摘要:

The response of unbiased tantalum capacitors to ionizing radiation has been measured for both small and large dose rates. The results have been analyzed using a two‐trap model for the Ta2O5dielectric and an equivalent circuit model is presented. A significant reduction in the response of slug capacitors can be achieved by connecting two capacitors in the back‐to‐back or inverted‐parallel configuration.

ISSN:0021-8979    

DOI:10.1063/1.1662385

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Migration velocities of fission‐gas bubbles and solid fission‐product inclusions in uranium‐plutonium mixed oxide under irradiation have been obtained. Trails behind migrating second‐phase particles are observed upon etching a polished metallographic section from an irradiated fuel pin. It was determined from the microstructure and the reactor power history that these trails were produced during one reactor power cycle of known duration. Particle velocity was computed from the observed trail length and the duration of the power cycle. Velocities varied between 1 and 10 Å/sec for particles with diameters between 1 and 10 &mgr;. The temperature was between 1585 and 1850°C, and the average temperature gradient was[inverted lazy s]5400∘C/cm. In all cases, the particles moved in the direction of increasing temperature. The measured velocities for both bubbles and solid inclusions are shown to be in agreement with the calculated velocities based on a surface‐diffusion mechanism withQs*, the surface heat of transport, equal to 100 kcal/mole.

ISSN:0021-8979    

DOI:10.1063/1.1662296

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The continuing development of microelectronic circuits toward greater complexity has stimulated interest in new materials and processes compatible with the currently known silicon device technology. Tungsten has been considered as the first‐level conductor for a multilevel structure due to its relatively low electrical resistivity, its thermal expansion coefficient which matches fairly well to that of silicon, its demonstrated good adherence to the dielectrics of interest, and its ability to withstand high‐temperature processing. The present work is a part of a study of the dependence of the properties of low‐voltage triode sputtered tungsten films upon deposition parameters. The effects on internal stress and resistivity of tungsten films are reported here. Tungsten films have been deposited with thicknesses from 1000 to 15000 Å and with resistivities as low as 8 &mgr;&ohgr; cm (1.55 of the bulk). These films were deposited at 1 &mgr; argon pressure at rates in the range of 50–400 Å/min. The electrical resistivity was observed to increase with increasing deposition rate, decreasing film thickness, and decreasing substrate temperature. The impurity concentration was found to be small by electron microprobe and ion probe techniques and, hence, did not completely account for the observed changes in resistivity. The internal stress was determined by two x‐ray methods: (i) precision lattice parameter determination and (ii) a two‐exposure technique. In general, depending upon the deposition conditions, tensile or compressive stresses of the order 109−1010dyn/cm2were observed. The compressive stress was observed to increase with decreasing film thickness and increasing deposition rate. Increasing the substrate temperature caused the compressive stress to decrease to zero and become tensile. This changeover temperature was observed to be 650°C for a 5000‐Å film deposited at 115 Å/min. The observed results are discussed briefly in terms of microstructure changes.

ISSN:0021-8979    

DOI:10.1063/1.1662297

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Measurements of the pressure and temperature dependence of the second‐order elastic constants of LiBr and LiCl single crystals have been made by the ultrasonic interferometric technique at temperatures from 220 to 340°K, and pressures up to 3.5 kbar. The adiabatic elastic constants (in units of 1011dyn/cm2) and the isothermal pressure derivative of the adiabatic constants (unitless) at 295°K are as follows (whereC00=(1/2)[C11+C12+ 2C44]): For LiBr,C11= 3.959,C44= 1.909,C00= 4.843,dC11/dP= 10.42,dC44/dP= 1.67,dC00/dP= 8.27. For LiCl,C11= 4.963,C44= 2.503,C00= 6.124,dC11/dP= 10.42,dC44/dP= 1.70,dC00dP= 8.34. The three measured quantitiesC11,C44, andC00are given, respectively by&rgr;&ngr;112,&rgr;&ngr;442, and&rgr;&ngr;002, where &rgr; is the density and thev's are the sound velocities at a specific pressure and temperature. The Deybe temperatures are calculated from the second‐order elastic constants at four temperatures on the interval 220–340°K.

