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M E Sánchez Vergara, R Salcedo, Bertha Molina, R Carrera-Téllez, J R Álvarez-Bada, A Hernández-García, V Gómez-Vidales
The present study reports the doping of a semiconducting molecular material through the formation of hydrogen bonds between the macrocycle Cu(II)(TAAB) and the electronic acceptor TCNQ. According to density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) analysis, the doped compound has the shape of a distorted square pyramid, with four nitrogen atoms in the equatorial position and the apical oxygen atom from the water ligands. These water molecules can generate strong hydrogen bonds with TCNQ and the TAAB metallic complex...
April 11, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Liu Changshi, Zhang Jianxin
The voltage-dependent current is a crucial parameter for determining the electrical properties of microelectronic devices. In this study, we aimed to extend a generic dc model to successfully explain the drain current (Id ) for metal-oxide semiconductors (MOSs) and thin-film transistors (TFTs) based on the gate voltage (Vg ), where the threshold voltage (Vth ) could also be obtained from this model in a nature manner. This dc model meets the requirements for compact modeling, including modeling computer circuit simulators...
April 4, 2018: Applied Radiation and Isotopes
Xuetao Wang, Guangjun Li, Jianling Zhao, Ying Song, Jianghong Xiao, Sen Bai
The eye lens is recognized as one of the most radiosensitive structures in the human body. The widespread use of intensity-modulated radiotherapy (IMRT) complicates dose verification and necessitates high standards of dose computation. The purpose of this work was to assess the computed dose accuracy of eye lens through measurements using a metal-oxide-semiconductor field-effect transistor (MOSFET) dosimetry system. Sixteen clinical IMRT plans of head and neck patients were copied to an anthropomorphic head phantom...
April 17, 2018: Medical Dosimetry: Official Journal of the American Association of Medical Dosimetrists
Akshay A Murthy, Teodor K Stanev, Jeffrey D Cain, Shiqiang Hao, Trevor LaMountain, Sung Kyu Kim, Nathaniel A Speiser, Kenji Watanabe, Takashi Taniguchi, Chris Wolverton, Nathaniel P Stern, Vinayak P Dravid
Understanding the electronic transport of monolayer transition metal dichalcogenides (TMDs) and their heterostructures is complicated by the difficulty in achieving electrical contacts that do not perturb the material. Typically, metal deposition on monolayer TMDs leads to hybridization between the TMD and the metal, which produces Schottky barriers at the metal semiconductor interface. In this work, we apply the recently reported hexagonal boron nitride (h-BN) tunnel contact scheme to probe the junction characteristics of a lateral TMD heterostructure grown via chemical vapor deposition...
April 20, 2018: Nano Letters
Shinae Hwang, Seongjae Lee, Jaehyeon Ko, Moongyu Jang
Microscale-pyramidal-structure-arrayed patterned silicon membranes are manufactured using semiconductor processes and potassium hydroxide (KOH) etching techniques for filter applications. The silicon nitride on silicon on the insulator wafer functions as a masking layer, and the roughness of the silicon (100) plane strongly depends on the etching temperature and KOH concentration. To fabricate the membrane filter, a series of dry and wet etching using 45 wt% KOH solutions at the constant temperature of 70 °C was performed...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Younghwan Hyeon, Pyungho Choi, Sangsub Kim, Minsoo Kim, Jeonghyun Lee, Kiwon Lim, Soonkon Kim, Kwangjun Koo, Byoungdeog Choi
In this study, the charge polarity of aluminum fluoride (AlF3) as a function of varying thickness (tAlF3 = 20, 35, 50, 65, and 80 nm) was discussed. AlF3 films were deposited onto p-Si wafers via electron beam sputtering. Thickness dependent charge polarity and reliability issues under bias-temperature stress conditions were identified using a capacitance-voltage (C-V) characterization method. AlF3 was found to possess negative fixed charges, leading to a C-V curve shift toward the positive gate bias direction as tAlF3 was increased up to 50 nm...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Sangwan Kim, Woo Young Choi
