摘要:

SrTiO3thin film has been formed on Si(100) substrates with various single buffer layers such as SrO, CeO2, CaF2, CoSi2and a multibuffer layer, YSZ/Y2O3/YBa2Cu3O7by ArF excimer laser ablation. The relation of lattice orientation of buffer layers with SrTiO3layer has been elucidated. The orientation of SrTiO3film is influenced not only by lattice matching but by crystal structure and chemical bonding of the buffer layers. As well, the multibuffer layer more effectively forms preferentialc‐axis oriented SrTiO3film on Si(100), while CoSi2buffer is more effective for improving the dielectric constant of SrTiO3than other buffer layers. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360433

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The temperature dependent dielectric constants in the vicinity of room temperature have been measured for bulk ceramics which are phase‐mixtures of Pb2(Nb,Mg,Ti)2O6+xpyrochlores and Pb(Nb,Mg,Ti)O3perovskites. A band of compositions is found in which the negative temperature coefficient of dielectric constant for the pyrochlore is very closely compensated by the positive temperature coefficient of dielectric constant of the perovskite. These compositions have dielectric constants near 200, with measuredQ’s near 200 at 100 kHz. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360434

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Selected tensor property coefficients of the nonlinear optical crystal LiB3O5are reported. The full set of pyroelectric, dielectric, and thermal expansion coefficients were measured as a function of temperature. The five independent piezoelectric coefficients, the full set of electromechanical coupling coefficients, along with the compliance constants, were measured at room temperature. The material was found to be quite anisotropic in most property coefficients. The piezoelectric and electromechanical coupling coefficients were reasonably low, and comparisons are made between LiB3O5and other borate crystals. The material showed strong ionic conductivity along the ⟨001⟩ direction, with a calculated activation energy for Li transport of 0.43 eV. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360435

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The complex effective dielectric constant &egr;* of matrix–particle composites is considered. Such composites consist of separated inclusions of material of type one embedded in a matrix of material of type two. The analytic continuation method is used to derive a series of bounds which incorporate a nonpercolation assumption about the inclusions. The key step in obtaining these improved bounds is to observe that the nonpercolation assumption restricts the support of the measure in the integral representation for &egr;* (O. Bruno, Proc. R. Soc. London A433, 353 (1991)). The further the separation of the inclusions, the tighter the restriction on the support. The new bounds are applied to sea ice, which is assumed to consist of a pure ice matrix with random brine inclusions. Using experimental measurements of the average size and separation of the brine pockets, end points of the support of the measure can be determined, and subsequently used to find the allowed range of values of the effective dielectric constant of sea ice. The new bounds are compared with experimental data taken at 4.75 GHz, and exhibit significant improvement over previous fixed volume fraction and Hashin–Shtrikman bounds. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360436

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A study of the threshold of stimulated emission for optically pumped PbSe and PbTe is presented. The influence of external parameters such as magnetic field and misfit strain on the threshold as well as the differential quantum efficiency of stimulated emission are analyzed. It is shown that effective energy gap shifts caused by the external parameters only weakly influence the threshold, whereas the main effect arises from the redistribution of the carriers in the multivalley band structure when the degeneracy of the carriers in the valleys at theLpoints of the Brillouin zone is lifted. A consistent qualitative theoretical explanation for the effects is given. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360437

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The real dielectric constant for chemical vapor deposition 3C‐SiC grown on silicon (Si) has been determined at 300 K and at 5 K from an analytic fit to interference fringes in transmission over the spectral range from the near infrared to the submillimeter region. This technique is capable of high accuracy being limited typically by the sample thickness and accuracy with which the thickness is measured. The resulting real dielectric constant is lower than the values usually attributed to this material. We find: at 300 K &egr; 0=9.52 and &egr; ∞=6.38; at 5 K &egr;0=9.28 and &egr; ∞=6.22. In all cases the estimated error is ±0.8%. The observed ratio &egr;0 /&egr;∞agrees with the Lyddane–Sachs–Teller relation to 0.1% at 300 K and 0.2% at 5 K. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360438

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In electroluminescent devices electrons move every half period from the cathodic to the anodic interface of the phosphor layer and excite atoms which can lose their energy by the emission of a photon. It has been found experimentally by others that the efficiency for excitation of the luminescent atoms is largest close to the cathodic interface. By comparing transient measurements with the steady state situation we show that in steady state the efficiency is reduced and the difference between cathodic and anodic efficiency is larger. Both phenomena could be ascribed to creation of positive space charge during the first current pulses. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360439

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The Raman scattering by longitudinal‐optical (LO) phonon‐plasmon‐coupled (LOPC) mode in carbon‐dopedp‐type InGaAs with indium compositionx≊0.3 and hole concentration from 1017to 1019cm−3grown by metalorganic molecular beam epitaxy was studied experimentally. Only one LOPC mode appears between the GaAs‐like and InAs‐like LO modes was observed. The peak position of the LOPC mode is near the GaAs‐like transverse‐optical mode frequency and is insensitive to the hole concentration. The linewidth and intensity of the LOPC mode are dependent strongly on the carrier concentration, while the two LO modes decrease and become invisible under the high doping level. It was shown that the plasmon damping effect plays a dominant role in Raman scattering by LOPC mode for thep‐type InGaAs. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360440

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Infrared multiple internal reflection (MIR) spectroscopy has been applied here to the characterization (exsitu) of thin amorphous silicon layers on crystalline silicon substrates. The specimens are tightly clamped against a Ge prism with 45° bevel angle for the entrance and exit sides, allowing for up to 25 multiple internal reflections. This greatly enhances the thin‐film absorption, and the stretching bands of SiHnbonds in amorphous Si are detected in a range of film thickness from 3 to 600 nm. Very thin films (with thickness less than 50 nm) exhibit a different hydrogen bonding compared to the thin ones, due to hydrogenated sublayers that are not visible in IR spectra for larger film thickness. Sublayers are found both at the film/substrate interface and at the film free surface. Another transitional layer, with increased concentration of SiH2groups and considerably less than 30 nm, is found at the film/substrate interface. MIR is also applied to study the step‐by‐step etching in CF4/O2of a 70‐nm‐thick amorphous silicon layer. This experiment is able to define the location of the sublayers. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360374

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have developed a fabrication process for isolated quantum wire structures, using advanced atomic layer epitaxy (ALE) techniques based on the self‐limiting effect. We describe several advantages of the self‐limiting effect for the fabrication process of quantum nanostructures. We also present characterizations of the quantum wire structures including photoluminescence (PL) measurements. Due to the fact that the ALE is localized on a nanometer scale and that a growth mode switching technique between isotropic and anisotropic ALE was used, well‐defined GaAs quantum wires with structure control were successfully realized. Also, quantum confinement effects of one‐dimensional systems have been observed clearly in the quantum wires via PL measurements. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360375

出版商:AIP    

年代:1995

数据来源: AIP