WorldWideScience

Sample records for composite polycrystalline semiconductor

  1. Obtaining of polycrystalline silicon for semiconductor industry

    International Nuclear Information System (INIS)

    Mukashev, F.; Nauryzbaev, M.; Kolesnikov, B.; Ivanov, Y.

    1996-01-01

    The purpose of the project is to create pilot equipment and optimize the process of obtaining polycrystalline silicon on semi-industrial level. In the past several decades, the historical experience in the developing countries has shown that one of the most promising ways to improve the economy,of a country is to establish semiconductor industry. First of all, the results can help increase defense, national security and create industrial production. The silane method, which has been traditionally' used for obtaining technical and polycrystalline silicon, is to obtain and then to pyrolyzed mono-and poly silanes. Although the traditional methods of obtaining silicon hydrides have specific advantages, such as utilizing by-products, they also have clear shortcomings, i.e. either low output of the ultimate product ( through hydrolysis of Mg 2 Si) or high contents of by-products in it or high contents of dissolving vapors (through decomposing Mg 2 Si in non-water solutions)

  2. Physics of grain boundaries in polycrystalline photovoltaic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Yanfa, E-mail: yanfa.yan@utoledo.edu; Yin, Wan-Jian; Wu, Yelong; Shi, Tingting; Paudel, Naba R. [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Ohio 43606 (United States); Li, Chen [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Poplawsky, Jonathan [The Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Wang, Zhiwei [Department of Physics and Astronomy and Wright Center for Photovoltaics Innovation and Commercialization, The University of Toledo, Ohio 43606 (United States); National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Moseley, John; Guthrey, Harvey; Moutinho, Helio; Al-Jassim, Mowafak M. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Pennycook, Stephen J. [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)

    2015-03-21

    Thin-film solar cells based on polycrystalline Cu(In,Ga)Se{sub 2} (CIGS) and CdTe photovoltaic semiconductors have reached remarkable laboratory efficiencies. It is surprising that these thin-film polycrystalline solar cells can reach such high efficiencies despite containing a high density of grain boundaries (GBs), which would seem likely to be nonradiative recombination centers for photo-generated carriers. In this paper, we review our atomistic theoretical understanding of the physics of grain boundaries in CIGS and CdTe absorbers. We show that intrinsic GBs with dislocation cores exhibit deep gap states in both CIGS and CdTe. However, in each solar cell device, the GBs can be chemically modified to improve their photovoltaic properties. In CIGS cells, GBs are found to be Cu-rich and contain O impurities. Density-functional theory calculations reveal that such chemical changes within GBs can remove most of the unwanted gap states. In CdTe cells, GBs are found to contain a high concentration of Cl atoms. Cl atoms donate electrons, creating n-type GBs between p-type CdTe grains, forming local p-n-p junctions along GBs. This leads to enhanced current collections. Therefore, chemical modification of GBs allows for high efficiency polycrystalline CIGS and CdTe thin-film solar cells.

  3. Polycrystalline silicon availability for photovoltaic and semiconductor industries

    Science.gov (United States)

    Ferber, R. R.; Costogue, E. N.; Pellin, R.

    1982-01-01

    Markets, applications, and production techniques for Siemens process-produced polycrystalline silicon are surveyed. It is noted that as of 1982 a total of six Si materials suppliers were servicing a worldwide total of over 1000 manufacturers of Si-based devices. Besides solar cells, the Si wafers are employed for thyristors, rectifiers, bipolar power transistors, and discrete components for control systems. An estimated 3890 metric tons of semiconductor-grade polycrystalline Si will be used in 1982, and 6200 metric tons by 1985. Although the amount is expected to nearly triple between 1982-89, research is being carried out on the formation of thin films and ribbons for solar cells, thereby eliminating the waste produced in slicing Czolchralski-grown crystals. The free-world Si production in 1982 is estimated to be 3050 metric tons. Various new technologies for the formation of polycrystalline Si at lower costs and with less waste are considered. New entries into the industrial Si formation field are projected to produce a 2000 metric ton excess by 1988.

  4. Physically-based modelling of polycrystalline semiconductor devices

    International Nuclear Information System (INIS)

    Lee, S.

    2000-01-01

    Thin-film technology using polycrystalline semiconductors has been widely applied to active-matrix-addressed liquid crystal displays (AMLCDs) where thin-film transistors act as digital pixel switches. Research and development is in progress to integrate the driver circuits around the peripheral of the display, resulting in significant cost reduction of connections between rows and columns and the peripheral circuitry. For this latter application, where for instance it is important to control the greyscale voltage level delivered to the pixel, an understanding of device behaviour is required so that models can be developed for analogue circuit simulation. For this purpose, various analytical models have been developed based on that of Seto who considered the effect of monoenergetic trap states and grain boundaries in polycrystalline materials but not the contribution of the grains to the electrical properties. The principal aim of this thesis is to describe the use of a numerical device simulator (ATLAS) as a tool to investigate the physics of the trapping process involved in the device operation, which additionally takes into account the effect of multienergetic trapping levels and the contribution of the grain into the modelling. A study of the conventional analytical models is presented, and an alternative approach is introduced which takes into account the grain regions to enhance the accuracy of the analytical modelling. A physically-based discrete-grain-boundary model and characterisation method are introduced to study the effects of the multienergetic trap states on the electrical characteristics of poly-TFTs using CdSe devices as the experimental example, and the electrical parameters such as the density distribution of the trapping states are extracted. The results show excellent agreement between the simulation and experimental data. The limitations of this proposed physical model are also studied and discussed. (author)

  5. Semiconductor composition containing iron, dysprosium, and terbium

    Science.gov (United States)

    Pooser, Raphael C.; Lawrie, Benjamin J.; Baddorf, Arthur P.; Malasi, Abhinav; Taz, Humaira; Farah, Annettee E.; Kalyanaraman, Ramakrishnan; Duscher, Gerd Josef Mansfred; Patel, Maulik K.

    2017-09-26

    An amorphous semiconductor composition includes 1 to 70 atomic percent iron, 15 to 65 atomic percent dysprosium, 15 to 35 atomic percent terbium, balance X, wherein X is at least one of an oxidizing element and a reducing element. The composition has an essentially amorphous microstructure, an optical transmittance of at least 50% in at least the visible spectrum and semiconductor electrical properties.

  6. A model of electric breakdown in polycrystalline semiconductors with highly nonlinear I - V characteristics

    International Nuclear Information System (INIS)

    Yildirim, E.H.; Tanatar, B.; Canessa, E.

    1993-07-01

    A deterministic algorithm to study the nonlinear current-voltage characteristics of polycrystalline semiconductors, such as ZnO-based metal oxide varistors, under dc bias and at room temperature is developed based on the electrical properties of individual grain boundaries. Assuming a thermionic emission type mechanism between individual grains and a nonuniform distribution of barrier heights at grain boundaries, the set of nonlinear Kirchhoff equations that determines the macroscopic current across the specimen and the nonlinearity coefficient α is solved numerically. The applied voltage dependence of the barrier height is found to be crucial to obtain α values reaching ∼50, indicating high nonlinearity as required by potential commercial applications. (author). 20 refs, 3 figs

  7. Polycrystalline semiconductor probes for monitoring the density distribution of an intense thermal neutron flux in nuclear reactors

    International Nuclear Information System (INIS)

    Graul, J.; Mueller, R.G.; Wagner, E.

