Vacuum Ultraviolet and Visible Optical Emission Spectra from Laser Ablation of Graphite at 193 NM: Application to Carbon Nitride Thin Films Deposition

Abstract

AbstractOptical emission spectra in the ultraviolet and visible range (110-600 nm) were recorded during pulsed ArF laser ablation of graphite targets in vacuum and in low pressure N2 atmospheres. During graphite ablation in vacuo, the recorded spectrum consists only of several atomic lines lying below 300 nm. They are due to radiative transitions from upper carbon excited states down to the fundamental one. The most intense atomic lines are observed at 247.85 nm and near 165.5 and 156 nm. During ablation in increasing nitrogen pressure, the spectra are quickly dominated by the bands of the CN violet system whereas the intensity of the atomic lines only slightly increases. We have observed the bands corresponding to the vibrational sequences Δv = +1 (358.4-369.7 nm), Δv = 0 (384.7-394.4 nm) and Δv = -1 (414.3-421.6 nm). They already appear at nitrogen pressure as low as 0.05 mbar. Their intensity reaches a broad maximum between 0.5 and 0.8 mbar and slowly decreases.Taking into account the results of this optical study, the deposition of carbon nitride thin films has been undertaken. The surface analysis by X-ray photoelectron spectroscopy (XPS) of the obtained C1-xNx deposits shows a correlation law between the nitrogen incorporation (x) and the pressure of nitrogen.