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https://www.readbyqxmd.com/read/29216149/on-chip-wavelength-locking-for-photonic-switches
#1
Akhilesh S P Khope, Takako Hirokawa, Andrew M Netherton, Mitra Saeidi, Yujie Xia, Nicolas Volet, Clint Schow, Roger Helkey, Luke Theogarajan, Adel A M Saleh, John E Bowers, Rod C Alferness
We present an on-chip wavelength reference with a partial drop ring resonator and germanium photodetector. This approach can be used in ring-resonator-based wavelength-selective switches where absolute wavelength alignment is required. We use the temperature dependence of heater resistance as a temperature sensor. Additionally, we discuss locking speed, statistical variation of heater resistances, and tuning speed of the switches.
December 1, 2017: Optics Letters
https://www.readbyqxmd.com/read/29216107/fabrication-of-ultra-high-numerical-aperture-geo2-doped-fiber-and-its-use-for-broadband-supercontinuum-generation
#2
P Harshavardhan Reddy, A V Kir'yanov, Anirban Dhar, Shyamal Das, Debjit Dutta, Mrinmay Pal, Y O Barmenkov, J A Minguella-Gallardo, Shyamal Kumar Bhadra, Mukul Chandra Paul
We report the fabrication, characterization, and application (broadband supercontinuum [SC] generation) of ultra-high numerical-aperture heavily (50 mol. %) GeO2-doped optical fiber, obtained through a modified chemical vapor deposition process and rod-in-tube method. The formation of Ge-related diamagnetic defect centers, such as germanium oxygen defect centers (GeODC) with nonbridging lone electron pairs, confirmed by x-ray photoelectron spectroscopy and optical absorption studies, inducing hypolarizable local dipoles, may be responsible in boosting the nonlinear effects and enhancing stimulated Raman scattering at pumping with high-power pulses, culminating in generation of broadband SC generation...
November 20, 2017: Applied Optics
https://www.readbyqxmd.com/read/29209014/a-mote2-based-light-emitting-diode-and-photodetector-for-silicon-photonic-integrated-circuits
#3
Ya-Qing Bie, Gabriele Grosso, Mikkel Heuck, Marco M Furchi, Yuan Cao, Jiabao Zheng, Darius Bunandar, Efren Navarro-Moratalla, Lin Zhou, Dmitri K Efetov, Takashi Taniguchi, Kenji Watanabe, Jing Kong, Dirk Englund, Pablo Jarillo-Herrero
One of the current challenges in photonics is developing high-speed, power-efficient, chip-integrated optical communications devices to address the interconnects bottleneck in high-speed computing systems. Silicon photonics has emerged as a leading architecture, in part because of the promise that many components, such as waveguides, couplers, interferometers and modulators, could be directly integrated on silicon-based processors. However, light sources and photodetectors present ongoing challenges. Common approaches for light sources include one or few off-chip or wafer-bonded lasers based on III-V materials, but recent system architecture studies show advantages for the use of many directly modulated light sources positioned at the transmitter location...
December 2017: Nature Nanotechnology
https://www.readbyqxmd.com/read/29203831/germanium-doped-metallic-ohmic-contacts-in-black-phosphorus-field-effect-transistors-with-ultra-low-contact-resistance
#4
Hsun-Ming Chang, Adam Charnas, Yu-Ming Lin, Peide D Ye, Chih-I Wu, Chao-Hsin Wu
In this work, we demonstrate for the first time an ultra-low contact resistance few-layered black phosphorus (BP) transistor with metallic PGex contacts formed by rapid thermal annealing (RTA). The on-state current of the transistor can be significantly improved and the ION/IOFF ratio increases by almost 2 order. The hole mobility is enhanced by 25 times to 227 cm2V-1s-1. The contact resistance extracted by the transfer length method is 0.365 kΩ∙μm, which is the lowest value in black phosphorus transistors without degradation of ION/IOFF ratio...
December 4, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29195163/environmental-impacts-of-heavy-metals-rare-earth-elements-and-natural-radionuclides-in-marine-sediment-from-ras-tanura-saudi-arabia-along-the-arabian-gulf
#5
Atef El-Taher, Fatimh Alshahri, Reda Elsaman
Ras Tanura city is one of the most important cities in Saudi Arabia because of the presence of the largest and oldest oil refinery in the Middle East which was began operations in September 1945. Also its contains gas plant and two ports. The concentration of natural radionuclides, heavy metals and rare earth elements were measured in marine sediment samples collected from Ras Tanura. The specific activities of 238U, 226Ra, 232Th, 40K and 137Cs (Bq/kg) were measured using A hyper-pure Germanium detector (HPGe), and ranged from (20...