ISSN:0021-8979    

DOI:10.1063/1.1662298

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The single‐crystal elastic moduli of V3Si have been measured for hydrostatic pressures to 2.5 Kbar and temperatures from 13.5 to 296°K to determine the influence of volume decreases on the anomalousC′ = (C11−C12)/2 shear mode softening in this A‐15 material. Moduli values were obtained by measuring the cw resonance frequencies of three thin specimens that did not undergo at room pressure the well‐known structural transformation exhibited by some V3Si crystals near 20°K. The measurements show all moduli to be linear in pressure.dBs/dP, which is nearly constant at 4 for temperatures down to 40°K, is near 7 at 13.5°K.dC′/dPvaries from unity at 296°K to −5 at 13.5°K, vanishing at near 90°K. These results are compared with those obtained earlier for largeC′‐type shear loads. The possibility of inducing a structural transformation with hydrostatic pressure is discussed.

ISSN:0021-8979    

DOI:10.1063/1.1662299

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

We have applied high electric fields to films of SiO2thermally grown on silicon. The films were not metallized and high fields were obtained by depositing charge directly onto the surface from a corona discharge in air. After terminating the discharge the surface potential was measured, using a vibrating capacitor plate mounted near the free surface. Both the surface potential and the current through the oxide decrease with time, rapidly at first and then more slowly. When the current level has dropped to 10−9A/cm2the surface potential is changing by only a few percent per minute and the field across the oxide has nearly a steady value,Es. We measureEsand compare it with the dielectric breakdown fields that have been reported by others. We distinguish between the operational quantityEsand the breakdown field as usually reported since there appears to be no destruction of the sample in our experiments. We find thatEsis independent of the conductivity type and the doping level of the silicon, even when it is degenerate. When the free surface is charged negatively,Esis about twice as large as it is for positive charging.

ISSN:0021-8979    

DOI:10.1063/1.1662300

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The elastic fields of line‐force couples have been shown to be applicable to the description of dislocation core fields. The conventional anisotropic elastic theory of line defects is extended to include such couples. Explicit results are presented for cases of high‐crystallographic symmetry for which the results can be expressed in simple analytical form.

ISSN:0021-8979    

DOI:10.1063/1.1662301

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A theory of the flow stress of metal crystals with high concentrations of solute atoms is developed with the help of the theory of stationary random functions. The dislocation model used to calculate the critical flow stress is a Frank‐Read source. Under the assumption that at high concentrations of solute atoms the dislocation will interact principally with groups of atoms spread out along the dislocation line rather than with single atoms, no thermal activation can take place. This results in a temperature‐independent critical flow stress, which is indeed observed in solid‐solution crystals as the so‐called plateau stress. The theory requires that the plateau stress increase with solute concentration proportional to [C(1−C)]1/2and, at fixed concentrations, be proportional to the magnitude of the interaction between solute atoms and dislocation.

ISSN:0021-8979    

DOI:10.1063/1.1662302

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A previously developed theory of the critical flow stress due to high concentrations of solute atoms is further specified by the calculation of the interaction between solute atoms and dislocations due to a size and modulus difference between solute and matrix atoms. It turns out that the first‐order interaction due to the size difference cancels identically. Therefore, only second‐order effects are responsible for the critical flow stress due to high concentrations of solute atoms. This is demonstrated by the agreement between the calculated stress and the available experimental data on Ag‐, Au‐, and Cu‐based binary alloys. The length of the dislocation segment that moves as a whole was determined from these data to be aboutL=3×10−4cm for all alloys, a value that is in agreement with the assumption that the length of the dislocation segment should be comparable to the distance between pinning points of a Frank‐Read source. This long dislocation segment does not allow for thermal activation and therefore is the basis for the temperature independence of the stress component, due to high concentrations of solute atoms.

ISSN:0021-8979    

DOI:10.1063/1.1662303

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A study has been made of thin electron‐beam‐evaporated yttrium oxide films. The oxide structure was found to be polycrystalline, with grain sizes of the order of 100 Å, by electron microscopy. dc conduction measurements were made and a Frenkel‐type of conduction mechanism was proposed. Step response and bridge dielectric loss measurements were compared. Internal photoemission was used to obtain metal/oxide barrier heights of 3.14 and 3.72 eV in an Al‐Y2O3‐Al structure.

ISSN:0021-8979    

DOI:10.1063/1.1662304

出版商:AIP    

年代:1973

数据来源: AIP