An Experimental Technique for Recording Surface Adsorbate-Concentration Profiles Based on Local Measurements of the Contact Potential

摘要

We have substantially improved the experimental technique, firstly proposed by Yu. S. Vedula, used for the determination of Adsorbate distributions in surface diffusion investigations. The technique is based on local measurements of the contact potential difference by the diode method (recording of the current-voltage characteristics in the retarding field regime). The surface is probed with a narrow beam of thermal (<=1 eV) electrons, which practically eliminates the damaging effects of the electrons. The beam is scanned over the surface with the aid of a magnetic field whose direction as programme-controlled varied. An automated system provides the scanning with discrete steps of 0.13 micrometer and the spatial resolution about 1 micrometer. The contact potential difference is recorded with a sensitivity of about 0.0001V which ensures the accuracy of Adsorbate coverage determination of 0.001-0.01 of a monolayer.