Quantifying the flux and spatial distribution of atomic hydrogen generated by a thermal source using atomic force microscopy to measure the chemical erosion of highly ordered pyrolytic graphite

A new method has been developed to quantify the flux and spatial distribution of atomic hydrogen (AH) produced from a thermal source. Experimentally, a partially masked highly ordered pyrolytic graphite (HOPG) substrate was chemically etched by AH under vacuum conditions. The resultant erosion profile (step edge) created on the HOPG substrate was analyzed ex situ with atomic force microscopy. By measuring the variation in the average step height as a function of exposure time, the AH source was shown to produce an average flux of 1.3×1017Hatoms∕scm2 at a source-sample distance of 3.5cm and a hydrogen pressure PH2 of 1.0×10−4Torr. Results demonstrating the ability of this method to measure the spatial distribution of AH flux on a solid substrate as well as the influence of different operating conditions on the average AH flux are also presented.