摘要:

Although rate coefficients are essential ingredients in modeling chemical processes such as chemical vapor deposition and plasma etching, the values measured as a function of temperature under well‐defined equilibrium conditions may be inappropriate for use in models of nonequilibrium systems. For this reason, it is important to have measurements ofinsiturates that can be used as input parameters or can provide stringent tests for reactor simulations. Using time‐resolved plasma‐induced emission and laser‐induced fluorescence spectroscopy, we measured quenching rates for Ar metastable states in radio‐frequency discharges through mixtures of Ar and the molecular gases SF6, Cl2, BCl3, and N2. After verifying the validity of modulation spectroscopy to measureinsiturates, the effects of discharge power, pressure, and flowrate are investigated. The most important effect occurs when the discharge power is increased; the decline in quenching rates with increased power is attributed to increased molecular dissociation that produces products with lower collision cross sections.

ISSN:0021-8979    

DOI:10.1063/1.341948

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The range distributions of 10–120 keV11B+in polycrystalline Co, Ti, CoSi2, and TiSi2targets have been measured by secondary ion mass spectrometry. The obtained projected rangesRpand projected range stragglings &Dgr;Rpare within 25% and 10%, respectively, of those predicted using the Monte Carlo computer programtrim. By comparison the one‐dimensional Boltzmann transport calculation insuprem‐3 tends to overestimateRpby as much as 300% at the highest ion energies.

ISSN:0021-8979    

DOI:10.1063/1.341949

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Planar channeling effects on the threshold voltage uniformity of GaAs metal‐semiconductor field‐effect transistors within 3‐in. GaAs wafers have been investigated using the stereographic projection method. This method is very useful for a quantitative understanding of the angular relationship between the direction of an incident ion beam and wafer orientation during implantation. The ratioN(X1)/N(X2) of the peak carrier concentration at a depth ofX1to the carrier concentration of a depth ofX2=2X1, obtained from the carrier depth profiles, was employed as a suitable parameter which effectively reflects the variation in the carrier profiles arising from the planar channeling effects. The conclusion, that the most uniform implants are attained at an azimuthal angle of 26.5° when tilting the wafer 10°, was analytically derived from the stereographic projection method and was experimentally confirmed.

ISSN:0021-8979    

DOI:10.1063/1.341950

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The origin and characteristics of the field‐off state optical properties of the general twisted nematic liquid‐crystal displays (LCD) are discussed. The optical field propagating normally in a uniformly twisted nematic structure can be represented by two mutually orthogonal elliptically polarized normal modes, one with left elliptical polarization and the other with right elliptical polarization. The interference between the two normal modes explains precisely, for the first time, the working mechanism for the field‐off state optical performance of all twisted nematic liquid‐crystal displays. The sum of the intensities of the two modes is independent of the polarizer orientation and always constitutes one half of the total intensity. The interference between the two modes contributes the second half of the total intensity and gives rise to two separate terms, each of which can be controlled by the entrance polarizer.Each of their contributions to the transmitted intensity can be minimized or maximized by the entrance polarizer in a complementary way. In addition, the ordinary and the extraordinary waves are always excited and strongly coupled in the twisted nematic (TN) structures. We also show that the field amplitudes of the waves are, in general, nonzero. The ordinary wave is zero only at some particular spatial points when the entrance polarizer is oriented parallel to entrance LC director; the extraordinary wave is zero only at the same particular spatial points when the entrance polarizer is oriented normal to the entrance LC director. In all other spatial points, both waves are nonzero even if the entrance polarizer is oriented parallel or normal to the entrance LC director.Using the solution for the optical field, analytic expressions are obtained for the field‐off state optical transmissions of the general twisted nematic liquid‐crystal displays with arbitrary polarizer orientations, liquid‐crystal indices of refraction, twist angle, surface pretilt angle, and cell thickness. The field‐off state optical working mechanism and characteristics of various twisted nematic liquid‐crystal displays, including the standard 90° twisted nematic, the lower‐twisted nematic, the optical mode interference, the supertwisted nematic, and the supertwisted birefringence effects liquid‐crystal displays, are discussed. All the previously reported analytic results for the TN LCDs can be shown to be special cases of our general transmission formula.However, the Gooch and Tarry approach contains a few major incorrect intermediate results, despite the correct final results. We also obtained a simple expression for the polarizer orientations, for which the field‐off state transmission has an extreme value under parallel or crossed polarizers. In general, for every twist geometry, there are two possible optimized polarizer orientations for the field‐off state with parallel (or crossed) polarizers configuration. In particular, for the 180° supertwisted devices, one polarizer condition describes the standard 180° supertwisted nematic display, and the second polarizer condition describes the black and white 180° optical mode interference display.

