Novel method for absolute quantification of the flux and angular distribution of a radical source for atomic hydrogen

In this article we present a novel method for absolute quantification of th e flux and angular distribution of a beam source for atomic hydrogen or ato mic deuterium. It is based on quantitative determination of the erosion of an amorphous, hydrogenated carbon (a-C:H) film. A heated tungsten capillary serves as the radical source. Atomic hydrogen is produced in this capillar y by thermal dissociation of hydrogen molecules. A large-area a-C:H film is exposed to the source at a substrate temperature of 650 K. Interaction of atomic hydrogen with the a-C:H film causes erosion. From the spatial variat ion of the erosion rate one can deduce the angular distribution of the impi nging hydrogen atoms. This angular distribution was also measured by mass s pectrometry and showed excellent agreement with the erosion profile. The ab solute flux of atomic hydrogen was also determined by mass spectrometry. Wi th the absolute flux of atomic hydrogen known from mass spectrometry, measu rement of the lateral variation of the erosion rate can be directly used as a probe for absolute quantification of the angular distribution of the imp inging H (D) flux. The erosion yield is (2+/-0.7)X10(-2), which is consiste nt with the microscopic erosion mechanisms of a-C:H by atomic hydrogen know n from the literature. (C) 2000 American Vacuum Society. [S0734-2101(00)010 03-4].