摘要:

In Sec. II of this work, we briefly recall the various ways of defining the diffusion coefficientDand discuss their identity in high‐field conditions and in very high frequency operations. In Sec. III, theoretical values obtained by the Monte Carlo method for high static field operations in Si and GaAs are reported and discussed. In Sec. IV, the variations of diffusion values with the operational frequency or with the ’’observation’’ or sample time are studied and tentatively explained.

ISSN:0021-8979    

DOI:10.1063/1.327713

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

High pressures were generated using a diamond indentor technique. The phase transition in silicon loaded in the [100] direction and silicon loaded in the [111] direction under high pressure was studied. From the behavior of electrical resistance of silicon loaded in the [100] direction, it was found that it becomes metallic at about 12.0 GPa in agreement with the previously reported results on silicon using different techniques. However, silicon loaded in the [111] direction becomes metallic at a lower pressure. The silicon transition is highly sensitive to the type of stress applied.

ISSN:0021-8979    

DOI:10.1063/1.327714

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The electrical characteristics of GaAs Schottky barrier diodes are investigated after fast‐neutron irradiation at fluences causing appreciable (≳75%) carrier removal. A significant change is seen in the forward current‐voltage (I‐V) characteristics, with one‐carrier space‐charge‐limited (SCL) current in the presence of distributed traps becoming the dominant conduction mechanism. Depending on preirradiation doping level and neutron fluence, both power law and exponential forwardI‐Vcharacteristics are obtained, signifying exponential and uniform trap distributions respectively. The trap parameters are evaluated from analysis ofI‐Vdata taken over a wide temperature range.

ISSN:0021-8979    

DOI:10.1063/1.327715

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The electron trapping and detrapping properties of As+‐implanted thermally grown SiO2layers incorporated into metal‐silicon dioxide‐silicon (MOS) structures have been studied. The samples were charged using avalanche injection from the silicon substrate or internal photoemission from either interface. The charge state of the MOS devices was investigated using capacitance‐vs‐voltage (C‐V) and photocurrent‐vs‐voltage (photoI‐V) measurements. After a 1×1013As+/cm2implant and a 1000 °C anneal in N2for 30 min, a dominant (in terms of trapping probability) trapping center with a capture cross section of (1–2) ×10−15cm2is found, together with various other centers with cross sections of (1–4) ×10−17, (2–5) ×10−16, and (0.4–1.6) ×10−14cm2, respectively. The sum of the trap densities for the various centers with cross sections in the range 10−15–10−16cm2is equal to 0.7–1 times the ion fluence, independent of ion energy (10–100 keV), avalanche injection current (5×10−11–5×10−10A), and oxide thickness (490–1430 A˚). The dominant trap density is proportional to the ion fluence over our experimental range (3×1012–1×1014As+/cm2). Increasing the anneal temperature from 600 to 1100 °C gradually decreases the electron trapping rate, without extensively changing the dominant‐trap parameters. The negative‐charge distribution centroid (measured with respect to the Al‐SiO2interface) is shown to be proportional to the ion energy but does not depend on trapped charge density (4×1011−1×1013cm−2), ion fluence (3×1012−1×1014cm−2), injection mechanism (avalanche injection or internal photoemission), oxide thickness (490–1430 A˚), anneal temperature (600–1100–°C), or ambient temperature (83–295 K). The charge centroids were found to be in excellent agreement with the experimentally determined (SIMS) ion distribution centroids, but systematically larger (up to 40%) than the values predicted by the theory of Lindhard, Scharff and Schio&slash;tt (LSS). It is shown that optical excitation removes the trapped negative charge from the trapping centers in a homogeneous way (i.e., with constant charge centroid). From the detrapping experiments, an effective photoionization cross section is determined as a function of photon energy with an absorption threshold of 3.3 eV. This is corroborated by a model which assumes that the electron trapping is related to the implanted arsenic ions, incorporated into the SiO2‐network at oxygen‐sites. Isothermal detrapping experiments (in the range 100–250 °C) and thermally stimulated current measurements are reported. Both experiments can be modeled by assuming a Gaussian trap distribution around a median thermal trap depthEm=1.2–1.3 eV with a standard deviation &Dgr;E=0.2 eV.

