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VC nanocomposite coatings with high carbon content were deposited by multi-arc ion plating at varied substrate bias voltages ranging from − 50 to − 250 V. There is a comprehensive study as to coating preparation and corresponding microstructure, phase contents and their relationship with mechanical properties. The results show that carbon bonding is significantly affected by bias voltage. For the coatings deposited at high bias voltage, the appropriate combination of inducing compressive stress and manipulating the nanostructure accounts for the effect of hardening and toughening. The tribological and corrosive responses of nanocomposite VC coatings are implemented in the condition of seawater. The hard yet tough nanocomposite structure makes the coatings have favorable wear resistance. Moreover, the smooth surface and dense structure obtained at high bias voltage jointly improve capacity of anti-corrosion resistance. The results are beneficial to the potential application of VC nanocomposite coating in seawater.

Cr C nanocomposite coatings were deposited by multi-arc ion plating with various argon/acetylene mixtures. The XRD, XPS and HRTEM characterization suggest that the coatings consist of a carbide phase and an amorphous carbon-rich phase. The carbide phase is shown to be CrC with a fcc NaCl (B1) structure. Experiment findings and theoretical calculations reveal phase segregation of sp2-carbon from carbides in which the excess amounts of carbon are incorporated. Nanoindentation, scratch test and Rockwell indentation were performed to investigate the toughness and adhesion ability. A significant improvement of adhesion and toughness is achieved by increasing C content at the expense of hardness. The wear resistance of Cr C coatings is controlled by the friction rather than hardness. Compared to dry friction, lower friction coefficients but higher wear rates were obtained under seawater condition. The corrosion behavior of Cr C nanocomposite coatings with different C % was determined by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). The coatings with higher Cr content display excellent anti-corrosion properties in seawater.

The flow differential equation for Magneto-rheological (MR) fluids in annular channels of MR fluid shock absorber is set up and several rational simplifications are made. Analytical shear stress profiles of MR fluids through annular channels are obtained via solution of the flow differential equation. An analytical study on MR fluid shock absorber is present employing shear stress profiles. Both boundary conditions and compatible conditions are established. Both flow velocity profiles and total volumetric flow rate are developed by integration by parts and numerical integration. The prediction method for damping force of MR fluid shock absorber is developed via simultaneous equations. The analytical study on MR fluid shock absorber is validated by means of reformative Herschel–Bulkley constitutive model, in which flow velocity profiles and flow regions boundary radii are drawed. A MR fluid shock absorber, which is designed and fabricated in Chongqing University, is tested by electro-hydraulic servo vibrator in National Center for Test and Supervision of Coach Quality. The experimental results reveal that the methodology is able to predict damping force of MR fluid shock absorber via shear rate profiles and experimental damping forces are in good agreement with analytical those.

MgZnO thin films were deposited on c-plane sapphire and fused quartz substrates with the same growth parameters by rf-reactive magnetron sputtering. Both the MgZnO thin films on the two substrates are single hexagonal phase and show similar Mg content. However, the absorption edge of MgZnO thin film on sapphire substrate shows a blue shift compared with that on fused quartz substrate. Similar shift also appears in the photoresponse of the detectors based on them. These phenomena were attributed to the more Mg atoms in grain boundary caused by the smaller grain size in MgZnO film on fused quartz substrate.

Wurtzite MgxZn1−xO thin films were grown on sapphire substrates by low-pressure metal-organic chemical vapor deposition. The as-grown films show clear exciton absorption at room temperature until the composition x = 0.25. A representative metal–semiconductor–metal structured photodetectors were fabricated from Mg0.06Zn0.94O film showed a peak responsivity of about 14.62 A/W at 340 nm, and the ultraviolet-visible rejection ratio (R340 nm/R400 nm) was more than two orders of magnitude at 3 V bias. The photodetector showed fast photoresponse with a rise time of 20 ns and a fall time of 400 ns.

