摘要:

Hot‐filament‐assisted chemical vapor deposition has been used to study the growth morphology of synthetic diamond deposited on silicon substrate in a dilute (1 vol %) CH3COCH3/H2at high substrate temperature (about 777 °C). Scanning electron microscope pictures of the diamond particles show that the surfaces of synthetic diamond consist of rough‐octahedral (111) faces and smooth‐cubic (100) faces, which is cubo‐octahedron. And also the (110) facets on the octahedral face are observed. The relative growth rate of (111) faces to that of (100) faces in the cubo‐octahedron is double that derived from the calculated specific surface energy. So the apparent growth rate of the octahedral face must be explained by the growths of two constituent crystallographic planes of (100) and (110). The observed roughness of (111) faces arises from the competing growths of (100) and (110) planes. The (110) faces separate the (111) faces into three (110) planes. For the study of diamond crystal growth during deposition, it is suggested that the growth mechanism of cubo‐octahedral diamond is the competing growths of (100) and (110) crystallographic planes.

ISSN:0021-8979    

DOI:10.1063/1.345373

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The effects of short pulsed ruby laser annealing on GaAs layers grown on Si substrates by metalorganic chemical vapor deposition have been characterized by Raman spectroscopy and double‐crystal x‐ray diffraction. After laser melting and regrowth, the stress‐released layer is formed in the near‐surface. The formation of the stress‐released layer results in the microcracking of the pulsed‐laser‐annealed GaAs surface. However, the high crystalline quality of this stress‐released layer is detected. Furthermore, when GaAs layer is overgrown on this stress‐released layer, this layer plays a role of blocking the dislocation threading into the overgrown GaAs layer.

ISSN:0021-8979    

DOI:10.1063/1.345374

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A full theoretical analysis of and experimental evidence for the optical generation and detection of acoustic waveguide modes (Lamb waves) in ultrathin solids using the transient grating (TG) technique is presented. The driving force due to the TG excitation is derived for a free, isotropic plate. In contrast to a bulk isotropic material in which a single wave is excited, the TG excites a number of modes with a variety of frequencies but with the same tangential component of the wavevector. The frequencies beat, resulting in a complex time‐dependent signal. Experimental results are presented for anthracene sublimation flakes. In addition to discussing the general features of Lamb wave generation, we also discuss the effects of mounting the crystal on a substrate, of varying the fringe spacing, of resonant probing, and of polarized detection. The nature of Lamb waves in anisotropic materials is illustrated, and the extent to which the isotropic theory can be applied to anisotropic systems is discussed.

ISSN:0021-8979    

DOI:10.1063/1.345380

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

A series of InxGa1−xAs films with different compositions aroundx=0.53 were grown on InP(001) substrates by molecular beam epitaxy. These layers were studied by double crystal x‐ray diffraction and secondary electron microscopy. It was found that the broadening of a layer Bragg peak is an indication of a large scale lattice relaxation in the highly strained heterolayer. In the less strained layers the peak widths are due to sample curvature and compositional grading. The morphologies of the strained layers suggested that the sign of strain is an important factor affecting the growth kinetics on the surface. In particular, an increasing tensile strain in the epitaxial layer tends to decrease the migration rate of the species on the growing surface.

ISSN:0021-8979    

DOI:10.1063/1.345381

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electrical transport properties between 80 and 300 K of polycrystalline samples of (CuIn)1−zMn2zTe2semimagnetic semiconducting alloys are studied. These are found to have disordered chalcopyrite &agr;(z≤0.1), ordered chalcopyrite &agr;’(0.1<z≤0.25), and ordered zinc‐blende &bgr;’(0.25<z≤0.57) structures. From an analysis of the electrical data, the values of the activation energyEA, density of states effective mass of the holesmp, valence‐band deformation potentialEac, and the concentration of the ionized impuritiesNifor the alloys are estimated. The linear behavior is observed ofmpwithz, with a discontinuity when the structure of the alloys changes from &agr;’to &bgr;’. However, the extrapolated value ofmpatz=0 from the region of chalcopyrite structure is in close agreement with that ofp‐type CuInTe2. On the other hand, the deformation potential of the valence‐band varies linearly withz.

