Surface and interface microchemistry of archaeological objects studied with x ray photoemission spectroscopy and scanning Auger microscopy

Corrosion investigation of fire-gilded bronze involving high surface resolution spectroscopic imaging

“…As also metallic Sn(0) was identified inside the corrosion crater, this chemical state should be considered as an artefact due to a partial reduction of oxidised Sn, linked to the Ar + cleaning step. This kind of artefact was already observed by other authors: the reduction phenomenon was also observed for Pb [21,40,42,60], but possibly also for Cu (3p) [22,26].…”

“…X-ray photoelectron spectroscopy (XPS) has been applied since more than thirty years to ancient bronzes and patinas, in order to analyse the chemical state of elements on the outermost surfaces and (by Ar + sputtering) to explore depth profile [20][21][22]. However, its use in cultural heritage materials science has been initially restricted, due to experimental constraints linked to sample size, analysed area (typically larger than 300 m in diameter) but also to charge effects linked to weakly conducting surfaces [21,22].…”

“…X-ray photoelectron spectroscopy (XPS) has been applied since more than thirty years to ancient bronzes and patinas, in order to analyse the chemical state of elements on the outermost surfaces and (by Ar + sputtering) to explore depth profile [20][21][22]. However, its use in cultural heritage materials science has been initially restricted, due to experimental constraints linked to sample size, analysed area (typically larger than 300 m in diameter) but also to charge effects linked to weakly conducting surfaces [21,22]. This technique was often coupled to scanning Auger microscopy (Auger electron spectroscopy-AES) as an associate method highlighting the differences in the microchemical composition thanks to a smaller spatial resolution compared to XPS techniques [20][21][22][23][24].…”

“…On ancient artefacts, XPS investigation was often associated to other analytical techniques (EDS-SEM, XRD, PIXE, SIMS, LA-MS) [31,[39][40][41][42][43][44]. XPS analysis usually were performed on surface fragments, sometimes coupled to depth profile measurement from Ar + sputtering [21,22,39,40] or laser ablation [44]. It should be noticed that several studies investigated the effect of X-ray beam or (Ar + ) ion sputtering on the surface evolution [21,24,26,28,39,41].…”

“…XPS analysis usually were performed on surface fragments, sometimes coupled to depth profile measurement from Ar + sputtering [21,22,39,40] or laser ablation [44]. It should be noticed that several studies investigated the effect of X-ray beam or (Ar + ) ion sputtering on the surface evolution [21,24,26,28,39,41]. They revealed that lead carbonate species as well as copper sulphate or copper oxide can be reduced, which can cause the interpretation of XPS and AES to be problematic for copper species.…”