@article {12123,
	title = {Observation of Ti4+ ions in a high power impulse magnetron sputtering plasma},
	journal = {Applied Physics Letters},
	volume = {93},
	year = {2008},
	month = {08/2008},
	pages = {71504},
	abstract = {<p>Multiply charged titanium ions including Ti<sup>4+</sup> were observed in high power impulse magnetron sputtering discharges. Mass/charge spectrometry was used to identify metal ion species. Quadruply charged titanium ions were identified by isotope-induced broadening at mass/charge 12. Due to their high potential energy, Ti<sup>4+</sup> ions give a high yield of secondary electrons, which in turn are likely to be responsible for the generation of multiply charged states.</p>},
	doi = {10.1063/1.2973179},
	author = {Joakim Andersson and Arutiun P. Ehiasarian and Andr{\'e} Anders}
}
@conference {1731,
	title = {Physics of High Power Impulse Magnetron Sputtering},
	booktitle = {ISSP2007: The 9th International Symposium on Sputtering \& Plasma Processes},
	year = {2007},
	abstract = {<p>High power impulse magnetron sputtering is characterized by discharge pulses whose target power density exceeds conventional sputtering power densities by two orders of magnitude or more; the goal is to provide a large flux of ionized sputtered material. The processes of pulse evolution are briefly reviewed, including secondary electron emission, self-sputtering, and rarefaction. Using a pulse power supply capable of providing constant voltage for target peak power densities up to 5 kW/cm<sup>2</sup>, the evolution of the current-voltage characteristics was investigated for copper and titanium. It is shown that the characteristic cannot be reduced to value pairs. Rather, a strong but reproducible development exists. The details depend on the argon pressure and applied voltage. Each target material exhibits a distinct and sharp transition to a high current regime that appears to be dominated by metal plasma. Despite the higher sputter yields for copper, the transition to the high current regime occurs much earlier and stronger for titanium, which may be attributed to a higher secondary electron yield and hence a higher density of electrons confined in the magnetron structure. At high currents, the closed-drift Hall current generates a magnetic field that weakens plasma confinement, thereby enabling large ion currents to reach a biased substrate.</p>},
	author = {Andr{\'e} Anders and Joakim Andersson and David Horwat and Arutiun P. Ehiasarian}
}
