Figure 1: Showing various high resolution XPS sectra of the Cu 2p region for a) a sample (BS002) which has no fingerprint, and has been cleaned in micro 90 before being placed in the XPS, b) a sample (BS009) which has had an eccrine fingerprint applied, and has been left in air for ~15 hours before being placed in the XPS, c) the same sample as b) left in air for a further ~ 17 hours, (~39 hours since fingerprint application), and d) a sample (BS011) which has had an eccrine fingerprint applied at the same time as the sample in b) and c), only has been left in air for ~65 hours (nearly 3 days) before taking the spectra. (Each spectrum has been normalised via the small O KLL peak seen at ~977 eV).

One can see the absence, or reduction of the Cu 2p peaks in the samples where a fingerprint was apparent. Also, there appears to be potential for this peak to be increasing with time, although with the current data, it is a bit too hard to be sure, and more data needs to be taken.