Influence of the Self-Heated Cathode Geometry on the Parameters of a Low-Pressure Discharge in Crossed <Emphasis Type="Italic">E×H</Emphasis> Fields

The parameters of a self-maintained low-pressure discharge in crossed E×H fields are compared for the Penning discharge with a self-heated disk cathode and the combined discharge with an axial self-heated rod electrode. Based on the continuity equation for the electron flux and the energy balance on the hot cathode, the parameters of the discharge in crossed E×H fields with the self-heated cathode are calculated for a wide range of variations of geometrical sizes of the discharge cell and work functions of cathode material. It is demonstrated that the examined systems differ significantly by radial distributions of fast electron concentration (uniform for the Penning cell and highly nonuniform for the combined discharge cell) and currents and that the volt-ampere characteristics of the examined cells are described by decreasing voltage-current dependences.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 73–80, January, 2005.     

”Reverse” annealing mechanism in ion-doped silicon layers subjected to electron beam heating

The annealing of silicon layers doped by high doses (10¹⁵-10¹⁶ cm^–2) of P⁺, As⁺, or Sb⁺ ions by means of an electron beam applied for 10–20 sec is studied. It is established that when a certain specimen temperature is exceeded, reverse annealing of the ion-implanted layers commences- a decrease in the degree of activation of the impurity introduced. The mechanism of reverse annealing in Si+> and Si+> layers is related to exit of P⁺ and As⁺ ions into interstices with their subsequent sublimation. In the case of heating of an Si+> layer reverse annealing is caused by exit of Sb⁺ ions into interstices and formation of impurity-defect complexes.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 97–102, August, 1989.     

Kinetics of Hydrogenation and Variations in Resistance of Vanadium Thin Films Treated in Atomic Hydrogen Flow

Methods of nuclear reactions, x-ray diffraction analysis, transmission electron and nuclear microscopy were used to investigate the mechanism of hydrogenation of thin vanadium films in their treatment in a flow consisting of a mixture of molecular and atomic hydrogen. It has been shown that the main component penetrating into the metal from the gas phase is atomic hydrogen. At a gas pressure of 10^–2 Pa and room temperature, the dissolution of particles which, in the gas phase, are in molecular form, occurs at a much lower rate. It has been established that the (initially high) rate of variation of the hydrogen concentration in the film decreases during hydrogenation and gradually approaches zero. As this takes place, the hydrogen concentration in vanadium reaches its limiting value equal to about 42.5 at. %. A mathematical model of the hydrogenation of a vanadium film is proposed which describes experimental results based on the relaxation dependence of the hydrogen concentration on hydrogenation time. Comparative analysis of the variations in hydrogen concentration in a film and in film resistance is performed. It has been established that the dependence of the resistance on hydrogen concentration for a thin film hydrogenated in a flow of atomic hydrogen differs from the similar dependence for a bulk material hydrogenated in the atmosphere of molecular hydrogen under the conditions of thermodynamic equilibrium. The features of the behavior of the resistance of a thin film on hydrogenation time revealed experimentally are caused, as in the case of a bulk material, by the formation of the phase of vanadium hydride in the film. The possibility of using vanadium thin films for measuring absolute values of the atomic hydrogen flow density is discussed.     

Effect of atomic hydrogen on the properties of metal-GaAs Schottky barrier contacts

The effect of treatment with atomic hydrogen on the properties of GaAs and the characteristics of Au−GaAs Schottky barrier contacts has been studied in terms of the ideality coefficient n of the I-V characteristics, the barrier height ϕ _b , and the reverse breakdown voltage V_r at 10 μA. The source of the atomic hydrogen was a generator based on an arc reflected Penning discharge with a self-heating element. It has been shown that there is an optimal treatment regime (temperature (T_tr) 200–250°C; duration (t_tr) 5 min) for which n and V_r reach a corresponding minimum and maximum. It is proposed that with lower T_tr and t_tr there is nonuniform etching of the surface oxides and with higher it is possible to have nonuniform etching of the GaAs itself. The barrier height depends on the treatment regime in a more complicated way but on the whole decreases. The effect of passive impurities (decrease in the charge carrier concentration) is already pronounced at T_tr=100°C and changes relatively little with further growth of the temperature. Annealing (reactivation of impuritics) is observed for T≥250°C with sufficiently slow cooling of the sample after treatment. State Scientific-Manufacturing Enterprise for NII Semiconductor Devices. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 115–121, August, 1997.     

Current-voltage characteristics of a reflex discharge with a hollow cathode and self-heating electrode

Results are presented from experimental studies of the current-voltage characteristics of a reflex discharge with a self-heating electrode used in a source of atomic hydrogen. The processes occurring in a discharge cell and governing the main features of the characteristics obtained are investigated theoretically. An explanation of the general features of the discharge is proposed. It is shown that an abrupt decrease in the discharge voltage with increasing hydrogen flow rate is associated with penetration of the plasma into the hollow cathode and the ignition of a hollow cathode discharge. It is demonstrated that, as the discharge current increases, the glow discharge gradually transforms into an arc discharge with a heated cathode.