摘要:

A scanning tunneling microscope in ultrahigh vacuum has been used to investigate the growth, morphology, and surface atomic structure of ultrathin titanium silicide films on Si(111) substrates. Microstructural considerations have been used to identify various stages of the silicide growth. Atomic resolution images of a titanium silicide crystallite facet, formed at 850 °C, have been identified as a 2×2 silicon termination of a C54‐TiSi2(010) surface. Possible epitaxial silicide/silicon relationships are provided. Theoretical consideration has been given to the interatomic bonding in the C54‐TiSi2lattice and the dangling bond density of ideally terminated silicide planes has been calculated. The highly reconstructed atomically flat surface of a large crystallite, formed at 1200 °C, has been assigned as a C54‐TiSi2(311) plane giving the epitaxial relation C54‐TiSi2(311)∥Si(111). The presence of pairs and linear chains of defects, with common orientations, is attributed to the decomposition of a diatomic gas on the facet, producing sites of preferential adsorption on the silicide surface. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.359747

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A recently developed model for simulating the dynamic behavior of silicate materials is applied to the loading and unloading properties of granite. Four time‐resolved wave profile measurements on granite are presented and used to supplement Hugoniot data to constrain the model. This model is based on a dynamic process‐dependent description of phase mixing. In the solid–solid mixed‐phase region, the loading states are determined from a simple two‐parameter constraint equation which relates the mass fraction of the high pressure phase &lgr; to the Gibbs free‐energy difference between the phases &Dgr;G. On release, the reverse phase transition is modeled as a two‐stage transition with each stage described by a two‐parameter equation with the same form as the loading equation. In all four of the simulations, the loading behavior of the shock‐wave experiment is well represented. For three of the experiments the release behavior is accurately simulated up to the point at which the measured interface speed reaches its first minimum. For the remaining experiment the simulation matches only the earliest release behavior and then rapidly deviates from the measured data.

ISSN:0021-8979    

DOI:10.1063/1.359748

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Existing data on then–ptype conversion of semi‐insulating GaAs during high temperature (1100–1200 °C) anneals are fit using a previously developed model in which EL2 is identified as the native defect AsGaVGa. In this model EL2 dissociates into the acceptor VGaand the donor AsGa. The latter defect then rapidly captures a divacancy to form the electrically neutral complex AsGaVAsVGa. The decrease in EL2 concentration, then–ptype conversion of GaAs, and the subsequent increase in hole concentration as the annealing temperature is increased are correlated in the model. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359749

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A series of optical transitions between higher conduction subbands and higher heavy‐hole subbands have been observed between 77 K and room temperature in photocurrent spectra ofp‐i‐nphotodiodes including 5‐nm‐wide InGaAs/InAlAs multi‐quantum wells. The quadratic dependence of the transition energy on the heavy‐hole quantum number,l=1,2 and 3, has been clarified for each conduction‐electron quantum number,n=1 and 2. This experiment evidences the applicability of a particle‐in‐a‐box model to the energy level determination. The carrier effective masses in InGaAs wells and the related band discontinuities were analyzed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359750

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence has been used to investigate the behavior of Si‐implanted InP, submitted to a postimplantation rapid thermal annealing. Compared with the non‐implanted material, the implanted crystal displays a new broad band around 1.382 eV, in the low temperature (2 K) spectra. This band appears to be made of two unresolved recombination paths ascribed to the electron–acceptor (e,A°) and donor–acceptor pair recombinations of the silicon acceptor impurity substituted on phosphorus site. Besides the Zn‐related transitions tosandpexcited states, the selective excitation of the donor–acceptor pairs reveals additional recombination paths, ascribed to transitions to 2s3/2and 2p5/2(&Ggr;7and &Ggr;8) excited states of silicon. The acceptor behavior of Si in InP is hence given a definite support by this work. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359751

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present here an approach for determining impact ionization coefficients for the spherical multiband model in silicon. Using random‐kapproximation, the impact ionization rate is determined to reflect the multiband density of states in silicon. To account for the actual density of states, we have solved four coupled Boltzmann transport equations by combining a generalized Legendre polynomial expansion method with numerical techniques using finite differences and sparse matrices. Calculated values for the impact ionization coefficients agree with experiments for electrons in silicon, while being obtained in significantly less CPU time than required by analogous Monte Carlo calculations. Different multiband transport parameter sets are also compared. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360699

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Pressure burst tests gave measured tensile strengths between 230 and 410 MPa for a total of six chemical‐vapor‐deposited (CVD) diamond disks in both transparent ‘‘white’’ and opaque ‘‘black’’ forms obtained from three different sources. The disks were nominally 0.635 cm in diameter and 254 &mgr;m thick. These strengths are explained by a theoretical model using a Young’s modulus of 1.05×106MPa and a fracture surface energy of 5.3 J/m2, appropriate for natural diamond, and with critical crack lengths between 33 and 105 &mgr;m. The latter lengths can fit, either on or inside, the tapered columnar crystal grains that grow vertically in synthetic CVD diamond films. The model is consistent with the observed inverse dependence of measured tensile strength on film thickness and with tensile strengths between 180 and 5190 MPa reported by other workers for synthetic CVD diamond. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359752

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The lattice sites of As ions implanted in diamond and the annealing of implantation damage were investigated in emission channeling measurements. A dose of 1.0×1013cm−273Se ions was implanted into IIa diamond at 300 K with an energy of 60 keV.73Se (t12=7.1 h) decays to73As (t1/2=80 d), which in turn decays to excited states in73Ge. Channeling effects were measured on conversion electrons emitted in the73Ge decay. Annealing studies in the range 873–1673 K showed an annealing stage of the implantation damage setting in at 1100 K. Comparison of the measured effects with simulations based on the dynamical theory of electron diffraction showed that after annealing at temperatures above 1100 K, 55(5)% of the implanted ions were located on substitutional lattice sites. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359753

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The theory of electron intersubband infrared absorptions forn‐type Si/GeSi and Ge/GeSi quantum wells in the waveguide structure is presented in order to compare with recently obtained experimental results. The absorption coefficient as a function of the polarization angle of incident light has been investigated by considering the degeneracies and the occupancies of the different valleys for conduction band. ©1995 American Institute of Physics. 

ISSN:0021-8979    

DOI:10.1063/1.359754

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on the drastic effect of a transverse high magnetic field on the low‐frequency current oscillations in semi‐insulating GaAs at room temperature, related to the propagation of slow high‐electric‐field domains. At a critical magnetic fieldBc, we find a sharp transition between two ranges of the domain drift velocity, indicating a substantial change in the behavior of the involved deep level.Bcdepends linearly on the applied voltage. The amplitude of the current oscillations decreases with increasing magnetic field, which reflects the interaction between the latter and the contact region. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359755

出版商:AIP    

年代:1995

数据来源: AIP