摘要:

Magnetic‐field penetration is characterized in a current conducting plasma between planar electrodes used as a plasma opening switch [G. G. Spanjers, E. J. Yadlowsky, R. C. Hazelton, and J. J. Moschella, J. Appl. Phys.77, 3657 (1995)]. The experiment is performed in a regime where Hall effects [Amnon Fruchtman, Phys. Fluids B3, 1908 (1991)] are predicted to describe the current channel migration. Measurements of the magnetic‐field penetration in two cases with opposite electrical polarity indicate that the Hall effects are not the dominate process. A one‐dimensional resistive magnetohydrodynamic model is used to show that current channels in agreement with those measured can be predicted through a coupling of a plasma snowplow motion with resistive diffusion. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361106

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The plasma characteristics of a new arc mode on carbon referred to as the ‘‘stationary cathodic arc’’ are reported. Particularly, optical emission spectroscopy, probe and ion energy distribution measurements are used to compare the properties of the stationary arc with the normal ‘‘random cathodic arc’’ on carbon. The measurements revealed that the plasma properties of both arc modes are similar. In addition, we have correlated the plasma characteristics to the film properties. Carbon films deposited using the stationary arc were found to have a surface particle density equivalent to those deposited using the filtered cathodic vacuum arc. The macro‐particle free films were found to be highly tetrahedral and compressively stressed. Both thesp3fraction and stress values were strongly dependent on the ion energy with maximum values of 85% and 9.4 GPa, respectively, occurring at ≊50 eV. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.362656

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Gliding arc discharges are the subject of renewed interest in applications to a variety of chemical reactions. A gliding arc is created by a weakly ionized gas flowing between two electrodes. The reacting gas introduced at the base blows the arc column upwards. These devices are used in industry mainly for decontamination and general gas treatment. Either ac or dc can be used as the power supply. In order to analyze gliding arc motion, a multi‐shot camera was designed with a very short exposure time. A high‐voltage dc arc is studied and a simple theoretical model is given which enables determination of the conduction radius and axial temperature. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361188

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The conversion efficiency of spectral emission from laser‐irradiated solid targets was investigated for short wavelength source development. The plasma brightness was quantified using absolutely calibrated detectors for 20 materials and spectra were obtained between 50 and 200 A˚. Laser parameters such as wavelength, pulse length, intensity, and spot size were systematically varied to establish a comprehensive database for source optimization. Qualitative differences in the underlying dominant emission features as a function of atomic number and laser wavelength were observed that accounted for the relatively high spectral conversion efficiencies produced. In the specific case of Sn, a conversion efficiency greater than 0.8%/eV has been observed in the technologically important region of &lgr;=134.0 A˚ using a laser intensity of 1–2×1011W/cm2.

ISSN:0021-8979    

DOI:10.1063/1.361149

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Optical emission characteristics of vacuum ultraviolet (VUV) light from large area (≊50 cm2) electrical gas discharges were investigated in order to develop a windowless photochemical vapor deposition (photo‐CVD) reactor and to prepare silicon‐based thin films at low temperature (≊300 °C). The electrodes configuration is such that the ions impact upon the substrate is strongly minimized. Among the four investigated gases (He, Ar, H2, and N2), argon is the best candidate because it provides the more monochromatic VUV light (121.5 nm) which corresponds well to the maximum of the silane and disilane photoabsorption curves. Emission spectra of the photo‐CVD induced in argon–silane mixtures clearly give evidence of the formation of molecular hydrogen and of Si* excited atoms and, indirectly, the part played by low hydrogen content radicals (namely, SiH). The deposition rate of hydrogenated amorphous silicon films obtained by windowless photo‐CVD using this strong emission band at 121.5 nm is proportional to the SiH4and Si2H6contents in argon up to 20% and 6%, respectively. The deposited films present a low average hydrogen concentration value of less than 10% and smooth surfaces (<20 A˚) for silicon hydride gas partial pressures lower than 15%. Over this value, the deposits become very rough (≳500 A˚), due to SiHnclusters formation in the gas phase. Finally, low temperature growth of silicon nitride films by the VUV dissociation of silane and/or disilane–nitrogen mixtures is demonstrated. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361150

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The secondary electron emission coefficient is evaluated for electron impact on anode, cathode, and electrically floating plasma‐facing surfaces. Two energy and angle distribution functions for electron impact on a plasma‐facing surface are derived and different relations for the secondary electron emission coefficient which functionally depend on energy and angle are integrated over the distributions. One integration is in closed form and provides a parametric expression for the secondary electron emission coefficient of a plasma‐facing surface. The other integrations are carried out numerically. Evaluation of the secondary electron emission coefficient for a variety of commonly‐used plasma‐facing materials shows that its value is near or above unity over a significant range of plasma temperatures. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361151

