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Tao Wu, Kaiming Deng, Weiqiao Deng, Ruifeng Lu
BNC x monolayer as a kind of two-dimensional material has numerous chemical atomic ratios and arrangements with different electronic structures. Via calculations on the basis of density functional theory and Boltzmann transport theory under deformation potential approximation, the band structures and carrier mobilities of BNC x (x  =  1,2,3,4) nanosheets are systematically investigated. The calculated results show that BNC2-1 is a material with very small band gap (0.02 eV) among all the structures while other BNC x monolayers are semiconductors with band gap ranging from 0...
October 19, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Peijian Wang, Michael D Barnes
We report on spatially correlated wavelength-resolved photoluminescence and Kelvin Probe Force Microscopy (KPFM) to probe ground state charge-transfer coupling and its correlation with pi-stacking order in nanoscale assemblies of a small molecule n-type organic semiconductor, tetraazaterrylene (TAT). We find a distinct upshift in surface potential contrast (SPC) corresponding to a decrease in work function in TAT in the transition from disordered spun-cast films to ordered crystalline nanowire assemblies, accompanied with a nanowire size dependence in the SPC shift suggesting that the shift depends on both ground state charge transfer interaction and a size-(volume) dependent intrinsic doping associated with the nitrogen substitutions...
October 19, 2017: Nano Letters
Daniel Prochowicz, Arkadiusz Kornowicz, Janusz Lewiński
Readily available cyclodextrins (CDs) with an inherent hydrophobic internal cavity and hydrophilic external surface are macrocyclic entities that display a combination of molecular recognition and complexation properties with vital implications for host-guest supramolecular chemistry. While the host-guest chemistry of CDs has been widely recognized and led to their exploitation in a variety of important functions over the last five decades, these naturally occurring macrocyclic systems have emerged only recently as promising macrocyclic molecules to fabricate environmentally benign functional nanomaterials...
October 19, 2017: Chemical Reviews
Anna M Cieślak, Emma-Rose Janeček, Kamil Sokołowski, Tomasz Ratajczyk, Michał K Leszczyński, Oren A Scherman, Janusz Lewiński
Herein, we show how the inherent light-induced redox properties of semiconducting nanocrystals (NCs) can be utilized for the photo-driven reversible modulation of dynamic supramolecular systems formed at their interfaces that, on their own, do not respond to light. This was achieved by the unprecedented combination of photoactive zinc oxide NCs (ZnO NCs) with a host-guest chemistry of cucurbit[8]uril (CB[8]) providing a route to the semiconductor-assisted light modulation of supramolecular assemblies (SALSA), here mediated by the photo-generation of viologen radical cations (MV˙(+)) at the NC corona and their further dimerization enhanced by CB[8] macrocycles...
October 19, 2017: Nanoscale
Bogdan C Raducanu, Refet F Yazicioglu, Carolina M Lopez, Marco Ballini, Jan Putzeys, Shiwei Wang, Alexandru Andrei, Veronique Rochus, Marleen Welkenhuysen, Nick van Helleputte, Silke Musa, Robert Puers, Fabian Kloosterman, Chris van Hoof, Richárd Fiáth, István Ulbert, Srinjoy Mitra
We present a high electrode density and high channel count CMOS (complementary metal-oxide-semiconductor) active neural probe containing 1344 neuron sized recording pixels (20 µm × 20 µm) and 12 reference pixels (20 µm × 80 µm), densely packed on a 50 µm thick, 100 µm wide, and 8 mm long shank. The active electrodes or pixels consist of dedicated in-situ circuits for signal source amplification, which are directly located under each electrode. The probe supports the simultaneous recording of all 1356 electrodes with sufficient signal to noise ratio for typical neuroscience applications...
October 19, 2017: Sensors
Elke Meissner, Maral Haeckel, Jochen Friedrich
In this paper, we report a failure case of blue LEDs returned from a field application, and propose a practical way to identify the physical and structural reasons for the observed malfunction by a combination of different electron microscope techniques. Cathodoluminescence imaging and electron beam induced current (EBIC) imaging are employed in order to visualize conductive paths through the device in conjunction with subsequent energy dispersive x-ray analysis (EDS), revealing a metal deposition along cracks in the semiconductor layer which short-circuit the device...