As-grown undoped zinc oxide (ZnO) films have been annealed in zinc-rich, oxygen-rich and vacuum ambient, and the electron concentration varied greatly after the annealing process. It decreased nearly two orders of magnitude after the sample was annealed in oxygen, while increased nearly three times after annealed in metallic zinc ambient, and increased slightly after annealed in vacuum. It was found that the variation trend of the electron concentration is always the same with the expected variation of oxygen vacancy (VO) under the three investigated conditions, it is thus speculated that VO may be the dominant donor source in ZnO. By supplying more oxygen during the growth process to suppress VO, ZnO films with lower electron concentration were obtained, which verifies the above speculation.

This paper will discuss the design and construction of BESIII, which is designed to study physics in the tau-charm energy region utilizing the new high luminosity BEPCII double ring e+e- collider. The expected performance will be given based on Monte Carlo simulations and results of cosmic ray and beam tests. In BESIII, tracking and momentum measurements for charged particles are made by a cylindrical multilayer drift chamber in a 1 T superconducting solenoid. Charged particles are identified with a time-of-flight system based on plastic scintillators in conjunction with dE/dx (energy loss per unit pathlength) measurements in the drift chamber. Energies of electromagnetic showers are measured by a CsI(Tl) crystal calorimeter located inside the solenoid magnet. Muons are identified by arrays of resistive plate chambers in the steel magnetic flux return. The level 1 trigger system, Data Acquisition system and the event filter system based on networked computers will also be described., 57 pages, 75 figures

Cubic MgZnO thin films were prepared on fused quartz substrate by radio frequency (rf) reaction magnetron co-sputtering technique, and composition modulation of cubic MgZnO films could be accomplished by changing rf power on Zn metal target. During growth process crystal quality of our MgZnO films can be improved by increasing the ratio of O 2 /Ar. Unlike reported growth of (1 1 1) plane cubic MgZnO films, our cubic MgZnO films show (2 0 0) plane growth properties. This phenomenon was assigned to a preferred selection growth characteristic of MgZnO on non-crystalline quartz substrate. Band gaps of cubic MgZnO films calculated by empirical formula are different from that obtained in the absorption spectrum. It is suggested that parts of Mg do not contribute to the band gaps of Mg x Zn 1− x O thin films.

The polar and non-polar ZnO thin films were fabricated on cubic MgO (1 1 1) and (0 0 1) substrates by plasma-assisted molecular beam epitaxy. Based on X-ray diffraction analysis, the ZnO thin films grown on MgO (1 1 1) and (1 0 0) substrates exhibit the polar c-plane and non-polar m-plane orientation, respectively. Comparing with the c-plane ZnO film, the non-polar m-plane ZnO film shows cross-hatched stripes-like morphology, lower surface roughness and slower growth rate. However, low-temperature photoluminescence measurement indicates the m-plane ZnO film has a stronger 3.31 eV emission, which is considered to be related to stacking faults. Meanwhile, stronger band tails absorbance of the m-plane ZnO film is observed in optical absorption spectrum.

The formation energies and transition energy levels of native point defects in wurtzite ZnO under applied hydrostatic pressure are calculated using the first-principle band-structure methods. We find that the pressure coefficient of the (2+/0) level for oxygen vacancy is larger than that of the (2+/1+) level for zinc interstitial, which demonstrates that the donor level of oxygen vacancy is deeper than that of zinc interstitial, therefore the latter is the more probable electron resource in native n-type ZnO. And the significantly different pressure dependence of the transition levels between them can be used to determine the origin of the green luminescence center in ZnO. Zinc octahedral interstitial and oxygen tetrahedral interstitial configurations became the dominant defects under 5 GPa at their favorable growth conditions, respectively. The formation of defects under applied pressure is the result of fine interplay between internal strains, charges on the defects and applied external pressures.

By tagging the largest energy of the assumed kaon in the final states of e + e − → hadrons , we measured the cross sections for e + e − → hadrons | non- D D ¯ in the range from 3.65 to 3.87 GeV. Analyzing these cross sections yields the branching fraction for the decay ψ ( 3770 ) → non- D D ¯ to be BF [ ψ ( 3770 ) → non- D D ¯ ] = ( 15.1 ± 5.6 ± 1.8 ) % , and the observed non- D D ¯ and D D ¯ cross sections to be σ had-non- D D ¯ obs = ( 1.08 ± 0.40 ± 0.15 ) nb and σ D D ¯ obs = ( 6.07 ± 0.40 ± 0.35 ) nb , respectively, at the center-of-mass energy E cm = 3.7724 GeV .

