摘要:

Reduced density function analyses for the bulk amorphous alloyZr41Ti14Cu12.5Ni10Be22.5and its decomposition and crystallization have been made by means of electron diffraction intensity measurement with imaging plate. The local atomic structure of the amorphous alloy as well as its development in the course of the decomposition and crystallization is described from the analysis of the atomic distribution function. The origin of the high thermal stability and the large glass forming ability of the alloy as well as the effect of the decomposition on the crystallization is discussed from the viewpoint of the local atomic structure characteristics of the alloy. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119725

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The bonding of alkyl monolayers to Si(111) surfaces has been studied by conventional x-ray photoelectron spectroscopy (XPS) and chemical-shift, scanned-energy photoelectron diffraction (PED) using synchrotron radiation. Two very different wet-chemical methods have been used to prepare the alkyl monolayers: (i) olefin insertion into the H–Si bond on the H–Si(111) surface, and (ii) replacement of Cl on the Cl–Si(111) surface by an alkyl group from an alkyllithium reagent. In both cases, XPS has revealed a C1ssignal chemically shifted to lower binding energy, which we have assigned to carbon bonded to silicon. PED has shown that both preparative methods result in carbon bonded in an atop site with the expected C–Si bond length of1.85±0.05 Å.Chemical-shift, scanned-energy photoelectron diffraction is a particularly valuable probe of local structure at surfaces that contain the same element in multiple, chemically distinct environments. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119726

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

This letter reports a simulation study of depth sensing nanoindentation on a rough surface. The estimated mean hardness and scatter are both influenced by roughness, irrespective of whether there is a genuine variation in mechanical property with deformation volume/depth. The scatter due to roughness always decreases with penetration depth. The roughness dependency of hardness is the product of two terms. The first term is independent of property variation with deformation volume/depth and arises due to the discrete nature of multiple contacts during indentation. The second term is due to property variation with deformation volume/depth, as changing roughness changes the aggregate strength of each contact island. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119727

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Studies of the influence of defect distributions and mobility on ferroelectric phase transformations in lead zirconate titanate have been performed by transmission electron microscopy, high resolution electron microscopy, polarization switching measurements, and dielectric spectroscopy. Investigations focused onLa3+andK1+modified lead zirconate titanates. Defects which could be randomly quenched-in from temperatures significantly above that of the ferroelectric phase transformation resulted in relaxor ferroelectric behavior characterized by polar nanodomains. However, defects which remained mobile until temperatures significantly below that of the phase transformation resulted in a normal ferroelectric state which was characterized by domain pinning. Mobile impurities/vacancies are revealed to order into chain fragments or clusters which diffuse to domain boundaries resulting in a pinning of the boundaries on cooling. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119728

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Ann-type semiconducting diamond thin film was obtained by microwave enhanced plasma chemical vapor deposition using phosphine(PH3)as a dopant source. A homoepitaxial diamond thin film with a thickness of about 300 nm was grown on the {111} surface of a type Ib diamond with a variety of dopant concentrations. Over a wide range of dopant concentrations (PH3/CH4:1000–20 000 ppm), then-type conduction was confirmed by Hall-effect measurements. The activation energy of carriers was 0.43 eV. The Hall mobility of about23 cm2/V shas been obtained at around 500 K for the 1000 ppm sample. No significant increase of hydrogen has been observed by secondary-ion-mass-spectroscopy analysis for the phosphorous doped layers. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119729

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A technique to characterize oxide charge detrapping in a Fowler–Nordheim stressedn-metal–oxide–semiconductor field effect transistor is proposed. This technique consists of two alternating phases, an oxide charge detrapping phase and a subthreshold current measurement phase. An analytical model relating a subthreshold current transient to oxide charge density and detrapping time constants was derived. By varying the gate bias in the detrapping phase and the ambient temperature, the field and temperature dependences of oxide charge detrapping can be obtained from the subthreshold current transients measured. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119730

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on the growth of near bulklike InSb on GaAs substrates by molecular beam epitaxy despite the 14&percent; lattice mismatch between the epilayer and the substrate. Structural, electrical, and optical properties were measured to assess material quality. X-ray full widths at half-maximum were as low as 55 arcsec for a 10 &mgr;m epilayer, peak mobilities as high as∼125 000 cm2/V s,and carrier lifetimes up to 240 ns at 80 K. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119731

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Low-temperature photoluminescence (PL) spectroscopy was used to study electronic states associated with threading dislocations (Dlines) in strain-relaxedSi1−xGexlayers. The structures investigated were grown by ultrahigh vacuum chemical vapor deposition at 550 °C and consist of a Si(001) substrate, followed by a stepwise graded buffer layer, followed by a thick uniform compositionSi1−xGexlayer. The PL peak positions of the fourDlines after isochronal annealing at temperatures between 600 and 800 °C were measured. We show that the large energy shift of theD1line is due to a change in the local band gap energy at the dislocation core due to strain-driven diffusion of Ge atoms away from the dislocation core with an activation energyEa,which varies with Ge mole fractionx. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119732

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An almost 100&percent; activation ratio{(NA-ND)/[N]}for a nitrogen-doped ZnSe molecular beam epitaxy (MBE) layer with the highest net acceptor concentration(NA-ND)of1.2×1018 cm−3was obtained using a high-power rf plasma source. Even at this highNA-NDvalue, a 4.2 K photoluminescence spectrum shows bound exciton emission and deep donor–acceptor pair emission with well-resolved phonon replicas. The high activation in nitrogen doping could be ascribed to the generation of the predominant atomic nitrogen and to the suppressed extraction of nitrogen ions and excited neutral nitrogen molecules due to the structure of the orifice placed between the MBE growth chamber and the plasma discharge tube of the high-power plasma source. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119733

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the demonstration of resonant tunneling of holes through an AlAs/GaAs0.7P0.3double-barrier heterostructure. The tensile strain in the quantum well is large enough to reverse the order of the light- and heavy-hole levels (the first light-hole level is the ground state). TheI(V)characteristic of this structure is measured and compared to a standard AlAs/GaAs unstrained one. As expected, the peak current density of the first light-hole resonance and its peak-to-valley current ratio are enhanced (they reach 28A/cm2and 3.4:1 at 15 K). Negative differential resistance is observed up to 250 K. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119734

出版商:AIP    

年代:1997

数据来源: AIP