摘要:

Reaction products in Si etching with a hot Cl2(Cl2*) molecular beam were measured by a quadrupole mass spectrometer. A major part of the product was shown to be SiCl4, and the reaction probability of Cl2*on a Si surface was obtained. It was found that the reaction probability increases rapidly with the increase in furnace temperature for Cl2*formation, and high reactivity of Cl2*was demonstrated. A reaction model (the activated complex Arrhenius model) is proposed to explain the experimental results, and the model parameters are determined. This model takes into account the effects of the translational and vibrational energies of a Cl2*molecule on the activation energy and the frequency factor in the ordinal Arrhenius model. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359587

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nitrogen containing tantalum was grown on silicon by electron‐beam evaporation of the metal under simultaneous irradiation with highly energetic nitrogen ions from an ion source. Phase analysis by means of x‐ray diffraction revealed that at low irradiation intensities the deposited material is tantalum metal with dissolved nitrogen. At high intensities a phase transformation to tantalum nitride takes place. By contrast to the stable TaN in the phase diagram, which is hexagonal, the material grown under ion bombardment exhibits a metastable cubic structure of the NaCl type. The crystallographic orientation of the grains is directly dependent on the ion irradiation intensity. Initially, the films show a [111] texture. With increasing ion irradiation intensity the [100] orientation appears additionally. This orientation is independent of the substrate. The lattice spacings are also dependent on the irradiation intensity. With increasing ion irradiation the lattice is widened, then the spacings decrease again. The results are discussed in comparison to data from the literature on sputter deposition with low‐energy ions. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359073

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A synthesis method that provides high‐purity diamond films is proposed employing direct current arc discharge plasma jet chemical vapor deposition. In the method, an electric current was supplied to a plasma jet stream by applying a bias voltage between a cathode and the substrate on which diamond films were deposited. The Raman spectral analysis showed that the purity of the synthetic diamond was remarkably improved by the application of the bias voltage during deposition. The alternating current calorimetric method was employed to measure the thermal diffusion coefficient of the synthesized diamond films. The thermal diffusion coefficient greatly increased for films deposited with biasing. This improved thermal diffusion coefficient suggests higher purity diamond films. Emission spectral analysis revealed that the quantity of the dissociated hydrogen contributing to the plasma emission near the substrate is greater when biasing is used. Thus, the dissociated and excited hydrogen atoms are considered to play a key role in removing the carbon allotropes other than diamond. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359074

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Tin nitride thin films were obtained by the reactive sputtering method. The metallic tin target was sputtered by nitrogen gas with rf magnetron sputtering equipment. To prevent the re‐evaporation of atomic nitrogen from the substrate, the depositions were made at the low substrate temperature of 60 °C. Polycrystalline films were obtained at an rf power lower than 90 W. The resistivity of polycrystalline film was 3–14×10−2&OHgr; cm, while the resistivity of amorphous film increased monotonically with decreasing sputtering pressure. For amorphous film, the change in resistivity is attributable to the change in carrier concentration. The decrease in carrier concentration is associated with an increase of –N=O combination in the film. The optical energy gap of tin nitride was 1.5 eV. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359075

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A study of infrared absorption due to intersubband transitions inp‐type Si1−xGex/Si quantum wells has been performed. The influence of the hole envelope wave‐function and the subband structure on the absorption characteristics is evaluated. In the calculation, the subbands in a SiGe strained layer are computed by using a bond orbital model, which combines thek⋅pand the tight‐binding methods, with a strain Hamiltonian. Both of the Poisson and the Schro¨dinger equations are solved self‐consistently to take into account a band‐bending effect. The calculated quantum efficiency in a 40 A˚ Si0.75Ge0.25/Si quantum well detector is compared favorably with an experimental result. The structural dependence of infrared absorption on quantum well width, doping and Ge content in a wavelength range of 3–15 &mgr;m is investigated. By varying a well width, our study reveals that a maximum absorption coefficient is obtained when the energy level of the excited‐state subband is near the top of a quantum well. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359076

