Download high power pulsed hollow cathode plasma source caracterization

HIGH POWER PULSED HOLLOW CATHODE PLASMA SOURCE
CHARACTERIZATION
V. Tiron1, A. V. Nastuta1, S. Irimiciuc1, C. Costin1, G. Popa1, C. Ionita2 and R. Schrittwieser2
1Faculty
of Physics, Alexandru Ioan Cuza University of Iasi, Blvd. Carol I, no. 11, 700506,
Iasi, Romania
2Institute for Ion Physics and Applied Physics, Leopold-Franzens University of Innsbruck,
Technikerstr. 25, A-6020, Innsbruck, Austria
Hollow cathodes (HC) discharges are rather simple plasma system used as light
sources or sputtering systems. Particularly, in this type of discharge a high ion density is produced by the electron pendulum effect inside the hollow cylinder cathode. The form of hollow
cathodes used as sputtering sources may vary from simple disc to cylinder [1]. Sometimes an
additional cavity is used for further enhancement of the pendulum effect of the electrons inside the cathode. Thus, high-density fluxes of energetic working gas ions are produced, which
intensively sputter the inner cathode walls. Usually the hollow cathode discharge operates at
low pressure between 1 and 10–3 mbar, in different working gases, powered by a DC power
supply. Recently, high impulse power supplies were used to ignite the HC discharge [2]. The
main purpose was to optimize discharge parameters for high quality thin films deposition.
One way is to increase the power density on HC in order to increase the plasma density, ionization degree, sputtering rate and therefore to improve the properties of thin films deposited.
In this contribution we present experimental results concerning the electrical and
optical diagnostics of a high power pulsed hollow cathode (HPP-HC) plasma source and its
application for the growth of Ti thin films, nanoparticles and clusters. Plasma parameters, applied voltage and discharge current, as well as plasma potential and saturation ion current,
were recorded for different pulse durations, repetition frequencies, average powers and gas
pressures. These parameters were studied in order to find optimum sputtering condition for
quality thin film deposition. The experimental results were obtained using a Ti hollow cathode
(3 cm height and 0.5 cm inner diameter) and Ar working gas in a pressure range from 10–1 to
10–3 mbar. The high power pulse hollow cathode (up to 5 kW) was characterized by very
short discharge pulses (5 µs) attaining peak cathode currents of about 6 A for a maximum applied voltage of 800 V, with a pulse repetition frequency of 10 kHz. These parameters may be
suitable for cluster formation and good quality thin film growth. The titanium films obtained
in these experiments were investigated by means of various material surface and bulk analysis
techniques (atomic force microscopy, X-ray photoelectron spectroscopy, secondary electron
microscopy, X-ray diffraction).
Acknowledgments: This research has been financially supported by the CEEPUS Network No. CIII-AT0063 and bilateral project Romania-Austria No. 550/2012.
References:
[1] R. Schrittwieser, C. Ionita, A. Murawski, C. Maszl, M. Asandulesa, A. V. Nastuta, G. B. Rusu, C.
Douat, S. B. Olenici, I. Vojvodic, M. Dobromir, D. Luca, S. Jaksch and P. Scheier, J. Plasma Phys. 76
(2010), 655.
[2] I. Pilch, D. Söderström, N. Brenning and U. Helmersson, Appl. Phys. Lett. 102 (2013), 033108.