Energy distributions of secondary ions for the Ar ion beam sputtering of indium tin oxide

Abstract

The energy distributions of secondary ions for the Ar ion beam sputtering of indium tin oxide were measured in dependence on geometric parameters (ion incidence angle, polar emission angle, scattering angle), ion energy, and O2 background pressure using energy-selective mass spectrometry. The most prevalent ion species were identified to be O+, O2+, Ar+, In+, and Sn+. The energy distributions of O+, In+, and Sn+ ions show a low-energy maximum between 10 and 20 eV, followed by a power-law decay if the scattering angle is γ>90°. If γ<90°, an additional high-energy structure evolves, which is assigned to anisotropy effects, namely, directly sputtered particles. The energy distributions of the Ar+ ions show a low-energy maximum and, in dependence on the scattering angle, up to two additional high-energy structures, which are also assigned to anisotropy effects. Here it is related to direct scattering events. All additional structures show systematic correlations with scattering angle and ion energy. The energy distributions of the O2+ ions exhibit a low-energy maximum followed by a sudden signal drop. There is almost no variation with scattering angle or ion energy. In general, increasing the O2 background pressure results in a decrease of the particle energy due to an energy loss upon interaction with background gas particles. The experimental results are compared and discussed with calculations based on elastic two-particle collision theory and using srim, and Monte Carlo simulations using SDTrimSP.