ISSN:0021-8979    

DOI:10.1063/1.345349

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

An exhaustive study of the photodielectric response of proustite at various temperatures over the frequency range 10−2–103Hz has revealed an extremely complex series of changes. These involve both negative and positive photoeffects which appear to arise from competing processes in the sample. A model based on a two‐layer dielectric system, in which one of the layers is established by space‐charge buildup at the electrode, appears to explain most of the observed results.

ISSN:0021-8979    

DOI:10.1063/1.345350

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

GdSi2and ErSi2polycrystalline thin films were studied using electrical resistivity in the temperature range 10–900 K, Hall effect from 10–300 K and reflectivity spectra from 0.2–100 &mgr;m at room temperature. Composition and structure in these films were investigated by Rutherford backscattering spectroscopy and x‐ray diffraction techniques. These silicides are metallic with (i) a remarkable difference in their residual resistivity, (ii) a phonon contribution to the resistivity which showed a negative deviation linearity, and (iii) low energy interband transitions. Resistivity data indicated that GdSi2and ErSi2have a Debye temperature of 328 and 300 K respectively and a limiting resistivity value much higher than that observed in other transition metal disilicides. The charge carrier concentration was estimated to be 4×1021cm−3at room temperature according to Hall measurements, and the mean free path was 63 A˚ and 320 A˚ for GdSi2and ErSi2, respectively, at 10 K. The parameters obtained by the optical analysis are in good agreement with those extracted from the transport measurements, thus permitting one to obtain a reasonable value for the Fermi velocity.

ISSN:0021-8979    

DOI:10.1063/1.345351

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The electrical characteristics ofp+‐njunctions in undoped InP fabricated by using a deep Si implant and a shallow Be implant are reported. It proved advantageous to anneal the two implants separately. The influence of annealing, implantation temperature, and Si dose on leakage current is studied systematically. It is found that prolonged anneals and elevated temperatures reduce leakage currents and that raising the implantation dose increases junction leakage considerably. It is shown that junction behavior can be modeled by assuming a trap‐assisted tunneling mechanism. In this model the magnitude of the electric field at the junction is the most decisive parameter. For a 15‐min‐long anneal at 850 °C leakage current densities <10−7A/cm2are obtained for an electric field of 40 V/&mgr;m at the junction.

ISSN:0021-8979    

DOI:10.1063/1.345352

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Measurements were made of the capacitance and the conductance of several capacitor structures with a copper phthalocyanine (CuPc) dielectric at different voltages and in the frequency range of 102–106Hz. A thermally evaporated CuPc film about 1300 A˚ thick was fabricated in a parallel‐plate capacitor between gold and aluminum electrodes (Al‖CuPc‖Au). Two distributions of relaxation times are observed in this frequency range. At low frequencies voltage‐dependent polarization (possibly interfacial polarization) appears to be the dominant mechanism of current conduction. At high frequencies a relatively voltage‐independent hopping within and/or between molecules appears to be dominant. The CuPc remains polarized for a long time. Measurements were also made of the capacitance‐voltage (C‐V) characteristic of a Al‖CuPc‖SiO2‖Si capacitor at 104, 105, and 106Hz for different scanning rates. The basic features of the device’sC‐Vcharacteristics are discussed.

ISSN:0021-8979    

DOI:10.1063/1.345353

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Insituinterfacial impedance measurements are used to study the effects of moisture at 80 °C on the interface between oxidized silicon and a diglycidyl ether of bisphenol A epoxy cured with diethylene triamine. Bulk impedance measurements follow Randles behavior; conduction in the bulk epoxy is ionic, and is diffusion controlled at low frequencies. An additional conduction process between interfacial electrodes is observed even though a water layer does not condense in the interface. Through comparative use of linear network models, it is found that the ‘‘interfacial’’ conduction path represents distributed bulk conduction in the epoxy with displacement current leakage into the conductive silicon substrate through an interfacial capacitance. Both electrochemical and bulk coating properties jump at humidities near 70%, indicating greatly increased ionic mobility, coating permittivity, and interfacial capacitances. The permittivity and ionic mobility behavior suggest the formation of large water‐swollen demains or highly elongated water clusters near the property jump threshold. Because humidity effects are resolved into bulk and interfacial components, interfacial impedance measurements appear to have great utility for theinsitustudy of transport and electrochemical properties of interfaces and coatings during environmental exposure.

ISSN:0021-8979    

DOI:10.1063/1.345354

出版商:AIP    

年代:1990

数据来源: AIP