摘要:

In this paper we describe the performance of CO laser power delivery over an As‐S glass fiber, which has a fluorinated ethylene propylene resin (Teflon FEP) cladding, as well as kinetics of melting break off of the fiber on power delivery. The maximum fiber power output of 15.3 W with an intensity of 12.2 kW/cm2was obtained by using a fiber whose core diameter was 400 &mgr;m and which was not forced cooled. Maximum transmission power was restricted by the thermal damage occurring at the end of the fiber. Kinetics of this thermal damage were investigated by measuring the temperature on the cladding surface and by estimating temperature distribution in the fiber through calculations. The localized heat input at the end of the fiber was estimated at approximately ten times higher than other portions of the fiber.

ISSN:0021-8979    

DOI:10.1063/1.340177

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A study of optical aging in bulk and extruded fibers of thallium bromo‐iodide (TlBr‐TlI) is presented. A variety of techniques including secondary ion mass spectrometry (SIMS), powder neutron and x‐ray diffraction, infrared spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy are used to probe the chemical and structural properties of both pristine and aged material. High concentration levels of a hydrogen bearing impurity have been detected by SIMS and neutron scattering in aged TlBr‐TlI, and have been shown to be localized in the surface layers of fibers as well as bulk samples. We present EPR evidence which indicates that the hydrogen bearing impurity is water.

ISSN:0021-8979    

DOI:10.1063/1.340178

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We have developed a technique to measure the amount of gas adsorbed on a porous solid using ultrasonic velocity measurements. This allows us to determine both the specific surface area and the porosity of the material. The technique has several advantages over conventional methods of determining absorption isotherms. No calibrated volumes or delicate balances are needed; the only measurements being of gas pressure and sound velocity. There is no need to know the mass of the sample or the dead volume of its container. Continuous and automatic measurements are possible, both during adsorption and desorption. We have demonstrated the usefulness and accuracy of this technique for two samples with very different surface areas (about 100 and 3 m2/g). In both cases, the results agree well with conventional volumetric measurements.

ISSN:0021-8979    

DOI:10.1063/1.340179

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The electron energy distribution in electron beam (ebeam) excited Ar/Kr and Ne/Xe gas mixtures is examined in detail. The binary rare‐gas mixtures are similar to those used in excimer lasers. Cooling processes for the secondary electrons generated in the gas mixture plasma by theebeam are calculated using a reduced Boltzmann equation in which elastic and electron‐electron collisions for electron energy distributions above the first excitation threshold of the rare gas are ignored. During the calculations for the Ar/Kr and Ne/Xe mixtures, all electron‐related reactions and the interaction between the two different rare gases in the mixture are simultaneously considered. The high‐energy secondary electrons produce a steady‐state distribution within a very short time; however, it is found that the distribution is not Maxwellian.Wvalues [eV/electron‐ion pair] and yields of rare‐gas excited states calculated from the steady‐state high‐energy electron distribution show a dependence on the mixture composition, especially for mixtures with low concentrations of the minor rare gas. This implies that the practice in excimer kinetics models of using theWvalues determined from pure rare gases is not entirely accurate.

ISSN:0021-8979    

DOI:10.1063/1.340180

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A beam diode was operated successfully at a pressure as high as 10−1–10−2Torr of gases (He, H2, Ne, N2, CO2, and SF6). Each gas had its optimum pressurepmat which electron beam currents were higher in peak values than those for conventional in‐vacuum operation by a factor of 1.5 or more. A relationshippm×&sgr;1.18H=const. was obtained where &sgr;His the total ionization cross section in gases at some hundred keV. A model was proposed for such operations, and those high‐pressure operations are preferable to the conventional if one needs higher currents.

ISSN:0021-8979    

DOI:10.1063/1.340181

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Visible‐UV spectral emissions from electron beam (700 kV, 12 kA, 50 ns) generated neon plasmas have been investigated over a wide pressure range (0.1–100 Torr) with and without axial magnetic guide field. The Ne I–III line emissions were viewed perpendicular to the beam propagation; attention was focused on a time delay of the onset of the emission with respect to the beam front arrival in the field of view, and on correlations of the subsequent intensity evolution with that of the beam and net (beam plus plasma) currents. The observations are interpreted as direct confirmation of the major processes for gas ionization and excitation that occur depending on the gas pressure and magnetic guide field.

