Boron carbide thin film surface characterization after graphitic carbon removal using low-pressure oxygen gas RF plasma

Abstract

B 4 C -coated thin film mirrors are used in high brilliance synchrotron and x-ray free electron laser beamlines due to their low absorption coefficient and high thermal stability. As in the case of gold, platinum, and other thin film mirrors, B 4 C -coated mirrors also are affected due to synchrotron radiation-induced carbon contaminations in beamlines. In the present study, a graphitic carbon ( C ) layer deposited on top of boron carbide ( B x C ) thin film surface is removed by five successive oxygen radio frequency (RF) plasma exposures (RF power, 10 W; O 2 flow, 30 sccm; exposure time, 10 min each). Before and after the carbon layer removal, structural and compositional properties of the B x C / C bilayer are characterized by soft x-ray reflectivity, x-ray photoelectron spectroscopy, grazing angle x-ray diffraction, and Raman spectroscopy techniques. Characterization results reveal that in the first four exposures the carbon layer thickness decreases continuously without affecting the B x C layer properties; however, in the fifth exposure, the carbon layer is completely removed along with a partial etching of the B x C layer too.