exhibiting minimum conductivity (1.7×10−7 Ω−1 cm−1) have been obtained for an H2:Ar flow ratio of 10:1 and a beam voltage and substrate temperature of 1500 V and 300 °C, respectively. These films contain a hydrogen concentration of 10.2 at. % and show an optical band gap of 1.25 eV. The IR studies have shown that a-Si28Ge72:H films prepared both at low beam voltages and at low substrate temperatures show the unusual preferential attachment of hydrogen to Ge rather than to Si.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.344243