    1975-05-01

    The applicability of semiconductor detectors for high thermal neutron flux densities is theoretically estimated and experimentally examined. For good thermal stability and low radiation capture rate silicon carbide is used as semiconductor material, produced in polycristalline layers to achieve high radiation resistance. The relations between crystallinity, photoelectric sensitivity and radiation resistance are shown. The radiation resistance of polycrystalline SiC-probes is approximately 100 times greater than that of conventional single crystal radiation detectors. For thermal neutron measurement they can be used in the flux range of approx. 10 10 13 (cm -2 sec -1 ) with operation times of 1.6 a >= tsub(b,max) >= 30 d, resp. (orig.) [de

  8. On the I-V characteristic in the non-linear tenary mixture model for polycrystalline semiconductors

    International Nuclear Information System (INIS)

    Nguyen Van Lien; Nguyen Hoai Nam

    2000-08-01

    A simple expression for the voltage dependence of grain-boundary potential barrier heights is proposed and the Effective Medium Approximation is extended for calculating the I-V characteristic in tenary mixtures of highly non-linear circuit elements. Numerical calculations are performed for the case of polycrystalline semiconductors, such as ZnO-based varistors, where the thermoionic emission is believed to be the dominant mechanism for the electric conduction across double Schottky barriers at room temperature. (author)

  9. Polycrystalline silicon ring resonator photodiodes in a bulk complementary metal-oxide-semiconductor process.

    Science.gov (United States)

    Mehta, Karan K; Orcutt, Jason S; Shainline, Jeffrey M; Tehar-Zahav, Ofer; Sternberg, Zvi; Meade, Roy; Popović, Miloš A; Ram, Rajeev J

    2014-02-15

    We present measurements on resonant photodetectors utilizing sub-bandgap absorption in polycrystalline silicon ring resonators, in which light is localized in the intrinsic region of a p+/p/i/n/n+ diode. The devices, operating both at λ=1280 and λ=1550  nm and fabricated in a complementary metal-oxide-semiconductor (CMOS) dynamic random-access memory emulation process, exhibit detection quantum efficiencies around 20% and few-gigahertz response bandwidths. We observe this performance at low reverse biases in the range of a few volts and in devices with dark currents below 50 pA at 10 V. These results demonstrate that such photodetector behavior, previously reported by Preston et al. [Opt. Lett. 36, 52 (2011)], is achievable in bulk CMOS processes, with significant improvements with respect to the previous work in quantum efficiency, dark current, linearity, bandwidth, and operating bias due to additional midlevel doping implants and different material deposition. The present work thus offers a robust realization of a fully CMOS-fabricated all-silicon photodetector functional across a wide wavelength range.

  10. Semiconductor interfaces of polycrystalline CdTe thin-film solar cells. Characterization and modification of electronic properties

    International Nuclear Information System (INIS)

    Fritsche, J.

    2003-01-01

    In this thesis for the first time the electronic properties of the semiconductor interfaces in polycrystalline CdTe thin-film solar cells, as well as the morphological and electronic properties of the single semiconductor surfaces were systematically characterized by surface-sensitive measuring methods. The morphological surface properties were analyzed by scanning force microscopy. As substrate materials with SnO 2 /ITO covered glass was applied, where the CdS and CdTe layers were deposited. Furthermore the electronic and morphological material properties of differently treated SnO 2 surfaces were characterized. Beside the studies with scanning force microscopy sputtering depth profiles and X-ray photoelectron spectroscopy were measured

  11. Metal-semiconductor, composite radiation detectors

    International Nuclear Information System (INIS)

    Orvis, W.J.; Yee, J.H.; Fuess, D.

    1992-12-01

    In 1989, Naruse and Hatayama of Toshiba published a design for an increased efficiency x-ray detector. The design increased the efficiency of a semiconductor detector by interspersing layers of high-z metal within it. Semiconductors such as silicon make good, high-resolution radiation detectors, but they have low efficiency because they are low-z materials (z = 14). High-z metals, on the other hand, are good absorbers of high-energy photons. By interspersing high-z metal layers with semiconductor layers, Naruse and Hatayama combined the high absorption efficiency of the high-z metals with the good detection capabilities of a semiconductor. This project is an attempt to use the same design to produce a high-efficiency, room temperature gamma ray detector. By their nature, gamma rays require thicker metal layers to efficiently absorb them. These thicker layers change the behavior of the detector by reducing the resolution, compared to a solid state detector, and shifting the photopeak by a predictable amount. During the last year, the authors have procured and tested a commercial device with operating characteristics similar to those of a single layer of the composite device. They have modeled the radiation transport in a multi-layered device, to verify the initial calculations of layer thickness and composition. They have modeled the electrostatic field in different device designs to locate and remove high-field regions that can cause device breakdown. They have fabricated 14 single layer prototypes

  12. Real time spectroscopic ellipsometry for analysis and control of thin film polycrystalline semiconductor deposition in photovoltaics

    Energy Technology Data Exchange (ETDEWEB)

    Koirala, Prakash; Attygalle, Dinesh; Aryal, Puruswottam; Pradhan, Puja; Chen, Jie [Center for Photovoltaics Innovation and Commercialization and Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Marsillac, Sylvain [Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23529 (United States); Ferlauto, Andre S.; Podraza, Nikolas J.; Collins, Robert W. [Center for Photovoltaics Innovation and Commercialization and Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States)

    2014-11-28

    Real time spectroscopic ellipsometry (RTSE) from the near-infrared to ultraviolet has been applied for analysis of the deposition of polycrystalline thin films that form the basis of two key photovoltaic heterojunction configurations, superstrate SnO{sub 2}/CdS/CdTe and substrate Mo/Cu(In{sub 1−x}Ga{sub x})Se{sub 2}/CdS. The focus of this work is to develop capabilities for monitoring and controlling the key steps in the fabrication of these device structures. Analysis of RTSE data collected during sputter deposition of CdS on a rough SnO{sub 2} transparent top contact provides the time evolution of the CdS effective thickness, or film volume per unit substrate area. This thickness includes interface, bulk, and surface roughness layer components and affects the CdS/CdTe heterojunction performance and the quantum efficiency of the solar cell in the blue region of the solar spectrum. Similarly, analysis of RTSE data collected during co-evaporation of Cu(In{sub 1−x}Ga{sub x})Se{sub 2} (CIGS; x ∼ 0.3) on a rough Mo back contact provides the evolution of a second phase of Cu{sub 2−x}Se within the CIGS layer. During the last stage of CIGS deposition, the In, Ga, and Se co-evaporants convert this Cu{sub 2−x}Se phase to CIGS, and RTSE identifies the endpoint, specifically the time at which complete conversion occurs and single-phase, large-grain CIGS is obtained in this key stage. - Highlights: • Real time spectroscopic ellipsometry (RTSE) study of CdS and CuIn{sub 1−x}Ga{sub x}Se{sub 2} (CIGS) films. • RTSE during CdS deposition provides the evolution of the CdS effective thickness. • RTSE for CIGS film enables to measure and control the composition and thickness. • The work leads to the development of optical models for processing steps.

  13. Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method

    International Nuclear Information System (INIS)

    Dolgonos, Alex; Mason, Thomas O.; Poeppelmeier, Kenneth R.

    2016-01-01

    The direct optical band gap of semiconductors is traditionally measured by extrapolating the linear region of the square of the absorption curve to the x-axis, and a variation of this method, developed by Tauc, has also been widely used. The application of the Tauc method to crystalline materials is rooted in misconception–and traditional linear extrapolation methods are inappropriate for use on degenerate semiconductors, where the occupation of conduction band energy states cannot be ignored. A new method is proposed for extracting a direct optical band gap from absorption spectra of degenerately-doped bulk semiconductors. This method was applied to pseudo-absorption spectra of Sn-doped In 2 O 3 (ITO)—converted from diffuse-reflectance measurements on bulk specimens. The results of this analysis were corroborated by room-temperature photoluminescence excitation measurements, which yielded values of optical band gap and Burstein–Moss shift that are consistent with previous studies on In 2 O 3 single crystals and thin films. - Highlights: • The Tauc method of band gap measurement is re-evaluated for crystalline materials. • Graphical method proposed for extracting optical band gaps from absorption spectra. • The proposed method incorporates an energy broadening term for energy transitions. • Values for ITO were self-consistent between two different measurement methods.

  14. Composite nanomaterials of semiconductors and noble metals as plasmonic photocatalysts

    DEFF Research Database (Denmark)

    Engelbrekt, Christian; Law, Matt; Zhang, Jingdong

    behavior, and can be more stable under operating conditions. Composite photocatalysts of semiconductor nanoparticles (SNPs) and PNPs exploit broadly the solar spectrum, provide new catalytic routes and expand the scope of solar photocatalysis. The newly initiated project aims at developing composite...

  15. Metal-semiconductor, composite radiation detectors

    International Nuclear Information System (INIS)

    Orvis, W.J.; Yee, J.H.; Fuess, D.A.