October 19, 2017: Materials
Giovanni DI Liberto, Valentina Pifferi, Leonardo Lo Presti, Michele Ceotto, Luigi Falciola
A concerted theoretical and experimental investigation of the silver/anatase hybrid nanocomposite, a very promising material for advanced sensing applications, is presented. We measure its exceptional electrochemical virtues in terms of current densities and reproducibility, providing their explanation at the atomic-scale level, and demonstrating how and why silver acts as a positive electrode. Using periodic plane-wave DFT calculations, we estimate the overall amount of electron transfer toward the semiconductor side of the interface at equilibrium...
October 19, 2017: Journal of Physical Chemistry Letters
Abbas Ghasempour Ardakani, Marzieh Sedaghatnejad
We first investigate a graphene based 1D plasmonic photonic crystal (PPC) composed of a graphene sheet deposited on an SiO2 grating whose grooves are filled with air by using finite-element method (FEM) software (COMSOL Multiphysics). The dispersion effect of SiO2 is considered in the simulation, and we show that this effect significantly affects the transmission spectrum of the proposed PPC. The transmission spectrum shows a stop band in the mid-infrared region, which is blueshifted by increasing the Fermi energy level of the graphene sheet...
September 1, 2017: Applied Optics
Zhuo Xu, Zhi-Yuan Dou, Jing Hou, Xiao-Jun Xu
We demonstrate an all-fiber widely wavelength-tunable thulium-doped fiber laser (TDFL) mode locked by a semiconductor saturable absorber mirror (SESAM). The tuning range spans 121 nm, from 1862 nm to 1983 nm. The central wavelength is tuned by a grating-based tunable filter in the ring laser cavity. To the best of our knowledge, this is so far the most widely wavelength-tunable TDFL mode locked by SESAM.
July 20, 2017: Applied Optics
Donghai Niu, Shiqi Sun, Qiang Xu, Minghui Jiang, Xibin Wang, Zhiyong Li, Changming Chen, Yuanda Wu, Daming Zhang
In this paper, the power-consumption characteristics of a polymeric thermo-optic (TO) switch consisting of a silica under-cladding on silicon substrate, a polymer core surrounded with polymer upper-cladding, and aluminum heating electrodes with different widths were investigated. Norland optical adhesive 73 with a larger TO coefficient was selected as the core layer, which could reduce the power consumption effectively. The silica under-cladding, with large thermal conductivity, could shorten the response time...
July 20, 2017: Applied Optics
Peng Zhang, Maohua Jiang, Renjiang Zhue, Dingke Zhang, Yanrong Song
GaAs/AlAs distributed Bragg reflectors (DBRs) are widely used in the gain chips of 1 μm wave band semiconductor disk lasers (SDLs) as an end/folded cavity mirror. Because the generated redundant heat in the active region of a gain chip mainly dissipates through the DBR, thermal conductivities of DBRs are crucial for the output performance of SDLs. For the purpose of more reasonable semiconductor wafer design, to improve the thermal management of SDLs, accurate thermal conductivities of DBRs with various layer thicknesses are under considerable requirement...
May 20, 2017: Applied Optics
Rana Asgari Sabet, Mostafa Sahrai, Hamed Sattari
We propose a multilayer medium with semiconductor quantum dot nano-structures as a defect layer for all-optical control of the 1.55 μm probe beam. The effect of the coupling field and incoherent pump on absorption and dispersion properties of the quantum dot defect layer is investigated. Depending on the intensity of the coupling field and rate of the incoherent pump field, the possibility of the absorption cancellation and even amplification are demonstrated. The optimum values of the coupling field intensity and incoherent pump field for complete transmission or amplification are obtained...
October 1, 2017: Applied Optics
Peep Adamson
A new optical method for determining anisotropic dielectric constants of graphene-like two-dimensional materials on semiconductor or metal substrates is developed. The method is based on the surface differential reflectance measurements at three different incident angles. The inversion problem is resolved analytically in a long-wavelength approximation, where graphene is discussed within the framework of macroscopic electrodynamics as a uniaxially anisotropic film with the optical axis perpendicular to the film surface...
October 1, 2017: Applied Optics
M Nisa Khan
We present measurement and analysis of color stability over time for two categories of white LED lamps based on their thermal management scheme, which also affects their transient lumen depreciation. We previously reported that lumen depreciation in LED lamps can be minimized by properly designing the heat sink configuration that allows lamps to reach a thermal equilibrium condition quickly. Although it is well known that lumen depreciation degrades color stability of white light since color coordinates vary with total lumen power by definition, quantification and characterization of color shifts based on thermal transient behavior have not been previously reported in literature for LED lamps...
