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For enhancing the photoelectric performance of the GaAs photovoltaic cell, the non-dominated sorted genetic algorithm-II (NSGA-II) is employed to solve the multi-objective optimization problem, which consists of the thicknesses of active layer (GaAs) and three anti-reflection (AR) films (TiO2-HfO2-SiO2). Through maximizing (minimizing) the light absorption of photons with energies higher (lower) than the bandgap in the active layer directly and reducing the cost at the same time, the Pareto optimal solution is obtained. An increment in the absorptance, short circuit current and photoelectric conversion efficiency by 50%, 43.4% and 44.9% is achieved by the optimal GaAs solar cell due to excellent AR properties obtained by NSGA-II optimization. We systematically investigate the effects of carrier lifetime, surface recombination velocity, carrier mobility as well as doping concentration on the photovoltaic parameters, and acquire the limitations of these parameters. The strong robustness of the optimal GaAs solar cell enables it to be adapted to wide-angle sunlight incident, and the probability to achieve an absorptance of 0.963 is 97% even if there is a 20% machining error.

The design and development of contrast agents for magnetic resonance imaging (MRI) with improved chemical stability and higher contrasting capability for clinical translation compared to conventional contrast agents are still of great interest. In this study, a facile and universal approach was explored for controllable functionalization of red-emissive carbon nanodots (RCNDs) with diethylenetriaminepentaacetic anhydride (DTPA) for chelation of gadolinium. A series of accurate characterizations were used to control each step of the synthesis. The functionalization did not alter the band gap of the carbon nanodots, preserving their inherent far-red fluorescence. The as-prepared RCND-DTPA-Gd displayed a high colloidal stability with negligible Gd leakage. The nanodots also showed a better magnetic resonance relaxivity than commercial MRI agents. RCND-DTPA-Gd had good biocompatibility in vivo even at high doses. The systemically injected RCND-DTPA-Gd were found to be efficiently excreted through the renal route, a feature that further minimizes the potential toxicity risks. All these properties suggest that carbon nanodots can be well designed as efficient carriers of Gd, resulting in potential clinical tools as dual MRI/fluorescence functional probes for imaging applications. The approach described here could pave the pathway to a flexible strategy for the controllable functionalization of small-sized nanoparticles including carbon dots, rendering them more versatile. This work is expected to promote the future translation of carbon nanodots into clinical trials., We gratefully acknowledge the Centre National de la Recherche Scientifique (CNRS) and International Center for Frontier Research in Chemistry (icFRC), and financial support from the Agence Nationale de la Recherche (ANR) through the LabEx project Chemistry of Complex Systems (ANR-10-LABX-0026_CSC) within the Investissement d’Avenir program (ANR-10-120 IDEX-0002-02). We wish to thank D. Lamon for injecting the mice and collecting the samples for the biochemical analyses, C. Royer and V. Demais for help with TEM analyses at the “Plateforme Imagerie in vitro” at the Center of Neurochemistry (INCI, Strasbourg, France), D. Ihiawakrim for HRTEM measurements, and S. Guo for his help in the XPS analyses. ICN2 acknowledges the financial support from the Spanish Ministry of Economy and Competitiveness through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2017-0706). B.B. acknowledges funding from Generalitat de Catalunya 2017 SGR 327. We wish to thank the Academy of Integrative Medicine, Fujian University of Traditional Chinese Medicine, Fujian Key Laboratory of Integrative Medicine on Geriatrics, and Prof. Jun Peng for the use of 7 T small-animal MRI scanner.

Intercellular glycoligand-receptor interactions are implicated in a number of disease-related processes. Effective tools that target these receptors may facilitate disease theranostics. However, owing to their low binding affinity, multivalent presentation of glycoligands is needed to increase the avidity with transmembrane receptors. While previous strategies focus on the covalent coupling of glycoligands to a synthetic backbone, we show here that the use of graphene oxide (GO) greatly enhances the cellular and tissue imaging ability of a small-molecule fluorescence glycoprobe. We determine that GO with an optimum size may serve as a clustering platform to reinforce the interaction of the glycoprobe with its selective receptor on a cancer cell. This phenomenon has been consistently observed with the xenograft tissue of a tumor-bearing mouse. Using this principle we have further constructed a supramolecular glycocomposite by co-assembling the glycoprobe and an anticancer drug onto a single GO surface. In addition to imaging ability, this material displays improved toxicity for liver cancer cells that over express the glycoprotein receptor, when compared to the control cells.

