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Alexander Gumennik, Etgar C Levy, Benjamin Grena, Chong Hou, Michael Rein, Ayman F Abouraddy, John D Joannopoulos, Yoel Fink
Crystallization of microdroplets of molten alloys could, in principle, present a number of possible morphological outcomes, depending on the symmetry of the propagating solidification front and its velocity, such as axial or spherically symmetric species segregation. However, because of thermal or constitutional supercooling, resulting droplets often only display dendritic morphologies. Here we report on the crystallization of alloyed droplets of controlled micrometer dimensions comprising silicon and germanium, leading to a number of surprising outcomes...
June 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
Adrian Podpirka, Woo-Kyung Lee, Jed I Ziegler, Todd H Brintlinger, Jonathan R Felts, Blake S Simpkins, Nabil D Bassim, Arnaldo R Laracuente, Paul E Sheehan, Laura B Ruppalt
The crystallization of amorphous germanium telluride (GeTe) thin films is controlled with nanoscale resolution using the heat from a thermal AFM probe. The dramatic differences between the amorphous and crystalline GeTe phases yield embedded nanoscale features with strong topographic, electronic, and optical contrast. The flexibility of scanning probe lithography enables the width and depth of the features, as well as the extent of their crystallization, to be controlled by varying probe temperature and write speed...
June 19, 2017: Nanoscale
Do Hwan Kim, Suklyun Hong
We have performed density functional theory (DFT) calculations of the atomic and electronic structures of ethylenediamine on Ge(100). The two amine groups in ethylenediamine can interact with germanium surface atoms through a N-H dissociative nucleophilic reaction and/or N-dative bonding with an electron-deficient down Ge atom. Of the monodentate and row-bridged bidentate structures that formed, the dative-bonded configurations were found to be more stable than the NH dissociative adsorption structures. The formation of row-bridged bidentate, structures is more favorable than that of on-top or end-bridged structures...
June 19, 2017: Physical Chemistry Chemical Physics: PCCP
Lingen Zhang, Zhenming Xu
Ge-monopnictides (GeAs) plays critical role in high-tech industry, especially in the field of advanced optical devices and infrared. As a secondary material, coal fly ash could be further recycled to retrieve germanium and prepare GeAs material with high added values. Hence, the aim of this paper is to propose a one-pot synthesis that uses vacuum flash reduction and inert-gas consolidation method to prepare GeAs ultrafine particles. Germanium in coal fly ash can be successfully recycled; simultaneously, GeAs ultrafine particles were prepared...
June 16, 2017: Scientific Reports
M K Bhaskar, D D Sukachev, A Sipahigil, R E Evans, M J Burek, C T Nguyen, L J Rogers, P Siyushev, M H Metsch, H Park, F Jelezko, M Lončar, M D Lukin
We demonstrate a quantum nanophotonics platform based on germanium-vacancy (GeV) color centers in fiber-coupled diamond nanophotonic waveguides. We show that GeV optical transitions have a high quantum efficiency and are nearly lifetime broadened in such nanophotonic structures. These properties yield an efficient interface between waveguide photons and a single GeV center without the use of a cavity or slow-light waveguide. As a result, a single GeV center reduces waveguide transmission by 18±1% on resonance in a single pass...
June 2, 2017: Physical Review Letters
Petya Racheva, Kirila Stojnova, Vidka Divarova, Vanya Lekova
The complex formation of the ion-pair formed between the anionic chelate of Ge(IV)-4-nitrocatechol (4-NC) and the cation of 1,4-diphenyl-3-(phenylamino)-1H-1,2,4-triazole (Nitron, Nt) in the liquid-liquid extraction system Ge(IV)-4-NC-Nt-H2O-CHCl3 was studied by spectrophotometry. The optimum extraction-spectrophotometric conditions for the complex formation were established. The validity of Beer's law was checked and some analytical characteristics of the system were calculated. The effect of co-existing ions and reagents on the process of complex formation was investigated...
June 2017: Acta Chimica Slovenica
Jian Hao, Yu Yang, Jiupeng Zhao, Xusong Liu, Frank Endres, Caixia Chi, Binsheng Wang, Xiaoxu Liu, Yao Li
With the growing demand for portable and wearable electronic devices, it is imperative to develop high performance Li-ion batteries with long life times. Germanium-based materials have recently demonstrated excellent lithium-ion storage ability and are being considered as the most promising candidates for the anodes of lithium-ion batteries. Nevertheless, the practical implementation of Ge-based materials to Li-ion batteries is greatly hampered by the poor cycling ability that resulted from the huge volume variation during lithiation/delithiation processes...
