Petter Larsson

Cross-field ion transport during high power impulse magnetron sputtering

In this study, the effect on thin film growth due to an anomalous electron transport, found in high power impulse magnetron sputtering (HiPIMS), has been investigated for the case of a planar circular magnetron. An important consequence of this type of transport is that it affects the way ions are being transported in the plasma. It was found that a significant fraction of ions are transported radially outwards in the vicinity of the cathode, across the magnetic field lines, leading to increased deposition rates directly at the side of the cathode (perpendicular to the target surface). Furthermore, this mass transport parallel to the target surface leads to that the fraction of sputtered material reaching a substrate placed directly in front of the target is substantially lower in HiPIMS compared with conventional direct current magnetron sputtering (dcMS). This would help to explain the lower deposition rates generally observed for HiPIMS compared with dcMS. Moreover, time-averaged mass spectrometry measurements of the energy distribution of the cross-field transported ions were carried out. The measured distributions show a direction-dependent high-energy tail, in agreement with predictions of the anomalous transport mechanism.

Transition between the discharge regimes of high power impulse magnetron sputtering and conventional direct current magnetron sputtering

Current and voltage have been measured in a pulsed high power impulse magnetron sputtering (HiPIMS) system for discharge pulses longer than 100 mu s. Two different current regimes could clearly be ...

On the electron energy in the high power impulse magnetron sputtering discharge

The temporal variation of the electron energy distribution function (EEDF) was measured with a Langmuir probe in a high power impulse magnetron sputtering (HiPIMS) discharge at 3 and 20 mTorr pressures. In the HiPIMS discharge a high power pulse is applied to a planar magnetron giving a high electron density and highly ionized sputtered vapor. The measured EEDF is Maxwellian-like during the pulse; it is broader for lower discharge pressure and it becomes narrower as the pulse progresses. This indicates that the plasma cools as the pulse progresses, probably due to high metal content of the discharge.

Ab initio calculations and synthesis of the off-stoichiometric half-Heusler phase Ni1−xMn1+xSb

We perform a combined theoretical and experimental study of the phase stability and magnetism of the off-stoichiometric Ni1−xMn1+xSb in the half-Heusler crystal phase. Our work is motivated by the need for strategies to engineer the magnetism of potentially half-metallic materials, such as NiMnSb, for improved performance at elevated temperatures. By means of ab initio calculations we investigate Ni1−xMn1+xSb over the whole composition range 0≤x≤1 of Ni replacing Mn and show that at relevant temperatures, the half-Heusler phase should be thermodynamically stable up to at least x=0.20 with respect to the competing C38 structure of Mn2Sb. Furthermore we find that half-Heusler Ni1−xMn1+xSb retains half-metallic band structure over the whole concentration range and that the magnetic moments of substitutional MnNi atoms display magnetic exchange interactions an order of magnitude larger than the Ni–Mn interaction in NiMnSb. We also demonstrate experimentally that the alloys indeed can be created by synthesizin...

The spatial and temporal variation of the electron energy distribution function (EEDF) in the HiPIMS discharge

We describe measurements of the plasma parameters in a high power impulse magnetron sputtering (HiPIMS) discharge. A Langmuir probe is used to determine the plasma parameters, such as the effective electron temperature Teff, the electron density ne, the floating potential Vfl and the plasma potential Vpl, as well as the electron energy distribution function (EEDF). The spatial and temporal variation of the plasma parameters and the EEDF are recorded in the pressure range 3–20 mTorr. The electron density peaks at 5 × 1018 m−3 for 40 – 80 mm distance from the target surface for all pressures investigated. The EEDF is more broad for lower discharge pressure. Furthermore, the EEDF becomes narrower as the pulse progresses, which indicates that the plasma cools off, probably due to increased presence of metal species in the discharge. The electron temperature reaches its peak value of 1.5–3 V at 80 microseconds after pulse initiation, in the pressure range 5–20 mTorr.