Repetitive continuous extrusion forming was employed as a continuous severe plastic deformation route and both Al-Fe-Cu alloy and Al-Mg-Si alloy were involved. Evolution of microstructures and properties during this process is investigated by optical microscope, electron-backscatter diffraction, transmission electron microscope, and tensile testing. The results show that in the Al-Fe-Cu alloy an obvious mechanical softening and grain refinement were observed, while in the Al-Mg-Si alloy it shows a slightly rising in strength and ductility as the extrusion passes increasing.

Here we demonstrate that 2D MoS2 can enhance the receptor-targeting and imaging ability of a fluorophore-labelled ligand. The 2D MoS2 has an enhanced working concentration range when compared with graphene oxide, resulting in the improved imaging of both cell and tissue samples.

Introduction Magnetically controlled shape memory alloy (MSMA) actuators take advantages of their large deformation and high controllability. However, the intricate hysteresis nonlinearity often results in low positioning accuracy and slow actuator response. Methods In this paper, a modified Krasnosel'skii-Pokrovskii model was adopted to describe the complicated hysteresis phenomenon in the MSMA actuators. Adaptive recursive algorithm was employed to identify the density parameters of the adopted model. Subsequently, to further eliminate the hysteresis nonlinearity and improve the positioning accuracy, the model reference adaptive control method was proposed to optimize the model and inverse model compensation. Results The simulation experiments show that the model reference adaptive control adopted in the paper significantly improves the control precision of the actuators, with a maximum tracking error of 0.0072 mm. Conclusions The results prove that the model reference adaptive control method is efficient to eliminate hysteresis nonlinearity and achieves a higher positioning accuracy of the MSMA actuators.

Poly(3,4-ethylenedioxythiophene) (PEDOT):poly(styrene sulfonic acid) (PSSA) nanoparticles for dielectrophoretic display were prepared by in situ polymerization of 3,4-ethylenedioxythiophene in the PSSA nanoparticle, which was obtained from the sulfonation of polystyrene nanoparticles prepared by a conventional emulsion technique. The properties of the resulting nanoparticle were characterized by Fourier transform infrared spectrascopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and the dynamic light scattering (DLS) technique. The particle was uniform in spherical shape with an average diameter of ca. 300∼320 nm, and showed high thermal stability up to 340 °C. The electrical conductivity of the PEDOT:PSSA nanoparticle was measured to be as high as 0.11 S/cm. The dielectrophoretic display cell prepared from the colloidal PEDOT:PSSA nanoparticle dispersed in nematic liquid crystal showed significant optical change in response to electric field variation. Open image in new window

Fullerene/polystyrene (C60/PS) nano particle was prepared by using emulsion polymerization. Styrene and fullerene were emulsified in aqueous media in the presence of poly(N-vinyl pyridine) as an emulsion stabilizer, and polymerization was initiated by water soluble radical initiator, potassium persulfate. The obtained nano particles have an average diameter in the range of 400-500 nm. The fullerene contents in the nano particle can be controlled up to 15 wt % by varying the feed ratio, which was confirmed by themogravimetric analysis (TGA) and elemental analysis (EA). The structure and morphologies of the C60/PS nano particles were examined by various analytical techniques such as dynamic light scattering (DLS), scanning electron microscope (SEM), transmission electron microscope (TEM), electron diffraction (ED) pattern, X-ray powder diffraction (XRD), and UV spectroscopy. Unlike conventional C60/PS particles initiated by organic free radical initiators, in which the fullerene is copolymerized forming a covalent bond with styrene monomer, the prepared C60/PS nano particles contain pristine fullerene as secondary particles homogeneously distributed in the polystyrene matrix.

Polyethylene wax is prepared from LDPE through orthogonal experiments. It is found that temperature, time and the ratio of solvent to the feed can affect the experiment. The optimal condition is 310°C, 5h and 1 : 1.5. The result of experiment under the optimal condition is better than that in the orthogonal experiments. The color of products is from white to yellow. Finally, PEW is obtained from pyrolyzing waste PE bag under the optimal condition and the best condition in the orthogonal experiments. It can be seen that the former result is better than the later. The average molecular weight of polyethylene wax ranges from 1970 g/mol to 2700 g/mol.