    1991-12-01

    In 1989, Naruse and Hatayama of Toshiba published a design for an increased efficiency x-ray detector. The design increased the efficiency of a semiconductor detector by interspersing layers of high-z metal within it. Semiconductors such as silicon make good, high-resolution radiation detectors, but they have low efficiency because they are low-z materials (z = 14). High-z metals, on the other hand, are good absorbers of high-energy photons. By interspersing high-z metal layers with semiconductor layers, Naruse and Hatayama combined the high absorption efficiency of the high-z metals with good detection capabilities of a semiconductor. This project is an attempt to use the same design to produce a high- efficiency gamma ray detector. By their nature, gamma rays require thicker metal layers to efficiently absorb them. These thicker layers change the behavior of the detector by reducing the resolution, compared to a solid state detector, and shifting the photopeak by a predictable amount. During the last year, we have modeled parts of the detector and have nearly completed a prototype device. 2 refs

  16. Semiconductor

    International Nuclear Information System (INIS)

    2000-01-01

    This book deals with process and measurement of semiconductor. It contains 20 chapters, which goes as follows; semiconductor industry, introduction of semiconductor manufacturing, yield of semiconductor process, materials, crystal growth and a wafer forming, PN, control pollution, oxidation, photomasking photoresist chemistry, photomasking technologies, diffusion and ion injection, chemical vapor deposition, metallization, wafer test and way of evaluation, semiconductor elements, integrated circuit and semiconductor circuit technology.

  17. Electronic grain boundary properties in polycrystalline Cu(In,Ga)Se2 semiconductors for thin film solar cells

    International Nuclear Information System (INIS)

    Baier, Robert

    2012-01-01

    Solar cells based on polycrystalline Cu(In,Ga)Se 2 (CIGSe) thin film absorbers reach the highest energy conversion efficiency among all thin film solar cells. The record efficiency is at least partly attributed to benign electronic properties of grain boundaries (GBs) in the CIGSe layers. However, despite a high amount of research on this phenomenon the underlying physics is not sufficiently understood. This thesis presents an elaborate study on the electronic properties of GBs in CIGSe thin films. Kelvin probe force microscopy (KPFM) was employed to investigate the electronic properties of GBs in dependence of the Ga-content. Five CIGSe thin lms with various Ga-contents were grown by means of similar three stage co-evaporation processes. Both as grown as well as chemically treated (KCN etched) thin films were analyzed. The chemical treatment was employed to remove surface oxides. No difference in electronic GB properties was found with or without the chemical treatment. Therefore, we conclude that a moderate surface oxidation does not alter the electronic properties of GBs. In general, one can observe significant variations of electronic potential barriers at GBs. Under consideration of the averaging effect of the work function signal of nanoscale potential distributions in KPFM measurements which was quantified in the course of this thesis both positive and negative potential barriers in a range between ∼-350 mV and ∼+450 mV were detected. Additionally, variations in the defect densities at GBs between ∼3.1 x 10 11 cm -2 and ∼2.1 x 10 12 cm -2 were found. However, no correlation between the electronic properties of GBs and the Ga-content of CIGSe thin films was discovered. Consequently, one cannot explain the drop in device efficiency observed for CIGSe thin film solar cells with a high Ga-content by a change of the electronic properties of GBs. Combined KPFM and electron backscatter diffraction measurements were employed for the first time on CIGSe thin

  18. Electronic grain boundary properties in polycrystalline Cu(In,Ga)Se{sub 2} semiconductors for thin film solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Baier, Robert

    2012-06-25

    Solar cells based on polycrystalline Cu(In,Ga)Se{sub 2} (CIGSe) thin film absorbers reach the highest energy conversion efficiency among all thin film solar cells. The record efficiency is at least partly attributed to benign electronic properties of grain boundaries (GBs) in the CIGSe layers. However, despite a high amount of research on this phenomenon the underlying physics is not sufficiently understood. This thesis presents an elaborate study on the electronic properties of GBs in CIGSe thin films. Kelvin probe force microscopy (KPFM) was employed to investigate the electronic properties of GBs in dependence of the Ga-content. Five CIGSe thin lms with various Ga-contents were grown by means of similar three stage co-evaporation processes. Both as grown as well as chemically treated (KCN etched) thin films were analyzed. The chemical treatment was employed to remove surface oxides. No difference in electronic GB properties was found with or without the chemical treatment. Therefore, we conclude that a moderate surface oxidation does not alter the electronic properties of GBs. In general, one can observe significant variations of electronic potential barriers at GBs. Under consideration of the averaging effect of the work function signal of nanoscale potential distributions in KPFM measurements which was quantified in the course of this thesis both positive and negative potential barriers in a range between ∼-350 mV and ∼+450 mV were detected. Additionally, variations in the defect densities at GBs between ∼3.1 x 10{sup 11} cm{sup -2} and ∼2.1 x 10{sup 12} cm{sup -2} were found. However, no correlation between the electronic properties of GBs and the Ga-content of CIGSe thin films was discovered. Consequently, one cannot explain the drop in device efficiency observed for CIGSe thin film solar cells with a high Ga-content by a change of the electronic properties of GBs. Combined KPFM and electron backscatter diffraction measurements were employed for the

  19. Organic-Inorganic Composites of Semiconductor Nanocrystals for Efficient Excitonics.

    Science.gov (United States)

    Guzelturk, Burak; Demir, Hilmi Volkan

    2015-06-18

    Nanocomposites of colloidal semiconductor nanocrystals integrated into conjugated polymers are the key to soft-material hybrid optoelectronics, combining advantages of both plastics and particles. Synergic combination of the favorable properties in the hybrids of colloidal nanocrystals and conjugated polymers offers enhanced performance and new functionalities in light-generation and light-harvesting applications, where controlling and mastering the excitonic interactions at the nanoscale are essential. In this Perspective, we highlight and critically consider the excitonic interactions in the organic-inorganic nanocomposites to achieve highly efficient exciton transfer through rational design of the nanocomposites. The use of strong excitonic interactions in optoelectronic devices can trigger efficiency breakthroughs in hybrid optoelectronics.

  20. Polycrystalline strengthening

    DEFF Research Database (Denmark)

    Hansen, Niels

    1985-01-01

    for the understanding of polycrystalline strengthening is obtained mainly from surface relief patterns and from bulk structures observed by transmission electron microscopy of thin foils. The results obtained by these methods are discussed and correlations are proposed. A number of features characterizing the deformed...... structure are summarized and the behavior of a number of metals and alloys is reviewed with emphasis on the structural changes in the interior of the grains and in the vicinity of the grain boundaries. The models for strain accommodation during deformation are discussed on the basis of the microstructures...

  1. Facile synthesis and enhanced visible-light photocatalysis of graphitic carbon nitride composite semiconductors.

    Science.gov (United States)

    Li, Huiquan; Liu, Yuxing; Gao, Xing; Fu, Cong; Wang, Xinchen

    2015-04-13

    The semiconductor heterojunction has been an effective architecture to enhance photocatalytic activity by promoting photogenerated charge separation. Here, graphitic carbon nitride (CN) and B-modified graphitic carbon nitride (CNB) composite semiconductors were fabricated by a facile calcination process using cheap, sustainable, and easily available sodium tetraphenylboron and urea as precursors. The synthetic CN-CNB-25 semiconductor with a suitable CNB content showed the highest visible-light activity. Its degradation ratio for methyl orange and phenol was more than twice that of CN and CNB and its H2 evolution rate was ∼3.4 and ∼1.8 times higher than that of CN and CNB, respectively. It also displayed excellent stability and reusability. The enhanced activity of CN-CNB-25 was attributed predominantly to the efficient separation of photoinduced electrons and holes. This paper describes a visible-light-responsive CN composite semiconductor with great potential in environmental and energy applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Methods for synthesis of semiconductor nanocrystals and thermoelectric compositions

    Science.gov (United States)

    Chen, Gang (Inventor); Poudel, Bed (Inventor); Kumar, Shankar (Inventor); Dresselhaus, Mildred (Inventor); Ren, Zhifeng (Inventor); Wang, Wenzhong (Inventor)

    2007-01-01

    The present invention provides methods for synthesis of IV VI nanostructures, and thermoelectric compositions formed of such structures. In one aspect, the method includes forming a solution of a Group IV reagent, a Group VI reagent and a surfactant. A reducing agent can be added to the solution, and the resultant solution can be maintained at an elevated temperature, e.g., in a range of about 20.degree. C. to about 360.degree. C., for a duration sufficient for generating nanoparticles as binary alloys of the IV VI elements.

