摘要:

The AlGaInN semiconductor system is currently of high interest for applications in blue light emitting devices. AlInN is a prospective material for lattice matched confinement layers. We measure the refractive index as well as the band gap across the entire compositional range of high-quality polycrystalline AlInN samples. Strong band gap bowing is observed. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120112

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Silicon gratings with periods from 180 to 550 nm were fabricated with a laser ablation technique in which the interference fringe from an intense and coherent ultraviolet laser at 266 nm directly melted silicon surface. The scanning electron microscopy and atomic force microscopy pictures showed that the corrugations were in quite good quality with the depth as large as 70 nm. The measurement of grating period dependence on temperature showed that rapid thermal annealing could release the thermal strains, which were built during the melting and cooling process in laser ablation, and make the grating period variation more regular. Also, with an air gap between the sample and prism surfaces, the fabricated gratings had weaker thermal strains and more regular temperature dependencies. All the measurement results of temperature dependence were consistent with theoretical predictions. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120447

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Nanocomposite films comprising metal Cu nanocrystals embedded in anAl2O3matrix were deposited by alternating pulsed laser ablation from metallic Cu and ceramicAl2O3targets. The films were grown in vacuum on glass substrates held at room temperature. The as-grown films contain 4 nm Cu nanocrystals in an amorphousAl2O3matrix, with a total thickness of 190 nm. The films show a substantial third-order susceptibility with an electronic nonlinear refractive index of(2.93±1.08)⋅10−10 cm2 W−1and a nonlinear saturation of−(2.34±0.18)⋅10−5 cm W−1.©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120117

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This letter reports a new way of preparing wafer sized SiGe quantum dots on an ordered mesoporous sol gel silica coated Si. It was found from x-ray diffraction that very good regular layers of mesoscopic sized SiGe quantum dots can be formed in the silica. Initial low temperature photoluminescence measurements show much improved light emission of the buried dots. This technique is a potential low cost method for producing quantum dot arrays. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120085

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In order to increase the failure temperature of a Ta diffusion barrier for Cu, the suppression of silicide formation in a Ta/Si system by ion-beam-assisted deposition of Ta film was investigated. When the Ta layer was deposited without ion bombardment, the reaction between Ta and Si started at 600 °C. In the case where the Ta film was prepared with concurrent ion bombardment, however, the silicide formation was retarded up to 700 °C. The suppression of Ta silicide formation can be attributed to a densification of grain boundaries in the Ta film by ion bombardment, followed by a reduction of the chemical driving force for the initial stage of silicide formation. The Ta diffusion barrier deposited by ion-beam-assisted deposition effectively suppressed the reaction between Si and Cu layers up to 650 °C for 30 min. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120086

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Monomer solubility is identified as the primary factor determining network morphology in polymer stabilized cholesteric liquid crystal textures. Poorly soluble monomers form coarse structures composed of discrete, oblong grains, whereas soluble monomers yield smooth, continuous polymer networks. A crossover from smooth to grainy structure is observed as a function of monomer concentration. The grainy structure results from precipitation polymerization and the observed behavior is well described by the Flory–Huggins theory of polymer solubility. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120087

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Optical absorption spectra of Se chains formed in channels ofAlPO4-5(AFI) crystals are measured in the temperature range from 80 to 298 K. The excitonic energy of the isolated Se chains is observed to shift to lower energy linearly with increasing temperatures, in sharp contrast to the positive temperature coefficient in trigonal-Se crystal. The marked change in the temperature behavior of the excitonic energy is attributed to the greatly diminished interchain interaction in Se–AFI as well as the weakening of the electron-optical-phonon coupling in a low-dimensional system. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120113

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

X-ray diffraction texture analysis is employed to study heteroepitaxial layers of indium grown on GaAs(100) surfaces by molecular beam epitaxy. The results document the epitaxial relationshipsIn{101}∥GaAs{111}andIn⟨100⟩∥GaAs⟨110⟩.Furthermore, an In{101} plane is oriented nearly parallel to another GaAs{111} plane, with angular deviation less than 3.9°. Due to the symmetry of the zincblende structure, for each GaAs(111) plane, In crystallites are detected in three equivalent positions. The growth of In layers was strongly influenced by the polar character of the GaAs structure, because indium was found to grow preferably on{111}Aplanes. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120088

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Specular x-ray reflectivity (XRR) measurements were used to study the density and surface roughness of ultrathin hydrogen-free amorphous carbon films deposited by sputtering, of thickness varying from 25 to 325 Å. The film thickness and surface roughness obtained from XRR measurements are in good agreement with that found by spectroscopic ellipsometry (SE) and atomic force microscopy. The results for the film composition obtained from SE and XRR are supported by stress measurements. Films (especially those with thickness below 100 Å) deposited with positive substrate bias voltage were found to exhibit a reduction in density,sp3C–C bonding, and internal compressive stresses and an increase in surface roughness by increasing film thickness. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120089

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The influence of lattice misfit on the growth of Ti (0001) is investigated in the limit of small negative (−1&percent;) and large positive (+6.8&percent;) misfit by choosing MgO (111) andAl2O3 (0001) as substrate materials. Reflection high energy electron diffraction imaging and intensity measurements during growth reveal two-dimensional nucleation of islands on MgO, in contrast to three-dimensional nucleation onAl2O3.X-ray analysis of 30-nm-thick films on MgO shows a two-component line shape in transverse scans of the (0002) and (0004) reflections, pointing to a high degree of structural coherence in the weak disorder limit. The surface morphology of films grown on MgO depends strongly on the substrate temperature during growth. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.120090

出版商:AIP    

年代:1997

数据来源: AIP