The full regions of the electronic and optical properties of in-plane biaxial strained thin film ZnO are studied using pseudopotential plane-wave method. The fundamental band gap at the Γ point increase linearly with the increase of tensile strains, but decreased with the compressive ones. The strains affected the local tetrahedral symmetry, and so the splitting of crystal field energy. The band dispersion relation of the valence band maximum changes with the strains, which means the residual strains have effects on the effective hole mass, thus the transportation properties of the p -type ZnO. The changes tendency of optical properties up to full regions under strains have been shown and discussed.

We report the growth of cubic Mg x Zn 1− x O alloy thin films on quartz by electron beam evaporation. It can be found that all the samples have sharp absorption edges by the absorption measurements. X-ray diffraction measurements indicate the Mg x Zn 1− x O films are cubic phase with preferred orientation along the (1 1 1) direction. Energy dispersive spectrometry (EDS) demonstrates that the Mg concentration in Mg x Zn 1− x O films is much higher than the ceramic target used, and the composition can be tuned in a small scope by varying the substrate temperature and the beam electric current. The reasons of this phenomenon are also discussed.

Photoluminescence of CdSe thin films under different growth conditions was studied in this paper, and typical double emission peaks were observed at room temperature. Temperature and excitation intensity-dependent photoluminescence studies in combination with X-ray diffraction measurements revealed that the two emission peaks originate from cubic- and hexagonal-phased CdSe, respectively, which indicates that the crystalline phases of CdSe can be controlled by changing the growth conditions in metalorganic chemical vapor deposition process.

ZnO nanocrystals (NCs) embedded in a BaF2 matrix have been prepared by a radio-frequency magnetron sputtering technique followed by a thermal annealing process from 400 to 1100 °C. X-ray diffraction results show that ZnO NCs with a hexagonal wurtzite structure are formed in a BaF2 matrix. The average grain sizes are estimated ranging from 7.5 to 33 nm, corresponding to fabricated samples annealed at temperatures from 400 to 800 °C. Photoluminescence showed a very strong ultraviolet near-band-edge (NBE) emission located in the 364–383 nm spectral region. The emission intensity is enhanced and the linewidth is narrowed as the annealing temperature increases. The intensity ratio of ultraviolet NBE emission to deep-level visible is also increased with annealing temperature indicating that deep-level defects in ZnO are suppressed.

ZnO nanorods and ZnO nanotubes have been fabricated by thermally evaporating the metal Zn powder. The ZnO nanorod obtained on the ITO substrate located above the Zn source has the uneven diameter with the abrupt change in its middle, which may originate from the decrease of the Zn vapor in the system. The ZnO nanotubes with the rough surfaces were obtained in the upstream region. The negative thermal quenching of the photoluminescence can be observed in the ZnO nanotubes. This is related with the abundant surface/interface defects which can introduce a large number of middle states in the band gap. According to Shibata's model, the activation energy of the electrons from the middle states to the initial states can be obtained by fitting the experimental data of the temperature dependence of the ultraviolet photoluminescence intensity. The fitting energy values are as high as ∼100 meV, which may be responsible for the negative thermal quenching in a high-temperature range from 163.5 to 205.6 K.

Zn0.8Mg0.2O metal–semiconductor–metal ultraviolet photodiodes were fabricated on quartz by radio frequency magnetron sputtering. Dark current, spectral responsivity and pulse response experiments were carried out for the device. The photodetectors showed a peak responsivity at 330 nm. The ultraviolet-visible rejection ratio (R330 nm/R400 nm) was more than four orders of magnitude at 3 V bias. The photodetector showed fast photoresponse with a rise time of 10 ns and a fall time of 170 ns. In addition, the thermally limited detectivity was calculated to be 3.1 × 1011 cm Hz1/2 W−1 at 330 nm.