ISSN:0021-8979    

DOI:10.1063/1.341951

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The characteristics of ion implantation induced damage in InAs, GaSb, and GaP, and its removal by rapid thermal annealing have been investigated by Rutherford backscattering and transmission electron microscopy. There is relatively poor regrowth of these materials if they were amorphized during the implantation, leaving significant densities of dislocation loops, microtwins, and in the case of GaSb, polycrystalline material. For implant doses below the amorphization threshold, rapid annealing produces good recovery of the lattice disorder, with backscattering yields similar to unimplanted material. The redistribution of the implanted acceptor Mg is quite marked in all three semiconductors, whereas the donor Si shows no measurable motion after annealing of InAs or GaP. In GaSb, however, where it appears to predominantly occupy the group III site, it shows redistribution similar to that of Mg.

ISSN:0021-8979    

DOI:10.1063/1.341952

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Channeling is used to describe defects associated with molecular‐beam epitaxy growth of (001) ZnTe on (001) GaAs. A high dislocation density (2×1011/cm2) is found in the immediate vicinity of the interface, in addition to misfit dislocations at the interface. Channeling is found to be a strain sensitive method useful for misfit dislocation analysis. Direct scattering on misfit dislocations together with elastic theory calculations reveals that the extent of the misfit dislocation elastic field increases with the interface roughness.

ISSN:0021-8979    

DOI:10.1063/1.341953

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

In this work we describe a new experimental procedure for parallel‐plate rheometry of glassy polymers above the glass‐transition temperature range. This method has been used with an automated setup built by us which is linked to a HP‐86 desk computer. Both our experimental procedure and experimental setup allow us not only to determine the Newtonian viscosity in the wide 104–109Pa s range, but also the evaluation of a kind of retardation time. This is related to the time that the sample needs to reach the viscous behavior. Moreover, this time can be identified with the retardation time corresponding to the effects of the entanglements in the polymer melt, at least for the two polymers investigated here: polycarbonate and polysulfone.

ISSN:0021-8979    

DOI:10.1063/1.341954

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A detailed study has been made of interdiffusion in ZnSe‐ZnTe strained‐layer superlattices (SLSs) grown by molecular‐beam epitaxy (MBE) at a growth temperature of 320 °C. In x‐ray diffraction measurements, the satellite peak intensities relative to the zero‐order peak intensity decreased with annealing time. The interdiffusion coefficientDwas calculated assuming a linear diffusion model. The values ofD=3.6×10−21to 2.2×10−19cm2/s at an annealing temperature of 500 °C were obtained for the ZnSe‐ZnTe SLSs. In the high‐resolution transmission electron microscopy (HRTEM) image of as‐grown SLSs, the presence of fine superlattice structures was seen, but for interdiffused samples stripes due to the periodic superlattice structures were not visible and many dislocation lines were observed. These results suggest that the structure of SLSs is significantly modulated by thermal annealing at a temperature higher than the growth temperature.

ISSN:0021-8979    

DOI:10.1063/1.341955

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The kinetics of NiAl3phase growth is studied on lateral diffusion couples in the temperature range from 375 to 450 °C. The lateral diffusion couple consists of an Al‐rich source on a Ni2Al3thin film. Analytical electron microscopy is used to determine the crystal structures and chemical compositions of the growing phases. The results show that: (1) Al is the dominant moving species in the growing NiAl3phase; (2) an equilibrium concentration of Al is established during the growth; and (3) the growth has a parabolic dependence on the annealing time. The study of NiAl3growth kinetics on lateral diffusion couples bridges the gap between bulk and thin‐film diffusion couples in terms of reaction temperatures. The activation energy of NiAl3growth is 1.2±0.2 eV.

ISSN:0021-8979    

DOI:10.1063/1.341956

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The phase formation of NiAl3and Ni2Al3is studied on lateral diffusion couples of an Al‐rich source on a Ni thin film at temperatures from 375 to 500 °C. Analytical electron microscopy is used to determine the crystal structures, chemical compositions, and the widths of growing phases. Simultaneous growth of NiAl3and Ni2Al3is observed at 375 and 450 °C. Al atoms dominate the diffusion process in NiAl3and Ni2Al3. The growth of Ni2Al3has a parabolic dependence on annealing time, and the growth constant,X2/t, has an activation energy of 2.0±0.2 eV. The growth kinetics is further studied by comparing the growth rates of NiAl3in one‐ and two‐phase growth, and by applying the criteria proposed by Go¨sele and Tu to the simultaneous growth of NiAl3and Ni2Al3.

ISSN:0021-8979    

DOI:10.1063/1.341957

出版商:AIP    

年代:1988

数据来源: AIP