摘要:

We observed a very sharp photoluminescence peak from a single GaAs/AlGaAs quantum dot structure by using a microphotoluminescence measurement technique. The spectral linewidth was more suppressed by decreasing the excitation laser power, which is mainly due to reduction of the filling effect of quantized energy levels. The minimal spectral linewidth with low excitation laser power was 0.9 meV. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114890

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The viscosity of the Zr46.75Ti8.25Cu7.5Ni10Be27.5bulk metallic glass forming alloy in the supercooled liquid was measured using parallel plate rheometry. The measurements were carried out with different heating rates between 0.0167 and 1.167 K/s as well as isothermally. Because of the high thermal stability above the glass transition of this bulk metallic glass former with respect to crystallization, it was possible to measure viscosities in the range from 1010to 106poise. This region of viscosities has not been previously measured for supercooled metallic melts. Our measurements suggest that the viscosity of the supercooled liquid of this bulk glass former exhibits a small Vogel–Fulcher temperature relative to the glass transition temperature, similar to silicate glasses. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114891

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

SiNx:H films with a wide composition range and, some of them, with low oxygen content are deposited at room temperature. The defects observed in the films are attributed to Si‐dangling bonds, with a structure depending on film composition. For the N‐rich films they are of the form ⋅Si≡(N3), whereas for the films with similar [N]/[Si] ratio but containing oxygen, the predominant defect is proposed to be ⋅Si≡(Si2O), despite of the high N content and the low O content of these films. The spin density of the films has been related to the bonds that hydrogen establishes (either Si–H or N–H), with the maximum value corresponding to the minimum hydrogen content. Both maximum and minimum values, respectively, are obtained at the silicon percolation limit of the Si–Si bonds into the SiNx:H network,x∼1.10. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114892

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We present a simple calibration method for europium‐doped potassium halide dosimeters. The procedure is based on the self‐irradiation absorbed dose of potassium halide thermoluminescence dosimeters due to the natural content of the radionuclide40K in potassium halide crystals. In the small dose range of the order of 0.5 mGy, the precision of the proposed method is highly competitive with traditional calibration methods, without the need of artificial radiation sources and rather expensive and sophisticated measurement equipment. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114893

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Silicon nitride layers deposited by an excimer laser reactive ablation of silicon target in ammonia on Si(100) wafers kept at 300 or 600 °C have been studied by infrared absorption and angular resolved x‐ray photoelectron spectroscopy. Presence of hydrogen in the deposits unexpected at the high substrate temperatures is documented. The observed deposit thicknesses, stoichiometry, and the hydrogen content as a function of ammonia pressure suggest a picture of the deposition process with Si3N4synthesis taking place on the growing deposit surface, contrary to the liquid phase reaction model suggested for analogous TiN deposition. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114894

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Step flow growth patterns have been observed on single‐crystal (La,Ca)MnO&dgr;(LCMO) thin films by atomic force microscopy. These films were grown on (110) NdGaO3substrates by a simple facing‐target sputtering method. The steps, of monolayer height (0.2 nm), are surprisingly straight and evenly spaced. The best sample has an average step width of about 400 nm which is comparable to that found on the molecular beam epitaxially grown GaAs. The step edges are parallel to the LCMO [001] direction indicating that the growth rates are anisotropic. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.114895

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A method for bonding a piezoelectric crystal directly onto silicon, without any bonding agents, is reported. The interface microstructure, procedures of fabricating a lithium tantalate (LiTaO3&squflg;‐ on‐silicon resonator, and its resonant characteristics are described. This technique is very promising for miniaturizing electroacoustic integrated devices. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114896

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The defects induced by electron irradiation in epitaxially grown Si‐dopedn‐GaAs were investigated by deep level transient spectroscopy. In addition to observing the well‐known E1–E3 radiation induced defects, we detected another electron trap, E&bgr;3, with electronic properties, although similar to those of E3, not identical. E&bgr;3 is metastable and thus its energy level can be reproducibly removed by hole injection at 90–130 K and reintroduced by annealing above 160 K. We could induce E&bgr;3 by electron irradiation in Si‐doped GaAs, but not in undoped GaAs. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115219

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We demonstrate the preparation of narrow‐band porous‐silicon reflectors integrated on porous‐silicon layers by electrochemical etching. By carefully tuning the resulting photon cavity mode around the maximum of the porous silicon photoluminescence, we have obtained both a narrowing and enhancement of the emission line, and a highly concentrated radiation pattern. These results show that the porous silicon spontaneous emission is modified because of the coupling with the photon cavity mode. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115220

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The density of defects in the buried oxide of implanted oxide silicon‐on‐insulator material which cause low resistance paths between the substrate and top silicon layer has been greatly reduced by high temperature oxidation. The mechanism for this is the diffusion of oxygen through the top silicon layer to the buried oxide, where it oxidizes chains of silicon atoms. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115221

出版商:AIP    

年代:1995

数据来源: AIP