Ultra-thin hydrogenated amorphous germanium films,with various thickness from 160 nm to 5 nm were grown by plasma enhanced chemical vapor deposition technique.The film structure was characterized by Raman spectroscopy,which exhibited a broad band centered around 280 cm-1 indicating their amorphous nature.The film thickness and optical properties were evaluated by ellipsometer spectroscopy.The measured thickness was well consistent with the pre-designed value and the optical band gap was about 1 eV which slightly increased with the decrease of film thickness.The temperature dependent conductivity of the films was measured.The electronic transport was believed to occur in the extended-states and the corresponding activation energy is about 0.3~0.4 eV.The light emission in infrared region from the films can be detected at low temperature.The sample for 160 nm had a broad luminescence band which can be divided into two sub-bands centered at 0.78 eV and 0.67 eV,respectively.By decreasing the films thickness less than 10 nm,the luminescence band beaome narrower and only a band at 0.8 eV was observed.It may be due to the relatively more hydrogen in the ultrathin films,which passivated the defect states and suppressed the defect-related luminescence.The non-radiative activation energy increased in ultrathin films suggesting the improved efficiency.

Room-temperature deposited amorphous silicon nitride (a-SiNx:H) films exhibit intense green light emission after post-treated by plasma oxidation, thermal oxidation and natural oxidation, respectively. All the photolumines-cence (PL) spectra are peaked at around 500 nm, independent of oxidation method and excitation wavelength. Compared with the PL results from oxidized a-Si:H and as-deposited a-SiNx :H samples, it is indicated that not only oxygen but also nitrogen is of an important role in enhancing light emission from the oxidized a-SiNx:H. Combining the PL results with the analyses of the bonding configurations as well as chemical compositions of the films, the strong green light emission is suggested to be from radiative recombination in luminescent centres related to N–Si–O bonds.

An a-SiNx/nanocrystalline silicon [(nc-Si)/a-SiNx] sandwiched structure is fabricated in a plasma enhanced chemical vapour deposition (PECVD) system at low temperature (250° C). The nc-Si layer is fabricated from a hydrogen-diluted silane mixture gas by using a layer-by-layer deposition technique. Atom force microscopy measurement shows that the density of nc-Si is about 2 × 1011 cm−2. By the pretreatment of plasma nitridation, low density of interface states and high-quality interface between the Si substrate and a-SiNx insulator layer are obtained. The density of interface state at the midgap is calculated to be 1 × 1010 cm−2eV−1 from the quasistatic and high frequency C – V data. The charging and discharging property of nc-Si quantum dots is studied by capacitance-voltage (C – V) measurement at room temperature. An ultra-large hysteresis is observed in the C – V characteristics, which is attributed to storage of the electrons and holes into the nc-Si dots. The long-term charge-loss process is studied and ascribed to low density of interface states at SiNx/Si substrate.

Intensive blue photoluminescence (PL) was observed at room temperature from the nanocrystalline-Si/SiO2 (nc-Si/SiO2) multilayers (MLs) obtained by thermal annealing of SiO/SiO2 MLs for the first time. By controlling the size of nc-Si formed in SiO sublayer from 3.5 to 1.5 nm, the PL peak blueshifts from 457 to 411 nm. Combining the analysis of TEM, Raman and absorption measurement, this paper attributes the blue PL to multiple luminescent centres at the interface of nc-Si and SiO2.

Nanocrystalline Si/SiO2 multilayers are prepared by thermally annealing amorphous Si/SiO2 stacked structures. The photoluminescence intensity is obviously enhanced after hydrogen passivation at various temperatures. It is suggested that the hydrogen trapping and detrapping processes at different temperatures strongly influence the passivation effect. Direct experimental evidence is given by electron spin resonance spectra that hydrogen effectively reduces the nonradiative defect states existing in the Si nanocrystas/SiO2 system which enhances the radiative recombination probability. The luminescence characteristic shows its stability after hydrogen passivation even after aging eight months.

We investigate the properties of light emission from amorphous-Si:H/SiO2 and nc-Si/SiO2 multilayers (MLs). The size dependence of light emission is well exhibited when the a-Si:H sublayer thickness is thinner than 4 nm and the interface states are well passivated by hydrogen. For the nc-Si/SiO2 MLs, the oxygen modified interface states and nanocrystalline silicon play a predominant role in the properties of light emission. It is found that the light emission from nc-Si/SiO2 is in agreement with the model of interface state combining with quantum confinement when the size of nc-Si is smaller than 4 nm. The role of hydrogen and oxygen is discussed in detail.

