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Non-centrosymmetric superconductors have received considerable attention because of their possible possession of unconventional spin-triplet pairing.For this reason,the non-centrosymmetric Re3W with α -Mn structure has been widely concerned.However,almost all the previous studies support that the non-centrosymmetric phase of Re3W is a conventional weak-coupling s-wave superconductor.Later on,it is proved that Re3W has two different superconducting phases,one is the non-centrosymmetric phase and the other has a centrosymmetric hexagonal structure.Thus,a comparative study of these two superconducting phases could provide more information about the effect of non-centrosymmetric structure on the pairing symmetry of Re3W.In this paper,point-contact Andreev reflection experiments are carried out on Re3W/Au and the data can be well fitted by isotropic s-wave Blonder-Tinkham-Klapwijk (BTK) theory.In combination with our previous researches,we find that both centrosymmetric and non-centrosymmetric phases have similar temperature dependence of superconducting gap (△) with almost the same gap ratio of △/Tc.These results present strong evidence that both phases of Re3W are weak coupling Bardeen-Cooper-Schrieffer superconductors.Another interesting finding is that both phases of Re3W could easily form an ideal point-contact junction (i.e.,inelastic scatterings at the interface can be ignored) with a normal metal tip.This is manifested as an extremely small broadening factor (Γ) used in the fitting process,and indicates a clean (and possibly transparent) interface.Keeping this in mind,we can assume that the effective barrier (Z) at the interface mainly comes from the mismatch between the Fermi velocity of the superconductor and that of the normal metal,which can be estimated from the formula Z2=(1-r)2/4r,where r is the ratio between those two Fermi velocities.From this formula,we can obtain the Fermi velocity of Re3W by using the known value of Au's Fermi velocity and the fitting parameter Z for the Re3W/Au point contacts.It is interesting to find that the chemical property of Re3W is stable in the atmospheric environment.Even if the samples are exposed to the atmospheric environment for nearly six months,the inelastic scatterings are still very weak,and the superconducting properties are unchanged.Such an exceptional performance of Re3W can be utilized to study the physical properties of its counter electrode in a point contact.As an attempt,we build a point contact between Re3W and a ferromagnetic Ni tip,and measure its Andreev reflection spectra which are then fitted with a modified BTK model by considering spin polarization.The determined spin polarization of Ni is in good agreement with previously reported result. Moreover,using the Fermi velocities of Re3W and Ni,we can calculate the effective barrier to be around 0.3 in the Re3W/Ni interface,which coincides with the fitting parameter Z.These results self-consistently demonstrate the validity of the determination of Re3W's Fermi velocity and the cleanness/transparency of the studied point-contact interface.

We present a new method in which both positive and negative pulses are used to etch silicon for fabrication of porous silicon (PS) monolayer. The optical thickness and morphology of PS monolayer fabricated with different negative pulse voltages are investigated by means of reflectance spectra, scanning electron microscopy and photoluminescence spectra. It is found that with this method the PS monolayer is thicker and more uniform. The micropores also appear to be more regular than those made by common positive pulse etching. This phenomenon is attributed to the vertical etching effect of the PS monolayer being strengthened while lateral etching process is restrained. The explanation we propose is that negative pulse can help the hydrogen cations (H+) in the electrolyte move into the micropores of PS monolayer. These H+ ions combine with the Si atoms on the wall of new-formed micropores, leading to formation of Si–H bonds. The formation of Si–H bonds results in a hole depletion layer near the micropore wall surface, which decreases hole density on the surface, preventing the micropore wall from being eroded laterally by F− anions. Therefore during the positive pulse period the etching reaction occurs exclusively only at the bottom of the micropores where lots of holes are provided by the anode.

Porous silicon samples were prepared for optical studies by using the photoluminescence (PL), Raman scattering (RS), as well as the absolute reflectance and ellipsometry methods. Results show that the porous Si has low optic constants, and can trap the visible photons of more than 95%, but give no evidence of a strong interband transition existing in the visible region. The Bruggeman effective-medium-approximation (EMA) and Lorentz oscillator models were used in data analyses. Calculations show that the layer dispersion effect may result in a red shift of the PL peak. The possible mechanism for the PL and Raman enhancement as well as the photon trap phenomenon was discussed, and was attributed mainly to the random multiple micro-reflections in the porous-Si layer having extremely large internal micro-surfaces.

