M. Özer

Stability and current behaviour in semiconductor gas discharge electronic devices

Breakdown and range of stable discharge glow in a homogeneous dc electric field are studied at various distances d between the electrodes and different inner diameters D (5, 9, 12, 18 and 22 mm) of GaAs semiconductor cathode areas. The current–voltage characteristics of the gas discharge system have been studied in a wide range of pressure p (16–760 Torr), interelectrode distances d (10 µm–5 mm) and conductivities of the GaAs cathode. The initiation of electrical breakdown as a result of secondary electron emission from the semiconductor cathode in low gas pressure is presented in this paper. In a planar gas discharge cell with diameters much larger than an interelectrode distance, the effects of different parameters (overvoltage, electrode separation, diameter and conductivities of the GaAs cathode, gas pressure, glow current, etc) on electrical breakdown and spatial stabilization of the current have been studied. The distributed resistance of photosensitive semiconductor cathode and the impact of the ionizing component of the discharge plasma on the control of the stable operation of a planar gas discharge system at atmospheric pressure are also investigated. Through spatially uniform irradiation of the semiconductor cathode, non-stationary states which are non-homogeneous can be generated in a system. The loss of stability is primarily due to the formation of a space charge of positive ions in the discharge gap which changes the discharge from the Townsend to the glow type.

Electro-optical properties of porous zeolite cathode in the gas discharge electronic devices for plasma light source applications

The stable dc air cold plasma is investigated experimentally functions of pressure p (8–760 Torr), electrode gaps d (50–250 µm), and diameters (9–22 mm) of the cathode areas in the gas discharge electronic devices (GDED) with nanoporous zeolite cathode (ZC). It is found that the current density and plasma emission (PE) intensity increase if the amplitude of the applied voltage reaches given threshold. Moreover, uniform PE inside the ZCs develops from the surface and can be generated in air up to atmospheric pressure (AP). The effect of various diameter of the ZC area on the gas breakdown is also considered. It is shown that breakdown voltage UB is reduced significantly for the larger diameters of the ZC area. Because of the very small d in our GDED, the behavior of charged particles in the electric field is described with the dc Townsend breakdown theory, depending upon the pressure range.

Plasma Generation in a Gas Discharge System With Irradiated Porous Zeolite

The influence of pressure [from atmospheric pressure (AP) to 10-2 torr] and β-radiation (1-kGy β doses) on the current-voltage characteristics, charge trapping effects in porous surfaces, and breakdown voltage (UB) in AP microplasmas are discussed for the first time. This is due to the zeolite cathode (ZC) exposure to β-radiation resulting in substantial decreases in the UB, discharge currents, and conductivity due to increase in porosity of the material. Results indicated the enhancement of plasma light intensity and electron emission from the ZC surface with the release of trapped electrons which are captured by the defect centers following β-irradiation. The porosity of the ZC and radiation defect centers has a significant influence on the electrical and optical properties of the devices manufactured on its base.

The concentration of currents on the artificial surface inhomogeneities of semiconducting cathodes in ionization cells

The possibility of locally increasing the gas-discharge light emission for a given photosensitivity of a planar GaAs semiconductor cathode has been studied. The maximum emittance of gas-discharge light for given values of the residual pressure, the feeding voltage and the intensity of external illumination is determined by the photosensitivity of the semiconductor cathode. In a system with inserted metallic current concentrators the local density of gas-discharge light exceeds the density of uniform gas-discharge light in the ionization system as many times as the working area of the semiconductor cathode exceeds the total area of the current concentrators. The filamentation was primarily due to the formation of a space charge of positive ions in the discharge gap which changed the discharge from the Townsend to the glow type. The assessment of the image formation is then based on analysis of the discharge light emission, visualized by taking a photograph through the transparent anode plate. Means of locally increasing the light emission and improving the working characteristics are proposed.

Peculiarities of the charge transport in the gas discharge electronic device with irradiated porous zeolite

The influence of pressure and β-radiation (1 kGy β doses) on the charge transport mechanism, charge trapping effects in porous zeolite surfaces and breakdown voltage (UB) are discussed in atmospheric microplasmas for the first time. This is due to exposure the zeolite cathode (ZC) to β-radiation resulting in substantial decreases in the UB, discharge currents and conductivity due to increase in porosity of the material. Results indicated that the enhancement of plasma light intensity and electron emission from the ZC surface with the release of trapped electrons which are captured by the defect centers following β-irradiation. The porosity of the ZC and radiation defect centers has significant influence on the charge transport of the microstructure and optical properties of the devices manufactured on its base. Thus, we confirm that the ZCir is a suitable cathode material for plasma light source, field emission displays, energy storage devices and low power gas discharge electronic devices.

Enhancement of the Sensitivity of an Ionization Type Semiconductor Photographic System

AbstractThe investigation of the sensitivity of a ionization-type semiconductor photographic system with higli-resistivity cathode of large diameter (40-60 mm) is described. A photosensitive GaAs cathode with a resistivity ofiO6 Qcm, has been studied. With a gas discharge gap formed by a dielectric separator with the thickness ranging from 40 to 60 pm, a discharge has been formed in air at pressures from 20-760 Torr. The cathode was irradiated on the back with light in a particular wavelength range that was used to control the photoconductivity of the material. The semiconductor material was found to stabilize the discharge. A local change of the resistance inhomogeneity is determined by a local change of discharge radiation intensity. The assessment of the resistance distribution is then based on analysis of the discharge radiation, visualized by a photograph taken through the Sn02 film. Means of increasing the sensitivity and improving the working characteristics are proposed.

Field-Enhanced Transport Processes in the Gas Discharge System With Porous Zeolite

The pressure-driven charge transport processes in microdischarges with a nanoporous zeolite cathode (ZC) are examined according to enhanced effect of electric field. The distributed resistance of the ZC and the impact of the ionizing component of the plasma on the control of the stable operation of a gas discharge electronic device at atmospheric pressure (AP) are investigated for the first time. The contribution of charge carriers in conductivity varied in a wide pressure range up to AP air microplasmas in postbreakdown mode is discussed. The results show that the ionic transport predominated in low electric field while electronic transport predominated in the opposite conditions. Moreover, uniform gas discharge light emission inside the ZCs develops from the surface and can be generated in air up to AP.