  3. Physicochemical and Electrophysical Properties of Metal/Semiconductor Containing Nanostructured Composites

    Science.gov (United States)

    Gerasimov, G. N.; Gromov, V. F.; Trakhtenberg, L. I.

    2018-06-01

    The properties of nanostructured composites based on metal oxides and metal-polymer materials are analyzed, along with ways of preparing them. The effect the interaction between metal and semiconductor nanoparticles has on the conductivity, photoconductivity, catalytic activity, and magnetic, dielectric, and sensor properties of nanocomposites is discussed. It is shown that as a result of this interaction, a material can acquire properties that do not exist in systems of isolated particles. The transfer of electrons between metal particles of different sizes in polymeric matrices leads to specific dielectric losses, and to an increase in the rate and a change in the direction of chemical reactions catalyzed by these particles. The interaction between metal-oxide semiconductor particles results in the electronic and chemical sensitization of sensor effects in nanostructured composite materials. Studies on creating molecular machines (Brownian motors), devices for magnetic recording of information, and high-temperature superconductors based on nanostructured systems are reviewed.

  4. Polycrystalline silicon semiconducting material by nuclear transmutation doping

    Science.gov (United States)

    Cleland, John W.; Westbrook, Russell D.; Wood, Richard F.; Young, Rosa T.

    1978-01-01

    A NTD semiconductor material comprising polycrystalline silicon having a mean grain size less than 1000 microns and containing phosphorus dispersed uniformly throughout the silicon rather than at the grain boundaries.

  5. Fabrication and electrical properties of metal-oxide semiconductor capacitors based on polycrystalline p-Cu{sub x}O and HfO{sub 2}/SiO{sub 2} high-{kappa} stack gate dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Zou Xiao [Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan University, Wuhan, 430074 (China); Department of Electromachine Engineering, Jianghan University, Wuhan, 430056 (China); Fang Guojia, E-mail: gjfang@whu.edu.c [Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan University, Wuhan, 430074 (China); Yuan Longyan; Liu Nishuang; Long Hao; Zhao Xingzhong [Department of Electronic Science and Technology, School of Physical Science and Technology, Wuhan University, Wuhan, 430074 (China)

    2010-05-31

    Polycrystalline p-type Cu{sub x}O films were deposited after the growth of HfO{sub 2} dielectric on Si substrate by pulsed laser deposition, and Cu{sub x}O metal-oxide-semiconductor (MOS) capacitors with HfO{sub 2}/SiO{sub 2} stack gate dielectric were primarily fabricated and investigated. X-ray diffraction and X-ray photoelectron spectroscopy were applied to analyze crystalline structure and Cu{sup +}/Cu{sup 2+} ratios of Cu{sub x}O films respectively. SiO{sub 2} interlayer formed between the high-{kappa} dielectric and substrate was estimated by the transmission electron microscope. Results of electrical characteristic measurement indicate that the permittivity of HfO{sub 2} is about 22, and the gate leakage current density of MOS capacitor with 11.3 nm HfO{sub 2}/SiO{sub 2} stack dielectrics is {approx} 10{sup -4} A/cm{sup 2}. Results also show that the annealing in N{sub 2} can improve the quality of Cu{sub x}O/HfO{sub 2} interface and thus reduce the gate leakage density.

  6. Surface properties and photocatalytic activity of KTaO3, CdS, MoS2 semiconductors and their binary and ternary semiconductor composites.

    Science.gov (United States)

    Bajorowicz, Beata; Cybula, Anna; Winiarski, Michał J; Klimczuk, Tomasz; Zaleska, Adriana

    2014-09-24

    Single semiconductors such as KTaO3, CdS MoS2 or their precursor solutions were combined to form novel binary and ternary semiconductor nanocomposites by the calcination or by the hydro/solvothermal mixed solutions methods, respectively. The aim of this work was to study the influence of preparation method as well as type and amount of the composite components on the surface properties and photocatalytic activity of the new semiconducting photoactive materials. We presented different binary and ternary combinations of the above semiconductors for phenol and toluene photocatalytic degradation and characterized by X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area and porosity. The results showed that loading MoS2 onto CdS as well as loading CdS onto KTaO3 significantly enhanced absorption properties as compared with single semiconductors. The highest photocatalytic activity in phenol degradation reaction under both UV-Vis and visible light irradiation and very good stability in toluene removal was observed for ternary hybrid obtained by calcination of KTaO3, CdS, MoS2 powders at the 10:5:1 molar ratio. Enhanced photoactivity could be related to the two-photon excitation in KTaO3-CdS-MoS2 composite under UV-Vis and/or to additional presence of CdMoO4 working as co-catalyst.

  7. Anelasticity of polycrystalline indium

    Energy Technology Data Exchange (ETDEWEB)

    Sapozhnikov, K., E-mail: k.sapozhnikov@mail.ioffe.ru [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Golyandin, S. [A.F.Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Kustov, S. [Dept. de Fisica, Universitat de les Illes Balears, Cra Valldemossa km 7.5, E 07122 Palma de Mallorca (Spain)

    2009-09-15

    Mechanisms of anelasticity of polycrystalline indium have been studied over wide ranges of temperature (7-320 K) and strain amplitude (2 x 10{sup -7}-3.5 x 10{sup -4}). Measurements of the internal friction and Young's modulus have been performed by means of the piezoelectric resonant composite oscillator technique using longitudinal oscillations at frequencies of about 100 kHz. The stages of the strain amplitude dependence of the internal friction and Young's modulus defect, which can be attributed to dislocation - point defect and dislocation - dislocation interactions, have been revealed. It has been shown that thermal cycling gives rise to microplastic straining of polycrystalline indium due to the anisotropy of thermal expansion and to appearance of a 'recrystallization' internal friction maximum in the temperature spectra of amplitude-dependent anelasticity. The temperature range characterized by formation of Cottrell's atmospheres of point defects around dislocations has been determined from the acoustic data.

  8. Charge transport in conjugated polymer-semiconductor nanoparticle composite near the percolation threshold

    Science.gov (United States)

    Cardoso, L. S.; Gonçalves, G. E.; Kanda, D. H. F.; Bianchi, R. F.; Nagashima, H. N.

    2017-12-01

    This paper describes a new statistical model to predict the frequency dependence of the conductivity of conjugated polymer-semiconductor nanoparticle composites. The model considers AC conduction in an inhomogeneous medium represented by a two-dimensional model of resistor network. The conductivity between two neighboring sites in the polymer matrix and the semiconductor particles is assumed to obey the random free energy barrier model and the Drude model, respectively. The real and imaginary parts of the AC conductivity were determined using the transfer-matrix technique, and the statistical model was applied to experimental data of thin films composed of polyaniline (PANI) and indium-tin-oxide (ITO) nanoparticles. The conductivity critical exponent ( s) obtained in two dimensions for PANI/ITO films below the percolation threshold was found to be 2.7, which is greater than the universal value of s described by the classical percolation theory ( s = 1.3). This non-universality is explained by the existence of a local electric field distribution in the bulk of the nanocomposite. Finally, these results are discussed in terms of the distribution of potential barriers that vary according to the concentration of ITO amount in the composite.

  9. Crystallite-conjugation regions in polycrystalline transition and noble metals. 1. Composition and properties of point defects in the cores of crystallite-conjugation regions in polycrystalline Cr, Ta and W

    International Nuclear Information System (INIS)

    Klotsman, S.M.; Kajgorodov, V.N.; Ermakov, A.V.; Rudenko, V.K.