A series of Co-doped ZnO films were fabricated by an electrodeposition method. The X-ray diffraction results and absorption spectra show Co ions have been doped successfully into the ZnO crystal lattices. The as-grown samples have no ferromagnetism at room temperature. However, after plasma treatment used ammonia as reactive gas, the room temperature ferromagnetism was detected in ZnCoO samples. The Hall measurement reveals the resistivity of samples was increased by two orders of magnitude after the treatment. Although the aspect conductivity is an n type, some holes generated by N doping still play an important role to induce the room temperature ferromagnetic properties for Co-doped ZnO samples.

The undoped ZnO thin films grown on Si (1 1 1) substrates by plasma-assisted molecular beam epitaxy (P-MBE) were reported. The effects of growth temperature, the thickness of low temperature ZnO buffer layer and Zn/O ratio on the quality of high-temperature-overgrown ZnO main layer were studied by atomic force microscopy (AFM), X-ray diffraction (XRD) and room-temperature photoluminescence (PL) spectra. These results showed that it was difficult to directly obtain high quality ZnO films on Si substrate. By introducing a thin ZnO buffer layer at 350 °C, c -axis preferred orientation ZnO films with improved optical properties were obtained at 750 °C. However, the thickness of ZnO buffer layer and Zn/O ratio in the ZnO main layer greatly influenced the quality of high-temperature-overgrown ZnO main layer.

A co-activating route was employed to fabricate ZnO light-emitting diode (LED) by using molecular beam epitaxy. N 2 was used as the acceptor dopant source and O 2 was used as assistant gas for N 2 decomposing more than only oxygen source. Emission spectra of the N 2 +O 2 mixture plasma were monitored in situ in order to adjust growth parameters timely. Under the assistance of O 2 , N atoms content in the plasma of the mixture shows a significant increase compared to the case without O 2 assistance. Electrical measurements of the as-grown p-type ZnO on sapphire show a carrier concentration of 1.2×18 cm −3 and a mobility approaching 1 cm 2 V −1 s −1 . A ZnO LED was fabricated by depositing undoped n-type ZnO on the p-type layer. The turn-on voltage at 100 K is about 3.70 V, which approaches the bandgap of ZnO. Electroluminescence spectra show two bands: one is centered at 423 and the other centered at 523 nm, respectively.

Fe-based cadmium sulfide alloy thin films have been grown on c-plane sapphire substrates by a low-pressure metalorganic chemical vapor deposition technique at different growth temperatures. From X-ray diffraction and absorption spectra of the samples, the evolutions with growth temperature show an inflexion at the growth temperature of 300 degrees C. This was attributed to the phase transformation from zinc-blende to wurtzite. With increasing growth temperature from 270 degrees C to 360 degrees C, Fe concentration in the films increases monotonously. The electronic states of Cd1-xFexS were investigated by X-ray photoelectron spectroscopy. Magnetic measurement shows Van Vleck paramagnetism of the Cd1-xFexS thin film in the temperature region below 7 K. (C) 2006 Elsevier Ltd. All rights reserved.

Using 14M psi(2S) events accumulated by BESII at the BEPC, a covariant helicity amplitude analysis is performed for psi(2S) -> pi(+)pi(-)J/psi, J/psi -> mu(+)mu(-). The pi(+)pi(-) mass spectrum, distinctly different from phase space, suggests or production in this process. Two different theoretical schemes are used in the global fit to the data. The results are consistent with the existence of the sigma. The sigma pole position is determined to be (552(-106)(+84) -i(232(-72)(+81)) MeV/c(2). (c) 2006 Elsevier B.V. All rights reserved.

N-doped ZnO samples were grown on sapphire substrate by plasma-assisted molecular beam epitaxy (P-MBE) method. The electrical properties of the samples were investigated by temperature-dependent Hall measurement. It was found that the carrier concentration and mobility of the samples showed some unstable characteristics under different magnetic fields at a certain temperature. However, the conductivity was a much more stable parameter. By fitting the dependence of conductivity on temperature and theoretical calculating, it was believed that the conduction mechanism was possibly the mix of band and hopping conduction mechanisms. The coexistence of a huge density of donor and acceptor defects was considered to cause the instability of some electrical properties (carrier concentration and mobility) and the appearance of the hopping conduction mechanism in N-doped ZnO samples.

