1 INTRODUCTION Surface analysis of thin films can be achieved by different techniques where those that yield ultra-low (parts-per-million, ppm) sensitivity often have low penetration (e.g. secondary ion mass spectroscopy, SIMS) or low escape depths (e.g. Auger electron spectroscopy, AES) and so typically need to be combined with destructive depth profiling1, 2 while those with high penetration (e.g. proton-induced X-ray generation, medium energy ion scattering)3 are often hard to quantify.