    2004-01-01

    With the use of available results of theoretical investigations on structure and properties of crystallite conjugation regions (CCR) the types and relaxation volumes of point defects arising in a core of the CCR of polycrystalline Ta, W and Cr after vacuum annealing (10 -6 - 10 -5 torr) are determined. Temperature dependences are studied for isomer shifts δ 1 and δ 2 of -1 and -2 components of emission spectra of NGR-irradiation 57 Co( 57 Fe) atomic probes localized in a core of the CCR and in adjacent zones of the lattice of polycrystalline solid solutions of O(Ta), O(W) and O(Cr). A comparison of the dependences obtained is carried and the specific features observed are explained for O(Cr) [ru

  10. Polycrystalline indium phosphide on silicon by indium assisted growth in hydride vapor phase epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Metaferia, Wondwosen; Sun, Yan-Ting, E-mail: yasun@kth.se; Lourdudoss, Sebastian [Laboratory of Semiconductor Materials, Department of Materials and Nano Physics, KTH—Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Pietralunga, Silvia M. [CNR-Institute for Photonics and Nanotechnologies, P. Leonardo da Vinci, 32 20133 Milano (Italy); Zani, Maurizio; Tagliaferri, Alberto [Department of Physics Politecnico di Milano, P. Leonardo da Vinci, 32 20133 Milano (Italy)

    2014-07-21

    Polycrystalline InP was grown on Si(001) and Si(111) substrates by using indium (In) metal as a starting material in hydride vapor phase epitaxy (HVPE) reactor. In metal was deposited on silicon substrates by thermal evaporation technique. The deposited In resulted in islands of different size and was found to be polycrystalline in nature. Different growth experiments of growing InP were performed, and the growth mechanism was investigated. Atomic force microscopy and scanning electron microscopy for morphological investigation, Scanning Auger microscopy for surface and compositional analyses, powder X-ray diffraction for crystallinity, and micro photoluminescence for optical quality assessment were conducted. It is shown that the growth starts first by phosphidisation of the In islands to InP followed by subsequent selective deposition of InP in HVPE regardless of the Si substrate orientation. Polycrystalline InP of large grain size is achieved and the growth rate as high as 21 μm/h is obtained on both substrates. Sulfur doping of the polycrystalline InP was investigated by growing alternating layers of sulfur doped and unintentionally doped InP for equal interval of time. These layers could be delineated by stain etching showing that enough amount of sulfur can be incorporated. Grains of large lateral dimension up to 3 μm polycrystalline InP on Si with good morphological and optical quality is obtained. The process is generic and it can also be applied for the growth of other polycrystalline III–V semiconductor layers on low cost and flexible substrates for solar cell applications.

  11. Surface Properties and Photocatalytic Activity of KTaO3, CdS, MoS2 Semiconductors and Their Binary and Ternary Semiconductor Composites

    Directory of Open Access Journals (Sweden)

    Beata Bajorowicz

    2014-09-01

    Full Text Available Single semiconductors such as KTaO3, CdS MoS2 or their precursor solutions were combined to form novel binary and ternary semiconductor nanocomposites by the calcination or by the hydro/solvothermal mixed solutions methods, respectively. The aim of this work was to study the influence of preparation method as well as type and amount of the composite components on the surface properties and photocatalytic activity of the new semiconducting photoactive materials. We presented different binary and ternary combinations of the above semiconductors for phenol and toluene photocatalytic degradation and characterized by X-ray powder diffraction (XRD, UV-Vis diffuse reflectance spectroscopy (DRS, scanning electron microscopy (SEM, Brunauer–Emmett–Teller (BET specific surface area and porosity. The results showed that loading MoS2 onto CdS as well as loading CdS onto KTaO3 significantly enhanced absorption properties as compared with single semiconductors. The highest photocatalytic activity in phenol degradation reaction under both UV-Vis and visible light irradiation and very good stability in toluene removal was observed for ternary hybrid obtained by calcination of KTaO3, CdS, MoS2 powders at the 10:5:1 molar ratio. Enhanced photoactivity could be related to the two-photon excitation in KTaO3-CdS-MoS2 composite under UV-Vis and/or to additional presence of CdMoO4 working as co-catalyst.

  12. Growth of polycrystalline Pr_2NiO_4_+_δ coating on alumina substrate by RF magnetron co-sputtering from composite targets

    International Nuclear Information System (INIS)

    Sediri, A.; Zaghrioui, M.; Barichard, A.; Autret, C.; Negulescu, B.; Del Campo, L.; Echegut, P.; Laffez, P.

    2016-01-01

    Polycrystalline Pr_2NiO_4_+_δ coatings have been deposited on alumina substrates at room temperature by RF magnetron co-sputtering from Pr and Ni metallic composite target. The mixed target's area and the sputtering conditions were optimized to reach an atomic ratio Pr/Ni of 2. A subsequent annealing, at 1050–1100 °C, allowed obtaining Pr_2NiO_4_+_δ phase after in situ high temperature x-ray diffraction study performed on as-deposited film. Microstructural analyses (SEM and AFM) revealed dense and rough microstructure. Normal spectral emittance measurements performed at 794 °C in the spectral range 400–5000 cm"-"1 showed an emissivity of ε ≈ 0.8. - Highlights: • Pr_2NiO_4_+_δ coatings deposited by RF magnetron co-sputtering • Crystallization kinetic studied by X-ray diffraction versus temperature • SEM and AFM observations showed dense and rough microstructure • Normal spectral emittance reaches to ε = 0.8 at 794 °C in the opaque zone.

  13. Growth of polycrystalline Pr{sub 2}NiO{sub 4+δ} coating on alumina substrate by RF magnetron co-sputtering from composite targets

    Energy Technology Data Exchange (ETDEWEB)

    Sediri, A., E-mail: amal.sediri@univ-tours.fr [Université François-Rabelais de Tours, GREMAN UMR 7347 CNRS, IUT de Blois 15 rue de la chocolaterie CS 2903, 41029 Blois Cedex (France); Zaghrioui, M.; Barichard, A.; Autret, C.; Negulescu, B. [Université François-Rabelais de Tours, GREMAN UMR 7347 CNRS, IUT de Blois 15 rue de la chocolaterie CS 2903, 41029 Blois Cedex (France); Del Campo, L.; Echegut, P. [CNRS, UPR 3079 CEMHTI, 45071 Orléans Cedex 2 (France); Laffez, P. [Université François-Rabelais de Tours, GREMAN UMR 7347 CNRS, IUT de Blois 15 rue de la chocolaterie CS 2903, 41029 Blois Cedex (France)

    2016-02-01

    Polycrystalline Pr{sub 2}NiO{sub 4+δ} coatings have been deposited on alumina substrates at room temperature by RF magnetron co-sputtering from Pr and Ni metallic composite target. The mixed target's area and the sputtering conditions were optimized to reach an atomic ratio Pr/Ni of 2. A subsequent annealing, at 1050–1100 °C, allowed obtaining Pr{sub 2}NiO{sub 4+δ} phase after in situ high temperature x-ray diffraction study performed on as-deposited film. Microstructural analyses (SEM and AFM) revealed dense and rough microstructure. Normal spectral emittance measurements performed at 794 °C in the spectral range 400–5000 cm{sup -1} showed an emissivity of ε ≈ 0.8. - Highlights: • Pr{sub 2}NiO{sub 4+δ} coatings deposited by RF magnetron co-sputtering • Crystallization kinetic studied by X-ray diffraction versus temperature • SEM and AFM observations showed dense and rough microstructure • Normal spectral emittance reaches to ε = 0.8 at 794 °C in the opaque zone.

  14. High Photoluminescence Quantum Yields in Organic Semiconductor-Perovskite Composite Thin Films.

    Science.gov (United States)

    Longo, Giulia; La-Placa, Maria-Grazia; Sessolo, Michele; Bolink, Henk J

    2017-10-09

    One of the obstacles towards efficient radiative recombination in hybrid perovskites is a low exciton binding energy, typically in the orders of tens of meV. It has been shown that the use of electron-donor additives can lead to a substantial reduction of the non-radiative recombination in perovskite films. Herein, the approach using small molecules with semiconducting properties, which are candidates to be implemented in future optoelectronic devices, is presented. In particular, highly luminescent perovskite-organic semiconductor composite thin films have been developed, which can be processed from solution in a simple coating step. By tuning the relative concentration of methylammonium lead bromide (MAPbBr 3 ) and 9,9spirobifluoren-2-yl-diphenyl-phosphine oxide (SPPO1), it is possible to achieve photoluminescent quantum yields (PLQYs) as high as 85 %. This is attributed to the dual functions of SPPO1 that limit the grain growth while passivating the perovskite surface. The electroluminescence of these materials was investigated by fabricating multilayer LEDs, where charge injection and transport was found to be severely hindered for the perovskite/SPPO1 material. This was alleviated by partially substituting SPPO1 with a hole-transporting material, 1,3-bis(N-carbazolyl)benzene (mCP), leading to bright electroluminescence. The potential of combining perovskite and organic semiconductors to prepare materials with improved properties opens new avenues for the preparation of simple lightemitting devices using perovskites as the emitter. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Pulsed laser deposition of semiconductor-ITO composite films on electric-field-applied substrates

