摘要:

Computations using a one‐dimensional computer program have been performed to determine fragment mass distributions for exploding cylinders of HF‐1 steel. Experiments were performed to guide the computations. Nucleation and growth models were used to simulate the brittle fracture and shear band damage that occurred in the metal cylinders prior to complete fragmentation. Material input parameters for these models have been previously determined. Computations were performed for two heat treatments of HF‐1 steel. The calculated brittle crack and shear band distributions were converted to fragment mass distributions using one of the experimental fragment shapes. Based upon the experimental results, suggestions are made for future refinements in the area of fragmentation modeling.

ISSN:0021-8979    

DOI:10.1063/1.336140

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The interdiffusivity and chemical ordering in compositionally modulated (&Lgr;=20 to 40 A˚) amorphous Fe70Si30/Si thin films have been measured from the decay of the satellite intensities of the (000) x‐ray scattering peak during isothermal anneals in the temperature range 373–473 K. Diffusivities as low as 10−26to 10−25m2 s−1have been measured. A linear dependence ofD˜&Lgr;on 1/&Lgr;2has been observed, providing the evidence of chemical ordering in Fe‐Si alloy and leading to the determination of a critical wavelength.

ISSN:0021-8979    

DOI:10.1063/1.336141

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The solid‐phase reaction of a thin film and a substrate induced by a transient annealing in the solid phase is analyzed in detail. The technique is based on the scanning of a line‐shaped energy beam. At a given point on the sample the transient process can be considered equivalent to an isothermal one at an effective temperature for an effective time. Whatever the assumed reaction process is, it has an exponential dependence on the temperature; moreover, the real annealing time of the transient treatment is quite short so that the effective temperature can be chosen equal to the maximum value reached and the effective time can be computed by solving the heat equation numerically. The beam scanning induces a temperature gradient on the sample along the scanning direction so that each irradiated point is annealed at slightly different effective temperatures. In the present work the annealing temperatures range from 600 °C up to 1100 °C and the effective times from 0.7 to 1.5 sec, owing to the different experimental conditions. Such ranges make the transient annealing a powerful tool for the investigation of reaction processes on a time scale which is not accessible in a furnace treatment. As an application, the early stages of the reaction between a clean titanium film and a silicon substrate are described in the temperature range 700–900 °C. In this temperature range, the kinetics are first dominated by diffusion through the Ti‐rich silicides which are formed. This process, with presumably high activation energy and large preexponential factor, cannot be observed in standard furnace annealing where a continuous TiSi2layer is formed at the interface during the temperature rise time and the silicon supply is limited by the diffusion through this layer.

ISSN:0021-8979    

DOI:10.1063/1.336142

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Dielectrically isolated silicon was produced by anodically bonding together a pair of silicon wafers whose surfaces were covered with an electrically nonconductive micron layer of thermally grown oxide. Although anodic bonding normally requires a conductive oxide, anodic bonding works with nonconductive silicon oxide if the total layer of silicon oxide is less than ten microns thick. The time needed for the anodic bonding process decreases monotonically with temperature because the increase in the deformability of silicon oxide overcomes the decrease in the maximum permissible anodic bonding voltage with temperature. However, factors such as silicon degradation and electrode reactions at very high temperatures indicate that a compromise temperature range of 850–950 °C is best for the anodic bonding of silicon oxide. Bonding voltages of 30–50 V for times of about an hour produced the best bonding yields at these temperatures. Anodically bonded silicon wafers were examined with infrared and ultrasonic transmission microscopy for bond quality. Small scattered nonbonded zones comprising on the average 5% of the total wafer area were found in all wafers. These nonbonded zones were the result of dust particles, entrapped gas, and dimensional mismatches between multiple bonding fronts.

ISSN:0021-8979    

DOI:10.1063/1.336143

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Plasma‐deposited silicon nitride,a‐SiN:H, has been deposited at low ammonia‐to‐silane gas ratios. The nitrogen‐to‐silicon ratio in the film is proportional to the NH3/SiH4flow ratio in the reactor. The Si‐H peak in the infrared spectrum of thea‐SiN:H shifts to lower frequency as the N/Si of the film decreases. We use the random bonding model to calculate the average electronegativity that a Si‐H bond experiences for a particular N/Si ratio in the film. The measured Si‐H frequency correlates with the calculated electronegativities and agrees with a similar correlation of Si‐H obtained for molecules. For N/Si less than 0.27 we observe an additional peak at 650 cm−1that also appears in the spectrum of plasma‐deposited amorphous Si and is the Si‐H wagging vibration. The random bonding model predicts amorphous Si to be the predominant constituent for N/Si less than 0.27, in agreement with the infrared data.

