Anodization at elevated temperatures in nitric acid has been used for the production of highly porous and thick tungsten trioxide nanostructured films for photosensitive device applications. The anodization process resulted in platelet crystals with thicknesses of 20-60 nm and lengths of 100-1000 nm. Maximum thicknesses of approximately 2.4 microm were obtained after 4 h of anodization at 20 V. X-ray diffraction analysis revealed that the as-prepared anodized samples contain predominantly hydrated tungstite phases depending on voltage, while films annealed at 400 degrees C for 4 h are predominantly orthorhombic WO3 phase. Photocurrent measurements revealed that the current density of the 2.4 microm nanostructured anodized film was 6 times larger than the nonanodized films. Dye-sensitized solar cells developed using these films produced 0.33 V and 0.65 mA/cm2 in open- and short-circuit conditions.

Among the available metal oxide nanostructures, tungsten oxide has remained, at times, troublesome to fabricate, with many synthetic methods often requiring exotic equipment and or reagents. In this work, we present a systematic investigation demonstrating a new method for the deposition of anhydrous and hydrated nanostructured tungsten oxide thin films via spin coating. The attributes of these materials include the following: high surface area, controllable deposition, and compatibility with existing semiconductor fabrication infrastructure making this method a suitable candidate for application in the manufacture of gas sensors and dye sensitized solar cells. We will show that it is possible to form micrometer thick highly crystalline nanostructured thin films and, using Raman, SEM, XRD, XPS, and TEM analysis, will prove that these nanostructures can be rendered into anhydrous or partially or fully hydrated tungsten oxides. We further demonstrate the application of these materials in the fabrication of an inexpensive NO2 gas sensor, capable of sensing sub-ppm levels of NO2 concentrations at a modest operating temperature of 175 °C.

A few-electron double quantum dot was fabricated using metal-oxide-semiconductor(MOS)compatible technology and low-temperature transport measurements were performed to study the energy spectrum of the device. The double dot structure is electrically tunable, enabling the interdot coupling to be adjusted over a wide range, as observed in the charge stability diagram. Resonant single-electron tunneling through ground and excited states of the double dot was clearly observed in bias spectroscopy measurements.

Pt/graphene nanosheet/SiC based devices are fabricated and characterized and their performances toward hydrogen gas are investigated. The graphene nanosheets are synthesized via the reduction of spray-coated graphite oxide deposited onto SiC substrates. Raman and X-ray photoelectron spectroscopies indicate incomplete reduction of the graphite oxide, resulting in partially oxidized graphene nanosheet layers of less than 10 nm thickness. The effects of interfaces on the nonlinear behavior of the Pt/graphene and graphene/SiC junctions are investigated. Current-voltage measurements of the sensors toward 1% hydrogen in synthetic air gas mixture at various temperatures ranging up to 100 °C are performed. From the dynamic response, a voltage shift of ∼100 mV is recorded for 1% hydrogen at a constant current bias of 1 mA at 100 °C.

Carbonate determination in dental apatites such as dentine and enamel is important for studying the dynamics of dental caries and developmental defects of these tissues. Traditionally, these determinations have been performed by acidic digestion with the subsequent measurement of released carbon dioxide gas. As an alternative, Raman spectroscopy has been used for the determination of carbonate in synthetic carbonated apatites with at least four analytical methods published thus far. However, these methods have not been applied to biological apatites. The aim of this comparative study was to test the suitability of these four methods for the determination of B-type carbonate in human enamel and dentine. A method for determining the A-type carbonate content of enamel using the Raman technique is also presented. Raman spectra were obtained from 10 human enamel and dentine samples and analysed with each of the four methods using either a single or multiple ν₁(PO₄^3–) band spectral fitting model. Each of the methods resulted in a different determination for the carbonate content when using the same measurement data. The method that used the full-width-at-half-maximum of the ν₁(PO₄^3–) band to determine the B-type carbonate concentration was found to be in best agreement with (i) the results (using the acid digestion method) of teeth collected from the same sample population and (ii) previously reported values for both enamel and dentine. The use of a multiple-band spectral fitting model produced the highest determination precision (particularly in the case of dentine).