Enhanced photoluminescence (PL) at room temperature from thermally annealed a-Si:H/SiO2 multilayers is observed through the step-by-step thermal post-treatment. The correlation between the PL and the crystallization process is studied using temperature-dependent PL, Raman, cross section high-resolution transmission electron microscopy (X-HRTEM) and x-ray diffraction (XRD) techniques. An intensified PL band around 820 nm is discovered from the sample annealed near the crystallization onset temperature, which is composed of two peaks centred at 773 nm and 863 nm, respectively. It is found that the PL band centred at 863 nm is related to the pseudo nanocrystal (p-nc-Si) silicon, and the PL band centred at 773 nm is attributed to Si = O bonds stabilized in the p-nc-Si surface.

We report the crystallization and photoluminescence (PL) properties of amorphous Si:H/SiNx:H multilayer (ML) films treated by step-by-step laser annealing. The results of Raman measurements show that the nanocrystalline Si (nc-Si) grains are formed in the a-Si:H layers under the constrained growth mechanism. The blue shift of PL peak with grain size is observed and can be attributed to the quantum confinement effect. For comparison, we also report the crystallization and PL of a-Si:H/SiNx:H ML samples by normal one-step treatment. This method of step-by-step laser treatment will be a candidate to make nc-Si quantum dots in amorphous Si:H/SiNx:H ML as an active layer in microcavities.

The self-assembly processes of gold nanoparticles on nanometre-step-patterned Si surface and polished Si surface are investigated by the convective self-assembly method. The convective self-assembly method is used to deposit the colloids dispersed in benzene onto the substrates. The SEM results show that the configurations of the gold arrays depend on the surface morphology of the substrates. On the nanometre-step-patterned Si surface, the nanoparticles self assemble into parallel lines, and the distance between the neighbouring lines is around 35 nm. On the polished Si surface the nanoparticles form compact domains. In each domain the particles are close-packed in a two-dimensional hexagonal superlattice and are separated by uniform distances. The analysis shows that on the nanometre-step-patterned Si surface, the steps play critical roles in the self-assembly process of gold nanoparticles. The capillary force from the steps drives the particles to lines along the steps. Therefore, the particles tend to self-assemble into one-dimensional line structures when the solvent evaporates. For the polished Si substrate there is a little difference that the particles form two-dimensional hexagonal superlattices without the directional confinement.

Structures of nanocrystalline-Si (nc-Si) sandwiched between two asymmetric ultrathin SiO2 layers were fabricated. The nc-Si (dot density of 1011 cm−2) was formed by decomposition of hydrogen-diluted silane and the ultrathin SiO2 layers (about 2 nm) were prepared by plasma oxidation at a lower temperature (250 degrees C). The whole fabrication processes were completed in situ in a plasma-enhanced chemical vapour deposition system. By using the capacitance–voltage (C–V) and conductance–voltage (G–V) spectroscopy, we studied the electronic properties of the annealed samples. The experimental results show that there are distinct capacitance peaks and conductance plateau or peaks for annealed samples at room temperature, which can be explained by direct tunnelling of electrons into the nc-Si. At the same time, Coulomb blockade plays an important role in the electronic transport in the nc-Si. The effect of thermal annealing in N2 ambient on the electronic properties was studied and the results indicate that high temperature (1000 degrees C) annealing can improve the size uniformity of the nc-Si prepared by decomposition of hydrogen-diluted silane.

Generally, an entire blank is heated in the stamp forming process. Since it will cause difficulty in the transferring process and errors in dimensions and waste more energy, a stamp forming process with locally heated specimen is proposed in this work. Three stamping parameters including working temperature, heated range, and holding time are considered. To evaluate the quality of stamp formed parts, they are macroscopically characterized for part angle actually formed and microscopically examined for delamination and fiber buckling. In addition, the maximum load that the deformed part can suffer is measured. The results indicate that locally heated part is competitive to entirely heated part in maximum load and final angle, even though wrinkles are still observed in locally heated part. Also, 260 °C working temperature, 20 mm heated range, and 1 s holding time are recommended for stamp forming process with locally heated specimen.

A method in which nanometre-thick film deposition was alternated with hydrogen plasma annealing (layer-by-layer method) was applied to fabricate hydrogenated amorphous carbon films in a conventional plasma-enhanced chemical vapour deposition system. It was found that the hydrogen plasma treatment could decrease the hydrogen concentration in the films and change the sp2/sp3 ratio to some extent by chemical etching. Blue photoluminescence was observed at room temperature, as a result of the reduction of sp2 clusters in the films.

