Sputtering and surface state evolution of Bi under oblique incidence of 120 keV Ar+ ions

The sputtering and surface state evolution of Bi/Si targets under oblique incidence of 120 keV Ar+ ions have been investigated over the range of incidence angles 0o ≤ θi ≤ 60o. Increasing erosion of irradiated samples (whose surface thickness reduced by ∼3% at normal incidence up to ∼8% at θ = 60o) and their surface smoothing with reducing grain sizing were pointed out using Rutherford backscattering (RBS), atomic force (AFM) and X-ray diffraction (XRD) techniques. Measured sputtering yield data versus θi with fixed ion fluence to ∼1.5 x 1015 cm-2 are well described by Yamamura et al. semi-empirical formula and Monte Carlo (MC) simulation using the SRIM-2008 computer code. The observed increase in sputter yield versus incidence angle is closely correlated to Bi surface topography and crystalline structure changes under ion irradiation.