摘要:

CuPt‐type ordering in off‐stoichiometric III‐V semiconductor alloys has been investigated by a Monte Carlo method based on an Ising‐like crystal growth model for the layer‐by‐layer stacking on a (001) substrate. (110) Fourier power spectra of the atom configurations thus obtained exhibit superlattice spots due to the CuPt ordering. In the (11¯0) spectra, satellite reflections arise, flanking the fundamental lattice spots of the zinc‐blende structure and their intensity increases with the progress of ordering. The results are in good agreement with the experimental results previously obtained by transmission electron microscopy. The calculated atomic arrangement confirmed that the compositional modulation is the cause of the satellite reflections along the [110] direction. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358760

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Rapid thermal annealing (RTA) of Sn‐implanted InP has been investigated with a variety of analytical techniques including electrical measurements, Rutherford backscattering spectrometry, transmission electron microscopy and secondary‐ion‐mass spectrometry. RTA is shown to yield high electrical activation with negligible dopant diffusion. Incomplete electrical activation can result from dopant/defect complexes, native defect compensation, nonstoichiometry and dopant precipitation where the relative contribution of a given factor is dependent on both ion dose and annealing temperature. P coimplantation is shown to increase electrical activation through an increase in the number of ionized donors via a decrease in the number of dopant/defect complexes (in contrast to lattice site switching characteristic of dopant amphoteric character). ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358761

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new theory of nonspecular x‐ray scattering from layered systems with random rough interfaces based on the distorted‐wave Born approximation is presented. Calculations of the diffuse scattering from a single gold layer and two W/Si multilayer mirrors has been carried out. The theory explains the existence of maxima and minima in the angular distribution of diffusely scattered intensity resulting from standing‐wave‐enhanced scattering and other dynamical effects. The influence of the mutual correlation between individual interface profiles on x‐ray scattering is discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358762

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Line‐focus beam acoustic microscopy has been used to study changes in the elastic constants of GaAs during amorphization produced by implantation with Si+ions at liquid‐nitrogen temperature. The distribution of amorphous material was determined by Rutherford backscattering and channeling. Values ofc11andc44were estimated by fitting theoretical curves to the measured angular dispersion of surface acoustic waves in the (001) plane. The implanted material was modeled as a statically stressed anisotropic layer on an unmodified GaAs substrate. The values ofc11andc44were found to decrease with increasing ion fluence. At the highest fluence the implanted region was completely amorphous, and it was observed that the softening ofc44(41%) was significantly greater than that ofc11(17%). ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358763

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The nucleation and emission of dislocations from the crack tip under mode II loading are analyzed by the molecular‐dynamics method in which the Finnis–Sinclair potential has been used. A suitable atom lattice configuration is employed to allow one to fully analyze the nucleation, emission, dissociation, and pileup of the dislocations. The calculated results show that although the pure mode II loading is applied, the crack tip generally exhibits a combined mode. The stress distributions before the dislocation emission are in agreement with the elasticity solution, but are not after the emission. The critical stress intensity factor corresponding to the dislocation nucleationKIIeis dependent on the loading rateK˙II. The separations of a pair of partial dislocations and the full dislocations are also dependent on the loading rate. When the first partial dislocation is blocked, a pileup of dislocations can be set up. It is also found that the dislocation can move at subsonic wave speed (less than the shear wave speed) or at transonic speed (greater than the shear wave speed but less than the longitudinal wave speed) depending on the loading rate, but at the longitudinal wave speed which just corresponds toK˙II=1.15 MPa &sqrt;m/ps for copper, the atom lattice breaks down. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358764