Using the data sample of about 33 pb(-1) collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we have studied inclusive (K) over bar (0)/K-0 and K*(892) -/+ decays of D-0 and D+ mesons. The branching fractions for the inclusive (K) over bar (0)/K-0 and K*(892)(-) decays are measured to be BF(D-0, (K) over bar (0)/(KX)-X-0) = (47.6 +/- 14.8 +/- 3.0)%, BF(D-0 -> (KX)-X-0) = (60.5 +/- 15.5 +/- 3.3)%, BF(D-0, K*X-) = (15.3 +/- 8.3 +/- 1.9)% and BF(D+ -> K*X-) = (5.7 +/- 5.2 +/- 0.7)%. The upper limits of the branching fractions for the inclusive K*(892)(+) decays are set to be BF(D-0 -> K*+X) K*X+) < 20.3% at 90% confidence level. (c) 2006 Elsevier B.V. All rights reserved.

Electrical transport properties of p-type ZnO:N films grown by thermal activation of the nitrogen dopant were investigated via the temperature-dependent Hall effect. The Hall mobility increases with decreasing temperature. Varied scattering mechanisms have been analysed including lattice vibration scattering, ionized impurity scattering and dislocation scattering. A fit of the theory to temperature-dependent hole mobility experimental data in p-type ZnO:N films gives dislocation densities in the order of 1012 cm−2. The analysis shows dislocation scattering is indeed important for the p-type ZnO films grown on the mismatched substrate. The thermal ionization energy of the nitrogen acceptor is estimated to be 170 meV in terms of the temperature-dependent hole concentration. On the other hand, the emission related to the acceptors is observed in PL spectra.

In this work, ZnS thin films with single-phase zinc blende structure were fabricated on silica glass substrates by plasma-assisted metalorganic chemical vapor deposition (PA-MOCVD). Dimethyl zinc and hydrogen sulfide were used as the precursors. The films were characterized using X-ray diffraction and photoluminescence spectroscopy. The optimal temperature for ZnS growth, 350 °C, was confirmed via a series of growth at different temperatures. In order to obtain stoichiometric ZnS films using PA-MOCVD, larger VI / II gas flow ratios was needed than the one used without plasma assistance. The reason for this phenomenon is discussed.

A set of ZnO/MgZnO heterostructures with well widths, L w , varying from 2 to 20 nm has been grown by plasma-assisted molecular-beam epitaxy (P-MBE). We present a room-temperature (RT) study of the well-width-dependent photoluminescence (PL) spectra and carrier lifetimes in ZnO/MgZnO heterostructures. Bi-exponential process is seen at RT time-decay curves of the luminescence from the well layers. The fast process is from the recombination of the free exciton, while the slow process is attributing to the recombination of the localized exciton in the interface of ZnO and MgZnO. It is also confirmed from the PL peak shift of time-resolved PL spectra. With decreasing the well thickness, the fast process gradually increases and dominantly contributes to the PL spectrum due to the interface improvement.

In this paper, highly oriented and vertically arranged ZnO nanotubes are prepared on Al 2 O 3 (0001) substrate without employing any metal catalysts by plasma-assisted molecular beam epitaxy. The photoluminescence (PL) spectra at room temperature are studied under high excitation densities. Under lower excitation density (

ZnMnO nanoclusters were synthesized by the sol–gel method. The structural and magnetic characters were investigated. The XRD spectrum shows ZnMnO nanoclusters are hexagonal wurtzite structures and a small quantity of ZnMn2O4 phase is also present in the spectrum. The percentages of Zn and Mn elements in the ZnMnO nanostructure are 97% and 3%, respectively, which are induced from XPS data. EPR spectrum with g = 1.9961 shows the signal of Mn2+. The magnetization curve measured at room temperature shows a hysteresis loop. XRD and XPS analyses prove that ferromagnetic ordering arises from ZnMn2O4 in all probability.

