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Zuhui Zheng, Shan Cong, Wenbin Gong, Jinnan Xuan, Guohui Li, Weibang Lu, Fengxia Geng, Zhigang Zhao
Semiconductor-based surface-enhanced Raman spectroscopy (SERS) substrates represent a new frontier in the field of SERS. However, the application of semiconductor materials as SERS substrates is still seriously impeded by their low SERS enhancement and inferior detection sensitivity, especially for non-metal-oxide semiconductor materials. Herein, we demonstrate a general oxygen incorporation-assisted strategy to magnify the semiconductor substrate-analyte molecule interaction, leading to significant increase in SERS enhancement for non-metal-oxide semiconductor materials...
December 8, 2017: Nature Communications
Da-Jin Kim, Jang-Soon Park, Cheol Ho Kim, Jae Hur, Choong-Ki Kim, Young-Kyun Cho, Jun-Bong Ko, Bonghyuk Park, Dongho Kim, Yang-Kyu Choi
This paper describes the fabrication and characterization of a reconfigurable Yagi-Uda antenna based on a silicon reflector with a solid-state plasma. The silicon reflector, composed of serially connected p-i-n diodes, forms a highly dense solid-state plasma by injecting electrons and holes into the intrinsic region. When this plasma silicon reflector is turned on, the front-realized gain of the antenna increases by more than 2 dBi beyond 5.3 GHz. To achieve the large gain increment, the structure of the antenna is carefully designed with the aid of semiconductor device simulation and antenna simulation...
December 8, 2017: Scientific Reports
Antoine Carof, Samuele Giannini, Jochen Blumberger
We have recently introduced an efficient semi-empirical non-adiabatic molecular dynamics method for the simulation of charge transfer/transport in molecules and molecular materials, denoted fragment orbital-based surface hopping (FOB-SH) [J. Spencer et al., J. Chem. Phys. 145, 064102 (2016)]. In this method, the charge carrier wavefunction is expanded in a set of charge localized, diabatic electronic states and propagated in the time-dependent potential due to classical nuclear motion. Here we derive and implement an exact expression for the non-adiabatic coupling vectors between the adiabatic electronic states in terms of nuclear gradients of the diabatic electronic states...
December 7, 2017: Journal of Chemical Physics
Xianhe Liu, Binh H Le, Steffi Y Woo, Songrui Zhao, Alexandre Pofelski, Gianluigi A Botton, Zetian Mi
Semiconductor light sources operating in the ultraviolet (UV)-C band (100-280 nm) are in demand for a broad range of applications but suffer from extremely low efficiency. AlGaN nanowire photonic crystals promise to break the efficiency bottleneck of deep UV photonics. We report, for the first time, site-controlled epitaxy of AlGaN nanowire arrays with Al incorporation controllably varied across nearly the entire compositional range. It is also observed that an Al-rich AlGaN shell structure is spontaneously formed, significantly suppressing nonradiative surface recombination...
November 27, 2017: Optics Express
Sanghwa Yoo, Joon Ki Lee, Kwangjoon Kim
We present a simple and effective method for suppressing thermally induced wavelength drift in a widely tunable digital supermode distributed Bragg reflector (DS-DBR) laser monolithically integrated with a semiconductor optical amplifier (SOA). For fast thermal compensation, pre-compensatory currents are injected into the gain medium section of the DS-DBR laser and the SOA. This method can be easily applied to existing commercial tunable lasers, since it is implemented without any modification to manufacturing process...
November 27, 2017: Optics Express
Mitsuru Takenaka, Shinichi Takagi
We have numerically investigated the properties of an InP-on-SiC wafer as a photonic integrated circuit (PIC) platform. By bonding a thin InP-based semiconductor on a SiC wafer, SiC can be used as waveguide cladding, a heat sink, and a support substrate simultaneously. Since the refractive index of SiC is sufficiently low, PICs can be fabricated using InP-based strip and rib waveguides with a minimum bend radius of approximately 7 μm. High-thermal-conductivity SiC underneath an InP-based waveguide core markedly improves heat dissipation, resulting in superior thermal properties of active devices such as laser diodes...
November 27, 2017: Optics Express
Richard Wolf, Ingo Breunig, Hans Zappe, Karsten Buse
We demonstrate cascaded Stimulated Raman Scattering (SRS), Second-Harmonic Generation (SHG), and Sum-Frequency Generation (SFG) in integrated on-chip whispering-gallery resonators (WGRs). These lithium niobate-based WGRs are fabricated using highly-parallel semiconductor manufacturing techniques coupled with specialized polishing as a post-processing step and thus represent a novel means for batch fabrication of this family of non-linear devices. We achieved record high Q-factors for on-chip lithium niobate WGRs reaching up to 3 × 106...