September 20, 2017: Applied Optics
Chee-Wei Lee, Doris Keh-Ting Ng, Min Ren, Yuan-Hsing Fu, Anthony Yew Seng Kay, Vivek Krishnamurthy, Jing Pu, Ai Ling Tan, Soo Bin Choo, Qian Wang
Electrically pumped heterogeneously integrated III-V/SiO2 semiconductor on-chip lasers with different types of etched facet reflectors are designed and fabricated and their lasing performances are characterized and compared. The III-V quantum-well-based epitaxial layers are bonded on silica-on-silicon substrates and fabricated to form Fabry-Perot lasers with dry-etched rear facets. Three types of reflectors are demonstrated, which are etched facets terminated by air, benzocyclobutene, and metal with a thin layer of SiO2 insulator in-between...
June 10, 2017: Applied Optics
Travis W Sawyer, Kyle S Hawkins, Michael Damento
High-resolution spectrographs extract detailed spectral information of a sample and are frequently used in astronomy, laser-induced breakdown spectroscopy, and Raman spectroscopy. These instruments employ dispersive elements such as prisms and diffraction gratings to spatially separate different wavelengths of light, which are then detected by a charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) detector array. Precise alignment along the optical axis (focus position) of the detector array is critical to maximize the instrumental resolution; however, traditional approaches of scanning the detector through focus lack a quantitative measure of precision, limiting the repeatability and relying on one's experience...
June 20, 2017: Applied Optics
Shayan Saeidi, Kashif M Awan, Lilian Sirbu, Ksenia Dolgaleva
We propose several designs of nonlinear optical waveguides based on quaternary III-V semiconductors AlGaAsSb and InGaAsP. These semiconductor materials have been widely used for laser sources. Their nonlinear optical properties, however, yet remain unexplored, while the materials definitely hold promise for nonlinear photonics on-a-chip. The latter argument is based on the fact that III-V compounds tend to exhibit high values of the nonlinear optical susceptibilities, while the nonlinear absorption in these materials can be minimized in the wavelength range of interest through a proper selection of the material composition...
July 1, 2017: Applied Optics
Zecen Zhang, Geok Ing Ng, Haodong Qiu, Wanjun Wang, Xin Guo, Mohamed S Rouifed, Chongyang Liu, Hong Wang
Compact all-pass and add-drop microring resonators (radius=10  μm) integrated with grating couplers working at 2 μm wavelength are designed, fabricated, and characterized on a commercial 340-nm-thick-top-silicon silicon-on-insulator platform. They are suitable for high-volume integrated optical circuits at 2 μm wavelength as the fabrication process involved are uncomplicated and complementary metal-oxide-semiconductor (CMOS)-process compatible, thus making them more convenient to be utilized. The performance of the grating couplers, based on four most important parameters, has been simulated and optimized...
July 1, 2017: Applied Optics
Liping Chen, Jiabao Cui, Xia Sheng, Tengfeng Xie, Tao Xu, Xinjian Feng
Semiconductor photoelectrodes that simultaneously possess rapid charge transport and high surface area are highly desirable for efficient charges generation and collection in photoelectrochemical devices. Herein, we report mesostructured ZnO nanowires (NWs) that not only demonstrate a surface area as high as 50.7 m(2)/g, comparable to that of conventional nanoparticles (NPs), but also exhibit a 100 times faster electron transport rate than that in NP films. Moreover, using the comparison between NWs and NPs as an exploratory platform, we show that the synergistic effect between rapid charge transport and high surface area leads to a high perfor-mance photoelectronic formaldehyde sensor that exhibits a detection limit of as low as 5 ppb and a response of 1223% (at 10 ppm), which are, respectively, over 100 times lower and 20 times higher than those of conventional NPs-based device...
October 19, 2017: ACS Sensors
Long Xu, Zhiyuan Zhao, Mingchao Xiao, Jie Yang, Jian Xiao, Zhengran Yi, Shuai Wang, Yunqi Liu
The exploration of novel electron-deficient building blocks is a key task for developing high-performance polymer semiconductors in organic thin film transistors (OTFTs). In view of the situation of the lack of strong electron-deficient building blocks, we designed two novel π-extended isoindigo-based electron-deficient building blocks, IVI and F4IVI. The strong electron-deficient nature and the extended π-conjugated system for the two acceptor units endow their copolymers containing 2,2'-bithiophene donor units, PIVI2T and PF4IVI2T, deep lying HOMO/LUMO energy levels and the strong intermolecular interactions...
October 19, 2017: ACS Applied Materials & Interfaces
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