November 20, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/29185770/producing-atomically-abrupt-axial-heterojunctions-in-silicon-germanium-nanowires-by-thermal-oxidation
#6
Hsin-Yu Lee, Tzu-Hsien Shen, Chen-Yu Hu, Yun-Yi Tsai, Cheng-Yen Wen
Compositional abruptness of the interfaces is one of the important factors to performance of Group IV semiconductor heterojunction (Si/Ge or Si/SiGe) nanowire devices. However, forming abrupt interfaces in the nanowires using the common Vapor-Liquid-Solid (VLS) method is restricted, because large solubility of Si and Ge in the Au eutectic liquid catalyst makes gradual composition change at the heterojunction after switching the gas phase components. According to the VLS growth mechanism, another possible approach to the formation of an abrupt interface is making a change of the semiconductor concentration in the eutectic liquid before precipitation of the second phase...
November 29, 2017: Nano Letters
https://www.readbyqxmd.com/read/29184064/low-threshold-optically-pumped-lasing-in-highly-strained-germanium-nanowires
#7
Shuyu Bao, Daeik Kim, Chibuzo Onwukaeme, Shashank Gupta, Krishna Saraswat, Kwang Hong Lee, Yeji Kim, Dabin Min, Yongduck Jung, Haodong Qiu, Hong Wang, Eugene A Fitzgerald, Chuan Seng Tan, Donguk Nam
The integration of efficient, miniaturized group IV lasers into CMOS architecture holds the key to the realization of fully functional photonic-integrated circuits. Despite several years of progress, however, all group IV lasers reported to date exhibit impractically high thresholds owing to their unfavourable bandstructures. Highly strained germanium with its fundamentally altered bandstructure has emerged as a potential low-threshold gain medium, but there has yet to be a successful demonstration of lasing from this seemingly promising material system...
November 29, 2017: Nature Communications
https://www.readbyqxmd.com/read/29173810/monte-carlo-simulation-of-the-full-energy-peak-efficiency-of-an-hpge-detector
#8
Waseem Khan, Qingmin Zhang, Chaohui He, Muhammad Saleh
This paper presents a Monte Carlo method to obtain the full energy peak efficiency (FEPE) curve for a High Purity Germanium (HPGe) detector, as it is difficult and time-consuming to measure the FEPE curve experimentally. The Geant4 simulation toolkit was adopted to establish a detector model since detector specifications provided by the nominal manufacturer are usually insufficient to calculate the accurate efficiency of a detector. Several detector parameters were optimized. FEPE curves for a given HPGe detectors over the energy range of 59...
November 15, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/29169063/measurement-of-absolute-%C3%AE-ray-emission-probabilities-in-the-decay-of-235-u
#9
M Marouli, G Lutter, S Pommé, R Van Ammel, M Hult, S Richter, R Eykens, V Peyrés, E García-Toraño, P Dryák, M Mazánová, P Carconi
Accurate measurements were performed of the photon emission probabilities following the α decay of (235)U to (231)Th. Sources of highly enriched (235)U were characterised in terms of isotopic composition by mass spectrometry and their activities were standardised by means of alpha-particle counting at a low defined solid angle. The standardised sources were subsequently measured by high-resolution γ-ray spectrometry with calibrated high-purity germanium detectors to determine the photon emission probabilities...
October 29, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/29166084/on-the-electron-density-localization-in-elemental-cubic-ceramic-and-fcc-transition-metals-by-means-of-a-localized-electrons-detector
#10
Yosslen Aray, Ricardo Paredes, Luis Javier Álvarez, Alejandro Martiz
The electron density localization in insulator and semiconductor elemental cubic materials with diamond structure, carbon, silicon, germanium, and tin, and good metallic conductors with face centered cubic structure such as α-Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au, was studied using a localized electrons detector defined in the local moment representation. Our results clearly show an opposite pattern of the electron density localization for the cubic ceramic and transition metal materials. It was found that, for the elemental ceramic materials, the zone of low electron localization is very small and is mainly localized on the atomic basin edges...
