摘要:

Epitaxial growth of Fe(211) was achieved at a room temperature on MgO(110) with a dc facing targets sputtering system. The epitaxial relation was confirmed by electron diffraction: ⟨111⟩ in the Fe(211) plane is parallel to ⟨110⟩ in the MgO(110) plane with a 6:5 coincident site lattice. Crystallographic and magnetic properties could be controlled by changing the rf power of substrate bias and substrate temperature. The magnetocrystalline anisotropy energy for Fe(211) was calculated and compared with experimental results. The film deposited at 400 °C with 10 W of rf bias had a small stress and showed almost theoretical behavior in a torque measurement. The difference in the in‐plane anisotropy energy between the film and bulk was attributed to the effect of uniaxial anisotropy energy.

ISSN:0021-8979    

DOI:10.1063/1.354367

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Two‐dimensional reactive‐flow simulations of a hot‐filament chemical‐vapor‐deposition system were carried out. The set of coupled partial differential equations maintaining steady‐state conservation of mass, momentum, energy, and chemical species was numerically solved with set boundary conditions to obtain spatial distributions of the gas temperature, fluid velocity, and partial pressures of the chemical species. From the obtained temperature distribution, it is shown that most of the source gas is not heated to the level of the filament temperature. This is due to the friction between the fluid and the filament, so that the gas velocity around the filament is greatly decreased. The species diffusion makes a uniform species distribution between the filament and the substrate; in particular, atomic hydrogen diffuses broadly, suppressing the formation of gaseous C2−species. However, the product distribution among H, H2, CH3, and CH4is not influenced by the effect of diffusion, since the reaction H+CH4&rlarr2;H2+CH3is in partial equilibrium with the superequilibrium of H atoms; in other words, the plug‐flow assumption reported in the literature is valid for the product distribution among those species. The numerical results are compared with a previous deposition study for a wide variety of deposition parameters. It was found that the CH3concentration agreed well with the deposition rate in terms of the variation in the deposition parameters. This finding supports CH3being a growth species in the CH4‐H2hot‐filament system.

ISSN:0021-8979    

DOI:10.1063/1.354368

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The reactivation kinetics of hydrogen‐passivated Mg acceptors in InP have been studied by annealing experiments carried out with different reverse biases. It is shown using a new analysis that the actual dissociation energy of the Mg‐H complexes can be estimated even without applying a sufficient reverse bias to overcome retrapping of H at the dopant site. The dissociation process follows a first‐order kinetics and the dissociation frequency and activation energy were estimated at various depths ranging from the surface up to 0.5 &mgr;m using an empirical analysis of the experimental data. A bias‐independent dissociation energy of 1.40±0.08 eV was obtained when estimated at the surface. An apparently higher dissociation energy results when calculated in the bulk. This overestimation is pronounced for low‐bias anneals and is explained as a result of retrapping. The concentration profile data is consistent with the positively charged state of the diffusing H inp‐InP.

ISSN:0021-8979    

DOI:10.1063/1.354369

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The photochromic effect of thin amorphous WO3films, i.e., the coloration upon exposing the sample to ultraviolet light, has been investigated by means of optically excited surface plasmons. Due to the high sensitivity of this technique, it was possible to investigate the dynamics of this effect on a scale as short as seconds. Our results demonstrate the dominant role of oxygen during the coloration and bleaching processes. We found clear evidence of an oxygen exchange between the sample and the ambient atmosphere during the photochromic process, which is at variance with the widely accepted double charge injection model. The coloration rate shows the same wavelength dependence as that of the creation rate of electron‐hole pairs formed by optical excitation. The results can be explained by the light‐induced decomposition of the incorporated water.

