OPTICAL AND ELECTROPHYSICAL PROPERTIES OF 95% In 2 O 3 + 5% SnO 2 /ns-Si HETEROSTRUCTURE PACS 68.37 Hk, Optical and electrical properties of 95% In2O3 + 5% SnO2/ns-Si heterostructures with films 6 and 12 nm in thickness deposited on a nanostructured silicon surface by the magnetron sputtering have been considered. It is shown that the 6-nm film is characterized by several peaks in the optical absorption spectrum, while the 12-nm film has no absorption peaks in the same spectral interval. The influence of the environment and the optical irradiation on the electrical properties of 95% In2O3 + 5% SnO2/ns-Si structures is determined. Their response to the gas environment is shown to be governed by the dielectric permittivity of an adsorbate. The results obtained can be used in the development of resistive gas sensors based on 95% In2O3 + 5% SnO2/ns-Si films.K e y w o r d s: current-voltage characteristics, absorption spectrum, thin films, transparent oxides.
The addition of scandium in dispenser cathodes as the monoxides is one of the way for increasing of their emissive property [I]. The researches of such type cathodes is very important because today they have the most attractive operational parameters in comparison with ordinary dispensed and oxide-coated cathodes. Now the role of scandium in improvement of parameters of cathodes has not been studied enough. For example, there are no information why the positive effect of scandium entering does not depend on the technological step of the cathodes formation. 12 10 s 6-5-4 -3 1 . , . , 0 10 20 30 40 50 60 70 V ''Za Fig. 1 I-V curves for the oxide-coated (I), ordinary (2). Sc-Ba (3) mspenser cathodes, 4the law "3R"The researches were carried out in UHV chamber and the pressure of residual gases did not exceed 5.10-9 torr. The structure of the cathodes surface was investigated by the Auger electron spectroscopy (AES). The measurement of emission properties of cathodes was made in a flat d i d e system in a pulse mode. The anode was the mdybdenum plate ( 2~2~0 . 2 nun.), which was heating to the high temperature by the electron impact. Spacing interval the cathodeanode was equal to 1 mm and has been carefully controlled. Pulse duration of the anodic voltage is 4 p, The amplitude of anodic voltage can change np to 5 kV. A work function of the samples was calculated by the method of a full current.The experiment has shown, that there is a close correlation between the level of emission of the Sc-Ba dispenser cathode and presence of the scandium components on its working surface.The behavior of currentvoltage (I-V) curves for the dispenser cathodes in the field of limitation of the anodic current by the space charge is not subject to the law "3/2" as it takes place in case of the oxide-coated cathode (see fig. 1).It allows to speak about thermo-field mechanism of the dispensed cathodes' emission; maybe the role of the scandium components in dispenser cathodes consist in the creation of the condition for increase of the field emission component in the anodic current, promoting increase of the quantity and change of the shape of the emitting centersthe crystallites of the rarely earth metals oxides. Probably, that another way of the influence of the scandium components on the field emission component in the anodic current is creation of the condition for increase the electric field penetration into the emitting centers on the cathode surface.
The effect of tungsten powder fineness and microstructure parameters of the tungsten skeleton on the emission of dispenser cathodes (DC) in the stages of degassing and high-temperature activation are studied. Quantitative analysis of the cathode surface microstructure is investigated. It is established that the work function of the DC after high-temperature activation does not depend upon the size of tungsten powder particles in the test range of fineness (average particle size 1.4-20 μm) and porosity of the tungsten skeleton (22 and 35%). The time for reaching the maximum DC activity increases with an increase in particle size and skeleton porosity. The highest emission uniformity is exhibited by cathodes with a uniform microstructure prepared from tungsten powder with an average size of 1 and 4 μm. It is shown that the DC emission capacity is connected with the marked three-dimensional structure of BaO − CaO at the cathode surface, and also monatomic films (Ba − O and Ba) and excess oxygen at the surface of the tungsten phase.
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