June 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29166050/plane-wave-pseudopotential-implementation-and-performance-of-scan-meta-gga-exchange-correlation-functional-for-extended-systems
#11
Yi Yao, Yosuke Kanai
We present the implementation and performance of the strongly constrained and appropriately normed, SCAN, meta-GGA exchange-correlation (XC) approximation in the planewave-pseudopotential (PW-PP) formalism using the Troullier-Martins pseudopotential scheme. We studied its performance by applying the PW-PP implementation to several practical applications of interest in condensed matter sciences: (a) crystalline silicon and germanium, (b) martensitic phase transition energetics of phosphorene, and (c) a single water molecule physisorption on a graphene sheet...
June 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29150881/genotoxicity-of-11-heavy-metals-detected-as-food-contaminants-in-two-human-cell-lines
#12
B Kopp, D Zalko, M Audebert
Heavy metals, such as arsenic (As), antimony (Sb), barium (Ba), cadmium (Cd), cobalt (Co), germanium (Ge), lead (Pb), nickel (Ni), tellurium (Te), and vanadium (V) are widely distributed in the environment and in the food chain. Human exposure to heavy metals through water and food has been reported by different international agencies. Although some of these heavy metals are essential elements for human growth and development, they may also be toxic at low concentrations due to indirect mechanisms. In this study, the genotoxic and cytotoxic properties of 15 different oxidation statuses of 11 different heavy metals were investigated using high-throughput screening (γH2AX assay) in two human cell lines (HepG2 and LS-174T) representative of target organs (liver and colon) for food contaminants...
November 18, 2017: Environmental and Molecular Mutagenesis
https://www.readbyqxmd.com/read/29149659/validation-of-differential-cross-sections-by-means-of-252-cf-spectral-averaged-cross-sections
#13
Martin Schulc, Michal Košťál, Stanislav Simakov, Vojtěch Rypar, Davit Harutyunyan, Jan Šimon, Nicola Burianová, Evžen Novák, Bohumil Jánský, Martin Mareček, Jan Uhlíř
The results of systematic evaluations of the spectrum-averaged cross section measurements performed in the spontaneous fission (252)Cf neutron field are presented. The Following threshold reactions were investigated: (23)Na(n,2n)(22)Na, (54)Fe(n,p)(54)Mn, (54)Fe(n,α) (51)Cr, (27)Al(n,p)(27)Mg, (27)Al(n,α)(24)Na, (19)F(n,2n)(18)F, (90)Zr(n,2n)(89)Zr and (89)Y(n,2n)(88)Y. The spectrum-averaged cross sections for (23)Na(n,2n)(22)Na, (54)Fe(n,α)(51)Cr and (89)Y(n,2n)(88)Y reactions were measured for the first time...
November 8, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/29144722/transport-across-heterointerfaces-of-amorphous-niobium-oxide-and-crystallographically-oriented-epitaxial-germanium
#14
Mantu K Hudait, Michael Brian Clavel, Jheng-Sin Liu, Aheli Ghosh, Nikhil Jain, Robert J Bodnar
Due to the high carrier mobility of germanium (Ge) and high dielectric permittivity of amorphous niobium pentoxide (a-Nb2O5), Ge/a-Nb2O5 heterostructures offer several advantages for the rapidly developing field of oxide-semiconductor-based multifunctional devices. To this end, we investigation the growth, structural, band alignment, and metal-insulator-semiconductor (MIS) electrical properties of physical vapor deposited Nb2O5 on crystallographically oriented (100)Ge, (110), and (111)Ge epilayers. The as-deposited Nb2O5 dielectrics were found to be in the amorphous state, demonstrating an abrupt oxide/semiconductor heterointerface with respect to Ge, when examined via low- and high-magnification cross-sectional transmission electron microscopy...
November 16, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29134215/li3ge3se6-the-first-ternary-lithium-germanium-selenide-with-interesting-%C3%A2-ge6se12-n-chains-constructed-by-ethane-like-ge2se6-6-clusters
#15
Guangmao Li, Ni Zhen, Yu Chu, Zhongxiang Zhou
Li3Ge3Se6, the first compound of the ternary Li/Ge/Se system, has been synthesized. Note that interesting 1D ∞[Ge6Se12]n chains constructed by ethane-like [Ge2Se6](6-) clusters were discovered in its structure. Investigations on the structures of all the [Ge2Se6](6-) cluster-containing compounds have shown that only in Li3Ge3Se6 are there 1D chains composed of [Ge2Se6](6-) clusters, which result from the space limitation within the tunnels surrounded by LiSe6 octahedra. Raman spectrum was obtained to demonstrate the existence of Ge-Ge bonds...