We have developed a novel class of simple materials for sensing monosaccharides by the functionalization of graphene oxide (GO) with boronate-based fluorescence probes (BA1 and BA2). The composite materials were characterized by atomic force microscopy, Raman spectroscopy, and UV–vis/fluorescence spectroscopy. The strong fluorescence of the BA probes is quenched in the presence of GO through fluorescence resonance energy transfer. The BA@GO composite sensors formed provide a useful platform for fluorogenic detection of monosaccharides based on the strong affinity between the boronic acid receptor and monosaccharides. The BA@GO composite sensor displayed a “turn-on” fluorescence response with a good linear relationship toward fructose over a range of other saccharides.

We have prepared nearly monodisperse CdSe nanocrystallites with diameters of 1-4 nm from the rapid pyrolysis of organometallic precursors in a hot coordinating solvent. The nanocrystal structures have been characterized by transmission electron microscopy and electron diffraction. From the absorption spectrum, we have observed the prominent peak of 1S-1S excitonic transition, which is obviously blue-shifted from the bulk bandgap and the largest shift is about 1.25 eV. We have used a theoretical model based on the tight binding approximation to analyze the quantum size effect of these nanocrystallites. The results have been compared with those of the effective mass approximation model.

A series of hydrogenated amorphous silicon carbide films (a-SiC:H) were prepared by rf plasma-enhanced chemical vapor deposition method. The optical band gap(Egopt) of the films can be extended to 2.6 eV. The as-deposited films were then irradiated by a KrF excimer laser. During the irradiation process, hydrogen escaped out of the films, and the structure of the films was changed from an amorphous phase to mixed phases of nanocrystallites of silicon and amorphous silicon carbide. The room-temperature dark conductivity of the laser irradiated films is 6-7 orders of magnitude larger than that of the as-deposited films, which was attributed to the modification of the conductivity mechanism resulting from the structural change.

A series of hydrogenated amorphous silicon-germanium alloys have been fabricated by high hydrogen dilution method. The Ge content in the film increases from 0.4 to 0.8 and the corresponding optical bandgap is in the range of 1.48-1.22 eV. The photoconductivity is 3.6 × 10-6 S/cm and photosensitivity is as high as 7.3 × 103 at an optical bandgap of 1.48 eV. The deterioration of photoelectric properties with increasing Ge content could be attributed to the decrease of the bonded hydrogen content and the inhomogeneous structure in the alloy network.

We report a two-stage mechanism of formation of the two-dimensional surperlattices in colloidal gold nanoparticles. The first stage is the formation and growth of holes. When the film is thinner than the ``pancake'' thickness and because the solvent volatility holes nucleate and grow, the dry solid surface is exposed. The second stage corresponds to the reorganization of the colloids in the impacted areas between several holes, in which the particles gathering along the rims order due to the van der Waals-type attraction between colloids and the confinement by the length of dodecanethiol. Then at a compromised distance and perfect position giving the minimum free energy, ordering occurs in small domains along the boundary of the hole. When the ordered domains become closer because of the hole growth, they rotate at certain angles and the further ordering appears.

Four kinds of a-Si:H films deposited in the PECVD system with different Ts are studied by 1H NMR technique. Direct evidence is given to confirm hydrogen atoms in the diluted and clustered phases. The local bonding configurations for hydrogen and the density of dangling bonds are analyzed by ESR and infrared absorption spectroscopy. The behaviour of hydrogen in a-Si:H films is discussed.

We have applied the layer-by-layer deposition technique to the growth of nano-crystalline silicon films by varying the hydrogen plasma exposure time. The tailoring effect of hydrogen plasma has been studied. The novel optical and electronic properties of these films have also been reported.

Highly monodispersed colloidal silica spheres in sub-micrometre size with distribution standard deviation less than 5% were synthesized by a chemical method. Using the self-crystallization of the silica spheres, we successfully obtained the three-dimensional close-packed face-centred-cubic silica matrices and artificial opals. Then, a colloidal photonic crystal embedded with CdS quantum dots (QDs) was also chemically prepared by using artificial opals as a template. A reflection spectra study reveals that both artificial opals with and without CdS QDs possess (111) directional photonic bandgap features.

