Boron-rich plasma by high power impulse magnetron sputtering of lanthanum hexaboride

Boron-rich plasmas have been obtained using a LaB6 target in a high power impulse sputtering (HiPIMS) system. The presence of B-10(+), B-11(+), Ar2+, Ar+, La2+, and La+ and traces of La3+, C-12(+), N-14(+), and O-16(+) have been detected using an integrated mass and energy spectrometer. Peak currents as low as 20 A were sufficient to obtain plasma dominated by B-11(+) from a 5 cm planar magnetron. The ion energy distribution function for boron exhibits an energetic tail extending over several 10 eV, while argon shows a pronounced peak at low energy (some eV). This is in agreement with models that consider sputtering (B, La) and gas supply (from background and recycling). Strong voltage oscillations develop at high current, greatly affecting power dissipation and plasma properties. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759310]