Cesium-Ion Bombardment of Aluminum Oxide in a Controlled Oxygen Environment

Abstract

Sputtering of aluminum oxide (sapphire) by 2.5 to 10 keV cesium ions has been investigated using neutron activation analysis. The sputtering yield (aluminum atoms/ion) was measured as a function of ion energy, target temperature, and R, the ratio of background oxygen molecular flux arriving at the target surface to the sputtered aluminum and oxygen flux leaving the surface. Positive-charge accumulation on the dielectric surface was neutralized by electron flooding of the ion-beam area while the ion current was measured by a periodic beam deflection technique. In all measurements the ion beam was normal to the target surface and the (001) crystallographic plane. The yield increased monotonically from 0.40 (aluminum atoms/ion) at 2.5 keV to 0.52 at 10 keV and was unaffected for R<0.1. The yield decreased slightly as R was increased, and for R>10 it approached the saturation value of monocrystalline aluminum. The yield exhibited a temperature dependence decreasing from 0.55 at 77°K to 0.48 at 475°K. The results were reproducible to within 5%.