It is demonstrated in this paper that the infrared-up-conversion luminescence generation from porous silicon, considered as an enhanced third-order nonlinear optical effect by the recent work, is anisotropic as the polarization vector of normally incident fundamental light is rotated. A new method has been used to determine the anisotropy parameter σ of the third-order nonlinear optical tensor χ(3). Due to the sensitivity of σ to the crystal structure and microscopic electronic properties, the difference in σ's between porous and crystalline silicon, particularly in their phases, demonstrates that the nanometer structure of porous silicon induces a dramatic change of the electronic band structure, but the strongly anisotropic crystal property remains unchanged.

The C60@SWNT (peapod) samples were prepared by the vapor diffusion method. Polymerization of C60 molecules in single walled carbon nanotubes (SWNTs) under high pressure and simultaneous irradiation of UV laser (325 nm) has been carried out for the first time by using diamond anvil cell. Raman spectra of the peapod samples decompressed from high pressure indicated that C60 molecules form one-dimensional orthorhombic polymer in SWNTs under UV laser irradiation at a high pressure of 21.5GPa, which is lower than that for the polymerization of samples induced by high pressure only. The polymerization is an irreversible phase transition in the peapod.

The special physicochemical environment caused by sonic_vacating provides an important outlet for the preparation of highly efficient luminescent porous silicon films.Experimental results show that sonic_chemical treatment is an effective t echnology for the improvement of the microstructure of porous silicon,and the luminescent efficiency and stability thereof.Luminescent porous silicon films,prep ared by ultrasonic-enhanced anode electrochemical etching,display better qualiti es than the samples prepared by conventionai methods widely used at present.This ultrasonic_chemical effect roots in sonic_vacating,i.e. the generation,formatio n and rapid collapse of bubbles in the etching solution.In the process of the po rous silicon being etched,the escape rate and caving_in of hydrogen bubbles in t he pores is increased as a result of the work of the ultrasonic waves,which is h elpful to the vertical etching of the pores.

We report on fluorescence and upconversion emissions of Er3+-doped TeO2-ZnO-PbCl2 tellurite-based oxyhalide glasses under 977nm laser diode excitation. A strong 153μm emission from 4I13/2→4I15/2 transition with a full width at half maximum of ～69 nm, and three intense infrared -to-visible upconversion emissions at 524, 546 and 668 nm, corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F11/2→4I15/2 transitions of Er3+ ions, respectivel y, have been observed under 977 nm excitation and the mechanisms involved have b een explained. The intensity parameters Ωt (t=2,4,6) of Er3+-doped TeO2-ZnO-PbCl2 oxyhalide glasses have been calculated according to the Judd- Ofelt theory, and the results are Ω2=59×10-20cm2，Ω4=2 1×10-20cm2，and Ω6=12×10-20cm2，respectively. The e mission cross_section has also been calculated from the absorption cross-section and the emission spectrum by using the McCumber theory. The maximum emission cr oss_section is 875×10-21cm2 at 153μm. Our results indicate that Te O2_ZnO_PbCl2 oxyhalide glasses are promising candidates for optical amplifie rs and upconversion lasers in comparison with the glasses such as silicate, phos phate, and fluoride glasses.

Electroluminescence (EL) from Sibased organic microcavity has firstly been reported in the literature. The microcavity is made up of the central active multilayers sandwiched between a silver film and a porous silicon Bragg reflector (PSDBR), formed by electrochemical etching of p+Si substrate in the electrolyte of HF: C2H5OH:H2O. The central active multilayers consist of Al (1 nm) / LiF (05 nm) / Alq3 / Alq3: DCJTB / NPB / CuPc / ITO / SiO2． The reflectivity (relative to an Al mirror) of the PSDBR is up to 99%, and the stopband is about 160 nm wide. Resonant cavity mode appears as a tip in the reflectivity spectrum of the Sibased organic multilayer films, indicating that the Sibased organic multilayer structure is indeed a microcavity. The peak widths of the EL spetra are greatly reduced from 70 nm to 12 nm as compared with those measured from noncavity structures. Note that the EL emission from the cavity devices is singlemode, and the offresonant optical modes are highly suppressed. Moreover, an increase of a factor of about 4 of the resonant peak intensity is observed. In addition, the currentbrightnessvoltage characteristics and the effect of parameters on the lifetime of the cavity devices are also discussed. The present technique for obtaining enhanced EL emission from Sibased organic microcavity may also be another novel effective method for realizing allSibased photonic devices and optoelectronics device integration.