November 27, 2017: Optics Express
Andrej Marculescu, Seán Ó Dúill, Christian Koos, Wolfgang Freude, Juerg Leuthold
Optical spectra of signals at the output of semiconductor optical amplifiers (SOA) provide useful insight into amplifier nonlinearities. In this work, we determine the parameters of an analytical SOA model with a pump-probe experiment by evaluating the measured spectra of the pump and probe pulses at the SOA output. The analytical lumped SOA model considers carrier depletion, carrier recovery, spectral hole burning, two-photon absorption, and we include an additional effect termed 'two-photon induced free-carrier absorption', that is responsible for creating an identifiable blue-shifted component in the spectra...
November 27, 2017: Optics Express
Jian Zhou, Yonggang Wu, Zihuan Xia, Xuefei Qin, Zongyi Zhang
Single nanowire solar cells show great promise for next-generation photovoltaics and for powering nanoscale devices. Here, we present a detailed study of light absorption in a single standing semiconductor-dielectric core-shell nanowire (CSNW). We find that the CSNW structure can not only concentrate the incident light into the structure, but also confine most of the concentrated light to the semiconductor core region, which boosts remarkably the light absorption cross-section of the semiconductor core. The CSNW can support multiple higher-order HE modes, as well as Fabry-Pérot (F-P) resonance, compared to the bare nanowire (BNW)...
November 27, 2017: Optics Express
Matthew Hayman, Scott Spuler
We present a demonstration of a diode-laser-based high spectral resolution lidar. It is capable of performing calibrated retrievals of aerosol and cloud optical properties at a 150 m range resolution with less than 1 minute integration time over an approximate range of 12 km during day and night. This instrument operates at 780 nm, a wavelength that is well established for reliable semiconductor lasers and detectors, and was chosen because it corresponds to the D2 rubidium absorption line. A heated vapor reference cell of isotopic rubidium 87 is used as an effective and reliable aerosol signal blocking filter in the instrument...
November 27, 2017: Optics Express
Aritra Bhaduri, Amitava Banerjee, Subhrajit Roy, Sougata Kar, Arindam Basu
We present a neuromorphic current mode implementation of a spiking neural classifier with lumped square law dendritic nonlinearity. It has been shown previously in software simulations that such a system with binary synapses can be trained with structural plasticity algorithms to achieve comparable classification accuracy with fewer synaptic resources than conventional algorithms. We show that even in real analog systems with manufacturing imperfections (CV of 23.5% and 14.4% for dendritic branch gains and leaks respectively), this network is able to produce comparable results with fewer synaptic resources...
December 8, 2017: Neural Computation
Zhi-Gang Yu
Free-carrier absorption (FCA) in a semiconductor provides information about the band on which the free carriers reside, and in the classical limit, follows the $\omega^{-2}$ law with $\omega$ being the photon frequency. In hybrid organic-inorganic perovskites (HOIPs), the colossal Rashba effect (RE) results in a new band dispersion, characterized by wavevector $|{\bm k}|=k_0$ of band extremum and effective mass $m^*$. Here we show that the colossal RE in 2D HOIPs greatly enhances phonon-assisted FCA with a modified frequency dependence and induces a direct transition between the subbands with a resonance at $\hbar\omega=4R \equiv 2 \hbar^2 k^2_0/m^*$, which, under a magnetic field, exhibits a strong oscillatory magnetic circular dichroism (MCD)...
December 8, 2017: Journal of Physical Chemistry Letters
Jong Min Kim, Sung Kim, Sung Won Hwang, Chang Oh Kim, Dong Hee Shin, Ju Hwan Kim, Chan Wook Jang, Soo Seok Kang, Euyheon Hwang, Suk-Ho Choi, Sherif H El-Gohary, Kyung Min Byun
Recently, we have demonstrated that excitation of plasmon-polaritons in a mechanically-derived graphene sheet on the top of a ZnO semiconductor considerably enhances its light emission efficiency. If this scheme is also applied to device structures, it is then expected that the energy efficiency of light-emitting diodes (LEDs) increases substantially and the commercial potential will be enormous. Here, we report that the plasmon-induced light coupling amplifies emitted light by ~1.6 times in doped large-area chemical-vapor-deposition-grown graphene, which is useful for practical applications...
December 8, 2017: Nanotechnology
Matheus Paes Lima
The synthesis of Silicon Nanotubes realized since the last decade demonstrates multi-walled tubular structures comprised of $Si$ atoms in the $sp^2$ and the $sp^3$ hybridizations. However, most of the theoretical models were elaborated taking as the starting point $sp^2$ structures analogous to the Carbon Nanotubes. These structures are unfavorable due to the natural tendency of the $Si$ atoms to undergo $sp^3$. In this work, through {\it ab-initio} simulations based on Density Functional Theory, we investigated double-walled Silicon Nanotubes proposing layered tubes possessing most of the $Si$ atoms in a $sp^3$ hybridization, and few $sp^2$ atoms localized at the outer wall...
