Yield enhancements of secondary negative molecular ions consisting of matrix elements under cesium primary ion bombardment of GaAs

Abstract

A high secondary negative molecular ion yield that is high relative to the secondary negative monomer ion yield has been observed. The secondary negative ion spectrum of a GaAs chemical compound semiconductor sputtered by a cesium primary ion under the secondary ion mass spectroscopy dynamic mode was examined and it was found that the secondary negative GaAs dimer ion was as intense as the secondary negative arsenic monomer. The GaAs dimer ion was three times higher in its intensity than another dimer of the As2 ion. Moreover, the secondary matrix trimer ions containing at least one Ga atom have one order higher intensities than the arsenic trimer ions. At a stable state of the sputtering process, yield variations of secondary molecular ions made up of the matrix elements of GaAs have been examined as a function of the primary ion current density. The high yield of secondary molecular ion species consisting of the matrix elements of GaAs and containing at least one Ga atom is considered to be indirectly related to the arsenic depletion on the GaAs surface sputtered by cesium primary ions.