Abstract
The technique of helium atom scattering is intrinsically very sensitive to all types of surface defects. With dynamic sensitivites of order 105, or more, one is able to observe and characterise very low densities of either point[1] or linear type defects[2]. The diffuse elastic scattering from isolated step edge defects, for example, is able to give detailed information about the characteristic shape of a step edge, as observed by the thermal energy He probe[3]. The linear nature of a step edge ensures that the intensity is scattered predominately along certain crystallographic azimuths. The large angle diffraction, from the non-periodic defect, is dominated by the strongly repulsive part of the interaction potential. Hard wall calculations may be used to deduce the shape of single step edges. Experimentally, only a very small incident-energy dependence is found. However, it has been shown that a soft potential calculation may improve the optimum fits, or comparison between calculation and experiment[4]
© 1989 Optical Society of America
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