摘要:

An equivalent circuit model is presented for a planar rf plasma reactor. The physical properties of the plasma sheath adjacent to the electrodes are incorporated in the model. The sheath capacitances and the conduction currents through the sheaths are time varying and have a highly nonlinear dependence on the potentials across the plasma sheaths. The model shows that the waveforms of the voltage differences across the sheaths are highly nonsinusoidal and agree with reported measurements.

ISSN:0021-8979    

DOI:10.1063/1.337764

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Measurements of the electron density within a photo‐initiated, impulse‐enhanced, electrically excited (PIE) laser gas discharge are presented. Ion current measurements were made using a single Langmuir electrostatic probe positioned within the laser discharge volume. Calculations of the electron density were made utilizing a thick‐sheath analysis. The results indicate that the electron density increases by two orders of magnitude as the pulser power level is increased. In addition, the electron density was observed to decrease markedly as the dc discharge current was increased.

ISSN:0021-8979    

DOI:10.1063/1.337765

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The real and imaginary parts of the dielectric function of racemic and chiral CE8 have been measured between 30 Hz and 13 MHz at temperatures between 51 and 162 °C. Low‐ (1 kHz) and high‐(105Hz) frequency dielectric constants reflect changes in structure of the liquid‐crystal phases and differences in behavior of the two forms. The low‐frequency relaxation in the ferroelectric SmC* phase, near 1500 Hz, was studied in detail as a function of temperature and dc bias. The mean relaxation time does not present an obvious systematic variation with temperature although the low‐frequency dielectric constant and distribution of relaxation times do. The mean relaxation time in the SmC* phase shifts continuously to shorter times with the application of dc bias.

ISSN:0021-8979    

DOI:10.1063/1.337766

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

AuGe‐Ni is widely used for the fabrication of ohmic contacts ton‐GaAs. The alloying behavior of evaporated AuGe‐Ni alloyed by furnace and scanning electron beam (SEB) is characterized by Rutherford backscattering with 2‐MeV4He+ions. The redistribution and diffusion of constitutents involved in the ohmic contact formation is studied by comparing the experimental spectrum with theoretically computed spectra. The studies show that SEB‐alloyed contacts undergo less redistribution of contact constituents compared with furnace‐alloyed contacts. It is established that the penetration depth of Au for furnace‐alloyed contacts increases with metallization thickness, whereas for SEB‐alloyed contacts the penetration depth is independent of metallization thickness.

ISSN:0021-8979    

DOI:10.1063/1.337767

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The longitudinal distribution of midgap native donor concentration was investigated in detail using semi‐insulating liquid‐encapsulated Czochralski GaAs crystals grown from various melt compositions. The midgap native donor concentration was found to decrease with fractional solidification under Ga‐rich conditions, to increase under As‐rich conditions, and not to change under stoichiometric conditions. Moreover, it varied with the magnetic field intensity and the crystal‐pulling speed depending on the melt composition. These phenomena were consistently explained by assuming that the midgap native donor acts like a dopant with a certain segregation coefficientk, wherek<1 under As‐rich conditions,k=1 under stoichiometric conditions, andk>1 under Ga‐rich conditions. This is in good agreement with the expected segregation of As atoms determined from a phase diagram with a narrow solid‐solution region.

ISSN:0021-8979    

DOI:10.1063/1.337747

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

When a nematic liquid‐crystal cell is driven by a dc electric field, the capacitance of the cell increases in the first several tens of milliseconds, but after that the capacitance tends to decrease with a rather long relaxation time of the order of 1 s. This phenomenon can be explained by impurity ions which form the electrical double layer at the surface. The results calculated using this simple model qualitatively agreed with the exprimental results. The amount of charge in the double layer and the ion mobility are derived as 2×1011ions/cm2and 2.7×10−7cm2/V s, respectively.

ISSN:0021-8979    

DOI:10.1063/1.337721

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A combined cross‐sectional and plan‐view transmission electron microscope study of residual defects in 110‐keV, 5×1015/cm2BF+2‐ implanted (001)Si has been carried out. Complete amorphization of the surface layer to a depth of about 1400 A˚ from the surface was found in as‐implanted samples. The general trends of the amorphous/crystalline (a/c) regrowth were found to be similar in 550–900 °C annealed samples. ‘‘Paired’’ dislocations were observed in the first ∼600 A˚ of regrown layers. A high density of twins was found subsequently as thea/cinterface advanced to the surface. Small defect clusters, irregular dislocations, equiaxial loops, and rodlike defects were observed to distribute in bands underneath the originala/cinterface. The regrown layers were found to be almost dislocation‐ and twin‐free in 1000–1100 °C annealed specimens. The regrown layer, however, contained a high density of fluorine bubbles. The bubbles were concentrated near the orignala/cinterface and the surface. Irregular dislocation networks were found to develop near the orignala/cinterface. The origins of residual defects and their possible influences on device applications are discussed.

ISSN:0021-8979    

DOI:10.1063/1.337722

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Hashin–Shtrikman bounds are given for the effective bulk and shear moduli of randomly oriented aggregates of materials with trigonal (crystal classes 3, 3¯) and tetragonal (classes 4, 4¯, 4m) symmetry. The Hashin–Shtrikman bounds are narrower than the widely used Voigt and Reuss bounds by factors of 2–13. This study completes the development of explicit Hashin–Shtrikman bounds for polycrystals of all crystal symmetries and classes, except triclinic.

ISSN:0021-8979    

DOI:10.1063/1.337723

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The isotherms of very thin PdHxfilms (60 A˚<d<600 A˚) have been determined below room temperature by equilibrium potential measurements. One finds that the critical temperatureTcis lowered when the film thickness decreases: for the 60‐A˚ filmTcwould be near 173 K. This marked drop ofTcis attributed to clamping effects of the sample on the substrate, which decreases the effective H–H interaction and favors short‐range coherency effects.

ISSN:0021-8979    

DOI:10.1063/1.337724

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Growth characteristics of a laser metalorganic vapor‐phase epitaxy (laser MOVPE) and the electrical and optical properties of the epitaxial layer grown by the technique are examined. The growth rate under laser MOVPE decreases with increasing substrate temperature in contrast with conventional MOVPE. The growth rate also depends on the type of the substrate, total gas flow rate and the incident laser power. The mechanism of laser MOVPE seems not to be a photothermal effect but a surface photochemical effect. The intensity of the photoluminescence at room temperature for the epitaxial layer grown by the laser MOVPE is found to be stroger than that of the epitaxial layer grown without the laser irradiation under the same growth condition. The carrier concentration is also found to be modified by the laser irradiation. It is emphasized that the laser MOVPE is very useful as a new crystal growth technology.

ISSN:0021-8979    

DOI:10.1063/1.337725

出版商:AIP    

年代:1986

数据来源: AIP