摘要:

PbTiO3thin films were prepared by surface‐reaction enhanced metalorganic chemical vapor deposition. The deposition rate was limited by supply of a Ti precursor. In contrast, the deposition rate and composition were kept constant for a certain range of Pb‐source feeding, although the deposition rate of PbTiO3was lower than that of TiO2. From these results, we proposed a growth model for PbTiO3: stoichiometric PbTiO3film is grown by the Ti species arriving and reacting on the Pb‐covered surface. The Ti sticking coefficient is rather small on such a surface. This model qualitatively explains the change in step coverage. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115009

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Transient dielectric measurement is used to study the transitions among the planar, focal conic, and homeotropic states of cholesteric liquid crystals. If the initial state is the field‐induced homeotropic state, at low bias fields, the liquid crystal transforms to the planar state in a sequence of homeotropic‐transient planar–planar; at high bias fields, the liquid crystal transforms to the focal conic state. The homeotropic‐transient planar transition is on the order of 1 ms while the homeotropic‐focal conic transition is on the order of 100 ms. Large hysteresis is observed in the transitions between the homeotropic and the focal conic state. Based on the rapid homeotropic‐transient planar transition and the hysteresis effect in the focal conic‐homeotropic transition, we have designed a drive scheme which can address bistable reflective cholesteric displays at the speed of one line per millisecond. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115010

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Nanosize powders of alumina have been synthesized by high‐density ablation plasma produced by the irradiation of an intense, pulsed, light‐ion beam on an aluminum target in oxygen. Diameters of the powders, which are observed to be spherical, are typically 5–25 nm. At 1 Torr of oxygen, nanosize powders of aluminum are synthesized with those of a small amount of &ggr;‐alumina. At 10 Torr of oxygen, on the other hand, &ggr;‐alumina powders are produced with a small amount of aluminum powders. Annealing characteristics in nitrogen have also been studied on the transition from &ggr;‐ to &agr;‐alumina. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115011

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

If there is a temperature difference between tip and sample of a scanning tunneling microscope a thermovoltage is generated which is very sensitive to the electronic states involved in the tunneling process. This has been used, e.g., to distinguish between different metals of a heterogeneous metallic surface. To demonstrate the capability of this method it has been applied to copper islands on a Ag(111) surface. Knowing the thermopower for chemically homogeneous silver and copper surfaces of −45 and −15 &mgr;V/K, respectively, islands of copper on the silver substrate can be well identified with a lateral resolution of 1 nm. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115012

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The quantum carrier capture time in a quantum well laser is calculated as a function of temperature and bias current. The calculated results show good consistency with recent measurements on the small signal frequency response of a quantum well laser at cryogenic temperatures. This calculation reveals some of the characteristics of longitudinal optical phonon assisted quantum carrier capture phenomena in quantum well structures. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115013

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Ultrashallow junctions (∼60 nm) are obtained using low energy BF2(5 keV) implants in crystalline Si. The variation of junction depth as a function of the dose rate is studied for doses of 1×1014and 1×1015cm−2. Boron diffusion is retarded in the tail region for the higher dose rates and consequently the junction depth decreases as compared to the lower dose rates. The residual defect density after a 950 °C, 10 s anneal for a dose of 1×1015cm−2is reduced for the higher dose rate as compared to the lower dose rate. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115014

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Changes in the electrical resistance induced by electromigration in short (3–100 &mgr;m) pure Al lines show a rather well‐defined behavior. An applied dc current induces either an increase or a decrease of the resistance. For current densities below a critical value the resistance change saturates with time and the resistance fully recovers when the current is switched off. The length and temperature dependence of the resistance changes indicate that the observed time dependence is determined by grain boundary diffusion along the whole line length. Above the critical current density the resistance changes do not fully recover. Given the inevitable sample‐to‐sample variations, the product of the critical current density and the line length is constant. The value of this product is in good agreement with values of the constant product of threshold current density and line length found in drift velocity experiments. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115015

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We introduce a high sensitivity (1J/m2) scanning microcalorimeter that can be used at high heating rates (104 °C/s). The system is designed using ultrathin SiN membranes that serve as a low thermal mass mechanical support structure for the calorimeter. Calorimetry measurements of the system are accomplished via resistive heating techniques applied to a thin film Ni heating element that also serves as a thermometer. A current pulse through the Ni heater generates heat in the sample via Joule heating. The voltage and current characteristics of the heater were measured to obtain real‐time values of the temperature and the heat delivered to the system. This technique shows potential for measuring irreversible heat of reactions for processes at interfaces and surfaces. The method is demonstrated by measuring the heat of fusion for various amounts of thermally evaporated Sn ranging from 50 to 1000 A˚. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.115016

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We study the interplay of elastic and plastic strain relaxation of SiGe/Si(001). We show that the formation of crosshatch patterns is the result of a strain relaxation process that essentially consists of four subsequent stages: (i) elastic strain relaxation by surface ripple formation; (ii) nucleation of dislocations at the rim of the substrate followed by dislocation glide and deposition of a misfit dislocation at the interface; (iii) a locally enhanced growth rate at the strain relaxed surface above the misfit dislocations that results in ridge formation. These ridges then form a crosshatch pattern that relax strain elastically. (iv) Preferred nucleation and multiplication of dislocations in the troughs of the crosshatch pattern due to strain concentration. The preferred formation of dislocations again results in locally enhanced growth rates in the trough and thus leads to smoothing of the growth surface. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115017

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Charge transport in diamond is studied using the Monte Carlo method, in which the scattering of electrons by phonons is considered stochastically. It is assumed that electrons are injected into the diamond conduction band with an initial equilibrium energy distribution and they are then accelerated by the internal field subject to phonon scattering. It is found that the electron energy distribution is independent of the field up to &bartil;0.1 V/&mgr;m. For larger fields, ‘‘hot’’ electron transport is predicted, i.e., the distribution shows a tail which depends on the internal field and the thickness of the diamond film. It implies that if electron field emission is from the conduction band in a diamond film, the transport and the energy spectrum of the emitted electrons should exhibit hot electron features. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115018

出版商:AIP    

年代:1995

数据来源: AIP