Secondary Positive Ion Emission from a Tantalum Surface

Abstract

The secondary positive ions ejected from a tantalum target by a mass‐analyzed primary beam were detected and studied in a mass spectrometer. The secondary ion emission consisted of species characteristic of the metal (Ta⁺), metal compounds (oxides), and multiatomic ions of the metal (Ta₂⁺, Ta₃⁺). Reflection of normally incident gas ions from the Ta surface was not observed; the specular reflection coefficient of ions to ions is then less than 10⁻⁶. The relative secondary ion yields for tantalum, measured for normally incident Hg²⁰² ions at energies between 0.3–14 keV, were independent of the incident ion charge. A dependence of the Ta⁺ secondary yield on mass of the incident ion was observed. The dependence of the secondary ion yield on mass and energy of the incident ions was very similar to that observed for total sputtering yields.