INFLUENCE OF THE IMPLANTED K-CLUSTER SIZE DISTRIBUTION ON THE SHIFT OF W WORK FUNCTION

The shift of the work function up to 2 eV, at the surface of polycryst alline tungsten, due to implantation by 30-110 keV K+ ions, can be exp lained by the simple assumption bf small K-clusters formation inside t he metal surface layer. An improved model is proposed which takes into account most of the characteristic parameters for the implantation pr ocess and the alkali-cluster formation inside the surface. In particul ar, the cluster size distribution being one of the most critical param eter, it is essential to derive its influence on the shift of the work function at the metallic surface, and also on the other related param eters; Taking into account the previous experimental data, it is then possible to determine the most probable K-cluster size distribution, a nd also to estimate the limits of variation ranges of the characterist ic parameters. (C) 1998 American Institute of Physics.