Scanning Microscopy


A new ion scattering technique, called scattering and recoiling imaging spectrometry (SARIS), is being developed. The SARIS technique uses a large, position sensitive microchannel plate (MCP) and time-of-flight methods to capture images of scattered and recoiled particles from a pulsed ke V ion beam. These images combine the advantage of atomic scale microscopy and spatial averaging simultaneously since they are created from a macroscopic surface area but they are directly related to the atomic arrangement of the surface. This paper de-scribes the basis of the SARIS technique, the instrument which is under development, and the scattering and recoiling imaging code (SARIC) for simulation of the classical ion trajectories. Time-of-flight scattering and recoiling spectrometry (TOF-SARS) data are used to emulate the SARIS images for the case of 4 keV Ne+ scattering from a Pt{111} surface. The observed scattering intensity patterns are characterized by their complex and rich structure. These experimental images are simulated by use of the SARIC program. The abundance of information contained in the images can be used to identify the type of surface being studied and its structure. The extraction of numerical values for the interatomic spacings, relaxations, reconstructions, and adsorbate site positions is accomplished by comparing the experimental and simulated images. Quantitative comparisons are made through the use of a reliability, or R, factor, which is based on the differences between the two images. The SARIS development will move low energy ion scattering into the realm of surface imaging techniques.

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