Effects of hydrogen incorporation on structural, optical and electrical properties of germanium carbon films prepared with RF magnetron co-sputtering

Hydrogenated amorphous germanium carbon (a-Ge1-xCx:H) films were deposited by using magnetron co-sputtering starting from a mixed target of germanium and graphite in Ar and H2 mixture atmosphere. The structural, bonding, optical and electrical properties of the films were investigated as functions of H2 flow rate with the C and Ge contents in the films respectively kept constant. Both electrical resistivity and optical band gap of the a-Ge1-xCx:H films increased with increasing H2 flow rate from 0 to 15 sccm, while the refractive index stayed around 3.6. X-ray diffraction patterns and Raman spectra confirmed that the structural disorder degree of the a-Ge1-xCx:H films had declined with the rise in H2 flow rate. The results of X-ray photoelectron spectroscopy showed that the formation of sp3 hybridized C and CGe bonds in the films had been promoted by incorporation of hydrogen into the films. The relations between the chemical bonding and the structural, optical and electrical properties of the films were discussed.