    International Nuclear Information System (INIS)

    Narazaki, Aiko; Sato, Tadatake; Kawaguchi, Yoshizo; Niino, Hiroyuki; Yabe, Akira; Sasaki, Takeshi; Koshizaki, Naoto

    2002-01-01

    The DC electric-field effect on the crystallinity of II-VI semiconductor in composite systems has been investigated for CdS-ITO films fabricated via alternative pulsed laser deposition (PLD) of CdS and indium tin oxide (ITO) on electric-field-applied substrates. The alternative laser ablation was performed under irradiation of ArF excimer laser in mixture gas of helium and oxygen. The application of electric-field facilitated the preferential crystal-growth of CdS in nanometer scale at low pressure, whereas all the films grown without the field were amorphous. There is a large difference in the crystallization between the films grown on field-applied and heated substrates; the latter showed the crystal-growth with random orientations. This difference indicates that the existence of electric-field has an influence on the transformation from amorphous to crystalline phase of CdS. The driving force for the field-induced crystallization is also discussed in the light of the Joule heat

  16. Mixed conductivity, structural and microstructural characterization of titania-doped yttria tetragonal zirconia polycrystalline/titania-doped yttria stabilized zirconia composite anode matrices

    International Nuclear Information System (INIS)

    Colomer, M.T.; Maczka, M.

    2011-01-01

    Taking advantage of the fact that TiO 2 additions to 8YSZ cause not only the formation of a titania-doped YSZ solid solution but also a titania-doped YTZP solid solution, composite materials based on both solutions were prepared by solid state reaction. In particular, additions of 15 mol% of TiO 2 give rise to composite materials constituted by 0.51 mol fraction titania-doped yttria tetragonal zirconia polycrystalline and 0.49 mol fraction titania-doped yttria stabilized zirconia (0.51TiYTZP/0.49TiYSZ). Furthermore, Y 2 (Ti 1-y Zr y ) 2 O 7 pyrochlore is present as an impurity phase with y close to 1, according to FT-Raman results. Lower and higher additions of titania than that of 15 mol%, i.e., x=0, 5, 10, 20, 25 and 30 mol% were considered to study the evolution of 8YSZ phase as a function of the TiO 2 content. Furthermore, zirconium titanate phase (ZrTiO 4 ) is detected when the titania content is equal or higher than 20 mol% and this phase admits Y 2 O 3 in solid solution according to FE-SEM-EDX. The 0.51TiYTZP/0.49TiYSZ duplex material was selected in this study to establish the mechanism of its electronic conduction under low oxygen partial pressures. In the pO 2 range from 0.21 to 10 -7.5 atm. the conductivity is predominantly ionic and constant over the range and its value is 0.01 S/cm. The ionic plus electronic conductivity is 0.02 S/cm at 1000 o C and 10 -12.3 atm. Furthermore, the onset of electronic conductivity under reducing conditions exhibits a -1/4 pO 2 dependence. Therefore, it is concluded that the n-type electronic conduction in the duplex material can be due to a small polaron-hopping between Ti 3+ and Ti 4+ . -- Graphical abstract: FE-SEM micrograph of a polished and thermal etched surface of a Ti-doped YTZP/Ti-doped YSZ composite material. Display Omitted Research highlights: → Ti-doped YTZP/Ti-doped YSZ composite materials are mixed conductors under low partial pressures. → From 5 mol% of TiO 2 , Y 2 (Ti 1-y ,Zr y ) 2 O 7 pyrochlore is

  17. Synthesis and characterization of polymer matrix composite material with combination of ZnO filler and nata de coco fiber as a candidate of semiconductor material

    Science.gov (United States)

    Saputra, Asep Handaya; Anindita, Hana Nabila

    2015-12-01

    Synthesis of semiconductor composite using acrylic matrix filled with ZnO and nata de coco fiber has been conducted in this research. The purpose of this research is to obtain semiconductor composite material that has a good mechanical strength and thermal resistance. In situ polymerization method is used in this research and the composites are ready to be characterized after 12 hours. The main parameter that is characterized is the electric conductivity of the composite. Additional parameters are also characterized such as composite's elastic modulus and glass transition temperature. The composites that has been made in this research can be classified as semiconductor material because the conductivity is in the range of 10-8-103 S/cm. In general the addition of ZnO and nata de coco filler can increase the conductivity of the composite. The highest semiconductor characteristic in acrylic/ZnO composite is obtained from 30% volume filler that reach 3.4 x 10-7 S/cm. Similar with acrylic/ZnO composite, in acrylic/nata de coco fiber composite the highest semiconductor characteristic is also obtained from 30% volume filler that reach 1.15 x 10-7 S/cm. Combination of 20% volume of ZnO, 10% volume of nata de coco, and 70% volume of acrylic resulting in composite with electric conductivity of 1.92 x 10-7 S/cm. In addition, combination of ZnO and nata de coco fiber as filler in composite can also improve the characteristic of composite where composite with 20% volume of ZnO filler and 10% volume of nata de coco fiber resulting in composite with elastic modulus of 1.79 GPa and glass transition temperature of 175.73°C which is higher than those in acrylic/ZnO composite.

  18. Fundamentals of semiconductor devices

    CERN Document Server

    Lindmayer, Joseph

    1965-01-01

    Semiconductor properties ; semiconductor junctions or diodes ; transistor fundamentals ; inhomogeneous impurity distributions, drift or graded-base transistors ; high-frequency properties of transistors ; band structure of semiconductors ; high current densities and mechanisms of carrier transport ; transistor transient response and recombination processes ; surfaces, field-effect transistors, and composite junctions ; additional semiconductor characteristics ; additional semiconductor devices and microcircuits ; more metal, insulator, and semiconductor combinations for devices ; four-pole parameters and configuration rotation ; four-poles of combined networks and devices ; equivalent circuits ; the error function and its properties ; Fermi-Dirac statistics ; useful physical constants.

  19. Multiwavelength anomalous diffraction and diffraction anomalous fine structure to study composition and strain of semiconductor nano structures

    International Nuclear Information System (INIS)

    Favre-Nicolin, V.; Proietti, M.G.; Leclere, C.; Renevier, H.; Katcho, N.A.; Richard, M.I.

    2012-01-01

    The aim of this paper is to illustrate the use of Multi-Wavelength Anomalous Diffraction (MAD) and Diffraction Anomalous Fine Structure (DAFS) spectroscopy for the study of structural properties of semiconductor nano-structures. We give a brief introduction on the basic principles of these techniques providing a detailed bibliography. Then we focus on the data reduction and analysis and we give specific examples of their application on three different kinds of semiconductor nano-structures: Ge/Si nano-islands, AlN capped GaN/AlN Quantum Dots and AlGaN/AlN Nano-wires. We show that the combination of MAD and DAFS is a very powerful tool to solve the structural problem of these materials of high technological impact. In particular, the effects of composition and strain on diffraction are disentangled and composition can be determined in a reliable way, even at the interface between nano-structure and substrate. We show the great possibilities of this method and give the reader the basic tools to undertake its use. (authors)

  20. Polycrystalline Silicon: a Biocompatibility Assay

    International Nuclear Information System (INIS)

    Pecheva, E.; Fingarova, D.; Pramatarova, L.; Hikov, T.; Laquerriere, P.; Bouthors, Sylvie; Dimova-Malinovska, D.; Montgomery, P.

    2010-01-01

    Polycrystalline silicon (poly-Si) layers were functionalized through the growth of biomimetic hydroxyapatite (HA) on their surface. HA is the mineral component of bones and teeth and thus possesses excellent bioactivity and biocompatibility. MG-63 osteoblast-like cells were cultured on both HA-coated and un-coated poly-Si surfaces for 1, 3, 5 and 7 days and toxicity, proliferation and cell morphology were investigated. The results revealed that the poly-Si layers were bioactive and compatible with the osteoblast-like cells. Nevertheless, the HA coating improved the cell interactions with the poly-Si surfaces based on the cell affinity to the specific chemical composition of the bone-like HA and/or to the higher HA roughness.