ISSN:0021-8979    

DOI:10.1063/1.327716

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Silicon epitaxial layers have been made with virtually any doping profile by combining molecular beam epitaxial growth with simultaneous ion implant doping. Arsenic ions (As+) accelerated to energies between 400 and 800 eV have shown a high sticking coefficient on the heated silicon surface. Growth conditions have been defined at which epitaxial films with bulk characteristics are obtained.

ISSN:0021-8979    

DOI:10.1063/1.327717

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Electron microscopy has been used to study very thin Nb‐Ge films sputtered‐deposited onto copper substrates. Micrographs and selected‐area electron‐diffraction patterns reveal an interface region between the substrate and the first A15 Nb3Ge to form. This interface consists of microcrystalline Nb‐N‐O and a two‐phase region consisting of Nb‐N‐O grains and an unidentifiable tetragonal Nb‐Ge phase. The A15 Nb3Ge grains which form later in the growth of the film exhibit the same grain size and shape as the Nb‐N‐O grains. From the results a model for the role of the interface in the initial formation of A15 Nb3Ge is proposed.

ISSN:0021-8979    

DOI:10.1063/1.327718

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The introduction of a small volume fraction of &sgr;‐phase MoRu particles into an otherwise amorphous superconducting matrix of composition (Mo0.6Ru0.4)80Si10B10is observed to result in substantial flux‐pinning interactions and an increase of the sampleTc. The critical current density in the presence of an externally applied field is increased by two to three orders of magnitude as compared to that of the amorphous matrix alone. The proximity effect explains the observed increase ofTcwhich results from the &sgr;‐phase precipitate particles having aTchigher than that of the amorphous matrix.

ISSN:0021-8979    

DOI:10.1063/1.327719

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The dependence of the upper critical field (Hc2) and the critical current density ( jc) on fluence has been measured up to 1.2×1019cm−2(E≳1 MeV) for V3Si bulk material irradiated with neutrons at ambient reactor temperatures. Dislocation loops are identified by TEM as the part of the radiation induced defects responsible forjc. Using these results it is shown that the increase injcof irradiatedA15 superconductors with grain boundaries is not due to the raisedHc2but corresponds to the radiation induced dislocation loops. The volume pinning force of these defects has the same temperature dependence but quite a different field dependence than the grain boundary pinning. By superposing the dislocation loop pinning on the grain boundary pinning we obtain an enhancement ofjcwhich increases with increasing field in excellent agreement with the observed field dependent increase ofjcin neutron irradiatedA15 superconductors. Deviations from the experimental values for high‐jcmaterials and consequences for the high field mechanism of Kramer’s model are discussed.

ISSN:0021-8979    

DOI:10.1063/1.327720

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Measurements of sound velocity and attenuation changes at the spin‐reorientation region are reported. The measurements were carried out with a magnetic field applied along theaaxis of the orthorhombic crystal. A cw ultrasonic interferometer, which is described here in detail, was employed for these measurements. The observed velocity shifts are satisfactorily accounted for using a phenomenological model with a quadratic magnetoelastic term. The effect of magnetic domains on the attenuation peaks is also discussed.

ISSN:0021-8979    

DOI:10.1063/1.327721

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The correlation between electrical and mechanical losses in ferroelectric ceramics has been investigated theoretically and experimentally. The theoretical derivation is based on the assumption that both loss types are induced by 90° domain walls moving under the influence of electrical or mechanical fields. A proportionality between both loss types is found. The factor of proportionality includes material constants such as spontaneous polarization and striction, permittivity, and elastic compliance, but is independent of the specific energy dissipation mechanism of a moving domain wall. In a compositional series of differently doped PLZT ceramics with a broad range of losses the theoretically derived relations have been checked experimentally. Good agreement between the experimental and theoretical results was found.

ISSN:0021-8979    

DOI:10.1063/1.327722

出版商:AIP    

年代:1980

数据来源: AIP