摘要:

We present a systematic experimental investigation on the infrared (IR) vibrational absorption spectroscopy of then‐Si/acetonitrile interface utilizing the attenuated total internal‐reflection geometry in the near‐infrared (1.1–5 &mgr;m) spectral region. The IR absorption of the interface has been isolated selectively by electromodulation, and studied as a function of modulation potential. The electrochemical behavior of the interface has been checked by current/voltage and impedance measurements. The IR spectra are composed of a broad background and various sharp vibrational peaks. The background can be analyzed as the sum of two contributions: (i) absorption by surface states at shorter wavelengths (<2 &mgr;m), (ii) free‐carrier absorption at longer wavelengths. The free‐carrier contribution is itself composed of a Drude‐like component (proportional to &lgr;3/2) and an interband component. The vibrational peaks can be ascribed to the C≡N, C–H, Si–H, and (Si–)O–H chemical bonds. The shapes and magnitudes of the C≡N and C–H peaks can be quantitatively understood in terms of displaced ions and acetonitrile molecules near the surface upon the electrode potential modulation. The shape of the C≡N peak also gives an indication of a weak interaction of the acetonitrile molecules with the electrode surface. The Si–H and (Si–)O–H peaks can be interpreted in terms of Stark effect modulation of the infrared absorption of these species. The shape of the O–H peak indicates the presence of nonequivalent sites at the interface. Upon the electrode aging and oxidation the magnitude of the Si–H peak decreases and the (Si–)O–H peak increases and correspondingly the surface‐state density increases which provides a directinsituphysicochemical information regarding the slow oxidation of the electrode surface.

ISSN:0021-8979    

DOI:10.1063/1.337417

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Superelectrons passing through the weak link region of Josephson junctions are affected by the electric potential applied to this region, and are accelerated or decelerated. The effect would appear as the modulation of the supercurrent through the junction. The amount of the supercurrent is calculated using the time‐dependent Ginzburg–Landau equation for the device structures of superconductor‐insulator‐normal conductor‐insulator‐superconductor where the intermediate normal region is used to introduce the electric potential.

ISSN:0021-8979    

DOI:10.1063/1.337418

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The characteristics of a superconducting‐base transistor are derived. The device is similar to a bipolar transistor but uses quasiparticles in a superconductor as minority carriers. Injection, transport, recombination, and extraction of quasiparticles are discussed. Analytic expressions for the characteristics of the transistor are obtained.

ISSN:0021-8979    

DOI:10.1063/1.337791

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Films of (Y3−x−yBixPby) (Fe5−zGaz)O12(z=0–1.1) and (Y3−x−yBixPby) (Fe5−wInw)O12(w=0–0.6) garnets were prepared by liquid‐phase epitaxy. The effects of tetrahedral Ga and octahedral In substitution on the Bi‐based growth‐induced uniaxial anisotropy in (YBi)3Fe5O12films were measured. Both Ga and In resulted in a linear decrease in the anisotropy with increasing substitution. The effect of octahedral In was twice that of tetrahedral Ga.

ISSN:0021-8979    

DOI:10.1063/1.337419

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Garnet films of composition R3−x−yPrxBiyFe5O12with R=Lu, Y, and 0≤x≤1.8, 0≤y≤1.7 have been grown from different melt compositions and under various growth conditions onto substituted gadolinium gallium garnet substrates with (100), (110), (111), and (211) orientation. The dependence on composition and temperature of the saturation magnetizationMs, the uniaxial anisotropy constantKu, the Faraday rotation &thgr;F, and the Faraday ellipticity &psgr;F, have been investigated. The change ofMsas compared to that of Y3Fe5O12is essentially associated with the alignment of the Pr moment parallel to the net iron moment and the increase of the Curie temperature originating mainly from the bismuth. However, both contributions are negligible in the room‐temperature range. The uniaxial anisotropy is strongly affected by both Pr and Bi. The anisotropy contributions &Dgr;Ku/x<0 and &Dgr;Ku/y>0 turn out to be approximately additive. Both Pr and Bi give rise to a pronounced enhancement of the magneto‐optical effects. At &lgr;=633 nm &thgr;Fincreases linearly withxandyyielding atT=295 K the contributions &Dgr;&thgr;F/x=−3.8×105deg m−1and &Dgr;&thgr;F/y=−20.6×105deg m−1, respectively. The bismuth contribution compares well with that observed for various other Bi‐substituted rare earth iron garnets.

