| AVS 61st International Symposium & Exhibition | |
| Advanced Surface Engineering | Monday Sessions |
| Session SE+PS+TF-MoA |
| Session: | Pulsed Plasmas in Surface Engineering |
| Presenter: | Robert Franz, Montanuniversität Leoben, Austria |
| Authors: | R. Franz, Montanuniversität Leoben, Austria C. Clavero, Lawrence Berkeley National Laboratory R. Bolat, Nazarbayev University, Kazakhstan R. Mendelsberg, Lawrence Berkeley National Laboratory A. Anders, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
In high-power impulse magnetron sputtering (HiPIMS), a variation of pulsed magnetron sputtering, short high-voltage pulses are utilized to create discharges with high current densities and a high degree of ionization of the target atoms. In recent years, more complex pulse patterns than the single pulses used in the original or conventional HiPIMS have been developed, e.g. burst-HiPIMS where a series of very short (few µs) pulses are bunched to form bursts.
In the present work, the charge-state-resolved ion energies of HiPIMS discharges were measured, using a LaB6 target, as a function of charging voltage, pulse length, pulse frequency and on/off time ratio within applied HiPIMS bursts [1]. The highest charge states can reach +2 and +3 for boron and lanthanum ions, respectively. At high discharge powers, the B/La ion ratio can exceed the respective atom ratio in the target producing B-rich plasma with up to 98% boron ions. In the case of two-segmented bursts with high on/off time ratios, La3+ is the dominating lanthanum ion species and the ion energy distribution of B+ shows a pronounced high-energy tail extending up to 750 eV. The measured plasma compositions, ion charge states and ion energies are discussed within the established framework of HiPIMS discharges and the recent postulation that potential humps are associated with drifting ionization zones. The recorded high B/La ion ratios are a result of complex effects related to particle fluxes in the HiPIMS plasma of compound targets, as explained with the help of an expanded schematic representation of self-sputtering and gas atom recycling. The high energies of the B+ ions are based on a combination of the self-sputtering of boron, backscattering of incident boron ions on lanthanum atoms in the target and acceleration by localized potential humps [2]. Further evidence for potential humps is provided by the observed charge-state dependence of ion energies and features between the thermal peak and high-energy tail of the ion energy distribution functions.
[1] R. Franz, C. Clavero, R. Bolat, R. Mendelsberg, A. Anders, Plasma Sources Sci. Technol. 23 (2014) 035001.
[2] A. Anders, M. Panjan, R. Franz, J. Andersson, P. Ni, Appl. Phys. Lett. 103 (2013) 144103.