Cleaning of carbon layer from the gold films using a pulsed Nd:YAG laser

Abstract

Hydrocarbon cracking and carbon contamination of optical elements in soft X-ray spectrometers and synchrotron radiation beamlines is a severe problem. Carbon contamination seriously affects the optics performance. In the present work, an Nd:YAG laser providing 2mJ of pulse energy and 100ns of pulse duration has been used for carbon cleaning experiments. The laser cleaning is a non-contact, accurate, efficient and safe process. A surface area of 48cm2 having ∼20nm thick carbon layer on gold surface has been removed with six number of laser passes and with 80% laser spot overlapping without any change in surface roughness of the underneath gold film. Effect of laser beam on gold film after carbon removal has been analyzed using X-ray photoelectron spectroscopy, soft X-ray reflectivity techniques. Atomic force microscopy was used to analyze surface morphology before and after laser cleaning process. Power spectral density function was calculated over large frequency range of 10−1 to 10−4nm−1 to understand topographic data.