摘要:

A new zone‐melting‐recrystallization (ZMR) configuration with enhanced radiative heating has been developed for preparing silicon‐on‐insulator (SOI) films. With this configuration, in which the sample is positioned above the movable heater with the SOI film facing downward, subboundary‐free 0.5‐&mgr;m‐thick SOI films are obtained over a much wider range of experimental parameters than with the conventional ZMR configuration. The characterization of these films by defect etching, optical microscopy, and transmission electron microscopy shows that the principal defects are isolated threading dislocations with a density of ∼106cm−2. It should be possible to improve the material quality still further by optimizing experimental conditions for the new configuration.

ISSN:0003-6951    

DOI:10.1063/1.102465

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The change in electronic structure from a typeAto a typeBNiSi2/Si(111) interface is sufficient to explain the previously observed difference in the Schottky barrier heights of these two interfaces. This is supported by the observation by scanning tunneling microscopy of different contrast on the faulted triangle in a Si(111) 7×7 unit cell relative to the unfaulted one. The crystallographic differences in the two types of NiSi2/Si(111) interfaces are identical to those in two types of triangles inside a Si(111) 7×7 unit cell. A simple model with an interface dipole induced by the stacking fault is proposed to be responsible for the 0.13 eV difference in the Schottky barriers at typeBNiSi2/Si(111) interfaces relative to typeAinterfaces. The estimated dipole change is about 0.004e−per interface bond, in good agreement with a theoretical estimation at the stacking fault of bulk Si.

ISSN:0003-6951    

DOI:10.1063/1.102466

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Atomic layer epitaxy (ALE) of GaAs using trimethylgallium and triethylgallium by chemical beam epitaxy is reported. Reflection high‐energy electron diffraction is employed to monitor the formation of each individual monolayer directly. A new (4×8) surface reconstruction, characteristic of an ordered chemisorbed molecular Ga monolayer, is observed for the first time. Each Ga atom in this transitional layer has at least one alkyl radical cleaved away. The stability of this transitional stage varies depending on the alkyl group involved and the temperature. Dynamical evolution of this adsorbed layer is described. The chemical properties of this overlayer dictate the GaAs ALE growth conditions.

ISSN:0003-6951    

DOI:10.1063/1.101666

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have investigated the effects of Fe on the structure and properties of 110 K phase superconductor Bi‐Pb‐Sr‐Ca‐Cu‐O. The zero resistance temperature decreases and the x‐ray diffraction intensity ratio of (200) to (001_4_) peak increases, with the increasing of the Fe atom concentration. These samples are of single (2223) phase structure. It may be suggested that a 95 K superconducting phase exists. Its structure is very similar to that of the Bi2Sr2Ca2Cu3Oyphase. The Fe atoms make the 110 K phase turn into the 95 K phase.

ISSN:0003-6951    

DOI:10.1063/1.101667

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The effect of oxygen partial pressure on the stability of the highTcphase (>100 K) in a Bi‐Pb‐Sr‐Ca‐Cu‐O system has been studied using resistivity, x‐ray diffraction, and ac susceptibility measurements. It was observed that part of the highTcphase formed by sintering at 840 °C in a low oxygen partial pressure of 1/10 atmosphere was transformed into a lowTcphase (∼80 K) and an insulating phase by heating at the same sintering temperature in O2of one atmosphere. The original highTcphase was restored upon retreatment at the same temperature in a low oxygen partial pressure of 1/10 atmosphere.

ISSN:0003-6951    

DOI:10.1063/1.102467

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We studied the composition dependence of highTcphase Bi2Sr2Ca2Cu3Oxformation in Pb‐doped Bi system thin films. Films were prepared by rf magnetron sputtering using three targets and post‐annealed to synthesize superconducting films. In addition to a Bi‐Sr‐Ca‐Cu‐O target, PbO and CuO targets were used to dope sufficient Pb into the films and to optimize the Cu content. Although heavily Pb‐doped thin films form the highTcphase rapidly, they are multiphased and have poor morphology. The Cu content decreases slightly during sintering. Minimizing the amount of doped Pb needed for the highTcphase formation improves morphology, and slightly Cu‐rich composition is effective in forming the highTcphase. Nearly single‐phase highTcfilms were obtained from the as‐deposited compositions of Bi:Pb:Sr:Ca:Cu=1.02:0.80:1.00:0.99:1.64 after only one hour of sintering in air at 851 °C. The single‐phase highTcfilm forms in a very narrow sintering temperature range.

ISSN:0003-6951    

DOI:10.1063/1.102468

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Bi4Ca3Sr3Cu4Oyglass fibers a few centimeters in length were prepared by melt spinning. After heat treatment at 830 °C, the fibers became superconducting. The x‐ray diffraction pattern revealed that the heat‐treated fibers have the 75 K phase as the major phase and Bi2Sr2CuO6and CuO as minor phases. The resistivity measurement showed that the onset superconducting temperature of the fibers was ∼80 K.

ISSN:0003-6951    

DOI:10.1063/1.102469

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Superconducting Tl2CaBa2Cu2Oythin films have been successfully grown on the single‐crystal sapphire (11¯02) substrate by using the metalorganic chemical vapor deposition technique. The growth rate of the films was about 5 &mgr;m/h. The as‐deposited film was post‐annealed in a partially sealed ceramic crucible in the presence of a Tl2Ca2Ba2Cu3Oypellet to achieve the superconducting phase. The x‐ray data show strong diffraction from the Tl2CaBa2Cu2Oysuperconducting phase in addition to the trace amounts of Ca2CuO3and BaCO3. Superconducting transition temperatures with onset above 100 K and zero resistance at 94 K can be obtained by further heat treatment at 500 °C in oxygen.

ISSN:0003-6951    

DOI:10.1063/1.101892

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Insituepitaxial growth of YBa2Cu3O7−&dgr;thin films onY‐cut LiNbO3substrates using a standard laser ablation technique is reported. Resistance of the films shows a normal metallic behavior and a very sharp (<1 K) superconducting transition withTc(R=0) of 92 K. High critical current density ofJc(77 K)=2×105A/cm2is observed, which is in accordance with epitaxial growth. Film orientation observed from x‐ray diffraction spectra indicates that thecaxis is normal to the substrate plane and theaaxis is at 45° to the [11.0] direction of the hexagonal lattice of the substrate with two domains in mirror image to the (110) plane.

ISSN:0003-6951    

DOI:10.1063/1.102470

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The laser‐induced deposition of high‐purity aluminum metal has been achieved by pyrolytic decomposition of trimethylamine aluminum hydride. The chemical structure of the precursor affords a high ambient vapor pressure which results in rapid rates of aluminum film formation. In addition, the precursor is nonpyrophoric, in contrast to other trialkylaluminum precursors. These combined chemical and physical properties make trimethylamine aluminum hydride an ideal precursor for laser‐induced chemical vapor deposition of aluminun films.

ISSN:0003-6951    

DOI:10.1063/1.101629

出版商:AIP    

年代:1989

数据来源: AIP