摘要:

A response mechanism of nematic liquid crystals following the switching‐on and off of an in‐plane electric field when using the in‐plane switching (IPS) mode was investigated. Simplified theoretical expressions, which were derived with an assumption that an in‐plane electric field was applied to the liquid crystals, were used to explain the dynamical switching process in the IPS mode. In particular, the relaxation time of the liquid crystals when removing the electric field was described as a proportional relationship to the square of the cell gap. A thinner cell gap also proved to be effective in obtaining a fast response time in the IPS mode. By contrast, the switching‐on time when applying the in‐plane electric field proved to be inversely proportional to the difference between the square of the electric field strength and the square of the critical electric field strength at which the liquid crystals begin to deform. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117927

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Simulations based on a rate equation model for high‐field transport through a doped semiconductor superlattice are presented for the case that one barrier is chosen significantly wider than the others. The distinct impact of that local perturbation on the overall shape of the current–voltage characteristic is discussed and related to the spatial field distribution. The measured current–voltage characteristic of a superlattice, which was intentionally grown with one thicker barrier, confirms the strong asymmetry predicted by the model calculations. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117928

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In this letter the expression of the phase time is derived for a two‐dimensional coherent wave packet traveling through a generic mesoscopic system. The obtained analytical expression generalizes the definition of phase time for a single one‐dimensional scattering state to the case of coherent transport through two‐dimensional multichannel mesoscopic structures, and results in a suitable average of the single‐mode phase times. As an application, numerical results for a quantum wire and a double‐barrier resonant‐tunneling diode with and without an ionized impurity are also presented. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117929

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Changes in current by Cl2gas adsorption were measured at 200 °C for SnO2films sputtered on SiO2/Si substrates, with a varying electric field from the substrate. Properties of Cl2adsorption, such as sensitivity and reaction rate constant, under a positive (+5 V) substrate bias were almost the same with those under 0 V bias. However, under a negative (−5 V) substrate bias, the current decreased remarkably by Cl2adsorption and a high sensitivity was obtained. Moreover, the reaction rate constant was found to be about 10 times or more larger than those under 0 V and +5 V with positive biases. It was indicated that an external electric field affects the adsorption behavior of Cl2on SnO2surface. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117930

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Efficient carrier blocking by a single ‘‘attractive’’ potential is demonstrated using a strained Si0.85Ge0.15/Si quantum well (QW). The carrier blocking becomes pronounced at increased temperatures as most of the carriers at the QW bound state are thermalized with the barrier band edge. The carrier blocking efficiency at 100 K is almost of the order of unity as compared to insufficient carrier blocking due to a large ‘‘repulsive’’ potential associated with SiO2. The carrier blocking arises from efficient hole reemission from the QW that reflects a highly efficient carrier capture to the strained Si1−xGex/Si QWs from Si barriers. It is further shown that a single QW is the optimized geometry for efficient carrier blocking and that multiple well potentials lead only to a reduced blocking efficiency. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117931

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

It has been found that selective thermal desorption of SiO2on Si (111) substrate is induced by electron‐beam irradiation. By using this selective thermal desorption, a nanofabrication technique has been realized by focused electron beams. Open windows of 10 nm width in a SiO2film have been fabricated by this technique. A pattern transfer from the open windows to thin Si films has also been performed by Si growth and subsequent heating. This has produced Si wires of 10 nm width. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117932

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A new type of thermal treatment for air‐exposed AlGaAs surfaces,insitulow‐temperature H2annealing, has been developed regrowing AlGaAs in metalorganic vapor phase epitaxy. The quality of regrown interface was evaluated by photoluminescence (PL) spectrum from Al0.3Ga0.7As/GaAs/Al 0.3Ga0.7As quantum wells near the interface of the initial AlGaAs layer. Remarkable recovery of PL intensity was observed by this newly developed process, indicating that initial air‐exposed AlGaAs surface states are reduced. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117791

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Near‐field photocurrent measurements with multiwavelength excitation sources are applied to the investigation of a lateralp–njunction grown on patterned GaAs (111)A substrate. In order to probe the internal properties of this device, propagation modes into the sample are utilized retaining high resolution with the contribution of a penetration depth smaller than the aperture diameter. By systematically varying the penetration depth over a wide range up to 900 nm, photocurrent signals due to internal optical response clearly appear. The capability of ‘‘tomographic’’ diagnostics is demonstrated and the slant angle of thep–ninterface is determined to be 30±8°. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117792

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

CuInSe2films have been grown by molecular beam epitaxy on pseudo‐lattice‐matched substrates that consist of a 1‐&mgr;m‐thick In0.29Ga0.71As layer grown on a linearly composition‐graded InxGa1−xAs buffer (0≤x≤0.29) grown in turn on GaAs (001). The properties of these films have been compared with those of the films grown directly on GaAs (001). High resolution x‐ray diffraction analysis on CuInSe2grown on pseudo‐lattice‐matched substrates indicated substantial reduction on residual strain in the CuInSe2films. A photoluminescence spectrum dominated by sharp free exciton emissions has been observed for the first time from CuInSe2films indicative of significant improvement in crystalline quality and substantial reduction in the point defect density. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117793

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A model for the electronic interaction between additives and semiconducting oxide gas sensors is presented. The model is based on the depletion layer that is created due to the metal–semiconductor contact forced by the presence of a metallic additive. This depletion layer corresponds to an active grain size that is smaller than the geometrical one. Thus, the work function of the metal is connected to the change of sensor characteristics. Moreover, the dependence of the sensitivity on the amount of the deposited additive is explained on the same basis. Experimental results are presented in the case of tin oxide thin film gas sensors with Pd, Pt, and Ni in the presence of zero grade air and carbon monoxide. The experimental results are in excellent qualitative agreement with the proposed model. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117794

出版商:AIP    

年代:1996

数据来源: AIP