Argon atoms insertion in diamond: New insights in the identification of carbon C 1s peak in X-ray photoelectron spectroscopy analysis

Abstract

The C 1s peak's electron binding energy position in X-ray photoelectron spectroscopy (XPS) analysis of single crystal diamond (SCD) and crystalline and polycrystalline diamond and graphite films has been extensively investigated. A key issue is the experimental identification of C 1s peaks position from graphite sp2 and diamond sp3 C-atoms bonding in the diamond lattice, based on expected energy shifts of C 1s peaks from theory. Because of material charging upon electron photoemission, the absolute binding energy of the C 1s/sp3 related peak cannot be determined. The systematic study of C 1s peaks from XPS analysis of crystalline diamond, polycrystalline diamond films and graphite show key findings: 1) Ar+ ion bombardment is a reliable technique to characterize Diamond vs graphite materials during XPS analysis; 2) A low energy peak reported as C 1s/sp2 bonding, is attributed to the C 1s/sp3 in the presence of Ar atoms inserted in the lattice. 3) The data show direct correlation between the energy of the Ar+ ion beam used for surface sputter-cleaning and binding energy shifts of XPS C 1s peaks.