Velocity distribution of metal ions in the target region of HiPIMS: the role of Coulomb collisionsHigh power impulse magnetron sputtering (HiPIMS) discharges have become an important tool for the deposition of thin, hard coatings. Such discharges are operated at a very low working gas pressure in the order of 1 Pa. Therefore, elastic collisions between ions and other heavy particles are often calculated to occur with low frequency, using the hard sphere approximation. However, inside the magnetic trap region of the discharge, a very dense plasma is created and Coulomb collisions become the dominant collision process for ions. In this article, we show that Coulomb collisions are a necessary part of a complete description of ion movement in the magnetic trap region of HiPIMS. To this end, the velocity distribution function (VDF) of chromium and titanium ions is measured using high-resolution optical emission spectroscopy. The VDF of those ions is then described using a simple simulation which employs a direct simulation Monte Carlo scheme. The simulation describes the self-relaxation of the VDF that is initially a Thompson distribution as being created during the sputtering process. Measurement positions inside the discharge are matched to the simulation results choosing an appropriate relaxation time. In this fashion, excellent agreement between simulation and measurement is obtained. We find, that the distribution quickly becomes mostly Maxwellian with a temperature of 9 eV for titanium ions and 4.5 eV in the case of chromium ions. Only the high energy tail of the VDF retains the shape of the initial Thompson distribution. The observed high temperature is explained with an energy redistribution from the highly energetic Thompson distribution into an partly-thermalized Maxwell-like distribution. Finally, the temperature resulting from this energy redistribution is calculated using a simple analytical model which shows good agreement with the measurements.
]]>HiPIMSionsmagnetron sputteringVDFPlasma Modeling and Simulation, Plasma for Materials / Surfaces1974a45a-224b-45ca-99e7-ee5dab6577702020-11-11T14:19:00+01:002021-03-21T19:51:58+01:00en-USEP2Simulated velocity distribution functions for chromium (m=52amu) and titanium (m=48amu), self-relaxing from a Thompson to a Maxwell distributionVDF starts with a Thompson distribution of particles sputtered from the x,y plane. Files show the VDFs in three dimensions in 50 ns steps.
First line: velocity axis in m/s
Second line: VDF x direction
Third line: VDF y direction
Fourth line: VDF z direction
]]>2020-11-13T12:35:00+01:002021-01-04T15:05:11+01:00application/zipzip6852355https://rdpcidat.rub.de/dataset/velocity-distribution-metal-ions-target-region-hipims-role-coulomb-collisions/resourceWidth (FWHM) of the measured target parallel chromium ion VDFs as a function of target distanceColumn 1: target distance in mm
Column 2: mean width (FWHM) of the chromium VDF from three measurements
Column 3: standard deviation of the mean width
]]>2020-11-13T12:44:04+01:002021-01-04T15:05:32+01:00text/plaintxt825https://rdpcidat.rub.de/dataset/velocity-distribution-metal-ions-target-region-hipims-role-coulomb-collisions/resource-0Width (FWHM) of the measured target parallel titanium ion VDFs as a function of target distanceColumn 1: target distance in mm
Column 2: mean width (FWHM) of the chromium VDF from three measurements
Column 3: standard deviation of the mean width
]]>2020-11-13T12:49:53+01:002021-01-04T15:05:49+01:00text/plaintxt900https://rdpcidat.rub.de/dataset/velocity-distribution-metal-ions-target-region-hipims-role-coulomb-collisions/resource-1Measured VDF for chromium and titanium ionsVelocity distribution function (VDF) for chromium and titanium ions in the direction parallel to the target surface for different target distances (z=XX in filename, with XX as distance in mm). VDFs obtained by deconvolution of OES lines. Measurements were performed three times (i=1 to i=3).
In each file:
Column 1: velocity axis in m/s
Column 2: target parallel VDF [a.u.]
Please note that the velocity axis is different for every file.
]]>2020-11-13T13:03:19+01:002021-01-04T15:07:20+01:00application/zipzip62497https://rdpcidat.rub.de/dataset/velocity-distribution-metal-ions-target-region-hipims-role-coulomb-collisions/resource-2Measured optical emission spectra for the chromium and titanium dischargeMeasurements performed parallel to the target surface, at different distances to the surface (z=XX in filname, with XX as distance in mm). Three measurements per target distance (i=1 to I=3) for chromium and titanium as the target material.
Column 1: wavelength in nm
Column 2: plasma emission in counts
Column 3: simultaneously acquired emission from a hollow cathode lamp in counts
]]>2020-11-13T13:09:34+01:002021-01-04T15:07:39+01:00application/zipzip1291512https://rdpcidat.rub.de/dataset/velocity-distribution-metal-ions-target-region-hipims-role-coulomb-collisions/resource-3DKANhttps://rdpcidat.rub.de