摘要:

Shallow (<200 nm) Si profiles with doping levels in excess of 2×1018cm−3were reproducively obtained in GaAs by rapid thermal oxidation (RTO) of Si caps (50 or 160 nm) in 0.1% O2/Ar ambient at 850–1050 °C. The doping level as well as distribution of the diffused Si can be controlled by the thickness of the Si cap, RTO temperature, RTO time, and oxygen level in the annealing ambient. It appears that the generation of Si interstitials at the oxidizing surface of the Si cap during RTO is responsible for the Si diffusion into the underlying GaAs substrate.

ISSN:0003-6951    

DOI:10.1063/1.104084

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The use, transportation, and storage of the hazardous gas, arsine, raise serious safety issues. Consequently, there is considerable interest in the generation of arsine on demand from less hazardous substances. We report the first use ofinsitugenerated arsine for III‐V epitaxy. The gas has been generated electrochemically at an arsenic cathode in an aqueous electrolyte and used to supply a hydride vapor phase epitaxy reactor. InGaAs/InP test structures were grown on InP substrates and were similar to comparison structures grown using tank arsine. Recessed‐gate enhanced Schottky metal‐semiconductor field‐effect transistors were fabricated and exhibited well‐behaved current‐voltage characteristics.

ISSN:0003-6951    

DOI:10.1063/1.104136

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We discuss the results of a study of the effect of substrate preparation on the microstructure and superconductive properties of YBa2Cu3O7thin films formed by laser ablation on (001) MgO substrates. Thermal annealing of the substrates is found to be highly effective in producing at fairly low growth temperatures (670 °C), epitaxial,c‐axis normal films with good superconductive properties. Alternative surface treatments result in the formation of large angle tilt boundaries and inferior superconductive properties.

ISSN:0003-6951    

DOI:10.1063/1.104137

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Various orientations of YBa2Cu3O7−xgrains in polycrystalline films prepared on (001)MgO substrates byinsitulaser deposition were determined using electron diffraction. Eight different types of in‐plane orientations have been observed. These orientations agree well with the prediction of a simplified theory of near coincidence site lattice between YBa2Cu3O7−xand MgO. The YBa2Cu3O7−xgrains were found to have a high probability of forming low angle or low &Sgr; boundaries among themselves. These grain boundaries are of low energy and should exhibit a high connectivity of Cu‐O‐Cu chains. Therefore, YBa2Cu3O7−xthin films on MgO can attain aTcof ∼90 K and aJcof ∼106A/cm2at 77 K.

ISSN:0003-6951    

DOI:10.1063/1.104138

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The microstructure of high quality Pb‐doped Bi2Sr2CaCu2Oxsingle crystals grown by the flux technique has been studied by transmission electron microscopy (TEM). The single crystals have a superconducting transition temperature (Tc) of about 90 K as grown;Tcdrops to about 83 K after annealing in air at 600 °C. TEM results show that the as‐grown crystals exhibit twinning. The twin boundaries were found to be parallel to the (100) and (010) lattice planes. However, upon annealing the twin structure disappeared. This microstructure change is discussed in terms of a possible cause for theTcdecrease in the annealed crystals.

ISSN:0003-6951    

DOI:10.1063/1.104139

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

We report the results of femtosecond optical transient absorption experiments performed on <m1;&1p>the superconducting compounds YBa2Cu3O7−x(x∼ 0) and Bi2Sr2Ca2Cu3O10+&dgr;(&dgr; ∼ 0) and nonsuperconducting YBa2Cu3O6+y(y<0.4) for sample temperatures ranging from ∼7 K to room temperature. Nonequilibrium heating was found to occur on a subpicosecond time scale. A distinct, dramatic increase in the relaxation time was observed for the superconducting samples as the sample temperature was lowered below the critical temperatures of the respective films. Accompanying the increase in relaxation time was an increase in the peak fractional transmissivity change. No such changes were observed for the nonsuperconducting YBCO sample. We believe the above described behavior is electronic in origin and intimately related to the superconductivity of the compounds.

ISSN:0003-6951    

DOI:10.1063/1.104140

出版商:AIP    

年代:1990

数据来源: AIP