  1. Polaritons dispersion in a composite ferrite-semiconductor structure near gyrotropic-nihility state

    International Nuclear Information System (INIS)

    Tuz, Vladimir R.

    2016-01-01

    In the context of polaritons in a ferrite-semiconductor structure which is influenced by an external static magnetic field, the gyrotropic-nihility can be identified from the dispersion equation related to bulk polaritons as a particular extreme state, at which the longitudinal component of the corresponding constitutive tensor and bulk constant simultaneously acquire zero. Near the frequency of the gyrotropic-nihility state, the conditions of branches merging of bulk polaritons, as well as an anomalous dispersion of bulk and surface polaritons are found and discussed. - Highlights: • Gyrotropic-nihility state is identified from the dispersion equation related to bulk polaritons in a magnetic-semiconductor superlattice. • The conditions of branches merging of bulk polaritons are found. • An anomalous dispersion of bulk and surface polaritons is found and discussed.

  2. Polaritons dispersion in a composite ferrite-semiconductor structure near gyrotropic-nihility state

    Energy Technology Data Exchange (ETDEWEB)

    Tuz, Vladimir R., E-mail: tvr@rian.kharkov.ua

    2016-12-01

    In the context of polaritons in a ferrite-semiconductor structure which is influenced by an external static magnetic field, the gyrotropic-nihility can be identified from the dispersion equation related to bulk polaritons as a particular extreme state, at which the longitudinal component of the corresponding constitutive tensor and bulk constant simultaneously acquire zero. Near the frequency of the gyrotropic-nihility state, the conditions of branches merging of bulk polaritons, as well as an anomalous dispersion of bulk and surface polaritons are found and discussed. - Highlights: • Gyrotropic-nihility state is identified from the dispersion equation related to bulk polaritons in a magnetic-semiconductor superlattice. • The conditions of branches merging of bulk polaritons are found. • An anomalous dispersion of bulk and surface polaritons is found and discussed.

  3. Influence of chemical composition of CoFeB on tunneling magnetoresistance and microstructure in polycrystalline CoFeB/MgO/CoFeB magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Tsunekawa, Koji; Choi, Young-Suk; Nagamine, Yoshinori; Djayaprawira, David D.; Takeuchi, Takashi; Kitamoto, Yoshitaka

    2006-01-01

    We report, for the first time, the correlation between tunneling magnetoresistance (TMR) and the microstructure of polycrystalline CoFeB/MgO/CoFeB magnetic tunnel junctions with various Co/Fe ratios in the (CoFe) 81 B 19 reference and free layers. It is found that the Co/Fe ratio in the (CoFe) 81 B 19 reference layer strongly affects the (001) out-of-plane texture of the MgO tunnel barrier, resulting in the variation in TMR ratio. Further microstructure characterization of the magnetic tunnel junction with a higher TMR ratio and a stronger (001) out-of-plane texture in the MgO tunnel barrier reveals a grain-to-grain lattice match between the crystallized bcc CoFeB reference layer and MgO with a 45deg rotational epitaxial relationship, that is, CoFeB(001)[110]//MgO(001)[100]. (author)

  4. Uniaxially oriented polycrystalline thin films and air-stable n-type transistors based on donor-acceptor semiconductor (diC8BTBT)(FnTCNQ) [n = 0, 2, 4

    Science.gov (United States)

    Shibata, Yosei; Tsutsumi, Jun'ya; Matsuoka, Satoshi; Matsubara, Koji; Yoshida, Yuji; Chikamatsu, Masayuki; Hasegawa, Tatsuo

    2015-04-01

    We report the fabrication of high quality thin films for semiconducting organic donor-acceptor charge-transfer (CT) compounds, (diC8BTBT)(FnTCNQ) (diC8BTBT = 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene and FnTCNQ [n = 0,2,4] = fluorinated derivatives of 7,7,8,8,-tetracyanoquinodimethane), which have a high degree of layered crystallinity. Single-phase and uniaxially oriented polycrystalline thin films of the compounds were obtained by co-evaporation of the component donor and acceptor molecules. Organic thin-film transistors (OTFTs) fabricated with the compound films exhibited n-type field-effect characteristics, showing a mobility of 6.9 × 10-2 cm2/V s, an on/off ratio of 106, a sub-threshold swing of 0.8 V/dec, and an excellent stability in air. We discuss the suitability of strong intermolecular donor-acceptor interaction and the narrow CT gap nature in compounds for stable n-type OTFT operation.

  5. Polycrystalline diamond film UV detectors for excimer lasers

    International Nuclear Information System (INIS)

    Ralchenko, V G; Savel'ev, A V; Konov, Vitalii I; Mazzeo, G; Spaziani, F; Conte, G; Polyakov, V I

    2006-01-01

    Photoresistive metal-semiconductor-metal detectors based on polycrystalline diamond films are fabricated for recording cw and pulsed UV radiation. The detectors have a high spectral selectivity (the UV-to-VIS response ratio is ∼10 5 ) and a temporal resolution of the order of 10 9 s. 'Solar-blind' photostable diamond detectors are promising for applications in UV lithography, laser micromachining, medicine, and space research. (letters)

  6. Gyrotropic-nihility state in a composite ferrite-semiconductor structure

    International Nuclear Information System (INIS)

    Tuz, Vladimir R

    2015-01-01

    Characteristics of the gyrotropic-nihility state are studied in a finely-stratified ferrite-semiconductor structure, which is under an action of an external static magnetic field. Investigations are carried out with the assistance of the effective medium theory, according to which the studied structure is approximated as a uniform gyroelectromagnetic medium. The theory of the gyrotropic-nihility state is developed in terms of the eigenwaves propagation in such gyroelectromagnetic medium. The frequency and angular dependencies of the transmittance, reflectance and absorption coefficient are presented. It turns out that in the frequency band around the frequency of gyrotropic-nihility state the studied structure appears to be matched to free space with both the refractive index and the wave impedance which results in its high transmittance almost in the entire range of angles of the electromagnetic wave incidence. (paper)

  7. Interface Schottky barrier engineering via strain in metal-semiconductor composites

    Science.gov (United States)

    Ma, Xiangchao; Dai, Ying; Yu, Lin; Huang, Baibiao

    2016-01-01

    The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation demonstrates that strain can be an effective way to decrease the interface SBH and that the n-type SBH can be more effectively decreased than the p-type SBH. Astonishingly, strain affects the interface SBH mainly by changing the intrinsic properties of Au and TiO2, whereas the interfacial potential alignment is almost independent of strain due to two opposite effects, which are induced by strain at the interfacial region. These observed trends can be understood on the basis of the general free-electron gas model of typical metals, the tight-binding theory and the crystal-field theory, which suggest that similar trends may be generalized for many other metal-semiconductor heterostructures. Given the commonness and tunability of strain in typical heterostructures, we anticipate that the tunability of the interface SBH with strain described here can provide an alternative effective way for realizing more efficient applications of relevant heterostructures.The interfacial carrier transfer property, which is dominated by the interface Schottky barrier height (SBH), plays a crucial role in determining the performance of metal-semiconductor heterostructures in a variety of applications. Therefore, artificially controlling the interface SBH is of great importance for their industrial applications. As a model system, the Au/TiO2 (001) heterostructure is studied using first-principles calculations and the tight-binding method in the present study. Our investigation

  8. Silver-containing polymer composition used in spacecraft and semiconductor optoelectronics control systems

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, A. A., E-mail: alexchemtsu@rambler.ru; Tuev, V. I., E-mail: tvi-retem@main.tusur.ru [Tomsk State University of Control Systems and Radioelectronics, Tomsk, 634050 (Russian Federation)

    2015-10-27

    The copolymer of the vinyl chloride-maleic anhydride and silver nano- and microparticle (70 wt %) composition is offered as a conductive adhesive for fixing various chips on the dielectric substrate. The wiring volume resistivity is up to 3.1×10{sup −8} Ohm×m. The adhesive strength of the silver-containing polymer composition (70% of Ag) applied under a shear on the dielectric substrate is 106 N/mm{sup 2}. Adhesive layers obtained from these substances have a high thermal conductivity up to λ = 199.93 W/m×K that depends on the amount of Ag in the polymer composition.