We report a systematic investigation on the spectral splitting of negatively charged, nitrogen-vacancy (NV − ) photoluminescent emission in single-crystal diamond induced by strain engineering. The stress fields arise from MeV ion-induced conversion of diamond to amorphous and graphitic material in regions proximal to the centers of interest. In low-nitrogen sectors of a high-pressure-high-temperature diamond, clearly distinguishable spectral components in the NV − emission develop over a range of ∼4.8 THz corresponding to distinct alignment of sub-ensembles which were mapped with micron spatial resolution. This method provides opportunities for the creation and selection of aligned NV − centers for ensemble quantum information protocols. Gesellschaft large optical dipoles and, in the case of the negatively charged nitrogen-vacancy (NV − ) center, long-lived ground-state coherence [3].Although much of the interest in NV − -based QIP is centered on room-temperature processes and isolated centers, there is also considerable interest in applying ensemble QIP protocols to the optical transition of inhomogeneously broadened NV − centers. Indeed the dipole moment and transition frequency for NV − are comparable to that of rubidium, meaning that translation of protocols developed for vapor cells is natural. Protocols using ensembles were initially considered for the first NV − quantum computing [4,5] and optical quantum non-demolition experiments [6]. There have been observations of long-lived ground-state coherence [7], coherent population trapping [8], magnetometry [9] and magnetic coupling between NV − ensembles and superconducting circuits [10,11].Despite the interest in ensemble processing with NV − , there are major challenges to be overcome, which place NV − at a disadvantage when compared with atomic vapors. One of the largest problems is the inhomogeneous linewidth and the nature of this inhomogeneity. The inhomogeneous linewidth of the optical transitions in NV − typically varies with strain [12], implantation strategy [13,14] and electric field [15], leaving the job of controlling the linewidth as a major goal of NV − engineering. Coupled to this problem is that at room temperature, the linewidth appears to be dominated by spectral diffusion, although exceptional emitters with almost lifetime-limited emission can be discovered [16][17][18][19][20], and there are no reports of ensembles of purely homogeneously broadened NV − centers.Here we show a new approach to spectrally separating aligned subensembles of NV − . By engineering permanent strain fields into the diamond lattice through ion implantation, we demonstrate that it is possible to resolve the orientationally inequivalent NV − subensembles based upon their spectral properties. These results reveal new opportunities for the use of aligned, inhomogeneously broadened ensembles of NV − centers for QIP that is distinct from more traditional methods of applying external uniaxial strain to a lattice.In the study of defect-related optical transitions in cryst...

The novel design of a fiber-optic laser scanning confocal microscope is described. The optical fiber acts as a flexible light path for both the excitation and return beams and as the confocal pinhole of the microscope. The system is capable of imaging both reflective and fluorescent objects and offers considerable adaptability in use. With a mode-locked dye laser excitation source, avalanche photodiode detector and time-correlated photon counting electronics, spatially resolved fluorescence decay profiles from fluorescent dyes in solution and polymer films have been recorded.

We report the catalyst-free synthesis of the arrays of core−shell, ultrathin, size-uniform SiC/AlSiC nanowires on the top of a periodic anodic aluminum oxide template. The nanowires were grown using an environmentally friendly, silane-free process by exposing the silicon supported porous alumina template to CH 4 + H 2 plasmas. Highresolution scanning and transmission electron microscopy studies revealed that the nanowires have a single-crystalline core with a diameter of about 10 nm and a thin (1−2 nm) amorphous AlSiC shell. Because of their remarkable length, high aspect ratio, and very high surface area-to-volume ratio, these unique structures are promising for nanoelectronic and nanophotonic applications that require efficient electron emission, light scattering, etc. A mechanism for nanowire growth is proposed based upon the reduction of the alumina template to nanosized metallic aluminum droplets forming between nanopores. The subsequent incorporation of silicon and carbon atoms from the plasma leads to nucleation and growth from the top of the alumina template.