APPLICATION OF POSITRON-ANNIHILATION INDUCED AUGER-ELECTRON SPECTROSCOPY TO THE STUDY OF SURFACE-CHEMISTRY

Positron annihilation induced Auger Electron Spectroscopy (PAES), make s use a beam of low energy positrons to excite Auger transitions by an nihilating core electrons. This novel mechanism provides PAES with a n umber of unique features which distinguishes it from other methods of surface analysis. In PAES the very large collisionally induced seconda ry electron background which is present under the low energy Auger pea ks using conventional techniques can be eliminated by using a positron beam whose energy is below the range of Auger electron energies. In a ddition, PAES is more surface selective than conventional Auger Spectr oscopy because the PAES signal originates almost exclusively from the topmost atomic layer due to the fact that the positrons annihilating w ith the core electrons are trapped in an image correlation well just o utside the surface. In this paper, recent applications of positron Ann ihilation Induced Auger Electron Spectroscopy (PAES) to the study of s urface structure and surface chemistry will be discussed including stu dies of the growth, alloying and inter-diffusion of ultrathin layers o f metals, metals on semiconductors, and semiconductors on semiconducto rs. In addition, the possibilities for future application of PAES to t he study of catalysis and surface chemistry will be outlined.