Presence of a K adlayer will promote nitridation of GaAs(100) surfaces at room temperature, as is evidenced by photoemission measurements. Following exposure of K/GaAs to pure nitrogen, there appear remarkable variations in both valence band and core level spectra, i.e., recovery of work function to a certain extent, emergence of the N2p peak in the valence band spectra and creation of chemically shifted Ga2p and As2p components in the core level spectra. For the three different K coverages we studied (1/4, 1/2 and 1ML), the 1ML one shows the strongest promotion effect.

The temperature dependence of photoluminescence (PL) in porous silicon has been investigated. It is found that the PL peak from the low porosity samples shows a red shift with decreasing temperature, but the blue shift of the PL peak is always observed in the high porosity samples. The temperature dependence of the PL peak shift observed experimentally can be qualitatively explained by the simulated curves of the luminescent efficiency versus wavelength.

Synchrotron radiation photoelectron spectroscopy (SRPES) combined with scanning electron microscopy (SEM) and gravimetric method is used to study the neutralized (NH4)2S-passivated GaAs(100) surfaces- Compared to the conventional (NH4)2S alkaline solution treatment, a thicker Ga sulfide layer and stronger Ga—S bonding on GaAs surface can be formed by dipping GaAs in neutralized (NH4)2S solution- Gravimetric data show that the etching rate of GaAs in neutralized (NH4)2S solution is about 15% lower than that in the conventional (NH4)2S solution- From SEM observation, only fewer number of etching pits with smaller size on the neutralized (NH4)2S treated GaAs surfaces can be found

A novel passivation film on GaAs surface has been grown by microwave sulfur glow discharge technique.Auger electron spectroscopy and Rutherford back scattering measurements show that the film is mainly composed of sulfur and gallium,and atomic ratio of gallium to sulfur is about 1∶1.From X-ray diffraction spectroscopy measurememt,GaS is identified to be hexagonal polycrystalline material.The refraction index and dielectric constant of GaS have also been determined.

Two kinds of different electroluminescence from the porous silicon grown on p-type silicon wafers were observed by applying a forward bias to porous silicon in acidic aqueous system containing strong oxidizing agents (such as 1mol·L-1HCl, 1mol·L-1 SnCl4, and 1mol·L-1 H2SO4+0.1mol·L-1 Na2S2O8). One was the red emission with low applied voltage (V+≈1.4V). Its red peak shifted to shorter wavelength as the operation time increases. It is most possibly related to the quantum size effect. The other was the white emission exhibited after the red one was quenched and when high voltage was applied on (V+>30V). It is resulted from the hot electron injection under high electric field to the thin and continuos SiO2 sub-layer formed in the porous silicon after the red emission was quenched in the electrolyte.

A new method for post-treatment of PS(porous silicon), sulfur passivation by microwave plasma assistance in vacuum,is reported in this paper.Fourier transform infrared spectrum indicated that the treated sample surface is mainly covered by SiSx and SiOy.Compared with the as etched PS,the photoluminescence (PL) intensity of the sample is 3.5 times stronger,and the 4nm blueshift of the PL peak was observed experimentally;furthermore,the intensity decay of the PL peak hasnot been observed after 60d in the atmosphere.Therefore,sulfur passivation is an effective post treatment for enhancing PL intensity and stabilization of PS.

