APPARATUS FOR LOW-ENERGY ION-SCATTERING SPECTROSCOPIES - IMAGING ANGULAR-DISTRIBUTIONS AND COLLECTING ANGLE-RESOLVED ENERGY-SPECTRA
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abstract
An apparatus for using low-energy ion scattering to study surface crystallography is described. The ion source can produce highly collimated beams of either noble gas or alkali metal ions with energies up to 30 keV. A versatile manipulator has been built that enables the entire UHV chamber to be translated and rotated in order to easily orient it with respect to the ion beam. The sample is mounted on a manipulator with two independent rotations, three translations, and a tilt, and can be oriented such that the sample normal or an arbitrary bulk crystal axis may be parallel to the incident ion beam within 0.1. Ions that have scattered from a single crystal surface are detected with either a large solid angle two-dimensional imaging detector or with a high-resolution angle-resolving electrostatic analyzer. The backscattered ion image on the large area detector may be viewed in real time and with the aid of a video digitization system to determine the bulk stereogram of a crystal, and provide information about the near surface atomic structure. The electrostatic analyzer position is rotatable with respect to the incident ion beam direction, allowing scattering angles from 0 to 166 to be achieved. Examples of data collected with the instrument are presented.