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Inductively coupled plasma (ICP) reactors are being developed for low gas pressure (<10s mTorr) and high plasma density ([e]≳1011cm−3) microelectronics fabrication. In these reactors, the plasma is generated by the inductively coupled electric field while an additional radio frequency (rf) bias is applied to the substrate. One of the goals of these systems is to independently control the magnitude of the ion flux by the inductively coupled power deposition, and the acceleration of ions into the substrate by the rf bias. In high plasma density reactors the width of the sheath above the wafer may be sufficiently thin that ions are able to traverse it in approximately 1 rf cycle, even at 13.56 MHz. As a consequence, the ion energy distribution (IED) may have a shape typically associated with lower frequency operation in conventional reactive ion etching tools. In this paper, we present results from a computer model for the IED incident on the wafer in ICP etching reactors. We find that in the parameter space of interest, the shape of the IED depends both on the amplitude of the rf bias and on the ICP power. The former quantity determines the average energy of the IED. The latter quantity controls the width of the sheath, the transit time of ions across the sheath and hence the width of the IED. In general, high ICP powers (thinner sheaths) produce wider IEDs. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361152

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The ionization dynamics (iron ion and neutral atom absolute line densities) produced in the KrF excimer laser ablation of iron and a laser‐ablation‐assisted plasma discharge (LAAPD) ion source have been characterized by a new dye‐laser‐based resonant ultraviolet interferometry diagnostic. The ablated material is produced by focusing a KrF excimer laser (248 nm,<1 J, 40 ns) onto a solid iron target. The LAAPD ion source configuration employs an annular electrode in front of the grounded target. Simultaneous to the excimer laser striking the target, a three‐element, inductor–capacitor, pulse‐forming network is discharged across the electrode–target gap. Peak discharge parameters of 3600 V and 680 A yield a peak discharge power of 1.3 MW through the laser ablation plume. Iron neutral atom line densities are measured by tuning the dye laser near the 271.903 nm (a 5D–y 5P0) ground‐state and 273.358 nm (a 5F–w 5D0) excited‐state transitions while iron singly ionized line densities are measured using the 263.105 nm (a 6D–z 6D0) and 273.955 nm (a 4D–z 4D0) excited‐state transitions. The line density, expansion velocity, temperature, and number of each species have been characterized as a function of time for laser ablation and the LAAPD. Data analysis assuming a Boltzmann distribution yields the ionization ratio (ni/nn) and indicates that the laser ablation plume is substantially ionized. With application of the discharge, neutral iron atoms are depleted from the plume, while iron ions are created, resulting in a factor of ∼5 increase in the plume ionization ratio. Species temperatures range from 0.5 to 1.0 eV while ion line densities in excess of 1×1015cm−2have been measured, implying peak ion densities of ∼1×1015cm−3. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361153

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The evolution of the microstructure during the crystallization of amorphous Fe80B20alloys has been investigated by small‐angle neutron scattering (SANS) and transmission electron microscopy (TEM). Samples with an increasing degree of crystallization were obtained by performing different isothermal heat treatments on melt spun amorphous ribbons. The TEM measurements indicate that the crystallization occurs by nucleation and growth of Fe3B spherulites which include small finely divided &agr;‐Fe acicular crystallites. On the basis of the TEM results a model for the quantitative analysis of the SANS data has been formulated. The results show that, due to the high growth velocity of the nucleated particles, only their number increases with increasing annealing time, while their size and internal structure is not dependent on the degree of crystallization. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361154

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The profile of oxygen atoms diffused from SiO2films into Si substrates as interstitials during high temperature annealing has been studied by infrared absorption spectroscopy using18O as a tracer. The measured absorbance profile in the substrates can be explained in terms of a simple diffusion model in which the SiO2layer acts as a reservoir of O and there is no energy barrier to diffusion across the Si/SiO2interface. The driving force for diffusion is the temperature‐dependent solubility of oxygen interstitials in the Si. We find evidence both for the outdiffusion of oxygen from the SiO2layer into the Si during extended annealing and retrodiffusion back into the SiO2layer during temperature ramp down. From etchback profiling data on O interstitials we are able to revise the Arrhenius law for O diffusion in Si and obtain an activation energy of 2.57 eV and a preexponential factor of 0.22 cm2 s−1. It is further suggested that there is evidence for enhancement of the O diffusion coefficient in Si at low temperatures resulting from the presence of foreign species such as H. These observations are important in understanding the structure of a thermally grown SiO2/Si interface and annealing‐induced degradation in Si‐based devices. ©1996 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.361155

出版商:AIP    

年代:1996

数据来源: AIP