ISSN:0021-8979    

DOI:10.1063/1.340182

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The radiolysis of vacuum‐deposited thin films of cadmium chloride on silicon substrates has been studied in the energy range from 1 to 5 keV. Phase‐locked mass spectrometry was used for theinsitumonitoring of the evolution of the decomposition products, chlorine and cadmium, as a function of substrate temperature, current density, film thickness, and beam energy, for pure and doped films. Ellipsometric thickness and refractive index measurements, and scanning electron microscope examination of the morphology of irradiated films were carried out. The decomposition kinetics have been analyzed in terms of a model in which a fraction of the radiation‐generated electron‐hole pairs participate in the thermally activated decomposition reaction sequence at the film surface. A potential lithographic scheme has been established, in which decomposition patterns generated onto the films are transferred onto the SiO2underlayer by reactive ion etching, with a resolution approximately equal to the film grain size.

ISSN:0021-8979    

DOI:10.1063/1.340183

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Short‐range ordering and its kinetics in the structural relaxation of an amorphous Fe32Ni36Cr14P12B6alloy are studied by measurement of electrical resistance. When the specimens are annealed below 250 °C, the resistance rises and its temperature coefficient (TCR) decreases, while the resistance is reduced and the TCR increases when annealed above 250 °C. This fact is analyzed through the change of structure factor using Nagel’s approach for amorphous metals based on the extended Ziman theory. This analysis indicates that the structural relaxation can be classified into two types of short‐range rearrangement of atoms; a chemical short‐range ordering (CSRO) and a topological short‐range ordering (TSRO). Consequently, it can be concluded that the structure factorS(K) atK=2kFincreases when CSRO is formed, whereas it decreases in the progress of TSRO and the cause is attributable to the difference in the second moment of the atomic‐level internal stress distribution ⟨p2⟩ in both states. Furthermore, the kinetics in the formation of the CSRO are analyzed on the assumption that the relaxation time obeys logarithmic normal distribution and from there the distribution width and the mean activation energy are determined to be 3.4 and 1.83 eV, respectively.

ISSN:0021-8979    

DOI:10.1063/1.340184

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

An undoped, semi‐insulating GaAs crystal grown by the horizontal Bridgman method has been characterized by axial and radial resistivity and mobility measurements. Due to lower thermal gradients, defect densities for wafers from this crystal are less than those observed for liquid‐encapsulated Czochralski crystals. Cathodoluminescent images display uniform luminescent intensity around dislocated regions indicating an absence of impurity gettering in these areas. Concentrations of neutral EL2, a native defect and principal deep donor in undoped GaAs, are reported for seed, middle, and tail‐end wafers. The distribution of EL2 over the area of each wafer is shown. Wafers were also implanted with29Si and furnace annealed to form shallownlayers. Capacitance‐voltage profiles demonstrate reproducible peak carrier concentrations and penetration depths.

ISSN:0021-8979    

DOI:10.1063/1.340185

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Rapid thermal annealing with a lamp furnace and conventional furnace annealing have been applied to InP ⟨100⟩ implanted with Si ions of 40 and 350 keV and doses of 1013–1015cm−2. After examination of different capping layers, phosphorus silica glass was chosen. Sheet carrier concentration, Hall mobility, and carrier‐concentration depth profiles were measured. A time of 10 s at 800 °C is sufficient to activate the dopants. Rutherford backscattering channeling measurements show the damage and the recrystallization due to different annealing procedures. To optimize the annealing of the damage, a relatively long time for the heat treatment is necessary which, however, results in enhanced diffusion of the dopants.

ISSN:0021-8979    

DOI:10.1063/1.340186

出版商:AIP    

年代:1988

数据来源: AIP