June 12, 2017: Nanoscale
Hung Tan Pham, Minh Tho Nguyen
(Abstract) Recently, metallic hetero-fullerenes were experimentally prepared from mixed Ge-As clusters and heavier elements of groups 14 and 15. We found that shape of these hetero-fullerenes doped by transition metal appears to be a general structural motif for both silicon and germanium clusters when mixing with phosphorus and arsenic atoms. Structural identifications for MSi8P6, MSi8As6, MGe8P6 and MGe8As6 clusters, with M being a transition metal of group 6 (Cr, Mo and W), showed that most MA8E6 clusters, except for Cr-doped derivatives CrSi8As6, CrGe8P6 and CrGe8As6, exhibit a high symmetry fullerene shape in which metal dopant is centered in D3h A8E6 hetero-cage consisting of six A3E2 pentagonal faces and three A2E2 rhombus faces...
June 8, 2017: Journal of Physical Chemistry. A
J L Ma, Q Yue, Q Wang, J Li, H T Wong, S T Lin, S K Liu, L Wang, H Jiang, L T Yang, L P Jia, J H Chen, W Zhao
The characteristics of the surface inactive layer of a 1-kg-mass p-type point-contact germanium detector were studied. The thickness of the inactive layer and its uniformity on the top and lateral surfaces were measured. A charge collection efficiency function was developed according to the Monte Carlo simulation to describe the charge collection capacity along the depth within this inactive layer. In the energy range below 18keV, the surface, bulk, and total spectra of (57)Co, (133)Ba, (137)Cs, and (60)Co from simulations based on the charge collection efficiency function were well consistent with those from experiments...
May 30, 2017: Applied Radiation and Isotopes
Yuichi Kato, Masashi Kikugawa, Eiichi Sudo
The application of attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR SEIRA) to the analysis of fatty acids on silver nanoparticles was investigated. Attenuated total reflection measurements using four types of internal reflection elements (IREs)-zinc selenide, diamond, silicon, and germanium-were performed for silver nanoparticles modified with fatty acids, and germanium IRE was shown to be suitable for the analysis of silver nanoparticles, even when the sample had a high refractive index...
January 1, 2017: Applied Spectroscopy
Christopher H Hendon, Keith T Butler, Alex M Ganose, Yuriy Román-Leshkov, David O Scanlon, Geoffrey A Ozin, Aron Walsh
The archetypal silica- and aluminosilicate-based zeolite-type materials are renowned for wide-ranging applications in heterogeneous catalysis, gas-separation and ion-exchange. Their compositional space can be expanded to include nanoporous metal chalcogenides, exemplified by germanium and tin sulfides and selenides. By comparison with the properties of bulk metal dichalcogenides and their 2D derivatives, these open-framework analogues may be viewed as three-dimensional semiconductors filled with nanometer voids...
April 25, 2017: Chemistry of Materials: a Publication of the American Chemical Society
Xue-Lu Liu, He-Nan Liu, Jiang-Bin Wu, Han-Xu Wu, Tao Zhang, Wei-Qian Zhao, Ping-Heng Tan
Simultaneous Stokes and anti-Stokes ultralow-frequency (ULF) Raman measurement down to ∼2 cm(-1) or 60 GHz is realized by a single-stage spectrometer in combination with volume-Bragg-grating-based notch filters. This system reveals its excellent performance by probing Brillouin signal of acoustic phonons in silicon, germanium, gallium arsenide, and gallium nitride. The deduced sound velocity and elastic constants are in good accordance with previous results determined by various methods. This system can shorten the integration time of the Brillouin signal with a good signal-to-noise ratio by more than 2000-fold compared to a Fabry-Perot interferometer (FPI)...
May 2017: Review of Scientific Instruments
Jian Kang, Zhenzhou Cheng, Wen Zhou, Ting-Hui Xiao, Kimmy-Laure Gopalakrisna, Mitsuru Takenaka, Hon Ki Tsang, Keisuke Goda
We present a focusing subwavelength grating (SWG) for efficient coupling of mid-infrared (mid-IR) light into suspended membrane Ge photonic integrated circuits (PICs) that enable mid-IR applications in the entire fingerprint region. By virtue of their wide spectral transparency window and air-cladding device configuration, the suspended membrane Ge PICs are expected to be effective for mid-IR applications over the spectral region covering from 2 to 15 μm. Specifically, we demonstrate the maximum coupling efficiency of -11  dB with a 1-dB bandwidth of ∼58  nm at the SWG's center wavelength of 2...
