Sample erosion studies and modeling in a glow discharge ionization cell

Modeling of metastable argon atoms in a direct-current glow discharge

“…Besides the metastable argon atoms, the plasma is assumed to consist of neutral ground-state argon atoms at rest, uniformly distributed throughout the discharge, fast and slow electrons and argon ions, described in a hybrid model [24], fast argon atoms, and also sputtered atoms. The density of the latter is calculated by a simple one-dimensional diffusion equation [25,26] QnA *…”

Plasma diagnostics and numerical simulations: insight into the heart of analytical glow discharges

“…However, the measured density profiles exhibit a maximum at about 1 mm from the cathode, which could not be explained by the model because the latter predicted a steadily decreasing density with increasing distance from the cathode. The characteristic density profile, with a maximum shifted away from the cathode, was obtained later on by van Straaten et al, also using a simple diffusion model, in one dimension 129 and two dimensions, 130 but taking into account a thermalization profile of sputtered atoms as source term for the diffusion model (see also Section 4.2). Furthermore, van Straaten et al 129 calculated the sputter rate, based on Boltzmann equations for the electrons, Ar + ions and energetic Ar atoms in the CDS, and obtained satisfactory agreement with measured etch rates.…”

“…The characteristic density profile, with a maximum shifted away from the cathode, was obtained later on by van Straaten et al, also using a simple diffusion model, in one dimension 129 and two dimensions, 130 but taking into account a thermalization profile of sputtered atoms as source term for the diffusion model (see also Section 4.2). Furthermore, van Straaten et al 129 calculated the sputter rate, based on Boltzmann equations for the electrons, Ar + ions and energetic Ar atoms in the CDS, and obtained satisfactory agreement with measured etch rates. Based on the sputtering and back diffusion flux, information could also be obtained on the crater profile due to sputtering.…”

“…The cell is filled with a gas, usually argon, at a pressure ranging from below 100 Pa to several hundreds of Pa, depending mainly on the cell design. The two basic types of glow discharge cells, used nowadays commercially and in research laboratories, are the VG9000 type 9 and the Grimm-type. 10 In general, the VG9000 glow discharge cell operates at a pressure around 50-100 Pa, and the electrical current, which arises as a result of the potential difference, is of the order of a few mA.…”

Influence of discharge parameters on the resultant sputtered crater shapes for a radio frequency glow discharge mass spectrometry source

“…The differences in crater shape between PTFE and the other sputtered species to the cathode with the concentrated redepos-exists between the rf-power and dc-bias in an rf-GD-AES system, where an increase in power also results in a proportional increase in ablation rate (crater depth).40 Van Straaten and others have observed a similar linear correlation between the sputtered depth and power density for dc-GDs.41,43 However, dc-GD studies13,14,40,43 have shown that the crater shape is greatly affected by the applied power, whereas rf-GD studies17,18,32 indicated little effect on the resultant crater shapes. As mentioned previously, increased voltages produce greater potential gradients and more convex crater shapes due to higher erosion rates at the crater edges.41, 43 The reason for the lack of influence in rf-GD crater shapes likely lies in the fact that changes in power cause much smaller changes in voltage in the rf powering mode than in the dc case (tens vs. hundreds of volts). These findings can be used to the rf-GDMS analyst's advantage in different circumstances.…”