Composite germanium/C:H films prepared by DC unbalanced magnetron sputtering

Composite Ge/C:H films (germanium doped hard plasma polymer (C:H)) have been deposited using unbalanced planar magnetron equipped with germanium/graphite target and operated in argon/n-hexane gas mixture. The composition of the deposited films was determined by Rutherford back scattering (RBS), elastic recoil detection (ERD) and X-ray photoelectron spectroscopy (XPS) analytical methods. Contents of germanium from 0 up to 30 at,% was confirmed with rather homogenous distribution of germanium through the cross-section of the composite films. Transmission electron microscopy (TEM) investigation of the samples revealed that germanium forms clusters with a maximum diameter of 2 nm embedded in C:H and GeC alloy matrix. An optical gap ranging from 1.9 to 1.0 eV with corresponding refractive index ranging from 2 to 3 were determined. DC electrical properties were measured in the planar electrodes -composite film-configuration. The electrical conduction is strongly dependent on the germanium content and on the substrate temperature. Current-voltage characteristics are linear at low electrical field and become superlinear at higher field. (C) 1999 Elsevier Science S.A, All rights reserved.