Deposition and properties of germanium/carbon films deposited from tetramethylgermanium in a parallel plate RF discharge

Abstract

Thin germanium/carbon films were prepared by an RF glow discharge decomposition of tetramethylgermanium in a stream of argon using typical parallel plate reactor. Both the deposition yield and the physical properties of the films strongly depended on the power input used. Soft and semitransparent polymer-like materials, characterized by a strong dependence of their physical properties on the energetic conditions of deposition, were obtained at low power magnitudes. High power loads yielded hard, glassy, dark brown to black films of relatively high electrical conductivity (up to 4×10 −3 S/m) and refractive index (approximately 3.0), low value of optical gap (1.3 eV) and density amounting to about 2600 kg/m 3 with the above values for a relatively large range remaining independent of deposition conditions. Hard films exhibited extremely homogeneous surface (down to several nm) while that of soft films was characterized by circular inhomogeneities at the level of several dozen nanometres. FTIR spectroscopy revealed an incorporation of certain amount of oxygen, particularly in the case of the latter materials. Although there are differences in physical properties such as density or optical gap, as well as several structural differences between the resulting materials, the process to a large extent reminisces that of the deposition of Ge/C films from tetraethylgermanium in the same equipment.