Infrared and microwave absorption in amorphous Ge

The magnitude of the far-infrared ({} 150 cm^-1) and microwave absorption in evaporated films of amorphous Ge depends on the deposition rate. The intrinsic absorption not attributable to voids or dangling bonds indicates a large decrease at the lowest frequency in the matrix elements which couple the radiation to the phonons. A low-frequency absorption tail, similar to that observed in other amorphous materials, is observed in amorphous Ge. This absorption is temperature independent and proportional to the square of the frequency. A thermally activated conductivity is observed at the higher temperatures in the microwave region. This conductivity has the same activation energy as the dc conductivity but is of greater magnitude.