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

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.