A novel passivation film on GaAs surface has been grown by microwave sulfur glow discharge technique.Electronic properties of GaS/GaAs interface have been studied by C-V,I-V, and DLTS measurements.C-V measurement shows that the properties of GaS/GaAs interface are nearly ideal and interface state density is about 1012／（cm2·eV),which agrees with result from DLTS measurement.From leak current of MIS′s structure in I-V spectra,the resistivity of GaS is estimated about 1011Ω·cm.

After the treatment of porous Si by "amine immersion and rapid thermal oxidation", the peak position of the photoluminescence spectra has a blue shift to 500nm. Only a little change in photoluminescence was observed after 160d storing in dry air. FTIR spectra indicate that the compositions of such treated sample are mainly silicon and oxygen. ESR signal shows that the blue/green light-emitting sample has rather low density of dangling bonds. These results demonstrete that the quantum confinement effect and surface states play a key role in blue/green light emitting. This method is simple and practicable, to make blue/green light-emitting samples and its success ratio can achieve 70%.

The bright and stable porous silicon have been obtained by using damp oxidation at moderate temperature. EPR measurements showed that the density of Si dangling bonds in the sample is lower than that by dry oxidation. We also took FTIR measurements and concluded that the stabilization of the photoluminescence from porous silicon is due to the formation of SiH(O3), SiH(SiO2) and SiH(O2) structure.

The ion beam producing ionization of N= has been successfully utilized as the N source for nitride growth. Cubic GaN thin films are thus grown on GaAs(100) substrates. The width of the (200) X-ray diffraction peak of the epilayer is 23′ only, and the high-resolution electron energy loss spectroscopy measurements show that the optical surface phonon of cubic GaN appears at the loss energy of 82 meV.

Porous silicon of low porosity was oxidized in boiling HNO3 solution. Photo-luminescence, microluminescence and SEM studies show that the stability and the uniformity of the sample were greatly improved by such a treatment. This is a new method much easier to control than rapid thermal oxidation.

The typical Raman spectrum from light-emitting porous silicon shows a sharp peak near 520cm －１ . The peak wavenumber decreases with the increase of porosity. The lineshape analysis shows that both phonon confinment and strain effects in nanocrystal silicon must be taken into account for the measured Raman spectra. The strain in porous silicon film is estimated and the result is consistent with that given by X-ray diffraction studies. No light scattering from amorphous phase is observed.

The room temperature deposited α-P/GaAs(100) interfaces have been studied by XPS, UPS, and LEED. The results show that P is adsorbed as clusters on the surface of GaAs at the initial stage of the interface formation, α-P film is formed as the deposition amount is further increased. The valence structures of the films so obtained are similar to those of plasma deposited α-P:H films. There are about one monolayer of P atoms bonded to Ga atoms of the substrate at the interface, α-P overlayer results in 0.2 eV lowering of GaAs surface barrier.

Temperature effects on interaction between P and GaAs (100) surface have been studied by in-situ X-ray photoemssion, uhra violet photcemission, high resolution electron energy loss specrroscopy and low energy electron diffraction techniques. The results show that annealing will make most of the amorphous P, which are deposited on GaAs(lOO) surface at room temperature, desorb with some randomly distributed P-clusters left on the surface. In these clusters, some of the P atoms are bonded to the Ga atoms of the substrate, others exist in the form of element. Higher temperature annealing will make all the left P atoms interact with the substrate and form GaAsP thin layer. Film of GaAsP solid solution will be obtained when depositing P on high temperature GaAs substrate. This film is suggested to be a promissing passi-vating film for GaAs surface.

Various reconstructions (c(2×6), (1×3) and (2×3)) of the GaSb (100) surface have been studied by LEED, XPS and UPS. All the three reconstructed surfaces are terminated by Sb atoms with some rows missing. Annealing in an Sb environment of both MBE-prepared, Sbdimerized c(2×6) reconstruction and IBA-prepared, Gaislands-existing (2×3) reconstruction leads to the same (1×3) reconstruction.

Hel ultraviolet light has been used to take angle resolved ultraviolet photoelectron spectra (ARUPS) of GaP(Ⅲ) surfaces. The observed photoelectron peaks have been explained based on detailed analysis of the data The measured characteristics of the bulk band structure agrees well with the theoretical prediction.