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Metal/oxide multilayers composed of nickel and nickel oxide were prepared on silicon, fused quartz, and sapphire substrates in an ultrahigh vacuum deposition system using two different methods for growing oxide layers: an oxidation method of metal layering using pulsed oxygen molecular beam, and an evaporation method of NiO with an electron beam evaporator. With x‐ray diffraction and calculations using dynamical theory of x‐ray reflection, the films prepared via oxidation with more than 60 pulses of oxygen beam at 298 K, and the films prepared by evaporation below 473 K revealed multilayers of Ni/NiOxwith artificial periodicity. Multilayers prepared with the oxidation method on silicon and fused quartz have homogeneous bilayers composed of polycrystalline Ni and amorphous‐like NiO. In contrast, multilayers prepared by the evaporation method on a sapphire substrate are structurally graded, with layer structures which change gradually from single crystals (1st layer) to polycrystals (last layer). ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359077

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The microstructures of chemically polymerized polypyrrole films (100–800 A˚ thick) were studied by transmission electron microscopy, electron diffraction, and x‐ray photoelectron spectroscopy. In contrast to previous work where only amorphous polypyrrole was found, crystalline fiber structures were observed in the chemically polymerized thin films. The fibers are embedded in an amorphous matrix which forms a self‐reinforced composite. The shape of the fibers ranged from thin rods to ellipsoids depending on the preparation conditions. The density and size of the fibers were affected by the polymerization time and the concentration ratio of pyrrole and oxidants. Polypyrrole fibers were aligned along the thin‐film plane and were randomly oriented in the plane. The two‐dimensional orientation of the crystalline fibers produced strongly anisotropic electrical properties in the thin films. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359078

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Using a wind tunnel the evaporation rate of water at normal temperature and pressure was measured as a function of temperature, humidity, air velocity, and diameter of the vessel. In order to measure the temperature of the water surface and the boundary layer on the surface, the temperature above and below the surface was measured as a function of air velocity with a thermocouple of 0.076 mm diameter. The present experimental results are in agreement with the present theory for a laminar flow, which is based on the idea that the evaporation rate is equal to the diffusion velocity of water vapor in the boundary layer. For a turbulent flow the experimental evaporation rate was found to be proportional toU0.86±0.03, whereUis air velocity. This is consistent with the velocity dependence of the experimental thickness of the boundary layerd, which wasd∝U−0.90. A new semiempirical formula of the evaporation rate is proposed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359079

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Comparisons of magnetic anisotropy and switching behavior of CoCr‐based alloy and Co/Pd multilayer media were made using a vector vibrating sample magnetometer. Magnetic anisotropy energy was determined from angle‐dependent measurements of the transverse magnetization, using a simple approximate expression for transverse moment versus applied field and rotation angle. Switching behavior was deduced from hysteresis and angle‐dependent energy‐loss measurements. The multilayers were found to switch by curling and domain wall motion, while the Co78Cr17Ta5and Co70Cr15Ta5Pt10media were found to switch by nearly coherent (Stoner–Wohlfarth) rotation. Plasma oxidation of the multilayers was found to slightly reduce the amount of coupling, but degraded readback amplitude to a contact recording transducer. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359080

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

InAlAs/InGaAs heterojunction bipolar transistor with a 300 A˚ spacer inserted between emitter and base grown by molecular beam epitaxy was characterized by using photoreflectance spectroscopy. The energy features observed above the InGaAs fundamental band gap are attributed to the quantum confined subband transition of two‐dimensional electron gas which was confined in the spacer channel. A detailed lineshape fit makes it possible to evaluate the Fermi energy, and hence the two‐dimensional electron gas concentration. The behavior of two‐dimensional electron gas at temperatures between 10 and 300 K was also characterized and the sheet‐density in proportion to temperature was observed. Furthermore, using the temperature dependence of effective mass measured by cyclotron resonance combined with photoreflectance to analyze built‐in electric field is also reported. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359081

出版商:AIP    

年代:1995

数据来源: AIP