Ge:Si:O evaporated alloys as a thermosensitive layer for large area bolometers

摘要

A study of the composition and properties of amorphous Ge:Si:O thin films deposited at low temperature by reactive coevaporation is presented. Films with various compositions are obtained by separately controlling the evaporation rates of germanium and silicon. The composition of films is measured by combining Rutherford backscattering spectrometry (RBS), nuclear reaction analysis (NRA) and energy dispersive X-ray analysis (EDX) techniques. Films are characterized by FTIR absorption spectroscopy, VIS-NIR transmittance and temperature behaviour of the electrical resistivity. The analysis of all experimental data shows that oxygen incorporation depends on the silicon content in the films. Oxygen atoms appear mainly bonded to silicon and not to germanium. An uniformed distribution rather than a cluster structure of silicon oxide into a germanium matrix is suggested. Both optical band gap energy and thermal coefficient of the resistivity vary with composition of films. Preliminary studies of thin films with similar composition obtained using reactive sputtering from a composite target evince the coexistence of Si-O and Ge-O bonds.