June 1, 2017: Optics Letters
Michael Zürch, Hung-Tzu Chang, Lauren J Borja, Peter M Kraus, Scott K Cushing, Andrey Gandman, Christopher J Kaplan, Myoung Hwan Oh, James S Prell, David Prendergast, Chaitanya D Pemmaraju, Daniel M Neumark, Stephen R Leone
Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M4,5 edge...
June 1, 2017: Nature Communications
Ziwen Wang, Zhongying Xue, Miao Zhang, Yongqiang Wang, Xiaoming Xie, Paul K Chu, Peng Zhou, Zengfeng Di, Xi Wang
Direct growth of graphene on dielectric substrates is a prerequisite to the development of graphene-based electronic and optoelectronic devices. However, the current graphene synthesis methods on dielectric substrates always involve a metal contamination problem, and the direct production of graphene patterns still remains unattainable and challenging. Herein, a semiconducting, germanium (Ge)-assisted, chemical vapor deposition approach is proposed to produce monolayer graphene directly on arbitrary dielectric substrates...
May 31, 2017: Small
Haipeng Guo, Boyang Ruan, Lili Liu, Lei Zhang, Zhanliang Tao, Shulei Chou, Jiazhao Wang, Huakun Liu
Germanium (Ge) is a prospective anode material for lithium-ion batteries, as it possesses large theoretical capacity, outstanding lithium-ion diffusivity, and excellent electrical conductivity. Ge suffers from drastic capacity decay and poor rate performance, however, owing to its low electrical conductivity and huge volume expansion during cycling processes. Herein, a novel strategy has been developed to synthesize a Ge@N-doped carbon nanotubes (Ge@N-CNTs) composite with Ge nanoparticles uniformly distributed in the N-CNTs by using capillary action...
May 30, 2017: Small
B F P McVey, P B O'Mara, A J McGrath, A Faramus, V B Yasarapudi, V R Gonçales, V T G Tan, T W Schmidt, J J Gooding, R D Tilley
The role surface capping molecules play in dictating the optical properties of semiconductor nanocrystals (NCs) is becoming increasingly evident. In this paper the role of surface capping molecule polarity on the optical properties of germanium NCs (Ge NCs) is explored. Capping molecules are split into two groups: nonpolar and polar. The NCs are fully characterized structurally and optically to establish the link between observed optical properties and surface capping molecules. Ge NC optical properties altered by surface capping molecule polarity include emission maximum, emission lifetime, quantum yield, and Stokes shift...
June 7, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Peyman Taheri, Hossain M Fahad, Mahmut Tosun, Mark Hettick, Daisuke Kiriya, Kevin Chen, Ali Javey
A major challenge in transistor technology scaling is the formation of controlled ultrashallow junctions with nanometer-scale thickness and high spatial uniformity. Monolayer doping (MLD) is an efficient method to form such nanoscale junctions, where the self-limiting nature of semiconductor surfaces is utilized to form adsorbed monolayers of dopant-containing molecules followed by rapid thermal annealing (RTA) to diffuse the dopants to a desired depth. Unlike ion implantation, the process does not induce crystal damage, thus making it highly attractive for nanoscale transistor processing...
June 21, 2017: ACS Applied Materials & Interfaces
Christopher F Ahles, Jong Youn Choi, Steven Wolf, Andrew C Kummel
The selective etching characteristics of silicon, germanium, and Si0.5Ge0.5 subjected to a downstream H2/CF4/Ar plasma have been studied using a pair of in situ quartz crystal microbalances (QCMs) and X-ray photoelectron spectroscopy (XPS). At 50 °C and 760 mTorr, Si can be etched in preference to Ge and Si0.5Ge0.5, with an essentially infinite Si/Ge etch-rate ratio (ERR), whereas for Si/Si0.5Ge0.5, the ERR is infinite at 22 °C and 760 mTorr. XPS data showed that the selectivity is due to the differential suppression of etching by a ∼2 ML thick CxHyFz layer formed by the H2/CF4/Ar plasma on Si, Ge, and Si0...
June 21, 2017: ACS Applied Materials & Interfaces
Ming-Gang Ju, Jun Dai, Liang Ma, Xiao Cheng Zeng
The power-conversion efficiency (PCE) of lead halide perovskite photovoltaics has reached 22.1% with significantly improved structural stability, thanks to a mixed cation and anion strategy. However, the mixing element strategy has not been widely seen in the design of lead-free perovskites for photovoltaic application. Herein, we report a comprehensive study of a series of lead-free and mixed tin and germanium halide perovskite materials. Most importantly, we predict that RbSn0.5Ge0.5I3 possesses not only a direct bandgap within the optimal range of 0...
June 6, 2017: Journal of the American Chemical Society
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