ISSN:0021-8979    

DOI:10.1063/1.337420

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An expression for the temperature dependence of recoil‐free fraction of iron atoms was derived from the two‐band theory proposed previously by the present authors, and it was applied to investigate the bonding characteristics of iron in amorphous Fe83B17, Fe80B20, and Fe80P20alloys. The characteristic temperatures were found to be &thgr;1=605 K and &thgr;3=230 K for amorphous Fe83B17, &thgr;1=655 K and &thgr;3=185 K for amorphous Fe80B20, and &thgr;1=425 K and &thgr;3=185 K for amorphous Fe80P20. The comparison between these values with those obtained from the specific‐heat measurements showed a good agreement for &thgr;1, which is a measure of interatomic bond strength, indicating that metalloid atoms are not connected to each other in these Fe–mettalloid binary amorphous alloys but are bonded to iron atoms. Based on this result, the force constant was estimated for Fe–B, Fe–P, and Fe–Fe bonds. On the other hand, the values of &thgr;3obtained from the Mo¨ssbauer study were significantly different from those obtained from specific‐heat measurements.

ISSN:0021-8979    

DOI:10.1063/1.337421

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The eddy current tests of ferromagnetic materials are theoretically analyzed employing a Globus model for the magnetization process, and the impedance change of a coil due to the presence of flaws contained in a magnetic conductor is derived employing Green’s function technique. The results show that for an excitation field which is lower than the critical field, the impedance change is maximum when the residual magnetization (or the dc magnetic field applied for the magnetic saturation of the conductor) is absent but for a large field the impedance change becomes maximum when the appropriate dc magnetic field in which the differential permeability reaches its maximum value is applied. For small surface flaws, the volume inhomogeneity mainly contributes to the reactance change of the coil whereas the discontinuity in magnetic permeability contributes to both real and imaginary parts of the impedance change. The dependence of the impedance change on flaw shape is shown explicitly in the derived formula.

ISSN:0021-8979    

DOI:10.1063/1.337422

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Ferroelectric (Pb,La)(Zr,Ti)O3(PLZT) thin films have been epitaxially grown on thecplane of sapphire by rf‐planar magnetron sputtering. The sputtering conditions were investigated to obtain epitaxial and transparent films. Dielectric, piezoelectric, and electro‐optic properties of the films were measured. Piezoelectricity of the PLZT(28/0/100) film was confirmed and was as strong as that of BaTiO3. Excellent quadratic electro‐optic effects for PLZT(28/0/100) and PLZT(9/65/35) films and a linear electro‐optic effect for PLZT(21/0/100) film were observed at 0.633‐&mgr;m wavelength. Epitaxial PLZT thin film on sapphire is presently the most promising material for new functional devices.

ISSN:0021-8979    

DOI:10.1063/1.337423

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Using the velocity operator derived from the Heisenberg equation of motion, we have investigated second‐harmonic generation of acoustic waves propagating in nondegenerate piezoelectric semiconductors with a uniform dc magnetic fieldBdirected along the waves. Since we are interested in both high‐and low‐frequency regions, an electron relaxation time due to the scatterings in solids is taken into account. Results show that the second‐harmonic generation due to the piezoelectric polarization is insignificant in the very low‐frequency region. However, when the frequency is coming into the microwave region, the second‐harmonic generation increases quite rapidly with the sound frequency up to some maximum points at the range of frequency &ohgr;=1011–2×1011rad/s, and then decreases. There are two maximum points in this range of frequency at very low temperatures. When the temperature increases, these two maximum points will be reduced to only a single maximum point. It is also found that the second‐harmonic generation can be influenced by the dc magnetic field due to the nonlinear nature of energy bands in piezoelectric semiconductors.

ISSN:0021-8979    

DOI:10.1063/1.337424

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A series of V–O alloy films were sputter deposited on glass substrates using a vanadium target and rf-excited Ar/O2discharges containing 2%–8% O2. On the basis of x-ray results, the films were nominally identified as vanadium pentoxide. Optical transmission and reflection characteristics were measured by double-beam spectrophotometry in the 390- to 700-nm-wavelength region. From these measurements, the absorption coefficient &agr; was determined as a function of the incident photon energyh&ngr;. The absorption edge of all films showed two distinct regions of behavior: a high photon energy region in which &agr; varied linearly with (h&ngr;)2and a low-energy tail. The behavior of &agr; is discussed in terms of the structural and electronic changes in the films due to nonstoichiometry and compared to results obtained for single crystal V2O5.

ISSN:0021-8979    

DOI:10.1063/1.337425

出版商:AIP    

年代:1986

数据来源: AIP