摘要:

We report here a study of the Raman spectra of ternary Cu–In–S and Cu–In–Se polycrystalline film compounds as a function of thex=[In]/{Cu]+[In]} ratio. Using these spectra we were able to identify, with high resolution inx, the phases present in the films. We found that the single phase of chalcopyrite CnInSe2exists over the fairly wide composition range of 0.48⩽x⩽0.55, and that the lattice disorder increases with the increase of In content. No such single phase range was found for the Cu–In–S films. Considering the electrical properties of these materials aroundx=0.5, it is concluded that the native defect model accounts for the electrical properties of the Cu–In–Se films but does not account simply for the electrical properties of the Cu–In–S films. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117104

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Transmission electron microscopy, x‐ray diffraction, low‐temperature photoluminescence, and Raman spectroscopy were applied to study stress relaxation and the dislocation structure in a Si‐doped GaN layer in comparison with an undoped layer grown under the same conditions by metalorganic vapor phase epitaxy on (11.0) Al2O3. Doping of the GaN by Si to a concentration of 3×1018cm−3was found to improve the layer quality. It decreases dislocation density from 5×109(undoped layer) to 7×108cm−2and changes the dislocation arrangement toward a more random distribution. Both samples were shown to be under biaxial compressive stress which was slightly higher in the undoped layer. The stress results in a blue shift of the emission energy andE2phonon peaks in the photoluminescence and Raman spectra. Thermal stress was partly relaxed by bending of threading dislocations into the basal plane. This leads to the formation of a three‐dimensional dislocation network and a strain gradient along thecaxis of the layer. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117105

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A demonstration of quantum well intermixing using ion implantation in Si1−xGex/Si strained‐layer heterostructures is presented. The quantum‐well related photoluminescence lines of implanted and annealed samples are blue shifted by up to 40 meV relative to those measured in annealed‐only samples. Optical and structural qualities of the heterostructure remain high after implantation and annealing treatments. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117106

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Femtosecond time‐resolved reflectivity measurements, structural, and electrical analyses have been performed to investigate the effect of rapid thermal annealing (RTA) on GaAs implanted with 200 keV arsenic ions at 1016ions/cm2. Ultrashort carrier lifetimes from 0.48 fs to 2.3 ps were observed for samples annealed at temperatures between 600 and 800 °C. The time constants are somewhat shorter than those of RTA‐annealed low‐temperature molecular‐beam epitaxy grown material, while following the same trend of longer time constants and recovery of resistance at higher annealing temperatures. Arsenic precipitates were not observed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117107

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Epitaxial growth of NiSi2on (111)Si inside 0.1–0.6 &mgr;m oxide openings prepared by electron beam lithography has been studied by field emission scanning electron microscopy, transmission electron microscopy, and thin‐film stress measurement. Striking effects of size and shape of deep submicron oxide openings on the growth of NiSi2epitaxy were observed. Epitaxial growth of NiSi2of single orientation on (111)Si was found to occur at a temperature as low as 400 °C inside contact holes of 0.2 &mgr;m or smaller in size. Contact holes were found to be more effective in inducing the epitaxial growth of NiSi2of single orientation than that of linear openings of the same size. The effects of size and shape of lateral confinement on the epitaxial growth of NiSi2on (111)Si are correlated with the stress level inside oxide openings. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117108

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report results of quantitative magnetization studies on epitaxial thin films of La0.60Y0.07Ca0.33MnO3−&dgr;and La1−x&laplac;xMnO3−&dgr;, with &laplac; standing for vacancy on the La site. The magnetization in all samples shows significant field dependent broadening of the ferromagnetic transition. Classical mean‐field analysis of magnetization data in applied fields above a few Tesla leads to a magnetic cluster size of the order of a few unit cells. The density of such a magnetic cluster correlates with the doping concentrationxin the compound series La1−x&laplac;xMnO3−&dgr;. In thin films of La0.60Y0.07Ca0.33MnO3−&dgr;, a magnetic field dependent, non‐Curie–Weiss susceptibility was found in the paramagnetic state, indicating local ferromagnetic cluster formation above macroscopic ferromagnetic ordering temperature. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117966

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We are able to grow high quality La0.67Sr0.33MnO3(LSMO) colossal magnetoresistive (CMR) thin films on Y‐stabilized zirconia (YSZ) buffered (100) Si substrates using a Bi4Ti3O12texturing and lattice matching layer. The CMR films have very high structural perfection and show excellent transport and ferromagnetic properties, including the almost full saturation magnetization values and narrow ferromagnetic resonance peaks (15 Oe at 290 K). The lattice matching template/buffer layer approach is suitable for the high quality CMR films on Si. A close correlation between the magnetic hysteresis loop and the field dependence of MR is observed at lower temperatures. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117967

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

NaI and CsI protective coatings on visible cesium‐antimony photocathodes have been studied. With NaI protective films the photocathodes are shown to withstand exposure to considerable doses of oxygen and dry air. This opens the way to their handling and operation in gas media. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117968

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have proposed ReMnO3(Re:rare earth) thin films as a new candidate for nonvolatile memory devices. In this letter, we report on fabrication of (0001) YMnO3films on (111)MgO, (0001)ZnO:Al/(0001) sapphire, and (111)Pt/(111)MgO using rf magnetron sputtering. We succeeded in obtaining (0001) epitaxial YMnO3films on (111) MgO and (0001)ZnO:Al/(0001) sapphire substrate, and polycrystalline films on (111)Pt/(111)MgO. The dielectric properties of the epitaxial and polycrystalline YMnO3films are almost the same. The dielectric permittivities of both films are smaller than those reported for YMnO3single crystal. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117969

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The technique of transmission electron holography has been employed to investigate the nanoscale features of graphitic nanotubes (buckytubes) and their particulate derivatives. Reconstructed phase images of holograms offer a quantitative means to calculate the mean inner potential (MIP), thickness profiles, and three‐dimensional morphology for multi‐/single shell buckytubes, their ‘‘tips’’ and other enclosed structures. It is demonstrated that electron holography is also sensitive to the defect nature of termination and bending in buckytubes and their particulate derivatives. Phase sensitivity of about 0.1 rad is demonstrated for single‐layer buckytube, which corresponds to change in phase due to two monolayers of carbon. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117970

出版商:AIP    

年代:1996

数据来源: AIP