The energy dispersive relation of surface dangling bond state on InP() clean surface has been measured by the angle resolved photomission. The theoretical calculation based on a slab model and extended Huckel theory agreed well with the experimental result if a surface relaxed atomic structure model for InP() (1×1) is postulated.

The application of HREELS to the study of the Ag(100)/Na+O2 system reveals the presence of molecularly adsorbed oxygen species at room temperature. This may help explain why alkali metals can enhance the selectivity of an Ag catalyst towards the formation of C2H4O.

This note shows that the nontrivial third order cohomology cycle for gauge group implies the existence of anomalous associative law and consequently anomaly for Jacobi identity.

The idea of using grazing angle ion sputtering to minimize the formation of In islands on InP(111) surface has been presented and its correctness has been proved by the measurement of electron energy loss spectroscopy.

The room temperature adsorption of water on clean and sodium predeposited InP(lll) surface has been studied by UPS and HREELS. The sticking coefficient of water on InP(lll) surface increases significantly as the surface is covered with 0.3 moiiolayer of sodium. This sticking coefficient enhancement could be shown to be related to the charge transfer between the sodium atoms and the surface phosphorous atoms. Water species adsorb On the surface mainly in the form of undissociated molecules. The existence of P-H bond related loss energy peak at 282 meV observed in HREELS suggests that a portion of water molecules may interact with sodium atoms predeposited on the surface or possibly decomposed on the surface to release free hydrogen atoms which could make bonding with surface phosphorous atoms.

In this paper, we show that the SO(3) chiral field can be regard as the normal Vector field over the pseudo-spherical surface, and thus obtain the correspondence between chiral field and sine-Gordon system, as well as the geometrical interpretation of chiral field. By means of the dual symmetry between chiral field and the pseudo-spherical surface, we are able to connect chiral field with s-G system, and express Backlund transformation, Riccati equation in the gauge invariant representations of the related properties of the same dynamical system in different frames.

An explicit expression for any higher cocycles in translation group is given by means of Kronecker mapping from the n-dimensional flat space (translation group manifold) to the n-dimensional sphere. Physical interpretations can be made about the pull-back of the map.

The interactions of H2O and O2, with InP clean surface in the high vacuum chamber have been studied by means of Auger electron spectroscopy. It has been found that the water vapor plays a significant role responsible to the electron stimulated adsorption of oxygen than the pure oxygen. The In and P Auger signals change substantially during the oxygen adsorption process which is accessible as an occurence of electron stimulated oxidation (ESO). The oxygen atoms bond only with surface In atoms but not with P at the earliest stage, then they penetrate into the bulk and conbine with both In and P continually making the surface layer convert into oxide with an almost constant oxidation rate. As compared with the Auger depth profiling of InP native oxides, the similarity of the ESO and the ordinary oxidation processes is obvious. But the electron stimulated adsorpted oxygen could not fully oxidize the phosphorus in the surface layer while thermal oxidation and anodic oxidation do, the P concentration in the ESO oxide is higher than that in the thermal oxide but lower than the anodic oxide.

In this paper we analyze the topological obstruction in gauge group cohomology. By means of ?ech-de Rham double complex, we have used the region subdivision method to go over each order obstructions of operation d-1, and each order cocycle is connected with the index Z, so the global topological meaning of cocycle for gauge group has been-clarified.

The InP(l00) (4×2) reconstructed surface prepared by argon ion bombardment and post annealing under phosphorus pressure has been investigated by LEED, HREELS and UPS. It was found by HREELS that the forming of surface In-H and P-H bonds during hydrogen exposure happened almost simultaneously. By measuring the UP spectra using polarized light sources, it can be verified that the dangling bond states of surface P atoms do not possess the symmetrical characteristic with respect to the two basis vector directions of surface unit mesh. It could be deduced from the above evidences that there must exist some In vacancies on the In-rich InP (100) surface, and the dangling bonds of those P atoms which are located next to the In vacancies orientate off their normal directions. We propose here a missing row-dimer model for the atomic arrangement of InP (100) (4×2) stucture, which could explain the observed experimental qualitatively and might be used as a working model for seeking a precise surface structural model.