Decays of $\chi_{c0,2}\ar\ww$ are observed for the first time using a sample of $14.0\times 10^6$ $\psi(2S)$ events collected with the BESII detector. The branching ratios are determined to be ${\cal B}(\chi_{c0}\ar \ww)=(2.29\pm 0.58\pm 0.41)\times 10^{-3}$ and ${\cal B}(\chi_{c2}\ar\ww)=(1.77\pm 0.47\pm 0.36)\times 10^{-3}$, where the first errors are statistical and the second systematic. The significances of the two signals are $4.4\sigma$ and $4.7\sigma$, respectively.

The ZnO nanowire arrays were synthesized by a simple vapor–solid process. Wettability of nanowire arrays was studied by measuring contact angle. Under both oxygen plasma treatment and annealing at O2 atmosphere, the wettability of nanowire arrays changed from hydrophobic to super-hydrophilic. By measuring the photoluminescence spectra of modified samples, we affirm that the wettability conversion is not due to oxygen vacancies. It is thought that the oxygen related surface defect is the main reason to make this kind of change.

Using data collected with the BESII detector at Beijing Electron-Positron Collider, the measurements of relative branchin- fractions for seven Cabibbo-suppressed hadronic weak decays D-0 -> K-K+, pi-pi(+), pi(-)pi(+)pi(-) and pi-pi(+)pi(-), D-divided by -> (K) over bar K-0(divided by), K-K+pi(+) and pi(-),pi(+pi+) are presented. (c) 2005 Elsevier B.V. All rights reserved.

The decay psi' + pi(+)pi(-)pi(0) is analyzed using a sample of 14 million psi' events taken with the BESII detector at the BEPC, and the branching fraction is measured to be B(psi' -> pi(+)pi(-)pi(0)) = (18.1 +/- 1.8 +/- 1.9) x 10(-5). A partial wave analysis is carried out using the helicity amplitude method. psi' -> rho(770)pi is observed, and the branching fraction is measured to be B(psi' -> rho(770)pi) = (5.1 +/- 0.7 +/- 1.1) x 10(-5), where the first error is statistical and the second one is systematic. A high mass enhancement with mass around 2.15 GeV/c(2) is also observed. Attributing this enhancement to the p(2150) resonance, the branching fraction is measured to be B(psi' -> rho(2150)pi -> pi(+)pi(-)pi(0)) = (19.4 +/- 2.5(-3.4)(+11.5)) x 10(-5). The results will help in the understanding of the longstanding "rho pi puzzle" between J/psi and psi' hadronic decays. (c) 2005 Elsevier B.V. All rights reserved.

In this paper, Mg 0.12 Zn 0.88 O/ZnO heterostructures were fabricated on c -plane sapphire (Al 2 O 3 ) substrates by plasma-assisted molecular beam epitaxy (P-MBE). The quality of the Mg 0.12 Zn 0.88 O alloy thin film was characterized by X-ray diffraction (XRD) and reflection high-energy electron diffraction (RHEED). Optical properties of the Mg 0.12 Zn 0.88 O/ZnO heterostructure were studied by absorption and photoluminescence (PL) spectra. At room temperature (RT), Mg 0.12 Zn 0.88 O/ZnO heterostructures show two absorption edges originating from ZnO and Mg 0.12 Zn 0.88 O layers, respectively. In PL spectra, two ultraviolet emission bands related to the ZnO layer and the Mg 0.12 Zn 0.88 O layer were observed. The emission band from Mg 0.12 Zn 0.88 O layer dominates at moderately lower temperature, and the luminescence of ZnO becomes gradually important with increasing temperature. This is suggested to exist as a potential barrier in the interface and to restrict the relaxation of the carriers from the Mg 0.12 Zn 0.88 O layer to ZnO layer. As the thickness of ZnO layer decreases, the emission from the Mg 0.12 Zn 0.88 O layer becomes weaker and weaker. When the ZnO thickness is up to 2 nm, only the luminescence of the ZnO layer is observed at RT. The quenching of the emission corresponding to the MgZnO layer indicates the existence of a strong injection process in the samples with thinner ZnO layer.