November 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29132981/improvement-of-in-situ-gamma-spectrometry-methods-by-monte-carlo-simulations
#16
Dusan Mrdja, Kristina Bikit, Sofija Forkapic, Istvan Bikit, Jaroslav Slivka, Jan Hansman
Performing in-situ measurements of gamma radiation originating from soil requires adequate detection efficiency curves, which can be obtained by Monte-Carlo simulations. In simulations, soil density of 1.046 g/cm(3) was used, with the following elemental composition of soil in which gamma radiation was generated: O - 47%, Si -35%, Al - 8%, Fe - 3.9%, C - 2.1%, Ca - 1.4%, K - 1.3%, N - 0.6%, Mg - 0.6%, N - 0.1%. Soil matrix was represented by cylindrical volume of 1.5 m diameter and 0.5m thickness, while germanium detector was placed at 1 m height above the soil...
November 10, 2017: Journal of Environmental Radioactivity
https://www.readbyqxmd.com/read/29128851/study-on-the-pgnaa-measurement-of-heavy-metals-in-aqueous-solution-by-the-monte-carlo-library-least-squares-mclls-approach
#17
Yan Zhang, WenBao Jia, Robin Gardner, Qing Shan, Daqian Hei
In the present work, a prompt gamma neutron activation analysis (PGNAA) setup, which consists of a 300mCi (241)Americium-Beryllium (Am-Be) neutron source and a 4 × 4-in. Bismuth germanium oxide (BGO) detector, was developed for heavy metal detection in aqueous solutions. A series of standard samples with analytical purity were prepared by dissolving heavy metals in deionized water. Quantitative spectrum analysis was performed by the Monte Carlo-Least-Squares (MCLLS) approach to measure the standard samples...
November 7, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/29123148/radiological-investigation-of-high-background-radiation-areas
#18
Fawzia Mubarak, M Fayez-Hassan, N A Mansour, Talaat Salah Ahmed, Abdallah Ali
In this paper, we used the Hyper-Pure Germanium (HPGe) detector to measure 30 samples which are collected from north of Nile Delta near Rosetta beach in Egypt. The activity of primordial radionuclides, such as (238)U, (235)U, (232)Th, and (40)K was estimated. Concentrations ranged between 36.5-177.4, 50-397.5 and 56.1-168.9 Bq.kg(-1) for (238)U, (232)Th and (40)K respectively. Activity concentration of (235)U and the variation in uranium isotopic ratio (235)U/(238)U was calculated. External hazard indices (Hex) (or radium equivalent activity Raeq), activity concentration indices (I), alpha index (Iα), absorbed outdoor gamma dose rate (Dout), effective outdoor gamma dose rate (Eout) and Excess Lifetime Cancer Risk (ELCR) due to different samples are estimated...
November 9, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29123061/properties-and-potential-optoelectronic-applications-of-lead-halide-perovskite-nanocrystals
#19
REVIEW
Maksym V Kovalenko, Loredana Protesescu, Maryna I Bodnarchuk
Semiconducting lead halide perovskites (LHPs) have not only become prominent thin-film absorber materials in photovoltaics but have also proven to be disruptive in the field of colloidal semiconductor nanocrystals (NCs). The most important feature of LHP NCs is their so-called defect-tolerance-the apparently benign nature of structural defects, highly abundant in these compounds, with respect to optical and electronic properties. Here, we review the important differences that exist in the chemistry and physics of LHP NCs as compared with more conventional, tetrahedrally bonded, elemental, and binary semiconductor NCs (such as silicon, germanium, cadmium selenide, gallium arsenide, and indium phosphide)...
November 10, 2017: Science
https://www.readbyqxmd.com/read/29116815/tailoring-strain-and-morphology-of-core-shell-sige-nanowires-by-low-temperature-ge-condensation
#20
Thomas David, Kailang Liu, Antoine Ronda, Luc Favre, Marco Abbarchi, Marc Gailhanou, Pascal Gentile, Denis Buttard, Vincent Calvo, Michele Amato, Jean-Noël Aqua, Isabelle Berbezier
Selective oxidation of the silicon element of silicon germanium (SiGe) alloys during thermal oxidation is a very important and technologically relevant mechanism used to fabricate a variety of microelectronic devices. We develop here a simple integrative approach involving vapor-liquid-solid (VLS) growth followed by selective oxidation steps to the construction of core-shell nanowires and higher-level ordered systems with scalable configurations. We examine the selective oxidation/condensation process under nonequilibrium conditions that gives rise to spontaneous formation of core-shell structures by germanium condensation...
November 14, 2017: Nano Letters
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