Study of the sputtered Cu atoms and Cu+ ions in a hollow cathode glow discharge using a hybrid model

Abstract

Role of the fast Ar atoms, Ar + ions, and metastable Ar atoms in a hollow cathode glow discharge: Study by a hybrid modelThe role of the Cu atoms sputtered from the cathode material in a cylindrical hollow cathode discharge ͑HCD͒ and the corresponding Cu + ions are studied with a self-consistent model based on the principle of Monte Carlo ͑MC͒ and fluid simulations. In order to obtain a more realistic view of the discharge processes, this model is coupled with other submodels, which describe the behavior of electrons, fast Ar atoms, Ar + ions, and Ar metastable atoms, also based on the principles of MC and fluid simulations. Typical results are, among others, the thermalization profile of the Cu atoms, the fast Cu atom, the thermal Cu atom and Cu + ion fluxes and densities, and the energy distribution of the Cu + ions. It was found that the contribution of the Ar + ions to the sputtering was the most significant, followed by the fast Ar atoms. At the cathode bottom, there was no net sputtered flux but a net amount of redeposition. Throughout the discharge volume, at all the conditions investigated, the largest concentration of Cu atoms was found in the lower half of the HCD, close to the bottom. Penning ionization was found the main ionization mechanism for the Cu atoms. The ionization degree of copper atoms was found to be in the same order as for the argon atoms ͑10 −4 ͒.

Model of microsecond pulsed glow discharge in hollow cathode for mass spectrometry

“…Because the average speed of the slow particles is significantly less than the speed of the fast ones, the motion of the slow particles is calculated with a larger time step. This is the only difference between fast and slow particles in our model, in contrast to hybrid models used by others [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44], where different methods are used to simulate fast and slow particles. Trajectories and collisions of fast particles are calculated one after the other, with a time interval of 200 ps.…”

“…Processes in DC discharge in a HC were theoretically investigated in [35][36][37][38][39], millisecond pulsed discharges and afterglow were investigated theoretically in [40,41]. However, the significant instantaneous power of the microsecond PGD may lead to another picture of the basic processes in both the discharge and the afterglow, and a separate investigation of microsecond PGD is necessary.…”

“…Theoretical models for the simulation of a glow discharge in DC and RF modes for different applications have already been developed [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44], typically a hybrid model is used. Processes in DC discharge in a HC were theoretically investigated in [35][36][37][38][39], millisecond pulsed discharges and afterglow were investigated theoretically in [40,41].…”

“…In this work we present a model of a microsecond PGD and its afterglow in HC, and the application of the model for the optimization of a developing commercial Time-of-Flight mass spectrometer "Lumas-30" [22][23][24]45] with HC PGD as an ion source. In the hybrid model [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] different submodels are used for simulation of different particles. To avoid difficulties with the combination of these submodels, we have developed another model based on the Monte-Carlo method for all particles in the discharge and continuity equations in the afterglow.…”

The use of hollow cathodes in deposition processes: A critical review

“…Most models of the hollow cathode effect conclude that there are two groups of electrons, a low-energy population whose velocity distribution is Maxwellian and uniform throughout most of the negative glow, and a high-energy group generated from the bombardment of, and photoemission from, the cathode surface, as well as gas-phase ionization events caused by ion-impact collisions close to the cathode surface [37,50,121,128,129]. The low-energy group are a combination of the elastic-collision thermalized high-energy electrons and those electrons produced by gas-phase ionization of the neutral gas atoms by high-energy electrons within the central negative glow region.…”