ZnO nanowires array has been synthesized via a simple physical vapor deposition method at low growth temperature without using any catalyst. By controlling different growth parameters, the nanowires exhibit different shapes: needle-like with sharp tips or rod-like with flat tips. All the nanowires are single crystal with a growth direction along c-axis. The rod-like nanowires are well vertical aligned to the substrate surface with c-axis preferred orientation. The morphology difference of ZnO nanowires is believed originated from different growth mechanisms.

Catalyst-free needle-like ZnO nanowires have been grown on Si(111) substrate at 430??C via a simple solid?vapour process. The obtained nanowires are found to have a uniform size distribution with sharp tips. The lengths of the nanowires range from 2.8 to 3.2??m with diameters of about 100?nm for the root and 30?nm for the tip parts. The x-ray diffraction (XRD) result shows the nanowires are c-axis preferentially oriented. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) analysis reveal that every single nanowire is a well developed single crystal. The room temperature photoluminescence (PL) spectrum shows a dominant near-band-edge emission peak. The near-band-edge emission is further identified to originate from the radiative free exciton recombination by the temperature-dependent PL.

A partial wave analysis is presented of J/psi --> phipi(+)pi(-) and phiK(+)K(-) from a sample of 58M J/psi events in the BES II detector. The f(0)(980) is observed clearly in both sets of data, and parameters of the Flatte formula are determined accurately: M = 965 +/- 8(stat) +/- 6(syst) MeV/c(2), g(1) = 165 +/- 10 +/- 15 MeV/c(2), g(2)/g(1) = 4.21 +/- 0.25 +/- 0.21. The phipipi data also exhibit a strong pipi peak centred at M = 1335 MeV/c(2). It may be fitted with f(2)(1270) and a dominant 0(+) signal made from f(0)(1370) interfering with a smaller f(0)(1500) component. There is evidence that the f(0)(1370) signal is resonant, from interference with f(2)(1270). There is also a state in pipi with M = 1790(-30)(+40) MeV/c(2) and Gamma = 270(-30)(+60) MeV/c(2); spin 0 is preferred over spin 2. This state, f(0)(1790), is distinct from f(0)(1710). The phiK (K) over bar data contain a strong peak due to f(2)'(1525). A shoulder on its upper side may be fitted by interference between f(0)(1500) and f(0)(1710). (C) 2004 Elsevier B.V. All rights reserved.

New data are presented on J/psi --> omegaK(+)K(-) from a sample of 58M J/psi events in the upgraded BES II detector at the BEPC. There is a conspicuous signal for f(0)(1710) --> K+K- and a peak at higher mass which may be fitted with f(2)(2150) --> K (K) over bar. From a combined analysis with omegapi(+)pi(-) data, the branching ratio BR(f(0)(1710) --> pipi)/BR(f(0)(1710) --> K (K) over bar) is < 0.11 at the 95% confidence level. (C) 2004 Elsevier B.V. All rights reserved.

The cross sections for D 0 D ¯ 0 and D + D − production at 3.773 GeV have been measured with BES-II detector at BEPC. These measurements are made by analyzing a data sample of about 17.3 pb −1 collected at the center-of-mass energy of 3.773 GeV. Observed cross sections for the charm pair production are radiatively corrected to obtain the tree level cross section for D D ¯ production. A measurement of the total tree level hadronic cross section is obtained from the tree level D D ¯ cross section and an extrapolation of the R u d s below the open charm threshold.

Using a sample of 58 million J/psi events recorded in the BESII detector, the decay J/psi --> omegapi(+)pi(-) is studied. There are conspicuous omegaf(2)(1270) and b(1)(1235)pi signals. At low pipi mass, a large, broad peak due to the sigma is observed, and its pole position is determined to be (541 +/- 39) - i (252 +/- 42) MeV from the mean of six analyses. The errors, which are dominated by the systematic errors, cover the statistical and systematic errors in the six analyses, as well as the observed variation of the six analyses. (C) 2004 Elsevier B.V. All rights reserved.

