摘要:

Wall effects on the Freedericksz transition have been calculated and used to evaluate the interfacial interactions between nematic molecules and substrates. A total reflection method was developed to observe the Freedericksz transition. Both the easy axis and the anchoring strength were measured on the interfaces between MBBA and substrates with several surfactant layers. Experimental results indicate that the polar group of the surfactants plays several roles in their molecular orienting forces.

ISSN:0003-6951    

DOI:10.1063/1.90167

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

This paper concerns the use of Brillouin scattering measurements to study lattice attenuation in semiconducting CdS crystals. Measured acoustic fluxes are produced by the acoustoelectric domains. In order to measure the attenuation constant, an ultrasonic injection method is applied. A sample is divided into two parts; one part is used as a generation region of the acoustic flux [region (1)] and the other part is used as a propagation region of the injected flux [region (2)]. The acoustic attenuations of various frequencies are measured at region (2). The lattice attenuation is greatly affected by the rise time of an applied pulse in region (1). It is clear that acoustic flux in the acoustic domain which originates from the amplification of the pure thermally excited acoustic flux attenuates asf2and is in accordance with the Akhieser loss. On the other hand, a shock‐excited acoustic flux attenuates asf∼1.5.

ISSN:0003-6951    

DOI:10.1063/1.90184

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The scattered radiation patterns of surface cracks irradiated by acoustic surface waves are interpreted to provide estimates of crack size. The technique is demonstrated for cracks as small as 100 &mgr;m in radius with an accuracy of about 10%.The key features are the positions and spacings of nulls in the angular dependence of the backward scattered surface‐wave intensity. A simple model based on optical diffraction theory is presented and demonstrated on cracks (made with the identation technique) in commercial hot‐pressed silicon nitride studied at 100 MHz and on cracklike flaws in commercial aluminum studied at 2–10 MHz.

ISSN:0003-6951    

DOI:10.1063/1.90148

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The frequency dependence of thermoelectric power and the resistivity change induced by the infrared radiation from a chopped laser beam is used to estimate the Seebeck coefficient of semiconductor samples. The use of data on temperature dependence of resistivity eliminates the need for the measurement of rapidly varying temperature and its gradient within the sample. The method is tested forp‐Ge samples and good agreement is obtained with the results of usual dc measurement.

ISSN:0003-6951    

DOI:10.1063/1.90161

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The plasma production and containment system for a high‐power continuously operating magnetic multipole ion source has been designed and constructed. Preliminary tests on this system prior to high voltage extraction of large beams indicate advantageous performance for neutral‐beam injection applications. The source has produced 80 A to the extractor region at 0.33 A/cm2with a discharge of 330 A at 80 V. Density uniformity is better than 1% over a 16‐cm diameter, dropping to −4% at 18 cm, with plasma noise of less than 3%. Gas utilizaion efficiency and atomic (H+) species output are anticipated to be high due to a source length of 40 cm. This quiet efficient performance is attributed to the use of a hollow‐tube LaB6cathode and an improved magnetic multipole confinement system.

ISSN:0003-6951    

DOI:10.1063/1.90174

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

High‐temperature diffusion of boron or phosphorus into silicon leads to the formation of spherical precipitates and/or dislocation loops in the diffused layer which influence electrical junction characteristics. These diffusion‐induced imperfections can be removed by high‐energy pulse laser treatment. The boron or phosphorus atoms previously contained in the precipitates become electrically active and the resulting dopant concentration can exceed the solid solubility limit.

ISSN:0003-6951    

DOI:10.1063/1.90164

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

The diffusion rate of magnesium in tungstened nickel was measured at temperatures between 970 and 1330 K. The method consists of measuring the species and number of atoms collected on a collector in front of the evaporating surface in a well‐defined geometrical arrangement under ultrahigh‐vacuum conditions. The collected material is analyzed by means of AES. Experiments on the diffusion of magnesium in tungstened nickel yield an activation energy of 57 kcal/mole. The vapor collect method shows great potentialities for the measurement of evaporation rates and its dependence on surface contaminants.

ISSN:0003-6951    

DOI:10.1063/1.90165

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

A series of experiments are reported which demonstrate that donors or acceptors can dope polyacetylene tontype orptype, respectively, and that the two kinds of dopants can compensate one another. The formation of a rectifyingp‐njunction is demonstrated. These results suggest the possibility of utilizing doped polyacetylene in a variety of potential semiconductor device applications.

ISSN:0003-6951    

DOI:10.1063/1.90166

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

Recent results showing a crystallographic orientation dependence of growth kinetics, secondary defects, and stress relief in annealing of ion‐implanted Si are shown to be self‐consistent if interpreted in terms of the influence of stresses upon annealing processes. The stress influence proposed is microplastic shear which is induced in [112] directions on (111) planes inclined to the implant surface by the biaxial stress created in the implant region by ion‐implantation damage. The shear stresses are shown to be dependent on crystallographic orientation in a manner consistent with the model.

ISSN:0003-6951    

DOI:10.1063/1.90168

出版商:AIP    

年代:1978

数据来源: AIP

摘要:

We describe several versions of an integrated bistable optical device fabricated with Ti in‐diffused waveguides in LiNbO3. The ends of the LiNbO3crystal are cleaved to form a Fabry‐Perot resonator. These devices can be operated with as little as 1 pJ of optical switching energy.

ISSN:0003-6951    

DOI:10.1063/1.90175

出版商:AIP    

年代:1978

数据来源: AIP