Cross-contamination is observed on sample surfaces by Auger electron spectroscopy and X-ray photoelectron spectroscopy if multiple samples are mounted on one sample holder and a neighbouring sample was sputter depth profiling. During sputter depth profiling, sputtered material is deposited on inner surfaces of the instrument. In a secondary sputter process, which is due to species leaving the primary sputter target with higher kinetic energy, the previously deposited material is transported from the inner surfaces to the other samples mounted on the sample holder. This reflective sputtering is utilized to deposit ultrathin layers on sample surfaces for X-ray photoelectron spectroscopy binding energy referencing purposes and to build up ultrathin conductive layers to make possible Auger electron spectroscopy measurements on insulating samples.