ZnS quantum dots (QDs) synthesized in water and ethanol solutions were coated with polystyrene (PS) and SiO2 shells, respectively. The band edge emission was enhanced by nearly five times after PS coating and by about thirteen times after SiO2 coating, because the surface trap states were removed. From the photoluminescence properties of ZnS QDs coated with PS and SiO2 shells we have detected the improvement of thermal stability. This is due to the fact that the surface passivation can prevent the further growth of the ZnS QDs and the diffusion of oxygen on the surface of ZnS QDs during thermal oxidation.

Highly hydrogen-diluted silane plasma is used to fabricate microcrystalline silicon films in a plasma-enhanced chemical vapour deposition system. X-ray diffraction and micro-Raman scattering spectroscopy are utilized to characterize their microstructure properties. Dark conductivity and drift mobility are measured by the travelling wave method. With the decreasing gas flow ratio of silane-to-hydrogen from 2% to 0.2%, the crystalline volume fraction and the drift mobility increase at room temperature. Meanwhile, the dark conductivity increases initially and then decreases. The relationship between the microstructures and transport properties is discussed.

ZnS and Zn(OH)2 capped ZnS semiconductor quantum dots (QDs) have been synthesized by the colloidal chemical method using inorganic reagents. Transmission electron microscopy and electron diffraction results have shown that the monodispersed ZnS QDs have a diameter of 1-5 nm and the wurtzite structure. The polarities of the precursors and surfactant solvents have shown strong effects on the properties of the photoluminescence for ZnS QDs. For ZnS QDs capped with a wider band gap Zn(OH)2 shell, the surface trap states were passivated and hence the band-edge emissions have been enhanced.

The objective of this study was to form a rapid and firm soft tissue sealing around dental implants that resists bacterial invasion. We present a novel approach to modify Ti surface by immobilizing Ag nanoparticles/FGF-2 compound bioactive factors onto a titania nanotubular surface. The titanium samples were anodized to form vertically organized TiO(2) nanotube arrays and Ag nanoparticles were electrodeposited onto the nanotubular surface, on which FGF-2 was immobilized with repeated lyophilization. A uniform distribution of Ag nanoparticles/FGF-2 was observed on the TiO(2) nanotubular surface. The L929 cell line was used for cytotoxicity assessment. Human gingival fibroblasts (HGFs) were cultured on the modified surface for cytocompatibility determination. The Ag/FGF-2 immobilized samples displayed excellent cytocompatibility, negligible cytotoxicity, and enhanced HGF functions such as cell attachment, proliferation, and ECM-related gene expression. The Ag nanoparticles also exhibit some bioactivity. In conclusion, this modified TiO(2) nanotubular surface has a large potential for use in dental implant abutment.

The travelling wave method has been used to measure the drift mobility in the paramagnetic-insulator state of La0.75Sr0.11Ca0.14MnO3 films. The thermal activation of the drift mobility in manganites has been measured for the first time. The mobility varies from 2.5×10-2 cm2/Vs at 310 K to about 9.2×10-2 cm2/Vs at 400 K. The Arrhenius behaviours of the conductivity and drift mobility indicate that the transport process in manganites above the Curie temperature is dominated by the thermally assisted hopping of small polarons. PACS: 75. 30. Un, 62. 80. +f, 71. 38. +i, 73. 50. Dn

Hydrogenated amorphous silicon carbide (a-SiC:H) films were grown by using an organic source, xylene (C8H10), instead of methane (CH4) in a conventional plasma enhanced chemical vapor deposition system. The optical band gap of these samples was increased gradually by changing the gas ratio of C8H10 to SiH4. The film with high optical band gap was soft and polymer-like and intense photoluminescence were obtained. Room temperature electro-luminescence was also achieved with peak energy at 2.05 eV (600 nm) for the a-SiC:H film with optical band gap of 3.2 eV.

The hydrogenated amorphous silicon (a-Si:H)/silicon carbide (a-SiCx:H) quantum well (QW) and superlattice structures were fabricated by glow discharge deposition. Wavelength differential absorption spectroscopy has been applied to study the subband transition in a-Si:H/a-SiCx:H QW, and derivative spectra change clearly from a linear to a step-like form when a-Si:H well-layer thickness has decreased below 40 A. These results indicate that three-dimensional parabolic band transition is turned into subband transition in the a-Si:H QW.