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The codiffusion of As and B implanted in Si at high doses (1×1016cm−2) and with energies corresponding to the same projected range has been investigated at 900 and 1000 °C on the basis of dopant and carrier profile measurements. The comparison of the codiffusion data with the corresponding ones obtained by the diffusion of each element alone revealed some anomalous effects which can be explained by assuming the formation of neutral donor–acceptor pairs. These complexes are mobile with a diffusion coefficientDpair=17 exp(−4/kT) cm2/s, very close to the diffusion coefficient of As in intrinsic Si. Electrons are the majority carriers in the region where both dopants are present at high densities. On the basis of these features, a diffusion model that takes pairing into account is presented. A simulation program including this model allows one to foresee the anomalous phenomena occurring in the high‐concentration codiffusion of donors and acceptors in Si and in general shows a good agreement with experimental profiles. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358765

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Experimental results presented here show that at elevated temperatures (about 500 °C) silver can be mobile on tin oxide, as well as other metal oxide surfaces. Because the migrating species seems to be Ag+both diffusion and electrically assisted migration occurs. This movement is made visible in the form of tiny silver droplets on the glass surface by the presence of methanol vapor mixed in air. Without oxygen no migration occurs at all. It is clear that the movement requires a continuous or dynamic conversion of silver ions to silver oxide and back again, through the presence of both oxidizing and reducing agents. We show how it is possible to measure the diffusion constant and the electrical mobility constant by an appropriate analysis of the time evolution of a circular front of silver droplets measured with a video camera connected to a microscope zoom lens. Typical values on a roughened glass surface at 500 °C are for mobility, 42±13×10−6cm2/V s, and for diffusion 12±6×10−6cm2/s. Similar values for the electrical mobility on a smooth tin oxide surface have been measured. At this temperature diffusion on pure silica or even Pyrex glass powder is very slow, but the diffusion constant for MgO or CaO powder, annealed onto a sandblasted glass surface, is about 10−4cm2/s. These oxides may be responsible for the movement seen on soda glass surfaces. The activation energy is about 4 eV and seems related to the work function of silver metal. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358766

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence (PL) measurements were performed in order to investigate the carbon impurity effects on the intermixing behavior of GaAs/AlAs multiple quantum wells (MQWs) grown by molecular‐beam epitaxy. The GaAs/AlAs MQWs were annealed with a carbon source in a furnace annealing system. The PL spectra show that the magnitude of the intermixing of Al and Ga induced by thermal annealing in GaAs/AlAs MQWs increases with depth. This behavior is not in agreement with the intermixing mechanism considering vacancy injection of the surface. The nonuniformity of the intermixing as a function of the depth originated from the carbon impurities which were injected during thermal treatment. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358767

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A novel charge sensing technique, based on monitoring donor defects in near‐interfacial Si by electron spin resonance (ESR), has been applied to measure positive charge in buried oxide (BOX) layers of separation by implantation of oxygen material. This positive charge is introduced into the BOX layer by annealing in hydrogen in the temperature range 450–700 °C. Standard capacitance‐voltage (C‐V) analysis of the areal BOX‐charge densities was used as a crucial test for this ESR‐based method, yielding good agreement between the two techniques. Photoinjection of charges, optical excitation, andC‐Vand ESR etchback experiments have been performed on BOX layers subsequent to the hydrogen charging treatment leading to additional information on location, nature, and stability of the hydrogen‐induced positive centers. The results show that these centers are very stable (not even affected by electron injection) and that they are located near the two Si/BOX interfaces (within a layer of ≤20 nm). ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359571

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A series of thin CoCrPt layered structures has been studied with a view to understanding the nature and extent of any interactions present, both within and between the various constituent layers. In this investigation, we have utilized the principal remanence curves and their derivatives to characterize the bulk magnetic properties of the samples. In addition, we have employed a low energy broad beam Kaufman‐type ion source to sputter etch some of the layers, enabling unambiguous determination of the reversal fields of the various constituent layers. For each layered sample the magnetic layer grown on the thick Cr underlayer has the highest in‐plane coercivity. The second layer grown on a 100 A˚ Cr spacer has the next largest coercivity. All additional layers reverse at the same applied field strength. The coercivity of the layers is also insensitive to thickness reduction from 200 A˚downto80 A˚. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.358768

出版商:AIP    

年代:1995

数据来源: AIP