Secondary particle properties for the ion beam sputtering of TiO2 in a reactive oxygen atmosphere

Abstract This work deals with the properties of secondary particles, i.e., sputtered target and scattered primary particles, for the ion beam sputtering of TiO 2 in a reactive oxygen atmosphere. The angular and energy distributions in dependence on ion beam parameters (ion energy, ion species, or ion mass) and geometrical parameters (ion incidence angle, polar emission angle, or scattering angle) were investigated. The angular distributions of sputtered Ti particles were determined by the collection method, i.e., by growing TiO 2 thin films and measuring the thickness, composition, and mass density. The distributions can be described by the superposition of an isotropic and an anisotropic part. The anisotropic part relative to the isotropic part gets more pronounced with decreasing ion energy, increasing ion incidence angle or changing the process gas from Ar to Xe. An energy-selective mass spectrometer was used to measure mass and energy distributions of secondary ions. The most prevalent species were identified to be O + , O 2 + , Ti + , TiO + , Ar + , and Xe + ions. The energy distributions of Ti + and TiO + ions show a low-energy maximum between 10 eV and 30 eV, followed by an exponential decay. When decreasing the scattering angle, the high-energy tail extends to higher energies. O + , O 2 + , Ar + , and Xe + ions show a low-energy maximum between 5 eV and 20 eV, which is followed by a sudden signal drop for scattering angles larger than 90°. For scattering angles smaller than 90°, additional peak(s) at higher energy appear, which are assigned to direct scattering and/or direct sputtering events. The experimental results are compared to calculations based on elastic collision theory and to simulations done with the Monte Carlo code SDTrimSP. The results are also discussed in relation to secondary particle properties for the reactive ion beam sputtering of Ti and to properties of TiO 2 thin films grown by reactive ion beam sputter deposition with the same setup and the same parameters. Among others, it was found that sputtering of the TiO 2 target exhibits less anisotropy contributions than sputtering of the Ti target.