H. Hilal Kurt

Ionization effects and linear stability in a coaxial plasma device

AbstractA 2-D computer simulation of a coaxial plasma device depending on the conservation equations of electrons, ions and excited atoms together with the Poisson equation for a plasma gun is carried out. Some characteristics of the plasma focus device (PF) such as critical wave numbers ac and voltages Uc in the cases of various pressures Pare estimated in order to satisfy the necessary conditions of traveling particle densities (i.e. plasma patterns) via a linear analysis. Oscillatory solutions are characterized by a nonzero imaginary part of the growth rate

Townsend Instabilities in a Modified Discharge System With Coupled Narrow Gaps

\Im

Electrical Properties of ZnS and ZnSe Semiconductors in a Plasma-Semiconductor System

(σ) for all cases. The model also predicts the minimal voltage ranges of the system for certain pressure intervals.

Exploration of the Infrared Sensitivity for a ZnSe Electrode of an IR Image Converter

The stabilization of dc glow discharges in a dc plasma is studied experimentally in air and neon media functions of pressure p, interelectrode distances d, and diameter D of the cathode areas in the semiconductor gas discharge electronic devices (SGDED) with GaAs cathode. Comparison of current and discharge light emission (DLE) from SGDED are used for the determination of the stabilization under low- and atmospheric-pressure glow microdischarge conditions. It is found that uniform DLE can be generated in Ne up to atmosphere pressure different from the case in air under specific conditions. Apart from the homegeneous results, nonhomogeneous current-voltage characteristic forms are also observed for some parameter sets. The experimental results reveal different discharge behaviors in both gas media at atmospheric pressure.

Explorations of displacement and velocity nonlinearities and their effects to power of a magnetically-excited piezoelectric pendulum

Townsend-type discharge in a modified gas discharge cell with coupled narrow gaps between a high-resistivity semiconductor plate and two planar electrodes is experimentally studied in the range of gas pressure 28-352 torr for various interelectrode distances (d1 = 50 μm, d2 = 50 - 320 μm). The effect of various diameters on the photodetector area to the discharge (D = 9 - 12 - 15 mm) are considered as well. It is observed that Townsend discharge is unstable at low current densities for certain experimental parameters. The temporal dynamics of the current fluctuations is measured around I = 50 μA. Interactions of plasmas with surfaces and space charge effects in many cases are the main reason for the nonlinear effects in gas discharges with increasing current.

BIFURCATION ANALYSIS OF A RESISTOR-DOUBLE INDUCTOR AND DOUBLE DIODE CIRCUIT AND A COMPARISON WITH A RESISTOR-INDUCTOR-DIODE CIRCUIT IN PHASE SPACE AND PARAMETRICAL RESPONSES

The memory effect in the planar semiconductor gas discharge system at different pressures (15–760 Torr) and interelectrode distances (60–445 µm) was experimentally studied. The study was performed on the basis of current–voltage characteristic (CVC) measurements with a time lag of several hours of afterglow periods. The influence of the active space charge remaining from the previous discharge on the breakdown voltage (UB) has been analysed using the CVC method for different conductivities of semiconductor GaAs photocathode. CVC showed that even a measurement taken 96 h after the first breakdown was influenced by accumulated active particles deposited from the previous discharge. Such phenomena based on metastable atoms surviving from the previous discharge and recombined on the cathode to create initial electrons in the avalanche mechanism are shown to be fully consistent with CVC data for both pre-breakdown and post-breakdown regions. However, in the post-breakdown region pronounced negative differential conductivity was observed. Such nonlinear electrical property of GaAs is attributed to the existence of deep electronic defect called EL2 in the semiconductor cathode material. On the other hand, the CVC data for subsequent dates present a correlation of memory effect and hysteresis behaviour. The explanation for such a relation is based on the influence of long lived active charges on the electronic transport mechanism of semiconductor material.

Transport properties in semiconductor-gas discharge electronic devices

The objective of this study is to explore the electrical and optical characterization of zinc selenide (ZnSe) and zinc sulfide (ZnS) semiconductors as cathode materials of an Infrared image converter. The experiments and simulations have been performed for various converter parameters such as pressure, breakdown voltage, interelectrode distance and illumination. The plasma system has been excited by a dc source, and gas discharge phenomena has been determined under a wide atmospheric pressure range, p. The findings show that ZnS and ZnSe have similar electronic behavior in the image converter in general. The measured discharge currents vary for the two cathodes. In the simulations, the electron mobility, thermal velocity, 3D electron density, space and surface charge density, and mean electron energy have been explored in the Ar-filled converter. It has been proven that the two semiconductors exhibit different properties of discharge, in particular, the mobility of electrons, the ionization coefficients, the breakdown voltages UB, thermal velocities of electrons and surface charge densities. According to the experimental and theoretical findings, ZnSe shows better electrical and optical characteristics for the Ar-filled converter.

The Features of GaAs and GaP Semiconductor Cathodes in an Infrared Converter System

Significant improvement has been carried out in the field of the II–VI group semiconductor device technology. Semiconductors based on the II–VI group are attractive due to their alternative uses for thermal imaging systems and photonic applications. This study focuses on experimental work on the optical, electrical and structural characterization of an infrared (IR) photodetector zinc selenide (ZnSe). In addition, the IR sensitivity of the ZnSe has primarily been investigated by exploiting the IR responses of the material for various gas pressures, p, and interelectrode distances, d, in the IR converter. The experimental findings include the results of plasma current and plasma discharge emission under various illumination conditions in the IR region. The electron density distributions inside the gas discharge gap have also been simulated in two-dimensional media. Experimentally, the current–voltage, current–time, and discharge light emission plots are produced for a wide experimental parameter range. Consequently, the structural and optical properties have been studied through atomic force microscopy and Fourier-transform infrared spectroscopy techniques to obtain a comprehensive knowledge of the material.