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Manuel López-Vicente, Yuichi Onda, Junko Takahashi, Hiroaki Kato, Shinya Chayama, Keigo Hisadome
Owing to the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident a vast amount of radiocesium was released polluting the land. Afterwards, a variety of decontamination practices has been done, reducing the ambient dose rates. In this study we evaluated the effectiveness of eight forest decontamination practices by means of monitoring the radiocesium (137 Cs) concentration in soil and leaf samples, and the daily discharge rates in ten plots during 27 months (May 2013-July 2015). A forest plantation located 16 km southwest to the FDNPP and within the exclusion area was selected...
April 18, 2018: Environmental Pollution
Jae Hwa Seo, Young Jun Yoon, In Man Kang
The Ge/GaAs-based heterojunction gate-all-around (GAA) arch-shaped tunneling field-effect transistor (A-TFET) have been designed and optimized using technology computer-aided design (TCAD) simulations. In our previous work, the silicon-based A-TFET was designed and demonstrated. However, to progress the electrical characteristics of A-TFET, the III-V compound heterojunction structures which has enhanced electrical properties must be adopted. Thus, the germanium with gallium arsenide (Ge/GaAs) is considered as key materials of A-TFET...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Andrew Bernard, Keye Zhang, Daniel Larson, Katayoon Tabatabaei, Susan M Kauzlarich
Solvent effects on the microwave-assisted synthesis of germanium nanoparticles are presented. A mixture of oleylamine and 1-dodecene was used as the reaction solvent. Oleylamine serves as a reducing agent in the synthesis while both molecules act as binding ligands. Increased concentrations of 1-dodecene in the solvent mixture were found to increase the size of the formed nanoparticles. Crystallinity was also dependent on the solvent mixture. Amorphous nanoparticles were obtained at lower 1-dodecene concentrations, whereas, at higher concentrations, particles contained crystalline and amorphous domains...
April 19, 2018: Inorganic Chemistry
Hamed Simchi, Kayla A Cooley, Zelong Ding, Alex Molina, Suzanne E Mohney
Germanium telluride (GeTe) is a phase change material (PCM) that has gained recent attention due to its incorporation as an active material for radio frequency (RF) switches, as well as memory and novel optoelectronic devices. Considering PCM-based RF switches, parasitic resistances from Ohmic contacts can be a limiting factor in device performance. Reduction of the contact resistance (Rc) is therefore critical for reducing the ON-state resistance in order to meet the requirements of high-frequency RF applications...
April 18, 2018: ACS Applied Materials & Interfaces
Jenny Tempeler, Serhiy Danylyuk, Sascha Brose, Peter Loosen, Larissa Juschkin
In this study we analyze the impact of process and growth parameters on the structural properties of germanium (Ge) quantum dot arrays. The arrays were deposited by molecular beam epitaxy on pre-patterned silicon (Si) substrates. Periodic arrays of pits with diameters between 120 nm to 20 nm and pitches ranging from 200 nm down to 40 nm were etched into the substrate prior to growth. The structural perfection of the 2-dimensional quantum dot (QD) arrays was evaluated based on SEM images. The impact of two processing steps on the directed self-assembly of Ge QD arrays is investigated...
April 18, 2018: Nanotechnology
Guembou Shouop Cebastien Joel, Ndontchueng Moyo Maurice, Nguelem Mekongtso Eric Jilbert, Motapon Ousmanou, Strivay David
The combination of gamma-ray spectrometry, the development of related Monte Carlo method and the GEANT4 (GEometry ANd Tracking) toolkit have been developed for gamma spectrometry simulation. The main objective was to validate simulation models of broad energy germanium (BEGe) detector geometry built in our laboratory (BE6530 model). Monte Carlo simulation of the geometry of BE6530 detector for efficiency calibration was carried out with GEANT4 toolkit. The simulated efficiencies curves using MC were compared with experimental results...
April 10, 2018: Journal of Environmental Radioactivity
Weihua Wu, Zihan Zhao, Bo Shen, Jiwei Zhai, Sannian Song, Zhitang Song
Amorphous Ge8Sb92 thin films with various thicknesses were deposited by magnetron sputtering. The crystallization kinetics and optical properties of the Ge8Sb92 thin films and related scaling effects were investigated by an in situ thermally induced method and an optical technique. With a decrease in film thickness, the crystallization temperature, crystallization activation energy and data retention ability increased significantly. The changed crystallization behavior may be ascribed to the smaller grain size and larger surface-to-volume ratio as the film thickness decreased...