December 8, 2017: Nanotechnology
Chhabilal Regmi, Dipesh Dhakal, Soo Wohn Lee
Ag-loaded BiVO4 visible-light-driven photocatalyst was synthesized by microwave hydrothermal method followed by photodeposition. Photocatalytic performance of the synthesized samples were evaluated on the mixed dye (methylene blue and rhodamine B), as well as bisphenol A in aqueous solution. Similarly, the disinfection activities of synthesized samples towards the gram-negative Escherichia coli (E. coli) a model cell were investigated under visible light irradiation condition (λ≥420 nm). The synthesized samples have monoclinic-scheelite structure...
December 8, 2017: Nanotechnology
Arpita Varadwaj, Pradeep R Varadwaj, Koichi Yamashita
A relationship between reported experimental bandgaps (solid) and presently DFT-calculated binding energies (gas) is established for the first time for each of the four ten-membered lead (or tin) trihalide perovskite solar cell semiconductor series examined in this study, including CH3NH3PbY3, CsPbY3, CH3NH3SnY3 and CsSnY3, where Y = I(3 - x)Brx=1-3, I(3 - x)Clx=1-3, Br(3-x)Cl x=1-3, and IBrCl. The relationship unequivocally provides a new dimension for the fundamental understanding of the optoelectronic features of the solid state solar cell thin films using the 0 K gas-phase energetics of their corresponding molecular building blocks...
December 8, 2017: ChemSusChem
Kyuwan Cho, Jinseck Kim, So Yeon Yoon, Ka Yeon Ryu, Song-Rim Jang, Bogyu Lim, Kyungkon Kim
The performance of organic photovoltaics (OPVs) based on the small-molecule organic semiconductor p-DTS(FBTTh2 )2 is greatly improved by the addition of a conjugated block copolymer composed of difluoroquinoxaline and thienopyrrolodione blocks (D130). The power conversion efficiency (PCE) of the p-DTS(FBTTh2 )2 -based OPV is improved from 5.08% to 6.75% by the addition of 5 wt% D130 to the photoactive layer, which is composed of p-DTS(FBTTh2 )2 and a fullerene derivative. Current-voltage and grazing incidence wide-angle X-ray scattering analyses revealed that the addition of D130 significantly reduces the trap density of the device and changes the packing orientation of p-DTS(FBTTh2 )2 from mostly edge-on to partially face-on...
December 8, 2017: Macromolecular Rapid Communications
Biao Liu, Yu-Qing Zhao, Zhuo-Liang Yu, Lin-Zhi Wang, Meng-Qiu Cai
It was still a great challenge to design high performance of rectification characteristic for the rectifier diode. Lately, a new approach was proposed experimentally to tune the Schottky barrier height (SBH) by inserting an ultrathin insulated tunneling layer to form metal-insulator-semiconductor (MIS) heterostructures. However, the electronic properties touching off the high performance of these heterostructures and the possibility of designing more efficient applications for the rectifier diode were not presently clear...
December 4, 2017: Journal of Colloid and Interface Science
David Gutstein, David Lynall, Selvakumar V Nair, Igor Savelyev, Marina Blumin, Daniele Ercolani, Harry E Ruda
The conductance of semiconductor nanowires is strongly dependent on their electrostatic history because of the overwhelming influence of charged surface and interface states on electron confinement and scattering. We show that InAs nanowire field-effect transistor devices can be conditioned to suppress resonances that obscure quantized conduction thereby revealing as many as six sub-bands in the conductance spectra as the Fermi-level is swept across the sub-band energies. The energy level spectra extracted from conductance, coupled with detailed modelling shows the significance of the interface state charge distribution revealing the Coulomb landscape of the nanowire device...
December 7, 2017: Nano Letters
S Syubaev, A Porfirev, A Zhizhchenko, O Vitrik, S Kudryashov, S Fomchenkov, S Khonina, A Kuchmizhak
Laser irradiation of various materials including metals, polymers, and semiconductors with vortex beams was previously shown to "twist" transiently molten matter providing the direct easy-to-implement way to obtain chiral surface relief. Specifically for metals, this effect was attributed to transfer of an orbital angular momentum (OAM) carried by a vortex beam. In this Letter, we report the formation of twisted metallic nanoneedles on surfaces of silver and gold films under their irradiation by a zero-OAM laser beam with a spiral-shaped intensity distribution...
December 1, 2017: Optics Letters
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