The optical properties of amorphous GaP (a-GaP) films prepared by plasma enhanced transport deposition method in the system of Ga-PCl3H2 have been studied. The optical energy band gap Egopt of a-GaP films is about 1.6 eV which depends on the contents of Cl atoms. The results of exponential absorption edge indicate that there is a high density of band-tail states in the optical energy band gap.

Simulation on the properties of localized surface plasmon resonance (LSPR) of different sized hexagonal Ag nanoarrays embedded in the amorphous oxidized silicon nitride(a-SiNx:O) matrix has been carried out by using COMSOL Multiphysics and FDTD Solution simulation software. Through the calculation of the scattering and absorption cross section of Ag array with different radius, we find that the position of extinction peaks red-shift from 460 to 630 nm when the radius of nanoparticles of hexagonal Ag arrays increases from 25 to 100 nm with the distance between particles 100 nm. The enhanced scattering cross section of the localized surface plasmon (LSP) and blue-shift of the extinction peak can be obtained by tunning the distance between Ag nanoparticles from 100 to 50 nm with the radius of Ag nanoparticles fixed at 50 and 75 nm, respectively. However the mismatch between the extinction peak of hexagonal Ag nanoarrays and the blue light emission of 460 nm from a-SiNx:O films still exists. The novel overlap between the scattering cross section of LSP from hexagonal Ag arrays with a radius of 25 nm and the blue light emission of a-SiNx:O films at 460 nm further confirms that the hexagnoal Ag arrays with a radius of 25 nm is the optimal option to enhance the blue light emission from a-SiNx:O films. Therefore, strong coupling between LSP and blue light emission at 460 nm from a-SiNx:O films with a thickness of 70 nm can be realized when the radius of Ag nanoparticle is 25 nm. We also investigate the enhancement of near field radiative intensity of LSP from hexagnoal Ag arrays with a radius of 25 nm. When the excitation wavelength is 460 nm, the maximum enhancement of near field intensity of LSP from hexagnoal Ag arrays with a radius of 25 nm reaches 1.46104 V/m. The calculated polarization intensity and charge distribution of hexagonal Ag nanoparticle with a radius of 25 nm embedded in a-SiNx:O films reveal that the enhancement of electromagnetic field-intensity is through the dipolar plasmon coupling with the excitons in a-SiNx:O films in bright field mode under the excitation of 460 nm. Further calculation of perpendicular radiative intensity for LSP from the hexagonal Ag array with a radius of 25 nm embedded in a-SiNx:O films indicates that the maximum radiative intensity can be realized in a-SiNx:O matrix with an optimum thickness of 30 nm for a-SiNx:O films. Our theoretical calculations and analysis can provide valuable reference for the design of Si-base blue LED with light emission around 460 nm.

SiOx films (x=1.3) are deposited on the silicon substrates by electron beam evaporation. The resistive switching behaviors from the device consisting of indium tin oxide (ITO)/SiOx/Si/Al with annealed SiOx layer as the resistive layer are investigated. It is found that on/off ratio of the device increases with the annealing temperature rising. The maximum on/off ratio reaches 109. The analyses of X-ray photoelectron spectrum and electron paramagnetic resonance spectrum reveal that the silicon dangling bonds in different valence states can be formed at different annealing temperatures, which is the main source of the conducting filament pathway. The result of ellipsometer indicates that the increase of refractive index of annealed SiOx film leads to the increase of the resistance of high resistance state.