Using a sample of 58×10 6 J / ψ events collected with the BESII detector, radiative decays J / ψ → γγV , where V = ρ or φ , are studied. A resonance around 1420 MeV/ c 2 ( X (1424)) is observed in the γρ mass spectrum. Its mass and width are measured to be 1424±10(stat)±11(sys) MeV/ c 2 and 101.0±8.8±8.8 MeV/ c 2 , respectively, and its branching ratio B ( J / ψ → γX (1424)→ γγρ ) is determined to be (1.07±0.17±0.11)×10 −4 . A search for X (1424)→ γφ yields a 95% C.L. upper limit B ( J / ψ → γX (1424)→ γγφ ) −4 .

The ZnO whiskers were successfully fabricated by a simple thermal oxidation method. The morphologies of the samples were examined using a scanning electron microscope (SEM). The average length of the whiskers is about 0.7 μm with a diameter of about 100 nm. Intense ultraviolet photoluminescence was observed at room temperature. By studying the PL properties of ZnO whiskers at low temperature, a competitive process between the recombination of delocalized excitons and localized exciton emission is observed. The probable mechanism is discussed.

Using a sample of 5.8X10E7 J/$\psi$ events, the Beijing Spectrometer experiment has searched for the decay J/$\psi \to e\mu$. Four candidates, consistent with the estimated background, are observed, and an upper limit on the branching fraction of J/$\psi \to e\mu$ of 1.1X10E-6 at the 90% C.L. is obtained.

Crystal scintillators provide potential merits for the pursuit of low-energy low-background experiments. A CsI(Tl) scintillating crystal detector is being constructed to study low-energy neutrino physics at a nuclear reactor, while projects are underway to adopt this technique for dark matter searches. The choice of the geometrical parameters of the crystal modules, as well as the optimization of the read-out scheme, are the results of an R&D program. Crystals with 40 cm in length were developed. The detector requirements and the achieved performance of the prototypes are presented. Future prospects for this technique are discussed., 32 pages, 14 figures

Data are presented on the reaction J/psi--> p pbar eta using 7.8 million J/psi triggers collected by the BEjing Spectrometer (BES). A partial wave analysis is performed. A clear enhancement near the p eta(pbar eta) threshold is observed. It is fitted with a JP=1/2- resonance with mass $M= 1530\pm 10$ MeV and width $\Gamma = 95\pm 25$ MeV. In addition, there is a peak around 1650 MeV with JP=1/2- preferred also, fitted with $M =1647\pm 20$ MeV and $\Gamma = 145^{+80}_{-45}$ MeV. These two N* resonances are believed to be the two well established states, S11(1535) and S11(1650), respectively. It is the first partial wave study of the production of these resonances from J/psi decays.

Epitaxial growth of cubic Mg(0.33)Zn(0).(67)O films on MgO (1 0 0) substrate by metalorganic chemical vapor deposition (MOCVD) was reported. X-ray diffraction (XRD) omega-scans and phi-scans demonstrate the films exhibit single (2 0 0) orientation and highly uniform in-plane orientation with four-fold symmetry. The epitaxial relationship between the layer and substrate is MgZnO (1 0 0)//MgO (1 00). Smooth surface with the rms roughness of 1.8 nm in 5 x 5 mu m area is obtained. Atomic force microscopy (AFM) reveals formation of islands attributed to the strain in the epitaxial MgZnO films. These results demonstrate the high quality single crystal Mg(0.33)Zn(0.67)O films and their potential in high-performance deep ultraviolet optoelectronic devices. (C) 2010 Elsevier B.V. All rights reserved.

The formation process of CdSe self-assembled quantum dots (SAQDs) below the critical thickness was observed by atomic force microscopy (AFM) for the first time. Two monolayers (MLs) of CdSe coverage were grown directly on GaAs (1 0 0) surfaces by metalorganic chemical vapor deposition (MOCVD). AFM images were taken constantly of the same area of 1 μm 2 within several hours after the growth. It revealed that the formation of CdSe SAQDs under critical thickness was due to the effect of surface diffusion and strain release. Our results make it possible to directly observe the process of release strain and to obtain the actual information on the formation process of self-assembled quantum dots.