The distribution of an ion current density on a substrate with a discontinuous film consisting of islands of dimension 25-100 nm was studied numerically. It was found that the ion current distribution is highly non-uniform and islands of the discontinuous film are enclosed with sharply defined zones where the current density is very low. The total area of low current zones reaches 30-50% of the substrate area, depending on the voltage applied to the substrate. The ratio of island radius-low current zone width depends on the island size and equals approximately 1.0 for large islands and 0.5 for small islands. It is shown that the island distribution function may be controlled by bias voltage variation.
Ion current distribution in a system with crossed magnetic and electrical fields for plasma immersion ion implantation has been investigated. It is found that the ion current to a target has a nonmonotonic behavior with bias voltage when a magnetic field is applied. For instance, the current density has a maximum of about 150 A/m 2 at bias voltage of about 1 kV in the case of a magnetic field parallel to the target of about 0.035 T. These results are explained in terms of ionization by magnetized electrons in the EϫB system. Our findings suggest that the system with crossed fields can be used for intense plasma immersed processing.
Transition between different plasma configurations is studied in a system with negative biased cylindrical target in crossed E ϫ B fields. It was found that the diffuse plasma torus formed around the cylindrical target in relatively small magnetic field (0.02 T on target surface) changes the shape with magnetic field to form a thin disk with a width lower than 1 cm when target voltage is less than −400 V. The target current decreases sharply when the magnetic field reaches some critical value. When the target voltage exceeds 400 V, the target current increases with the magnetic field and the plasma has always toroidal shape. The plasma behavior can be understood taking in account the interaction of the drift currents and the magnetic field.
KNbO 3 in the form of films is a highly acclaimed material due to its potential application in surface acoustic wave (SAW), and nonlinear optic devices. Single-source powder flash evaporation MOCVD of epitaxial KNbO 3 films was accomplished, for the first time, with potassium tert-butoxide and niobium heteroligand complex, Nb(O i Pr) 4 (thd) used as volatile metal±or-ganic precursors. The microstructure of the films was found to be dependent on the substrate used (MgO or SrTiO 3 ) and deposition temperature. A new approach to reach cation stoichiometry of deposited films deficient in potassium, consisting of a post-deposition annealing with a KNbO 3 /K 3 NbO 4 powder mixture, was proposed. The device quality of the films was verified by high second harmonic generation (SHG) output. The effect of the oxygen non-stoichiometry of films on the phase transition temperature was proven.
Characteristics of electrical breakdown of a planar magnetron enhanced with an electromagnet and a hollow-cathode structure, are studied experimentally and numerically. At lower pressures the breakdown voltage shows a dependence on the applied magnetic field, and the voltage necessary to achieve the self-sustained discharge regime can be significantly reduced. At higher pressures, the dependence is less sensitive to the magnetic field magnitude and shows a tendency of increased breakdown voltage at the stronger magnetic fields. A model of the magnetron discharge breakdown is developed with the background gas pressure and the magnetic field used as parameters. The model describes the motion of electrons, which gain energy by passing the electric field across the magnetic field and undergo collisions with neutrals, thus generating new bulk electrons. The electrons are in turn accelerated in the electric field and effectively ionize a sufficient amount of neutrals to enable the discharge self-sustainment regime. The model is based on the assumption about the combined classical and near-wall mechanisms of electron conductivity across the magnetic field, and is consistent with the experimental results. The obtained results represent a significant advance toward energy-efficient multipurpose magnetron discharges.
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