Qianli Ma1*, Wei Wang1*, Paul K Chu2, Shenglin Mei1,2, Kun Ji3, Lei Jin4, Yumei Zhang11Department of Prosthetic Dentistry, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China; 2Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong, People's Republic of China; 3Department of Pediatric Dentistry, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China; 4Stomatology Department, Jinling Hospital, School of Medicine, Southern Medical University, Nanjing, People's Republic of China*These authors contributed equally to this workBackground: Titanium (Ti) implants are widely used clinically, but peri-implantitis remains one of the most common and serious complications. Healthy integration between gingival tissue and the implant surface is critical to long-term success in dental implant therapy. The objective of this study was to investigate how different concentrations of immobilized fibroblast growth factor 2 (FGF2) on the titania nanotubular surface influence the response of human gingival fibroblasts (HGFs).Methods: Pure Ti metal was anodized at 20 V to form a vertically organized titanium dioxide nanotube array on which three concentrations of FGF2 (250 ng/mL, 500 ng/mL, or 1000 ng/mL) were immobilized by repeated lyophilization. Surface topography was observed and FGF2 elution was detected using enzyme-linked immunosorbent assay. The bioactivity changes of dissolvable immobilized FGF2 were measured by methyl-thiazolyl-tetrazolium assay. Behavior of HGFs was evaluated using adhesion and methyl-thiazolyl-tetrazolium bromide assays.Results: The FGF2 remained for several days on the modified surface on which HGFs were cultured. Over 90% of the dissolvable immobilized FGF2 had been eluted by Day 9, whereas the FGF2 activity was found to diminish gradually from Day 1 to Day 9. The titania nanotubular surface with an optimal preparing concentration (500 ng/mL) of FGF2 immobilization exhibited improved HGF functions such as cellular attachment, proliferation, and extracellular matrix-related gene expression. Moreover, significant bidirectional as well as concentration- and time-dependent bioactivity was observed.Conclusion: Synergism of the FGF2-impregnated titanium dioxide nanotubular surface revealed good gingival-implant integration, indicating that these materials might have promising applications in dentistry and other biomedical devices.Keywords: dental implants, titanium dioxide nanotube, fibroblast growth factor 2, extracellular matrix, real-time polymerase chain reaction

The tunable single electron effect and Coulomb oscillations were observed in Si nanowire transistors. By measuring the channel current as function of applied back-gate and side-gate voltage, the tunable single electron effect and Coulomb oscillations are investigated. From the differential conductance characteristics, the Coulomb diamonds are clearly observed due to the gate voltage-induced quantum dots formation in the Si nanowire.

The a-SiNx/nc-Si/a-SiNx sandwiched structures are fabricated in a plasma enhanced chemical vapour deposition (PECVD) system on n-type Si substrate. The nc-Si layer in thickness of 5 nm is fabricated from hydrogen diluted silane gas by layer-by-layer deposition technique. The thicknesses of tunnel and control SiNx layer are 3 nm and 20 nm, respectively. Conductance-voltage and capacitance-voltage measurements are used to study the charges tunnelling and storage in the sandsiched structures. Distinct frequency-dependent conductance peaks due to charges tunneling into the nc-Si dots and capacitance-voltage hysteresis characteristic due to charges storage in the nc-Si dots are observed in the same sample. The experimental results demonstrate that by controlling the thickness of tunnel and control SiNx layers charges can be loaded onto nc-Si dots via tunnelling and be stored in a-SiNx/nc-Si/a-SiNx structures.

A nonvolatile memory device with nitrided Si nanocrystals embedded in a Boating gate was fabricated. The uniform Si nanocrystals with high density (3 × 1011 cm−2) were deposited on ultra-thin tunnel oxide layer (~ 3 nm) and followed by a nitridation treatment in ammonia to form a thin silicon nitride layer on the surface of nanocrystals. A memory window of 2.4 V was obtained and it would be larger than 1.3 V after ten years from the extrapolated retention data. The results can be explained by the nitrogen passivation of the surface traps of Si nanocrystals, which slows the charge loss rate.

Nanowire devices with back gate are fabricated in a heavy doped ultra thin SOI layer by electron beam lithography. Regular and periodic Coulomb oscillations with single dot behavior are observed in an appropriate back gate voltage range. The oscillation period can be determined by the back gate capacitance. The role of the back gate can control the electrical characteristics from the multi-dot junction regimes to the single dot junction regimes. These Coulomb oscillations due to single-electron tunneling are not smeared out by thermal vibration energy when the temperature is less than 40 K.

This paper reports that metal-oxide-semiconductor (MOS) capacitors with a single layer of Ni nanoparticles were successfully fabricated by using electron-beam evaporation and rapid thermal annealing for application to nonvolatile memory. Experimental scanning electron microscopy images showed that Ni nanoparticles of about 5 nm in diameter were clearly embedded in the SiO2 layer on p-type Si (100). Capacitance–voltage measurements of the MOS capacitor show large flat-band voltage shifts of 1.8 V, which indicate the presence of charge storage in the nickel nanoparticles. In addition, the charge-retention characteristics of MOS capacitors with Ni nanoparticles were investigated by using capacitance–time measurements. The results showed that there was a decay of the capacitance embedded with Ni nanoparticles for an electron charge after 104 s. But only a slight decay of the capacitance originating from hole charging was observed. The present results indicate that this technique is promising for the efficient formation or insertion of metal nanoparticles inside MOS structures.