SURFACE-REACTION INDUCED BY MULTIPLY-CHARGED IONS

The surface reactions induced by an electronic potential energy of mul tiply-charged ions are investigated. A small electron-beam impact type ion source for production of multiply-charged ions was manufactured f or this study. The charge state distribution of multiply-charged ions produced in the ion source greatly depends on the sample gas pressure and the potential barrier for ion trapping. In operation with an elect ron current of 7 mA at 2 keV, the ion-beam currents obtained for Ar5and Ar10+ are respectively at least 7 pA and 2 x 10(-3) pA. H+ ion des orption from a lightly etched GaAs surface are observed by bombarding with Ar-q+ ions (q=1-3). The desorption yield of H+ per Ar-q+ increase s proportionally with the sixth power of the charge state of Ar-q+. Th is charge state effect is discussed from the viewpoint of the electron ic interaction between the GaAs surface and Ar-q+ ions.