April 9, 2018: Nanoscale
Bochao Lu, Michel M Maharbiz
We demonstrate the use of germanium (Ge) films as water-soluble features that allow the patterning of proteins onto surfaces with commonly used organic solvents. This technique is scalable for manufacturing and is compatible with nano- and microfabrication processes, including standard lithography. We use Ge as a sacrificial layer to mask and protect areas of the substrate during surface functionalization. Since Ge dissolves in 0.35% hydrogen peroxide (H2O2) in water but not in organic solvents, Ge can be removed after patterning without significantly affecting protein activities...
2018: PloS One
Riccardo Suter, Ala'aeddeen Swidan, Charles L B Macdonald, Neil Burford
The synthesis and characterization of the tris(1-ethyl-benzoimidazol-2-ylmethyl)amine (BIMEt3 = L) complex of Ge(ii)2+ is described. Oxidation of [LGe]2+ with Selectfluor gives [LGeF2]2+, in a process that is envisaged to involve a tricationic complex [LGeF]3+ as an intermediate, which has been isolated by fluoride ion abstraction from [LGeF2]2+.
April 6, 2018: Chemical Communications: Chem Comm
Hongyu Ji, Bo Zhang, Wei Wang, Longfeng Lv, Jingling Shen
Active ultraviolet light-induced terahertz modulation of an indium oxide film is investigated. A large absorption modulation of ~66% is achieved upon illumination with a low intensity UV laser (11 mW/cm2 ). The interaction between indium oxide and a flexible metamaterial structure is investigated owing to the large UV-induced enhancement of photo carriers observed in an indium oxide film. We are able to realize absorption peak shifts of 37 GHz by changing the UV excitation light intensity. We also propose a multi-frequency switch by building a circular metallic split ring resonator whose gaps are filled with silicon, germanium, and indium oxide...
March 19, 2018: Optics Express
Yang-Yang Wu, Lin Xiong, Fei Jia, Ling Chen
The new selenide Cs2 Ge3 In6 Se14 , featuring its own structure type with germanium in mixed-valence states, is discovered via a solid-state reaction at 1173 K. The compound crystallizes in the R3̅ m space group with a = 7.9951(6) Å and c = 41.726(4) Å. Two adjacent condensed layers of InSe4 tetrahedra are linked by a [Ge2+ Se6 ] octahedron into a double slice that is further stacked along the c direction with a packing sequence of ··· abca··· through the [Ge3+ 2 Se6 ] dimer via its Ge-Ge metallic bond...
March 30, 2018: Inorganic Chemistry
B Pérez López, J F Navarro, M A López
Iodine-131 is one of the main concerns from the point of view of radiological protection in a short term after a nuclear accident. The WBC Laboratory of CIEMAT has developed a methodology for in vivo monitoring of radioiodine in the thyroid of exposed individuals in case of emergency. Thyroid-neck phantoms of different sizes are required for calibrating the detection systems in appropriate counting geometries for the measurement of exposed population. A Low-Energy Germanium (LEGe) detector and a Fastscan Counter were calibrated using a set of thyroid phantoms fabricated by CIEMAT...
March 23, 2018: Radiation Protection Dosimetry
John Russo, Kenji Akahane, Hajime Tanaka
Tetrahedral interactions describe the behavior of the most abundant and technologically important materials on Earth, such as water, silicon, carbon, germanium, and countless others. Despite their differences, these materials share unique common physical behaviors, such as liquid anomalies, open crystalline structures, and extremely poor glass-forming ability at ambient pressure. To reveal the physical origin of these anomalies and their link to the shape of the phase diagram, we systematically study the properties of the Stillinger-Weber potential as a function of the strength of the tetrahedral interaction [Formula: see text] We uncover a unique transition to a reentrant spinodal line at low values of [Formula: see text], accompanied with a change in the dynamical behavior, from non-Arrhenius to Arrhenius...
March 26, 2018: Proceedings of the National Academy of Sciences of the United States of America
Tiffany Mélanie Beaumont, Maeva Rimlinger, David Broggio, Pedro Caldeira Ideias, Didier Franck
In case of nuclear accident, the internal exposure monitoring of the population will preferably focus on the detection of <sup>131</sup>I in the thyroid by <i>in vivo</i> monitoring. In most cases the calibration of <i>in vivo</i> monitoring is performed with an adult thyroid phantom which raises doubts regarding the relevance of children exposure assessment.
 In this study, the influence on calibration of thyroid volume, counting distance and positioning variations are studied experimentally in a systematic way...
