@article {58925, title = {Drifting Ionization Zone in DC Magnetron Sputtering Discharges at Very Low Currents}, journal = {IEEE Transactions on Plasma Science}, volume = {42}, year = {2014}, month = {10/2014}, pages = {2578 - 2579}, abstract = {

Discharges with crossed electric and magnetic fields are known to develop instabilities that are crucial in the transport of charged particles. Sputtering magnetrons are no exception. While most recent studies focused on traveling ionization zones in high power impulse magnetron sputtering, we show here fast camera images of magnetron discharges at very low current. A single drifting ionization zone is always present, even down to the threshold current of about 10 mA.

}, issn = {0093-3813}, doi = {10.1109/TPS.2014.2334601}, author = {Andr{\'e} Anders and Pavel A Ni and Joakim Andersson} } @article {58924, title = {Drifting potential humps in ionization zones: The {\textquotedblleft}propeller blades{\textquotedblright} of high power impulse magnetron sputtering}, journal = {Applied Physics Letters}, volume = {103}, year = {2013}, month = {10/2013}, pages = {144103}, abstract = {

Ion energy distribution functions measured for high power impulse magnetron sputtering show features, such as a broad peak at several 10\ eV with an extended tail, as well as asymmetry with respect to E {\texttimes} B, where E and B are the local electric and magnetic field vectors, respectively. Here it is proposed that those features are due to the formation of a potential hump of several 10\ V in each of the traveling ionization zones. Potential hump formation is associated with a negative-positive-negative space charge that naturally forms in ionization zones driven by energetic drifting electrons.

}, keywords = {Electric fields, ionization, plasma ionization, sputter deposition, sputtering}, issn = {00036951}, doi = {10.1063/1.4823827}, author = {Andr{\'e} Anders and Matjaž Panjan and Robert Franz and Joakim Andersson and Pavel A. Ni} } @article {58923, title = {Drifting localization of ionization runaway: Unraveling the nature of anomalous transport in high power impulse magnetron sputtering}, journal = {Journal of Applied Physics}, volume = {111}, year = {2012}, month = {03/2012}, pages = {053304}, abstract = {

The plasma over a magnetron{\textquoteright}s erosion {\textquotedblleft}racetrack{\textquotedblright} is not azimuthally uniform but concentrated in distinct dense ionization zones which move in the E x B direction with about 10\% of the electron E x B/B2 drift velocity. The ionization zones are investigated with a gated camera working in concert with a streak camera for Al, Nb, Cu, and W targets in Ar or Kr background gas. It is found that each ionization zone has a high plasma density edge, which is the origin of a plasma-generating electron jet leaving the target zone. Each region of strong azimuthal plasma density gradient generates an azimuthal electric field, which promotes the escape of magnetized electrons and the formation of electron jets and plasma flares. The phenomena are proposed to be caused by an ionization instability where each dense plasma zone exhibits a high stopping power for drifting high energy electrons, thereby enhancing itself.

}, keywords = {Cameras, ionization, Magnetic fields, Plasma density, plasma ionization}, issn = {00218979}, doi = {10.1063/1.3692978}, author = {Andr{\'e} Anders and Pavel A Ni and Albert Rauch} } @article {58919, title = {Dynamically Modulating the Surface Plasmon Resonance of Doped Semiconductor Nanocrystals}, journal = {Nano Letters}, volume = {11}, year = {2011}, month = {10/2011}, pages = {4415 - 4420}, abstract = {

Localized surface plasmon absorption features arise at high doping levels in semiconductor nanocrystals, appearing in the near-infrared range. Here we show that the surface plasmons of tin-doped indium oxide nanocrystal films can be dynamically and reversibly tuned by postsynthetic electrochemical modulation of the electron concentration. Without ion intercalation and the associated material degradation, we induce a \> 1200 nm shift in the plasmon wavelength and a factor of nearly three change in the carrier density.

}, keywords = {doping, indium tin oxide, nanocrystal, spectroelectrochemistry, surface plasmon}, issn = {1530-6984}, doi = {10.1021/nl202597n}, author = {Guillermo Garcia and Raffaella Buonsanti and Evan L. Runnerstrom and Rueben J. Mendelsberg and Anna Llordes and Andr{\'e} Anders and Thomas J. Richardson and Delia J. Milliron} } @conference {1252, title = {Deposition Rates of High Power Impulse Magneton Sputtering}, booktitle = {51st Annual Technical Meeting of the Society of Vacuum Coaters}, year = {2008}, month = {04/2008}, abstract = {

High power impulse magnetron sputtering (HIPIMS) is seen by many as the new paradigm in sputtering. It provides significant self-ion assistance to film growth. However, many noticed that deposition rates are reduced, often to less than 50\%, compared to direct current (DC) sputtering rates at the same power input. It is argued here that the reduction is based on the physics of sputtering and self-sputtering, and it should not come as a surprise. Four effects can be distinguished (i) the yield effect caused by the less-than-linear increase of sputtering yield with ion energy, (ii) the impedance effect, influencing what fraction of the target-anode voltage drops in the sheath, (iii) the species effect associated with a change of ions causing sputtering, and (iv) the return effect associated with flux splitting in selfsputtering. The paper is completed by considering some business implications, in particular; it is argued that HIPIMS is a different technology and that its value should be judged comprehensively, not just by rates. Finally, the special case of temperature dependent sputtering is considered, which in some cases may lead to rates exceeding the DC rates.

}, author = {Andr{\'e} Anders} }