摘要:

The optical properties of liquid silicon and germanium have been determined at several laser wavelengths from 1.96 to 3.71 eV, using time‐resolved ellipsometric measurements during pulsed laser melting. The results from these transient melting experiments are compared with results from the literature for materials held above their melting temperatures for long periods of time. The results for liquid germanium agree well with those of J. N. Hodgson [Philos. Mag.6, 509 (1961)], but the results for liquid silicon disagree with the results of K. M. Shvarev, B. A. Baum, and P. V. Gel’d [High Temp.15, 548 (1977)].

ISSN:0003-6951    

DOI:10.1063/1.98438

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The present work clarifies the role of Hg diffusion in forming ion‐implanted junctions in HgCdTe. Two experiments indicate that displaced Hg acts as a limited diffusion source. The first experiment contrastsn/pjunction electrical profiles in two HgCdTe wafers, onepdoped primarily by cation vacancies and the other primarily by the addition of As in the liquid phase epitaxy melt. The second experiment compares the carrier concentration near the junction with the residual net background doping of the sample. The results indicate that Hg released from the implant region operates as a limited diffusion source in the post‐implant anneal process. Adjusting these material and process parameters allowsn‐on‐pjunctions to be formed with a controllable electrical profile.

ISSN:0003-6951    

DOI:10.1063/1.98439

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Sampling measurements of electrical transients generated photoconductively on a 5‐&mgr;m gold coplanar transmission line on GaAs were performed via multiphoton photoemission. A temporal resolution of 5 ps was achieved, with a voltage sensitivity of 10 mV/(Hz)1/2. These results confirm that the temporal resolution attainable by this technique is enhanced when the dimensions of the structure under examination are reduced.

ISSN:0003-6951    

DOI:10.1063/1.98440

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The excitation of zone‐folded longitudinal acoustic phonons in GaAs/InxGa1−xAs strained‐layer superlattices is observed by Raman scattering. The Raman data agree well with theory and are consistent with high indium concentrations achieved in the fabrication of these metastable superlattices of good crystalline quality.

ISSN:0003-6951    

DOI:10.1063/1.98441

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The fabrication of highly efficient indium phosphide solar cells is described. The cells are formed by metalorganic chemical vapor deposition. A shallow homojunction design is discussed and total area air mass zero efficiency of 17.9% is reported; air mass 1.5 efficiency is 20.4%. Electrical characterization identifying loss mechanisms is made, and areas for possible improvement are summarized.

ISSN:0003-6951    

DOI:10.1063/1.98442

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

We have determined the effect of elevated temperature on the crystal structure and lattice parameters of the single‐phase high‐temperature superconductor YBa2Cu3O7using high‐temperature x‐ray powder diffractometry. This compound is orthorhombic below about 550 °C (depending on oxygen partial pressure) and transforms to a tetragonal polymorph at higher temperatures. The reversibility of this transition depends on the oxygen partial pressure. An oxygen ‘‘hopping’’ mechanism with possible oxygen loss, which appears consistent with the known structural details, is proposed for the transition.

ISSN:0003-6951    

DOI:10.1063/1.98443

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Superconducting films (300–400 nm thick) of La2−xSrxCuO4have been prepared by a combined evaporation‐reaction method. Amorphous films of the oxide are formed initially on sapphire substrates at deposition temperatures of 25–400 °C. Crystallized films can then be obtained with the desired tetragonal structure and show superconducting resistive transitions, with onsets between 23–28 K and zero resistivities near 4.2 K. A diamagnetic transition consistent with the onset‐resistive transition is seen for different samples and a critical current density of 0.4 A/cm2is obtained.

ISSN:0003-6951    

DOI:10.1063/1.98444

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

Upper critical magnetic fieldsHc2(T) have been measured resistively for the high‐temperature (Tc≳90 K) superconductors TmBa2Cu3O9−&dgr;and YBa2Cu3O9−&dgr;in applied magnetic fieldsHup to 9 T. IfHat the resistive midpoint is defined asHc2, then the upper critical field slopes (dHc2/dT)Tcat the superconducting transition temperaturesTcare respectively −2.8 and −1.1 T/K. The Tm‐specimen initial slope is apparently the highest yet reported for 90 K superconductors. Extrapolations from this slope, based on standard, three‐dimensional, dirty‐limit Werthamer, Helfand, Hohenberg, and Maki theory, yield (1) zero‐temperature upper critical fieldsHc2(T=0)=99–175 T, where the range is determined by the degree of paramagnetic limitation; (2)Hc2(T=77 K)≊36 T, the upper critical field at the boiling point of liquid nitrogen.

ISSN:0003-6951    

DOI:10.1063/1.98445

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

An optical technique is presented which permits a simultaneous observation of domains and domain boundaries in transparent and opaque magnetic specimens. The Faraday or Kerr contrast combined with Bitter pattern agglomerations yields a maximum information transference for an investigation of magnetic fine structures. Some results obtained for a uniaxial ferrimagnetic film are discussed.

ISSN:0003-6951    

DOI:10.1063/1.98446

出版商:AIP    

年代:1987

数据来源: AIP

摘要:

The recently developed dynamic observation technique of R. Shimizu and T. Ikuta [Appl. Phys. Lett.44, 811 (1984)] for scanning electron microscopy, ‘‘line‐sampling stroboscopy,’’ was used for the observation of magnetic domains in an amorphous ferromagnetic ribbon. The image‐processing technique introduced turned out to be very useful, allowing the behavior of domain walls, which is often obscured by topological contrast, to be clearly observed.

ISSN:0003-6951    

DOI:10.1063/1.98447

出版商:AIP    

年代:1987

数据来源: AIP