In this manuscript, the compact potential model for double-gate (DG) Si1-xGex/Si heterojunction tunnel field-effect transistors (TFETs) is proposed by adopting several strategies to the previous model. Compared with the control model, the enhanced model can describe the effects of additional parameters such as electron permittivity and Si1-xGex affinity, doping dependent bandgap narrowing, temperature, built-in potential change due to degenerately doping condition and energy band off-sets. The model accuracy is examined by benchmarking against to the technology computeraided design (TCAD) device simulations in terms of electrostatic potential profiles, band diagrams and minimum tunneling barrier width (Wt, min)...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Joyce Lau, Sangsub Kim, Hyunki Kim, Kwangjun Koo, Jaeseob Lee, Sangsoo Kim, Byoungdeog Choi
Solution processed barium titanate (BTO) was used to fabricate an Al/BaTiO3/p-Si metal-insulator-semiconductor (MIS) structure, which was used as a gate insulator. Changes in the electrical characteristics of the film were investigated as a function of the film thickness and post deposition annealing conditions. Our results showed that a thickness of 5 layers and an annealing temperature of 650 °C produced the highest electrical performance. BaxTi1-xO3 was altered at x = 0.10, 0.30, 0.50, 0.70, 0.90, and 1...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Kiwon Lim, Pyungho Choi, Sangsub Kim, Hyunki Kim, Minsoo Kim, Jeonghyun Lee, Younghwan Hyeon, Kwangjun Koo, Byoungdeog Choi
Double stacked indium-zinc oxide (IZO)/zinc-tin oxide (ZTO) active layers were employed in amorphous-oxide-semiconductor thin-film transistors (AOS TFTs). Channel layers of the TFTs were optimized by varying the molarity of ZTO back channel layers (0.05, 0.1, 0.2, 0.3 M) and the electrical properties of IZO/ZTO double stacked TFTs were compared to single IZO and ZTO TFTs with varying the molarity and molar ratio. On the basis of the results, IZO/ZTO (0.1 M) TFTs showed the excellent electrical properties of saturation mobility (13...
September 1, 2018: Journal of Nanoscience and Nanotechnology
Takayuki Umakoshi, Hikari Udaka, Takayuki Uchihashi, Toshio Ando, Miho Suzuki, Takeshi Fukuda
Conjugates of semiconductor quantum dots (QDs) and antibodies have emerged as a promising bioprobes due to their great combination of QD's efficient fluorescence and the high specificity of antigen-antibody reactions. For further developments in this field, it is essential to understand the molecular conformation of the QD-antibody conjugates at the single-molecule scale. Here, we report on the direct imaging of QD-antibody conjugates at the single-molecule scale by using high-speed atomic force microscopy (HS-AFM)...
April 13, 2018: Colloids and Surfaces. B, Biointerfaces
Saravanan Rajamani, Kanika Arora, Anton Konakov, Alexey Belov, Dmitry Korolev, Alyona Nikolskaya, Alexey N Mikhaylov, Sergey Surodin, Ruslan Kryukov, Dmitri Nikolichev, Artem Sushkov, Dmitry Pavlov, David Tetelbaum, Mukesh Kumar, Mahesh Kumar
Semiconductor quantum dots (QDs) have attracted tremendous attention owing to their novel electrical and optical properties due to the size dependent quantum confinement effects. This provides an advantage of tunable wavelength detection, which is essential to realize spectrally selective photodetectors. We report the fabrication and characterization of high performance narrow band ultraviolet photodetector (UV-B) based on In2O3 nanocrystals embedded in Al2O3 matrices. The In2O3 nanocrystals are synthesized in Al2O3 matrix by sequential implantation of In+ and N2+ ions and post-implantation annealing...
April 20, 2018: Nanotechnology
Xiaoming Zhao, Tianjun Liu, Yuzhou Cui, Xueyan Hou, Zilu Liu, Xingyi Dai, Jie Kong, Wenda Shi, T John S Dennis
There are only a few reported methods by which the size and morphology of organic single crystals for high-performance organic field-effect transistors (OFETs) or other devices can be controlled. Here, a facile solution-processed antisolvent vapor diffusion method was employed to grow millimeter-length C60 single crystal microwires directly in solution. The size of the microwires can be controllably varied via the C60 concentration and/or the choice of antisolvent. OFETs fabricated from the as-produced microwires exhibit mobilities as high as 2...
April 20, 2018: Nanoscale
Jian Lv, Ting Zhang, Peng Zhang, Yingchun Zhao, Shibin Li
As a widely used semiconductor material, silicon has been extensively used in many areas, such as photodiode, photodetector, and photovoltaic devices. However, the high surface reflectance and large bandgap of traditional bulk silicon restrict the full use of the spectrum. To solve this problem, many methods have been developed. Among them, the surface nanostructured silicon, namely black silicon, is the most efficient and widely used. Due to its high absorption in the wide range from UV-visible to infrared, black silicon is very attractive for using as sensitive layer of photodiodes, photodetector, solar cells, field emission, luminescence, and other photoelectric devices...
