Electrode Gap Spacing Research Articles

Effects of Gas Dilution on the Growth and Properties of Glow Discharge a-Ge:H

ABSTRACTWe compare films of a-Ge:H deposited by plasma enhanced chemical vapor deposition (PECVD) using GeFLi diluted with H2, He and Ar. The nominal deposition conditions used were those which have produced high quality a-Ge:H with H2 dilution. Using H2 and He as diluents, three studies were done in which the parameters of substrate temperature, diluent gas flow and electrode gap spacing were independently varied. The photoelectronic properties of the films made with He dilution were quite good, although never better than those made with H2 dilution. The overall results indicated that for our nominal conditions hydrogen plays an important and crucial role in producing high quality films, and we believe that this role is mainly to reduce the probability of germane radical incorporation. In contrast to He and H2 dilution, dilution with Ar produced films with much poorer microstructure and a photoresponse two orders of magnitude lower. We attribute this to polymerization of the germane radicals which led to observed dust particles and a reduction in ion bombardment of the growing film.

Breakdown of transformer oil

Some of the factors affecting the dielectric strength of transformer oil are investigated. These factors include the stabilization phenomenon, oil and electrode pretreatment, the effect of oil velocity, the effect of a capacitance parallel to the test cell, and the effects of electrode area and gap spacing. The experimental apparatus and procedure are described, and the results are presented for each of the above factors. Suggestions for future research are offered. >

Nature of convection-stabilized DC arcs in dual-flow nozzle geometry. I. The cold flow field and DC arc characteristics

An experimental investigation of the steady-state low current air arcs in a dual-flow nozzle system is presented. The cold flow field with no arc was determined for various nozzle geometries, i.e. two- and three-dimensional and orifice nozzles, and nozzle pressure ratios. Supersonic flow separation and oblique and detached shock waves were observed in the flow field. Using a finite-element computer program, the Mach number contours were determined in the flow field for various nozzle-gap spacings and pressure ratios. In addition, the DC arc voltage and current measurements were made for an electrode gap spacing of approximately=5.5 cm and current levels of I approximately=25, 50, and 100 A for the three nozzle geometries. The arc voltage and arc power increased rapidly as the flow speed increased from zero to sonic velocity at the nozzle throat. The shock waves in the converging-diverging nozzles resulted in a decrease in the overall resistance by about 15%. >

Propagation of transverse bulk and surface acoustic waves in LiNbO/sub 3/ variable time-delay devices

Experimental measurements are reported on voltage-controlled acoustic time-delay lines operating at 1 GHz in the nearly pure shear-horizontal (S-H) mode in 38 degrees rotated Y-cut LiNbO(3). The high-acoustic velocity (4800 m/s) in conjunction with the large electroacoustic effect exhibited by this orientation allows high-frequency operation and optimum time-delay tuning sensitivity with a planar, single surface, device geometry. The authors demonstrate fractional time delay of 0.3x10(-6) V(-1 ) for surface electrodes that produce an in-plane E-field. However, the simultaneous excitation and propagation of both a leaky surface-acoustic wave (LSAW) and surface skimming bulk wave (SSBW), both as (nearly pure) S-H waves in these devices, seriously restricts the extent to which it is possible to maximize the time delay modulation sensitivity by reducing electrode gap spacing as done in similar SAW devices. The LSAW and surface-skimming body wave (SSBW) propagate at nearly the same velocity on a free surface, and perturbation of their velocity and relative attenuation rates by surface electrodes causes pronounced interference effects between the two modes for some device geometries.

Flashover between Closely Spaced Electrodes on an Insulating Surface

The dc breakdown field strength of copper electrodes separated by an epoxy-glass insulator in air shows a -0.04 (1/25) power dependence on the length of the electrode-insulator-gas triple junction in the range 10-2-102 cm. The breakdown field strength was found to have an electrode-gap spacing power dependence of -0.45 in the range ~ 10-3-~10-1 cm. This is a similar power factor to both that of the Paschen curve for air at atmospheric pressure and for dc-and microsecond-pulsed discharges over insulating surfaces in vacuum. These results may be applicable to various surface discharge switches and surface discharge plasma sources.

Low-Aberration Einzel Lens for a Focused-Ion-Beam System

A low-aberration electrostatic einzel lens for a finely-focused ion-beam system has been developed. The system design goal was a total aberration of 0.1 µm under the following conditions: beam half-angle, 2.5 mrad; working distance, 43 mm; beam energy spread, 10 eV; accelerating energy, 30 keV. The total aberration was reduced by using the following two guidelines: First, the einzel lens operated in the accelerating mode provides low chromatic and spherical aberrations. Second, spherical aberration is further reduced by enlarging the electrode gap spacing and central electrode bore. The design method for the accelerating mode lens to determine the lens dimensions which provide a low electrode voltage for the total aberration required is described.

Estimation of localized state distribution profiles in undoped and doped a-Si:H by measuring space-charge-limited current

The characteristic temperature which characterizes the localized states of amorphous silicon-hydrogen ( a-Si:H) has been obtained by measuring space-charge-limited (SCL) currents in planar structure gap cells for undoped and nitrogen doped films. The SCL current is confirmed by measuring the critical voltage as a function of electrode gap spacing. The characteristic temperature obtained is 1060 ± 150 K for undoped a-Si:H films. The value of nitrogen doped film prepared under the condition of 0.4% N 2 gas partial pressure becomes less than 400 K.

Arc motion reversal in crossed electric and magnetic fields in an argon atomosphere from 200 to 900 Torr

Steady retrograde motion of an argon arc discharge has been obtained at pressures up to 760 Torr, arc currents to 600 A, magnetic field strengths to 6500 G, and electrode spacing of 1.65 cm. This is at a significantly higher current and electrode gap spacing than employed for previously reported retrograde movement of an arc discharge. Erratic retrograde motion at 900 Torr was also observed. Photographs of the arc show the typical vacuum environment retrograde arc shape at pressures above atmospheric.