ISSN:0021-8979    

DOI:10.1063/1.354370

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The low‐frequency resistance noise of proton‐irradiatedn‐GaAs epitaxial layers was studied at temperatures from 77 to 300 K. Two types of 1/f noise were identified from the temperature dependence of the 1/f noise parameter &agr;. One type of 1/f noise that is dominating at high temperatures seems to be of intrinsic origin related to lattice phonon scattering. The other dominating one at lower temperatures is, then, of extrinsic origin induced by the irradiation. The extrinsic type of 1/f noise is consistent with the quantum ‘‘local‐interference’’ effect and can reasonably be described by the Dutta–Dimon–Horn model [P. Dutta and P. M. Horn, Rev. Mod. Phys.53, 497 (1981)].

ISSN:0021-8979    

DOI:10.1063/1.355288

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Hydrogenated amorphous silicon (a‐Si:H) films have been deposited at high growth rates by increasing the rf power density while the optoelectronic quality of the films has been concurrently taken care of by controlling powder formation due to gas‐phase polymerization in the plasma. This has been achieved by heating the cathode together with the anode in the capacitive coupling arrangement and keeping the cathode temperature close to that of the anode. This, together with hydrogen dilution of the source gas, has been used to control powder formation in the silane discharge. The films have been evaluated by optical and infrared vibrational spectroscopy, dark conductivity, secondary photoconductivity, and internal quantum efficiency measurements.

ISSN:0021-8979    

DOI:10.1063/1.354371

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

The properties of high‐resistivity InP with resistivity up to 107&OHgr; cm, obtained by thermal diffusion of Cu at 800 °C for over 20 h into undoped andp‐type InP samples, are investigated. Hall‐effect measurements showed that the compensation mechanism in the slowly cooled sample is different from that in the quickly cooled samples. Photoluminescence was quenched in the quickly cooled samples when annealed at 350 °C and the anneal temperature at which the sample resistivity and carrier mobility reached the maximum. It is shown that the electrical compensation in the slowly cooled sample could be understood by a simple deep‐level compensation model. However, the semi‐insulating behavior of the quickly cooled samples appears to be consistent with an internal Schottky depletion model associated with the Cu precipitates. The photoluminescence quenching is due to the Cu precipitates acting as effective nonradiative recombination centers.

ISSN:0021-8979    

DOI:10.1063/1.354372

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Iron pyrite thin films prepared by flash evaporation of pyrite powder have been annealed at different temperatures in a sulfur atmosphere. We present some results on the influence of the annealing temperature (from 250 to 450 °C) on the optical and electrical properties of three groups of samples with different thicknesses (&bartil;0.3, 0.6, and 1 &mgr;m, respectively). Sulfuration temperature has a clear influence on the optical absorption and electrical resistivity of the films, with some differences in their behavior depending on the film thickness. In light of the available present knowledge of pyrite thin films, interpretation of the obtained results is difficult, it suggests that the shape of the optical absorption curves (and their absorption edge) at low photon energies is determined by the density of point defects, which decreases on increasing the annealing temperature. On the other hand, the electrical resistivity seems to be influenced by both the film grain size and point defect density.

ISSN:0021-8979    

DOI:10.1063/1.354373

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

A quantitative relationship has been experimentally determined correlation the resolution degradation ofp‐type coaxial high‐purity germanium detectors to the concentration of residual hole‐trapping point defects. Detector diameters ranged from 48 to 65 mm, and the average electric‐field strength was 1500 V/cm. The concept of a ‘‘standard level’’ is proposed, which originates in the similar capture kinetics of many commonly observed residual acceptors in high‐purity germanium. A method for calculating the electric‐field dependence of hole capture is presented and used to compare the data reported here with published modeling results parameterized by the mean‐free‐drift length. Good general agreement is found.

ISSN:0021-8979    

DOI:10.1063/1.354374

出版商:AIP    

年代:1993

数据来源: AIP

摘要:

Electron scattering rates due to interaction with interface phonon modes in semiconductor quantum‐well structures in a quantizing magnetic field are studied. Numerical results for scattering rates in GaAs/GaAlAs quantum wells show oscillatory behavior with magnetic field. The scattering rate due to interface phonon modes is found to decrease with the increase of well width in contrast to that seen with bulk confined phonons.  

ISSN:0021-8979    

DOI:10.1063/1.355312

出版商:AIP    

年代:1993

数据来源: AIP