Abstract Amorphous germanium carbide (a-Ge 1− x C x ) thin films were prepared by reactive pulsed laser deposition technique using several methane pressures. Surface analysis was performed by X-ray photoelectron spectroscopy (XPS) to examine the composition and elemental bonding at the surface of the material. Optical analysis was carried out by spectroscopic ellipsometry to study the optical constants (n and k) and other parameters of the film. Results indicate that the carbon atoms to be incorporated in the germanium lattice, forming a-Ge 1− x C x alloy, for concentrations below about 10 atomic % where the Ge atoms are uniformly distributed. There is formation of graphitic agglomerates for higher carbon concentrations.