摘要:

An ultrahigh density seeding process of diamond thin‐film deposition is demonstrated. Diamond powders with average grain sizes of 0.038 and 0.101 &mgr;m were used to study the surface roughness as a function of deposition time, film thickness, and nucleation density. The diamond films, prepared by hot filament chemical vapor deposition, were characterized by atomic force microscopy, scanning electron microscopy, and Raman spectroscopy. An extremely high nucleation density on the order of 1011cm−2was achieved by coating 0.038 &mgr;m diamond powder on the surface of the Si substrate. One micron thick films were obtained with the mean surface roughness of 30 nm. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113528

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Low density microcellular foam from poly(4‐methyl‐1‐pentene) (PMP) has been metallized by laser‐induced chemical vapor deposition (LICVD). KrF excimer laser radiation (248 nm) was used to photolytically decompose molybdenum hexacarbonyl with and without a buffer gas. Metal oxycarbide deposits 100 &mgr;m in diameter were formed. The microstructure of the PMP foam was unaltered. The deposition was confirmed to be 100 &mgr;m using scanning electron microscopy and energy dispersive x‐ray spectroscopy. X‐ray fluorescence was used to determine that approximately 80 ng of material was deposited. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113529

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The temperature dependence of the surface peaks of the (001) SrTiO3substrate surfaces was studied for the sample temperature up to 750 °C by channeling. The temperature dependence of the Sr surface peaks was found to be due to the thermal vibration of the Sr atoms. However, an anomalous temperature dependence of the Ti surface peak was observed which may be due to the displacement of Ti surface atoms. The Ti surface peaks are maximum at 400 °C. For the reduced SrTiO3−&dgr;, surface reconstruction was observed on the Sr surface sublattice but the anomalous temperature dependence of the Ti surface peak disappeared. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113530

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Metal colloids in CaF2created by low energy electron irradiation are identified by their optical absorption bands. A mean colloid radius of 18 nm is deduced from a narrow colloid band found in crystals irradiated at room temperature. Absorption data reveal a strong influence of crystal temperature during irradiation on metallization efficiency, mean colloid size, and colloid size distribution. A reversible absorption band shift is observed when turning the electron beam on and off, which may indicate a decrease of colloid size during electron irradiation. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113531

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have realized by cleaved edge overgrowth a two‐dimensional electron gas system in a one‐dimensional lateral superlattice consisting of 100 periods of 120 A˚ GaAs/20 A˚ AlGaAs. These devices exhibit nonlinearI–V, including negative differential resistance, at high electric fields. We demonstrate, by monitoring the changes in the two‐dimensional electron density, that the nonlinearI–Vis due to high field induced electron trapping. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113532

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The authors present experimental evidence for thickness‐field excitation of thickness‐shear vibrations in GaAs as an example material for zincblende‐crystal semiconductors. The resonance frequency is shown to agree perfectly with theory. This gives an alternative to the composite resonators in miniaturized local oscillators for, e.g., monolithic microwave integrated circuit applications. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113533

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Surface normal optoelectronic devices operating at long wavelengths (≳1.3 &mgr;m), require distributed Bragg reflectors (DBRs) with a practical number (≤50) of mirror layers. This requirement implies a large refractive index difference between the mirror layers, which is difficult to achieve in the traditionally used phosphide compounds. We demonstrate a highly reflective AlAsSb/GaAsSb DBR grown nominally lattice matched to an InP substrate by molecular beam epitaxy. Reflectivity measurements indicate a stop band centered at 1.74 &mgr;m with maximum reflectivity exceeding 98%, which is well fitted by our theoretical predictions. Atomic force microscopy and transmission electron microscopy indicate reasonable crystal quality with some defects due to an unintentional lattice mismatch to the substrate. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114202

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The atomic‐level heterointerface structures of InP samples that contain growth interrupted and AsH3‐exposed surface, with 20 A˚ thick cap layer, were revealed by x‐ray crystal truncation rod scattering measurement. The As atom distribution, the thickness of the cap layer, and the tetragonal distortion of the lattices were obtained from the samples that have only single modified layer in the whole InP wafer. The calculated total amounts of As matched well with the value obtained by fluorescence x‐ray analysis. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114203

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The longitudinal optical mode shift with temperature was measured in two vertical cavity surface‐emitting laser (VCSEL) type optical resonators with different GaAs and AlAs layer structures. The measurements show distinct differences in the behavior of the cavities. From the data the thermal dependencies of the indices of refraction of GaAs and AlAs for wavelengths near 1 &mgr;m were determined to be (2.67±0.07)×10−4/°C and (1.43±0.07)×10−4/°C, respectively. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114204

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoluminescence excitation (PLE) studies were performed on GaAs‐Al0.25Ga0.75As quantum wells (QWs) with fractional monolayer differences. The quantized PLE peaks and their submonolayer shifts clearly show that the heterointerface of thin QWs prepared by growth‐interrupted molecular beam epitaxy has islands which extend out a lateral dimension larger than 100 A˚, but they themselves have the microroughness smaller than 30 A˚. The result of this work using exciton as the probe provides a clear evidence supporting the bimodal roughness model. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114205

出版商:AIP    

年代:1995

数据来源: AIP