Copper oxalate 1 �m-sized nanocrystalline assemblies with several shapes (cushions, lenses, drilled cushions, and square rods) have been obtained by aqueous precipitation without additive, with glycerol, with PEG and with HPMC. Respective influences of these additives on the nanocrystals self-assembly are suggested from the obtained particles morphologies to provide a better understanding of this assembly process. Raman spectroscopy is used to highlight fluorescence occurring on the copper oxalate samples synthesized with additives. This additive induced fluorescence is suggested to result from specific interactions between the nanocrystals and the adsorbed additives.

A systematic study on the effect of sputtering deposition parameters on material properties of Al doped ZnO (ZnO:Al) films prepared by an in-line rf magnetron sputtering and on surface morphology of the films after wet etching process was carried out. For application to silicon thin film solar cells as a front electrode, the as-deposited films were surface-textured by a dilute HCl solution to improve the light scattering properties such as haze and angle resolved distribution of scattered light on the film surfaces. The microstructure of as-deposited films is affected significantly by the working pressure and film compactness decreases with increasing working pressure from 1.5 mTorr to 10 mTorr. High quality ZnO:Al films with electrical resistivity of 4.25 × 10-4 Ω cm and optical transmittance of 80% in a visible range are obtained at low working pressure of 1.5 mTorr and substrate temperature of 100℃. Crater-like surface morphologies are observed on the textured ZnO:Al films after wet etching. The size and shape of craters are closely dependent on the microstructure and film compactness of as-deposited films. Haze values of the textured ZnO:Al films are improved in a whole wavelength of 300 – 1100 nm compared to commercial SnO2:F films (Asahi U type) and incident light on the textured films is scattered effectively with 30° angle.

Photoelectrochemical properties of photoelectrodes consisting of pressed layers of electrospun TiO2 nanofibers were investigated by wavelength-resolved photocurrent measurements in LiClO4 (0.1 M) aqueous electrolyte with or without addition of KI as an additional hole scavenger. The photocurrents on nanofiber electrodes were three-times lower as compared to electrodes based on Hombikat nanocrystalline particles. The calcination of electrodes was necessary to observe enhanced efficiencies in the presence of iodide. The most striking difference between nanofiber and particulate electrodes was found in the effect of calcination on the efficiency of water photooxidation.

A series of simulated microstructures containing nanometer-scale precipitates was created with an atom probe simulator. These data were then analyzed with the proximity histogram and the maximum separation method to determine the influence of the particular analysis method. For simulated 2-nm-radius spherical precipitates, the optimized voxel size and delocalization were found to be 0.5-0.6 nm and 1.0-1.5 nm, respectively. Under optimum analysis parameters, the voxelization/delocalization process only slightly degrades the interface width determined from the proximity histogram to ˜0.15±0.04 nm.

Proposed mechanisms so far on defect reactions in semiconductors are reexamined. Structural instability of point defects is explained in terms of the Jahn-Teller effect. It is found that the tetrahedral coordinated bonds, which do not have inversion symmetry, are not so rigid as we consider, especially for hole localization. Second topic is the phonon-kick mechanism for defect reactions under carrier injection. In order to discuss this mechanism in detail, we recall the configuration coordinate (c-c) diagram, which is often misunderstood in the literature. The proper relation is explained among the lattice distortion, the position of the electronic level in the band gap (thermal and optical depths), the total energy the multiphonon (e and h) carrier capture processes and the following induced lattice relaxation. A numerical simulation has been performed on phonon kick mechanism. It is found that a rapid increase of the transient lattice vibration around the defect is possible and the probability critically depends on the carrier concentrations and the phonon frequency distribution.

Thin films of vanadium dioxide (VO2) exhibit an interesting semiconductor to metal transition (SMT) when heated above ˜680C in which its resistivity changes by 3-4 orders of magnitude and its transmittance for IR wavelengths drops drastically. Integration of these thin films with Si (100) substrate is of immense technological importance due to its potential applications in sensor and memory based devices. Using pulsed laser deposition (PLD) we have demonstrated in this study that thin films of VO2 can be grown epitaxially on Si (100) substrate using an intermediate tetragonal Yttrium-Stabilized Zirconia (YSZ) layer without any further annealing. X-ray diffraction (XRD) and cross-section transmission electron microscopy studies were performed on the films and they are found to be of highly epitaxial nature. Electrical resistivity measurement were carried out using the four-point probe method and SMT parameters were extracted using Gaussian fit of the data. The S-M transition parameters are in close proximity with parameters obtained from vanadium oxide films deposited on oxide based substrates such as Al2O3 or TiO2.

Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and titanium dioxide (TiO2, titania) are of interest for bone-interfacing implant applications, because of their demonstrated osteoconductive properties. They were coated on the titanium implants using hydro-processes and investigated the in vivo performance. HAp coatings were formed on cp-titanium plates or rods by the thermal substrate method in an aqueous solution included 0.3 mM Ca(H2PO4)2 and 0.7 mM CaCl2. In the formation of carbonate apatite coating, CaHCO3 was added to the solution, and in HAp/gelatin and HAp/collagen composite coatings, acid-soluble collagen (Type I) was added. The coating experiments were conducted at 313-433 K and pH = 8 for 15 or 30 min. Titania films were formed on the titanium implants by anodizing at < 100 V in 0.1 M H2SO4, H3PO4, and NaOH aqueous solutions at 298 K. The properties for the coated samples were studied using XRD, EDX, FT-IR, and SEM. And the surface roughness of titania coatings was measured. In in vivo evaluations, the coated rod specimens were implanted in rats femoral for 2 weeks, the osteoconduction on them was evaluated. Two weeks postimplantation, new bone formed on the coated and non-coated titanium rods in the cancellous bone and cortical bone, respectively. Bone-implant contact ratio, RB-I, which was used for the evaluation of new bone formation, was significantly depended on the compound formed on titanium implants, and also the coating processes.

Single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) were functionalized with 3,4-diaminobenzoic acid via “direct” Friedel-Crafts acylation reaction in PPA/P2O5 to afford ortho-diamino-functionalized SWCNT (DIF-SWCNT) and MWCNT (DIF-MWCNT). The resultant DIF-SWCNT and DIF-MWCNT showed improved solubility and dispersibility. To improve interfacial adhesion between CNT and polymer matrix, the grafting of ABPBI onto the surface of DIF-SWCNT (10 wt%) or DIF-MWCNT (10 wt%) was conducted by simple in-situ polymerization of AB monomer, 3,4-diaminobenzoic acid dihydrochloride, in PPA. The resultant ABPBI-g-MWCNT and ABPBI-g-SWCNT showed improved the mechanical and electrical properties.

Recently, wavelength selective emitting materials have attracted extensive interest due to their potential of high optical-to-electricity conversion efficiency for thermal photovoltaic (TPV) cells and realizing high efficient incandescent light sources. A substantial increase in spectral control over thermal radiation and photon recycling can accomplish this objective by the development of high-temperature photonic structures (HTPS) that simultaneously suppress unwanted radiation and enhance emission in a desirable wavelength range. In this paper, we shall review the properties of HTPS as a wavelength selective emitter, the radiative energy transfer relation in real devices, and photon recycling scheme using wavelength selective filters.

The oxygen potentials at 1273 K of mixed oxide (MOX) fuels with Am and 26 kinds of fission product elements (FPs), simulating low-decontaminated MOX fuel and high burn-up of up to 250 GWd/t, have been measured by using thermogravimetric analysis (TGA). The oxygen potentials for simulated low-decontaminated MOX fuels were higher than the fuels without FPs and increased with increasing simulated burn-up.

We have demonstrated conformal deposition of amorphous GeSbTe films in high aspect ratio structures by MOCVD. SEM analysis showed the as-deposited GeSbTe films had smooth morphologies and were well controlled for void free amorphous conformal deposition. GeSbTe films adhere well to SiO2, TiN, and TiAlN. The morphology and adhesion are stable in 420°C post process. By annealing at 365°C, amorphous GeSbTe films converted into crystalline GeSbTe with polycrystalline grain sizes of 5nm. Film resistivity in the crystalline phase ranged from 0.001 to 0.1 Ω-cm, suitable for device applications. Phase change devices fabricated with confined via structures filled with MOCVD GeSbTe showed cycle endurances up to 1×1010 with a dynamic set/rest resistance of two orders of magnitude.

The structural and electronic properties of graphene nanoribbons (GNRs) modified by H, CO, and NH3 molecules at their edges under uniaxial strain is investigated by means of first principles calculations. It is found the bond length of the reconstructed edge of a H-terminated GNR modified by CO is larger than those of a bare GNR, a H-terminated GNR, and a H-terminated GNR modified by NH3. It is also found the band gaps of a H-terminated GNR and a H-terminated GNR modified by CO are twice the gap of a bare GNR, and the band gaps of a bare GNR and a H-terminated GNR increase with the increase of imposed strain.

There is a real need for a material which absorbs in the visible light of the solar spectrum, is stable in water and at the same time economical. One-dimensional vertically aligned nanotubes have contributed to a great extent towards the visible light driven photoelectrolysis of water. In this work, we give an overview of the different nanotubes obtained through anodization of various metals and their application in the photooxidation of water

