Local order in hydrogenated amorphous germanium thin films

The effect of the hydrogenation process on the local order in amorphous germanium has been studied by EXAFS spectroscopy. Measurements have been carried out on amorphous sputtered Ge:H films with 7, 10 and 15 at. % hydrogen concentration, as function of temperature from 11 to 300 K. The EXAFS data analysis has been carried out by the cumulant method and the first four cumulants of the first shell distance distributions have been extracted. The temperature dependence of cumulants gives information on dynamic local disorder and allows the quantitative determination of the influence of hydrogenation on static disorder. It is confirmed that the amorphous non-hydrogenated films are more disordered than the hydrogenated ones. Small but significant differences in the cumulants have been observed as function of the hydrogen content; they show that the larger the concentration the more ordered the germanium network. The first shell distribution functions have been reconstructed for the hydrogenated samples and compared with that of the non hydrogenated compound.