March 26, 2018: Journal of Radiological Protection: Official Journal of the Society for Radiological Protection
Amar S Katkar, Shobhnath P Gupta, Md Motin Seikh, Lih-Juann Chen, Pravin S Walke
The Cr doped tunable thickness core-shell Ge/GeOx nanowires were synthesized and characterized using X-ray diffraction, FESEM, TEM, EDS, XPS and magnetization studies. The shell thickness increases with the increase in synthesis temperature. The presence of metallic Cr and Cr3+ in core-shell structure was confirmed from XPS study. The magnetic property is highly sensitive to the core-shell thickness and intriguing room temperature ferromagnetism is realized only in core-shell nanowires. The magnetization decreases with increase in shell thickness and practically ceases to exist when there is no core...
March 19, 2018: Nanotechnology
Trevor A Hamlin, Marcel Swart, F Matthias Bickelhaupt
The reaction potential energy surface (PES) and, thus, the mechanism of bimolecular nucleophilic substitution (SN2) depend profoundly on the nature of the nucleophile and leaving group, but also on the central, electrophilic atom, its substituents, as well as on the medium in which the reaction takes place. Here, we provide an overview of recent studies and demonstrate how changes in any one of the aforementioned factors affect the SN2 mechanism. One of the most striking effects is the transition from a double-well to a single-well PES when the central atom is changed from a second-period (e...
March 15, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Nozomi Ito, Muhammad Akmal Kamarudin, Yaohong Zhang, Daisuke Hirotani, Qing Shen, Yuhei Ogomi, Satoshi Iikubo, Takashi Minemoto, Kenji Yoshino, Shuzi Hayase
Lead-based solar cells have gained ground in recent years, showing efficiency as high as 20 % which is on par with silicon solar cells. However, the toxicity of lead makes it non ideal candidate in solar cells. Alternatively, tin-based perovskites have been proposed due to their non-toxic nature and abundance in nature. Unfortunately, these solar cells suffer from low efficiency and stability. Here, we propose a new type of perovskite material based on mixed tin and germanium. The material showed a band gap around 1...
March 14, 2018: Journal of Physical Chemistry Letters
Jinkyoung Yoo, Towfiq Ahmed, Renjie Chen, Aiping Chen, Yeon Hoo Kim, Ki Chang Kwon, Chan Woong Park, Hee Seong Kang, Ho Won Jang, Young Joon Hong, Woo Seok Yang, Chul-Ho Lee
The preparation of crystalline materials on incommensurate substrates has been a key topic of epitaxy. van der Waals (vdW) epitaxy on two-dimensional (2D) materials opened novel opportunities of epitaxial growth overcoming the materials compatibility issue. Therefore, vdW epitaxy has been considered as a promising approach for the preparation of building blocks of flexible devices and thin film-based devices at the nano/microscale. However, an understanding of vdW epitaxy has not been thoroughly established...
March 13, 2018: Nanoscale
Zhijie Ma, Yi Li, Yang Li, Yandong Gong, Stefan A Maier, Minghui Hong
Planar optical chirality of a metasurface measures its differential response between left and right circularly polarized (CP) lights and governs the asymmetric transmission of CP lights. In 2D ultra-thin plasmonic structures the circular dichroism is limited to 25% in theory and it requires high absorption loss. Here we propose and numerically demonstrate a planar chiral all-dielectric metasurface that exhibits giant circular dichroism and transmission asymmetry over 0.8 for circularly polarized lights with negligible loss, without bringing in bianisotropy or violating reciprocity...
March 5, 2018: Optics Express
Yinghui Yang, Shuai Liu, Xiu-Fang Bian, Jinkui Feng, Yongling An, Chao Yuan
The lithium-storage performance of silicon (Si) can be enhanced by alloyed with germanium (Ge) because of its good electronic and ionic conductivity. Here we synthesized three-dimensional nanoporous (3D-NP) SiGe alloy as high performance lithium-ion battery (LIB) anode using a dealloying method with ternary AlSiGe ribbon served as precursor. The morphology and porosity of as-synthesized SiGe alloy can be controlled effectively by adjusting the sacrificial Al content of the precursor. With a Al content of 80%, the 3D-NP SiGe presents uniformly coral-like structure with continuous ligaments and hierarchical micropores and mesopores, which leads to a high reversible capacity of 1158 mA h g-1 after 150 cycles at a current density of 1000 mA g-1 with excellent rate capacity...
March 12, 2018: ACS Nano
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