The co-sputtered Cu-In precursor layers were characterized by bi-layer surface structure in which island-type crystals were formed in a small-crystalline matrix layer. The elemental composition of the island-type crystals corresponds to the compound CuIn2 and the matrix (area) consists of copper-rich Cu11In9 phase. The surface morphology of sequentially evaporated Cu-Zn-Sn precursor layers is determined by the deposition order of stacked consistent metal layers. Precursor Mo-Sn-Zn-Cu films exhibit a well-formed “mesa-like” structure of the surface in which larger crystals (about 1,5 μm) are located on a “small-crystalline” valley. For films with other sequences of metallic layers, the mesa like structure is not so well exposed and well formed flat precursor layers were produced replacing separate metallic Cu and Sn layers with Cu/Sn alloy layer. Selenization of both Cu-In and Cu-Zn-Sn precursor layers begins with the formation of binary Cu-selenides with compositions varying with the temperature. At temperatures higher than 3700C the selenization of Cu-In results in single-phase CuInSe2 films in contrast to the selenization of Sn-Zn-Cu films that results always in multi-phase films consisting of high quality Cu2ZnSnSe4 crystals and of separate small-crystalline phase of ZnSe.

We experimentally demonstrate a simple and efficient approach for silicon oxide nanowire growth by implanting Fe+ ions into thermally grown SiO2 layers on Si wafers and subsequently annealing in argon and hydrogen to nucleate silicon oxide nanowires. We study the effect of implantation dose and energy, growth temperature, and H2 gas flow on the SiOx nanowire growth. We find that sufficiently high implant dose, high growth temperature, and the presence of H2 gas flow are crucial parameters for silicon oxide nanowire growth. We also demonstrate the patterned growth of silicon oxide nanowires in localized areas by lithographic patterning and etching of the implanted SiO2 substrates before growth. This works opens up the possibility of growing silicon oxide nanowires directly from solid substrates, controlling the location of nanowires at the submicron scale, and integrating them into nonplanar three-dimensional nanoscale device structures.

Secondary-gate electrodes are introduced in organic thin-film transistors to reduce carrier-injection barriers into air-stable organic semiconductors. The additional gate electrodes buried in the gate insulators under the source and drain electrodes form “carrier-rich regions” in the vicinity of source and drain electrodes with the application of sufficiently high local electric fields. Fabricating the structure with dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene, known for its excellent air-stability, it turned out that the contact resistance is drastically reduced especially when operated at low gate voltage in the main channel. The result demonstrates carrier injection with a minimized potential barrier realizing that from the same semiconductor material in the absence of peculiar interfacial trap levels at metal-to-semiconductor junctions.

Glass-ceramics based on hypo-eutectic (GC1) and hyper-eutectic (GC2) compositions of the Wollastonite (W, CaSiO3) - Tricalcium Phosphate [TCP, Ca3(PO4)2] binary system, which are saturated with SiO2 during the glass melting stage, are synthesized by the petrurgic method, using cooling rates of 0.5, 1 or 2°C/h. All synthesized materials are subjected to in vitro bioactivity tests using Kokubo's Simulated Body Fluid (SBF). Primary a-Cristobalite is formed in all cases. Metastable Apatite [Ap, Ca10(PO4)6O] and W phases are additionally formed, in general, in the GC1 glass-ceramics, as well as in the GC2 material obtained at a cooling rate of 0.5°C/h. However, at faster cooling rates, TCP is formed instead of Ap phase in the latter composition. During the bioactivity tests, a hydroxyapatite [HAp, Ca10(PO4)6(OH)2]-like surface layer is formed in all materials. It is proposed that GC2 glass-ceramics cooled at a rate of 1°C/h have the potential to show good in vivo osseointegration properties.

We investigate the band offsets and stability for Ni/Bi2Te3 and Co/Bi2Te3 interfaces by first principles calculations. It is found that the surface termination strongly affects the band offsets. Ni and Co are found to form Ohmic contacts to Bi2Te3. The interface formation energies for Co/Bi2Te3 interfaces are much lower than those of Ni/Bi2Te3 interfaces. Our calculations are consistent with the experimental data.

The photoluminescence in a nc-Si/a-Si:H mixture has been investigated at varying excitation intensities, and temperatures We have also observed changes in the luminescence spectra, which are induced by sequential annealing at temperatures below the a-Si:H crystallization temperature (˜ 600°C). Two predominant luminescence peaks are observed at ˜ 0.95 eV and ˜ 1.30 eV, which are attributed to band tail-to-band tail transitions near the nc-Si grain boundaries and in the a-Si:H bulk, respectively. The 0.95 eV band saturates approaching 500 mW/cm2 excitation intensity. Annealing the nc-Si/a-Si:H mixture brings out a new low energy peak, centered at ˜ 0.70 eV, and which we believe to be due to oxygen defects.

We present femtosecond differential reflectivity studies of few-layer graphene from weak to strong excitation regime. Temporal profiles of the differential reflectivity exhibit strong non-exponential decay. A nonlinear, cubic root dependence of their peak amplitudes on the pump fluence is clearly observed under relatively high intensity excitation, which indicates three-particle decay of transient carrier population via Auger scattering. Our results identify the critical role of such three-particle scattering in the initial electronic relaxation in photo-excited graphene with increasing phase-space filling of the correlated Dirac Fermions.