摘要:

Some results from a systematic study on the impedance matching conditions and on the longitudinal power distributions in planar rf discharges forCO2lasers, are given. They show that both plasma impedance and voltage distribution are different in cw and pulsed discharge modes revealing the importance of parameters such as the interelectrode temperature distribution and the local gas density and composition. These parameters have to be taken into account when designing matching networks and voltage smoothing schemes. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119985

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The electron emission from a field emission trigger unit was matched to the requirements for the simultaneous ignition of all channels in a radial multichannel pseudospark switch for a large parameter range of the pseudospark discharge. In such trigger unit the electrons are extracted from the surface of a high-&egr; material by field emission after applying a pulsed voltage. Electron emission occurs in a pressure range from 1–50 Pa, where the pseudospark discharge is operated. The access to low working gas pressures (<10 Pa) using such trigger unit allows for achieving high hold-off voltages. The ignition of the pseudospark discharge was investigated by means of high speed photography and by a parallel observation of the electron beam of a single discharge channel, which occurs in hollow-cathode phase. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.119986

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The electrical switching properties of electrically conductive polymer composites are studied at high current densities. It is shown that the switching properties at high current densities are substantially different from those at low current densities which depend on a positive temperature coefficient of resistance effect. This type of switching appears to be a general feature of conductor-filled polymer composite materials and should lead to a new class of fast, current-limiting devices for power circuits. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119987

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Simulations of charging and profile evolution during etching of high aspect ratio polysilicon gates in typical high-density plasmas containing heavy ions (e.g.,BCl3+,Cl2+), predict a reduction in charging and notching when lighter ions (e.g.,He+) are added. The reduction occurs because of the influence of the ion mass on the ratioRof the ion sheath transit time to the rf period, which determines the spread in the ion energy distribution at the wafer. The effect is most pronounced whenR⩽0.1–0.2 for light ions and, simultaneously,R⩾0.6 for heavy ions; then, more light ions arrive at the patterned structure with low energies, where they help decrease localized charging. When the rf bias frequency is reduced so thatR⩽0.3 for all ions, the effect disappears. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119988

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Monte Carlo simulations of electron tunneling through a 3 nm gate oxide during etching of dense patterns of gate electrodes in uniform high-density plasmas reveal two current transients, which occur: (a) when the open area clears, and (b) when the polysilicon lines just become disconnected at the bottom of trenches. The first charging transient is fast (controlled by charging) and may be followed by a steady-state current which lasts until the lines get disconnected. The second charging transient lasts longer; the magnitude of the tunneling current generally decreases as the sloped polysilicon sidewalls become straighter. Most of the damage occurs at the edge gate when the open areas are covered by field oxide; however, the edge gate suffers no damage when the 3 nm oxide extends into the open areas. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119989

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Spherical carbon onions are generated by irradiating graphitic carbon soot withNe+ions of 3 MeV energy. Under continued irradiation, a transformation of their cores to cubic diamond crystals is observed. In comparison to earlier electron irradiation experiments, the yield of diamond is much higher. The output of the irradiation experiment is characterized by electron microscopy and electron energy loss spectroscopy. Knock-on displacements of carbon atoms byNe+ions are assumed to be responsible for a self-compression of the onions, leading to the nucleation of diamond in their cores. The increased diamond yield is explained by the higher displacement cross-section, the higher energy transfer, and the higher total beam current on the specimen. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119990

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Al/AlN multilayered thin films with periodic thickness &lgr; less than 24 nm were developed by ion beam assisted deposition. A considerably small surface roughness comparable to that of the silicon substrate and much smaller than those of both monolithic Al and AlN films was obtained. Over the investigated range of &lgr;, all the multilayers are harder than the homogeneous AlN film, and a significant hardness enhancement by a factor of ∼2 over that of the AlN film was observed in the multilayer with &lgr; of 6 nm. Moreover, the hardness enhancement is not at the expense of the multilayer toughness, with the multilayer Al/AlN films showing improved plasticity as compared with the AlN film. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119752

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The x-ray interference technique has been applied to evaluate the structural changes of high temperature grown chemical vapor deposited (CVD)SiO2film under several post annealing conditions. In annealing above 800 °C inO2ambient, a thermal oxide growth has been found at the CVDSiO2/Siinterface, and its precise thicknesses have been determined. The estimated diffusion coefficient of the oxidant in CVD film was about three times larger compared to that of thermal oxide. A threshold voltage shift in the oxide was found to strongly correlate to the thickness of the thermal oxide rather than to thermal modifications of the CVDSiO2itself. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119753

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A nondestructive methodology is reported to obtain the grain size distribution ofSnO2nanoparticles, with grain sizes below 10 nm, using low-frequency Raman scattering measurements. The position of the main low-frequency Raman bands depends on the grain size and can be correlated with the spheroidal vibration modes of a spherical elastic body with “rigid” boundaries. The grain size distributions deduced from Raman scattering are in agreement with the direct measurements from transmission electron microscopy, especially for the smaller grains. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119754

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have observed domain walls in ferroelectricLiTaO3crystals using a polarization and phase sensitive near-field scanning optical microscope. The strain induced birefringence was used to observe the domain walls. The domain walls are measured to be 1 &mgr;m wide and show a variation of strain along the domain walls probably due to defects. These measurements allow an estimate of the birefringence at the domain wall of6×10−5and associated shear strain of4×10−5.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119755

出版商:AIP    

年代:1997

数据来源: AIP