New method to calibrate binding energy using Au nanocolloids in X-ray photoelectron analysis of diamondlike carbon films with different electrical resistivities

A new method to calibrate the binding energy (EB) using Au nanocolloids as a calibrant in XPS analysis of diamondlike carbon (DLC) is proposed by considering the DLC films with different electrical resistivities. A few microliters of a dilute aqueous solution containing Au nanocolloids were dropped onto a small local surface area of the DLC film, which became a stain before XPS measurements by gradually drying in vacuo. The observed peak EB of the C 1s spectrum at another native surface (an area without Au nanocolloids) of the DLC film was calibrated by setting that of the Au 4f7/2 spectrum of the Au nanocolloids to 84.0 (83.98 ± 0.02) eV. The adequacy of this method was investigated by considering the correlation among the full width at half maximums (FWHMs) of the Au 4f7/2 spectra of the Au nanocolloids on the DLC surfaces and that of a Au plate as a reference. Consequently, the FWHM of the Au 4f7/2 spectrum of the Au nanocolloids on the DLC surface is a candidate to investigate the differential charging effect of the DLC surface, and the calibration method is reliable if the FWHM agrees with that of the Au plate.