Stress and thermomechanical properties of amorphous hydrogenated germanium thin films deposited by glow discharge

Stress measurements of a-Ge:H thin films deposited by rf glow discharge using a large variety of deposition conditions are reported. It was observed that the stress of the films is strongly related to their structure. Tensile films are usually porous or have many defects, while compressive films are usually homogeneous. High quality films are always compressive. A strong correlation of the stress in the films with the unbonded hydrogen concentration was observed, which may explain the origin of the compressive stress. There was no systematic or consistent link between the stress and the bonded hydrogen content or the deposition rate. The thermal expansion coefficient and the elastic constant were determined for high quality films.