The first aim of this project was the characterisation of the VG Scientific Clam 100 based, XPS (X-ray Photoelectron Spectroscopy). Spectrometer in the Physics department at Dublin City University Detailed energy scale and intensity scale calibrations were carried out using sputter-cleaned Au (Gold), Ag (Silver), Cu (Copper) and Pd (Palladium) foil samples. Analysis of these calibration spectra against standard reference spectra led to an accurate energy calibration and the production of individual transmission functions for the A1 Ka and Mg Ka x-ray radiation sources Reference spectra for both energy and intensity calibration were taken from the VAMAS, Versailles project on Advanced Materials and Standards, spectra library. The second part of the project was earned out in the area of thin film thickness determination, namely native oxide on germanium(lOO) and G e (lll) surfaces. An XPS study of the removal of the native oxides from these surfaces by a hydrofluoric (HF) acid based etch treatment was also completed. By consistently curvefitting the chemically shifted oxide peaks for the Ge 3d and Ge 2p3/2 core levels it was possible to accurately determine the thickness of the residual oxide coverage on the chemically etched surfaces Comparison of oxide re-growth rates with previously reported work for hydrogen passivated silicon surfaces suggests that the chemical etch used on germanium resulted in the formation of hydrogen terminated surfaces.