摘要:

A significant increase of the XeF laser efficiency has been observed in an electron beam pumped device. Mixtures of NF3, Xe, and Ne at 300 K and a density of 3 amagat were pumped at a rate of 300 kW/cm3with a 500‐ns pulse. This deposited 150 J/l into the laser cavity. Measurements were made for various mixtures and output couplings. The highest intrinsic laser efficiency (defined as the ratio of laser output energy toe‐beam energy deposited into the gas) observed was 4.7%.

ISSN:0003-6951    

DOI:10.1063/1.98774

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We investigated theoretically the efficiency enhancement of discharge‐pumped vacuum‐ultraviolet F2lasers using He/F2mixtures in terms of the laser kinetics. As a result, the high mixture pressure is found to be essential for the high‐efficiency operation. Intrinsic efficiency in excess of 1% may be obtainable. Using a 6‐atm mixture of He/F2=98.5/0.15%, intrinsic efficiency of 1.5% may be obtainable with a specific output energy of 2.6 J/l.

ISSN:0003-6951    

DOI:10.1063/1.98775

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Experiments have been carried out to demonstrate and study the interfacing of silicon sensors to silicon devices which represent first stage elements of an artificial neural network. Sensor outputs (network inputs) are photocurrents associated with infrared, visible, or ultraviolet light. First stage linear coding of input current into the pulse rate of a stereotypical neuronlike spiketrain output has been achieved with a dynamic range of more than 106. For 1 pA inputs, the estimated noise referred to input is 10 fA. Network elements are shown to obey equations of the same form as equations which occur in nonlinear neural network models recently analyzed by Hopfield [Proc. Natl. Acad. Sci.81, 3088 (1984)] and previously studied by Sejnowski [J. Math. Biology4, 303 (1977)].

ISSN:0003-6951    

DOI:10.1063/1.98776

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The current model for hydrocarbon formation upon the interaction of energetic hydrogen ions with graphite assumes a reaction of adsorbed hydrogen with carbon surface atoms requiring a temperature of 800–900 K. This model is strongly questioned by results of hydrocarbon formation from a layered13C/12C sample and by desorption measurements after room‐temperature implantation. The formation of13CD4and12CD4is monitored during deuterium bombardment of a pyrolytic graphite sample covered with a layer of 200 A˚ of13C. Only for ion energies corresponding to ranges smaller than 200 A˚13CD4dominates, while at higher energies only12CD4is found. The methane is thus formed at the end of ion range rather than in a surface reaction of back‐diffusing ions. Desorption experiments using a slow temperature range after room‐temperature implantation show the release of CD4prior to D2, thus indicating a diffusion‐limited release of CD4already formed during the implantation.

ISSN:0003-6951    

DOI:10.1063/1.98777

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We propose a mechanism for the self‐limiting effect which occurs in the low‐pressure chemical vapor deposition of tungsten. When W is deposited by silicon reduction of tungsten hexafluoride WF6, the deposition suddenly ceases at an early stage. No such effect is observed in the deposition of Mo using analogous chemistry. We believe the self‐limiting effect is due to the formation of nonvolatile lower fluorides of tungsten. Our hypothesis is supported by secondary ion mass spectroscopy studies which indicate the presence of fluorine (≊3%) in W films, whereas in Mo films the concentration of fluorine is an order of magnitude lower.

ISSN:0003-6951    

DOI:10.1063/1.98778

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A possibility for ferroelectric twinning of 60° domains existing in the phase‐I crystallite of poly(vinylidene fluoride) has been examined by the use of an x‐ray diffraction method. Interdomain interference causes anomalous splitting of the calculated diffraction peaks. Anomalous changes in the profiles are observed for the crystallites in a film under electric fields up to 120 MV/m, and can be explained in terms of the twin structure.

ISSN:0003-6951    

DOI:10.1063/1.98779

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The quality of crystal structure of CdTe(100) overlayers grown by molecular beam epitaxy on GaAs(100) substrates has been studied by x‐ray diffraction and Rutherford backscattering/channeling methods. The depth distribution of displaced atoms in the overlayers with thicknesses varying from 1.6 to 3.1 &mgr;m shows that a defect‐free surface is obtained when the film thickness is about 2 &mgr;m.

ISSN:0003-6951    

DOI:10.1063/1.98780

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We report measurements of the rate of growth of Ga and Sn clusters on clean Si surfaces. The volume rate of growth is linearly dependent on time, consistent with an Ostwald ripening mechanism for island growth. Activation energies for clustering, extracted from the temperature dependence, are shown to be sensitive to the underlying surface structure. This thermodynamical approach to the description of cluster formation is generally useful in determining the operational parameters and ultimate limits to heterostructure growth.

ISSN:0003-6951    

DOI:10.1063/1.98781

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Direct evidence of substitutional doping of nitrogen in ion beam deposited hydrogenated amorphous silicon, from analysis of infrared spectra and Si‐2pcore level shape measured with x‐ray photoelectron spectroscopy (XPS), is presented. For the first time the XPS technique has been used to deduce the upper limit for substitutional solid solubility of the impurity.

ISSN:0003-6951    

DOI:10.1063/1.98782

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

A new technique of growing nitrided oxide at low temperatures has been developed. Fluorine‐enhanced thermal oxidation of silicon in O2+NF3at temperatures below 800 °C and subsequent annealing of the fluorinated oxide in pure ammonia gas at the same temperature result in the formation of nitrided oxide. The dielectric breakdown strength of the fluorinated oxide is improved by the nitridation. Also, the nitrided oxide acts as a protective layer against alkaline ion contamination.

ISSN:0003-6951    

DOI:10.1063/1.98783

出版商:AIP    

年代:1987

数据来源: AIP