April 19, 2018: Nanoscale Research Letters
Yesim Mogulkoc, Mohsen Modarresi, Aybey Mogulkoc, Bora Alkan
The van der Waals (vdW) heterostructures are emerging as promising structures for future possible optoelectronic devices. Motivated by the recent studies on vdW heterostructures with their fascinating physical properties, we investigate the electronic and optical properties of boron phosphide/blue phosphorus heterostructures in the framework of density functional theory (DFT) and tight-binding (TB) approximations. We analyze the variation of the energy band gap, the characteristics of the energy band diagram, charge redistribution by stacking and the electrostatic potential along the perpendicular direction...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
Shundong Guan, Xiuli Fu, Yu Zhang, Zhijian Peng
Co-catalysis is regarded as a promising strategy to improve the hydrogen evolution performance of semiconductor-based photocatalysts. But developing a simple and effective technique to achieve the optimal synergy between co-catalysts and host photocatalysts has been a great challenge. Herein, hybrid photocatalysts consisting of β-NiS modified CdS nanowires (NiS/CdS NWs) have been synthesized via a simple and green hydrothermal route using CdS NWs as the template from thiourea and nickel acetate in the presence of sodium hypophosphite...
February 14, 2018: Chemical Science
Félix Musil, Sandip De, Jack Yang, Joshua E Campbell, Graeme M Day, Michele Ceriotti
Molecular crystals play an important role in several fields of science and technology. They frequently crystallize in different polymorphs with substantially different physical properties. To help guide the synthesis of candidate materials, atomic-scale modelling can be used to enumerate the stable polymorphs and to predict their properties, as well as to propose heuristic rules to rationalize the correlations between crystal structure and materials properties. Here we show how a recently-developed machine-learning (ML) framework can be used to achieve inexpensive and accurate predictions of the stability and properties of polymorphs, and a data-driven classification that is less biased and more flexible than typical heuristic rules...
February 7, 2018: Chemical Science
Daniel W Davies, Keith T Butler, Jonathan M Skelton, Congwei Xie, Artem R Oganov, Aron Walsh
The standard paradigm in computational materials science is INPUT: Structure; OUTPUT: Properties, which has yielded many successes but is ill-suited for exploring large areas of chemical and configurational hyperspace. We report a high-throughput screening procedure that uses compositional descriptors to search for new photoactive semiconducting compounds. We show how feeding high-ranking element combinations to structure prediction algorithms can constitute a pragmatic computer-aided materials design approach...
January 28, 2018: Chemical Science
Daryoush Shiri, Amit Verma, Reza Nekovei, Andreas Isacsson, C R Selvakumar, M P Anantram
Gunn (or Gunn-Hilsum) Effect and its associated negative differential resistivity (NDR) emanates from transfer of electrons between two different energy subbands. This effect was observed in semiconductors like GaAs which has a direct bandgap of very low effective mass and an indirect subband of high effective mass which lies ~300 meV above the former. In contrast to GaAs, bulk silicon has a very high energy spacing (~1 eV) which renders the initiation of transfer-induced NDR unobservable. Using Density Functional Theory (DFT), semi-empirical 10 orbital (sp3 d5 s* ) Tight Binding and Ensemble Monte Carlo (EMC) methods we show for the first time that (a) Gunn Effect can be induced in silicon nanowires (SiNW) with diameters of 3...
April 19, 2018: Scientific Reports
Ming-Min Yang, Dong Jik Kim, Marin Alexe
It is highly desirable to discover photovoltaic mechanisms that enable a higher efficiency of solar cells. Here, we report that the bulk photovoltaic effect, which is free from the thermodynamic Shockley-Queisser limit but usually manifested only in noncentrosymmetric (piezoelectric or ferroelectric) materials, can be realized in any semiconductor, including silicon, by mediation of flexoelectric effect. We introduce strain gradients using either an atomic force microscope or a micron-scale indentation system, creating giant photovoltaic currents from centrosymmetric single crystals of SrTiO3 , TiO2 , and Si...
April 19, 2018: Science
Miika Mattinen, Peter J King, Leonid Khriachtchev, Kristoffer Meinander, James T Gibbon, Vin R Dhanak, Jyrki Räisänen, Mikko Ritala, Markku Leskelä
Semiconducting 2D materials, such as SnS2 , hold immense potential for many applications ranging from electronics to catalysis. However, deposition of few-layer SnS2 films has remained a great challenge. Herein, continuous wafer-scale 2D SnS2 films with accurately controlled thickness (2 to 10 monolayers) are realized by combining a new atomic layer deposition process with low-temperature (250 °C) postdeposition annealing. Uniform coating of large-area and 3D substrates is demonstrated owing to the unique self-limiting growth mechanism of atomic layer deposition...
April 19, 2018: Small
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