摘要:

Ten million atom multiresolution molecular-dynamics simulations are performed on parallel computers to determine atomic-level stress distributions in a 54 nm nanopixel on a 0.1 &mgr;m silicon substrate. Effects of surfaces, edges, and lattice mismatch at theSi(111)/Si3N4(0001)interface on the stress distributions are investigated. Stresses are found to be highly inhomogeneous in the nanopixel. The top surface of silicon nitride has a compressive stress of+3 GPaand the stress is tensile,−1 GPa,in silicon below the interface. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121237

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The thermal stability of molecular beam epitaxy grownSi1−x−yGexCy/Siheterostructures (0⩽x<0.30,y∼0.008) was studied using infrared absorption spectroscopy. The local vibrational mode of C in Si andSi1−x−yGexwas used to quantify the loss of C atoms from substitutional sites with high temperature annealing. The activation energy(Ea=4.9 eV)for the loss of substitutional C achieved a maximum for the strain compensated alloy(x∼0.1).An additional increase of Ge content resulted in a rapid decrease inEa,which was found to be 3.4 eV forx∼0.27.The nonmonotonic behavior ofEaon Ge content is explained by the effect of the interface strain between the epitaxial layer and Si substrate. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121238

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We optically measure the molecular reorientation induced by an argon laser in homeotropically aligned chiral smectic-C films. Optical unwinding of the helix is observed and the critical unwinding intensity is determined. We have also developed a theory which not only explains the observed effect but also predicts a novel reentrance phenomenon of the unwinding state. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121264

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A reflective type of a liquid crystal (LC) display is proposed in a twisted hybrid aligned configuration with a reflective electrode and a single polarizer. A chiral dopant was introduced into a nematic LC to produce a proper amount of twist in a hybrid aligned geometry. Numerical simulations were performed to optimize the cell parameters so that the electro-optical switching between the black and white states could be easily achieved. It was experimentally demonstrated that this reflective mode gives wide viewing and fast response characteristics. The effect of an optical retardation film on the device performance is also discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121239

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We show here conclusively that the internal field originates from nonstoichiometric point defects inLiNbO3crystals. The switching fields required for 180° domain reversal in congruent crystals[C=Li2O/(Li2O+Nb2O5)=0.484]are ∼4–5 times larger than the switching fields for nearstoichiometric crystals(C=0.498).An internal field of ∼2.5 kV/mm observed in congruent crystals disappears in stoichiometric crystals. The concentration of hydrogen incorporated during crystal growth has no effect on the switching or internal fields. The measured spontaneous polarization,Ps=80±5&mgr;C/cm2is relatively insensitive to the crystal nonstoichiometry and the hydrogen content. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121491

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The precipitation of arsenic in superlattice structures of alternately undoped and[Be]=2.4×1019 cm−3doped GaAs grown at low temperatures has been studied using transmission electron microscopy. Novel precipitate microstructures were observed in annealed samples, including preferential accumulation of precipitates toward each interface of Be-doped GaAs and the following grown undoped GaAs. Specifically, after 800 °C annealing, the precipitates are totally confined in Be-doped regions, forming two-dimensional dot arrays near the aforementioned interfaces. Data are also presented to show that the heavily Be-doped GaAs has a smaller lattice constant than the undoped GaAs. A strain-induced mechanism was proposed to account for the segregation of As clusters. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121240

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We used scanning tunneling microscopy (STM) to investigate the local leakage current through ultrathin silicon dioxide(SiO2)films grown on Si substrates. Individual leakage sites, which were created by hot-electron injection from the STM tip under a high sample bias of+10 V,were identified from the local change in surface conductivity due to defect creation in the oxide films. When we reversed the stressing polarity (using a negative sample bias) no leakage sites were created in the oxide film. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121241

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report on the successful incorporation of arsenic (As) in GaN during metalorganic chemical vapor deposition (MOCVD). A characteristic room-temperature luminescence band centered around 2.6 eV (480 nm), similar to the peak position of the As ion-implanted GaN, is found to be related to the As impurity in the MOCVD grown GaN:As films. The arsenic incorporation efficiency as a function of experimental conditions and structure is presented. Temperature- and power-dependent cathodoluminescence measurements have been performed to help establish the nature of the As-related peak. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121242

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The doping-density dependence of scanning tunneling spectroscopy on lightly doped hydrogen-terminated Si(100) (resistivities in the range of 0.2–12 &OHgr; cm) was investigated in air with and without illumination. The observed doping-density dependence is consistent with a generation model in which the changes in the three-dimensional depletion region, induced by a scanning tunneling microscopy tip, contributes to changes in the concentration of thermally and/or photogenerated carriers in lightly doped samples. These results suggest that scanning tunneling spectroscopy can be used to image variations in dopant density in lightly doped samples. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121243

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report the fabrication of nonalloyed ohmic contacts onn-InxGa1−xAs(0.25⩽x⩽0.38)grown by molecular beam epitaxy (MBE) on GaAs(001). This result is obtained by suppression of the native Al/InGaAs Schottky barrier by means of the MBE growth of Si bilayers at the metal-semiconductor interface. Truly ohmic contacts are demonstrated by x-ray photoemission spectroscopy and current-voltage techniques. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121244

出版商:AIP    

年代:1998

数据来源: AIP