ISSN:0021-8979    

DOI:10.1063/1.336116

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

High‐power beams (4–10 W/cm2) of Ti ions have been used to heat Fe and steel substrates to 600–800 °C during high fluence (5×1017/cm2) implantation. Auger sputter depth profiles find a stoichiometric TiC surface layer, about 100 nm deep, graded continuously into both Fe and steel substrates. Secondary ion mass spectrometry of Fe and steels implanted in13CO atmospheres indicate that the carbon originates from the bulk in carbon steels but from the atmosphere in Fe foils. Transmission electron microscopy reveals a continuous layer of fine‐grained (50–100 nm) TiC crystallites in a preferred Baker–Nutting orientation relationship with respect to underlying Fe grains. Abrasive‐wear measurements performed with diamond paste (1–5 &mgr;m) show the TiC layer on hardened M2 steel is 3–10 times more wear resistant than the substrate. Sliding‐wear studies find an extremely durable layer that reduces friction by up to 60%, and increases by 50% the contact‐stress threshold of M2 tool steel to boundary lubrication. The metallurgical processes responsible for the TiC layer will be discussed, and the advantages of this high‐temperature treatment will be presented.

ISSN:0021-8979    

DOI:10.1063/1.336117

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Arsenic segregation at polycrystalline silicon/silicon and polycrystalline silicon/silicon oxide interfaces was examined directly by transmission electron microscopy (TEM) and scanning transmission electron microscopy(STEM). Segregation occurring precisely at these interfaces was identified. A simple model was proposed based on arsenic segregation to structural units containing dangling bonds and consequent bond saturation. The removal of these dangling bonds will then play an important role in the electrical properties of these interfaces. Furthermore substitutional arsenic segregation at a degenerate level at these interfaces was also proposed. The subsequent dopant ionization and localized charges at the interfaces was discussed.

ISSN:0021-8979    

DOI:10.1063/1.336118

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Quantum‐mechanically coupled well systems consisting of two GaAs wells 30 A˚ thick separated by an Al0.5Ga0.5As barrier whose thickness was varied from 12 to 40 A˚ have been grown by metalorganic chemical vapor deposition. The photoluminescence spectra of these systems indicated the splitting of a degenerate single well state into a doublet state, a symmetrical state, and an antisymmetric state. The location of the spectrum peak and shoulders agreed well with the calculated energies using Dingle’s connection rule which assumes 85% conduction band offset and the continuous first derivative of the wave function across the AlGaAs/GaAs heterojunction. Two other connection rules were tried, but the agreement was worse.

ISSN:0021-8979    

DOI:10.1063/1.336119

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Energy level and concentration profile measurements of two deep hole traps in boron‐implanted, phosphorus‐doped silicon are reported. The traps are present following annealing at temperatures near 400 °C. The energy levels and emission cross sections of the two traps areEV+(0.671±0.005) eV, (1.7±0.4)×10−15cm2, andEV+(0.471±0.007) eV, (2.2±0.8)×10−16cm2. The concentration profiles of both traps are highly peaked at about 0.31 &mgr;m from the silicon surface, in good agreement with nuclear energy loss profile calculations.

ISSN:0021-8979    

DOI:10.1063/1.336120

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Systematic investigations of trapping centers parameters have been carried out on the complete series of GaSxSe1−xsolid solutions by using space‐charge‐limited‐current and thermally stimulated current measurements. Crystals have been grown from the vapor by means of the iodine‐assisted transport method by varying the sulphur percentagexin steps of 0.1. Electron mobility, resistivity, and electron concentration have been carried out at room temperature by means of the Van der Pauw method, with the current flowing along the layers. Three well‐defined electron traps have been found, the energy depth of which varies continuously from GaSe to GaS.

ISSN:0021-8979    

DOI:10.1063/1.336094

出版商:AIP    

年代:1985

数据来源: AIP