Auger-electron-spectroscopy analysis of chemical states in ion-beam-deposited carbon layers on graphite

Abstract

The mechanism of formation of diamondlike carbon layers at room temperature by ion-beam deposition has been investigated. Mass-selected ${\mathrm{C}}^{+}$ ions with kinetic energy between 50 and 150 eV were deposited on cleaved graphite under UHV conditions with a maximum dose of ∼3×${10}^{17}$ ${\mathrm{C}}^{+}$/${\mathrm{cm}}^2$. Auger-electron spectroscopy (AES) was used to delineate the carbon chemical states that were formed. Similar experiments with a ${\mathrm{Ne}}^{+}$ ion beam revealed the extent of ion-induced defect formation. Factor analysis and least-squares fitting were applied for quantitative evaluation of the different carbon bonding states during film growth. A peak in the high-energy region of the KVV AES spectrum at 3.8±1 eV below the Auger line threshold is related to the degree of disorder in the different carbon phases. The carbon-layer growth can be described as a two-stage process: First, the graphite lattice is being damaged; then an amorphous network of tetrahedrally (${\mathit{sp}}^3$) and trigonally (${\mathit{sp}}^2$) coordinated carbon atoms forms.