  9. Hybrid composites of monodisperse pi-conjugated rodlike organic compounds and semiconductor quantum particles

    DEFF Research Database (Denmark)

    Hensel, V.; Godt, A.; Popovitz-Biro, R.

    2002-01-01

    Composite materials of quantum particles (Q-particles) arranged in layers within crystalline powders of pi-conjugated, rodlike dicarboxylic acids are reported. The synthesis of the composites, either as three-dimensional crystals or as thin films at the air-water interface, comprises a two...... analysis of the solids and grazing incidence X-ray diffraction analysis of the films on water. 2) Topotactic solid/gas reaction of these salts with H2S to convert the metal ions into Q-particles of CdS or PbS embedded in the organic matrix that consists of the acids 6(H) and 8(H). These hybrid materials...

  10. Composition influence on positron annihilation parameters in ZnO-based nanocrystal semiconductor powders

    Energy Technology Data Exchange (ETDEWEB)

    Damonte, L.C.; Hernandez Fenollosa, M.A.; Donderis, V.; Mari, B. [Departamento de Fisica Aplicada, Universidad Politecnica de Valencia, Cami de Vera s/n, Valencia, 46071 (Spain)

    2007-07-01

    Zn{sub 1-x}Mg{sub x}O powders at various compositions were obtained by mechanical milling from the binary oxides. The progressive incorporation of Mg atoms into the ZnO lattice was monitored by X-ray diffraction (XRD). The evolution of annihilation parameters with milling time and composition were analyzed and related to the possible types of mechanical and substitutional induced defect present. It was concluded that the average lifetime constitute a useful parameter to sense the complete cation substitution in the wurtzite structure. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Composition influence on positron annihilation parameters in ZnO-based nanocrystal semiconductor powders

    International Nuclear Information System (INIS)

    Damonte, L.C.; Hernandez Fenollosa, M.A.; Donderis, V.; Mari, B.

    2007-01-01

    Zn 1-x Mg x O powders at various compositions were obtained by mechanical milling from the binary oxides. The progressive incorporation of Mg atoms into the ZnO lattice was monitored by X-ray diffraction (XRD). The evolution of annihilation parameters with milling time and composition were analyzed and related to the possible types of mechanical and substitutional induced defect present. It was concluded that the average lifetime constitute a useful parameter to sense the complete cation substitution in the wurtzite structure. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. Evaluation of structural and optical properties of Ce3+ ions doped (PVA/PVP) composite films for new organic semiconductors

    Science.gov (United States)

    Ali, F. M.; Kershi, R. M.; Sayed, M. A.; AbouDeif, Y. M.

    2018-06-01

    Polymer blend films based on Polyvinyl alcohol (PVA)/Poly(vinylpyrrolidone) (PVP) doped with different concentration of cerium ions [(PVA/PVP)-x wt.% Ce3+] (x = 3%, 5%, 10% and 15%) were prepared by the conventional solution casting technique. The characteristics of the prepared polymer composite films were studied using X-ray diffraction (XRD), FT-IR and UV-Vis. spectroscopy. The XRD patterns of the investigated samples revealed a clear reduction on the structural parameters such as crystallinity degree and cluster size D of the doped PVA/PVP blend films compared with the virgin one whereas there is no big difference in the d spacing of the product composite films. Significant changes in FT-IR spectra are observed which reveal an interactions between the cerium ions and PVA/PVP blends. The absorption spectra in the ultraviolet-visible region showed a wide red shift in the fundamental absorption edge of (PVA/PVP)-x wt. % Ce3+ composites. The optical gap Eg gradually decreased from 4.54 eV for the undoped PVA/PVP film to 3.10 eV by increasing Ce3+ ions content. The optical dispersion parameters have been analyzed according to Wemple-Didomenico single oscillator model. The dispersion energy Ed, the single oscillator energy Eo, the average inter-band oscillator wavelength λo and the static refractive index no are strongly affected by cerium ions doping. Cerium ions incorporation in PVA/PVP blend films leads to a significant increase in the refractive index and decrease in the optical gap. These results are likely of great important in varieties of applications including polymer waveguides, organic semiconductors, polymer solar cells and optoelectronics devices.

  13. Characterization of semiconductor and frontier materials by nuclear microprobe technology

    International Nuclear Information System (INIS)

    Zhu Jieqing; Li Xiaolin; Yang Changyi; Lu Rongrong; Wang Jiqing; Guo Panlin

    2002-01-01

    The nuclear microprobe technology is used to characterize the properties of semiconductor and other frontier materials at the stages of their synthesis, modification, integration and application. On the basis of the beam current being used, the analytical nuclear microprobe techniques being used in this project can be divided into two categories: high beam current (PIXE, RBS, PEB) or low beam current (IBIC, STIM) techniques. The material properties measured are the thickness and composition of a composite surface on a SiC ceramic, the sputtering-induced surface segregation and depth profile change in a Ag-Cu binary alloy, the irradiation effects on the CCE of CVD diamond, the CCE profile at a polycrystalline CVD diamond film and a GaAs diode at different voltage biases and finally, the characterization of individual sample on an integrated material chip. (author)

  14. Application of polycrystalline diffusion barriers

    International Nuclear Information System (INIS)

    Tsymbal, V.A.; Kolupaev, I.N.

    2010-01-01

    Degradation of contacts of the electronic equipment at the raised temperatures is connected with active diffusion redistribution of components contact - metalized systems (CMS) and phase production on interphase borders. One of systems diffusion barriers (DB) are polycrystalline silicide a film, in particular silicides of the titan. Reception disilicide the titan (TiSi 2 ) which on the parameters is demanded for conditions of microelectronics from known silicides of system Ti-Si, is possible as a result of direct reaction of a film of the titan and a substrate of silicon, and at sedimentation of layer Ti-Si demanded stoichiometric structure. Simultaneously there is specific problem polycrystalline diffusion a barrier (PDB): the polycrystalline provides structural balance and metastability film disilicide, but leaves in it borders of grains - easy local ways of diffusion. In clause the analysis diffusion permeability polycrystalline and polyphase DB is made and recommendations for practical methods of increase of blocking properties PDB are made.

  15. Compound Semiconductor Radiation Detector

    International Nuclear Information System (INIS)

    Kim, Y. K.; Park, S. H.; Lee, W. G.; Ha, J. H.

    2005-01-01

    In 1945, Van Heerden measured α, β and γ radiations with the cooled AgCl crystal. It was the first radiation measurement using the compound semiconductor detector. Since then the compound semiconductor has been extensively studied as radiation detector. Generally the radiation detector can be divided into the gas detector, the scintillator and the semiconductor detector. The semiconductor detector has good points comparing to other radiation detectors. Since the density of the semiconductor detector is higher than that of the gas detector, the semiconductor detector can be made with the compact size to measure the high energy radiation. In the scintillator, the radiation is measured with the two-step process. That is, the radiation is converted into the photons, which are changed into electrons by a photo-detector, inside the scintillator. However in the semiconductor radiation detector, the radiation is measured only with the one-step process. The electron-hole pairs are generated from the radiation interaction inside the semiconductor detector, and these electrons and charged ions are directly collected to get the signal. The energy resolution of the semiconductor detector is generally better than that of the scintillator. At present, the commonly used semiconductors as the radiation detector are Si and Ge. However, these semiconductor detectors have weak points. That is, one needs thick material to measure the high energy radiation because of the relatively low atomic number of the composite material. In Ge case, the dark current of the detector is large at room temperature because of the small band-gap energy. Recently the compound semiconductor detectors have been extensively studied to overcome these problems. In this paper, we will briefly summarize the recent research topics about the compound semiconductor detector. We will introduce the research activities of our group, too

  16. Direct femtosecond observation of charge carrier recombination in ternary semiconductor nanocrystals: The effect of composition and shelling

    KAUST Repository

    Bose, Riya

    2015-02-12

    Heavy-metal free ternary semiconductor nanocrystals are emerging as key materials in photoactive applications. However, the relative abundance of intra-bandgap defect states and lack of understanding of their origins within this class of nanocrystals are major factors limiting their applicability. To remove these undesirable defect states which considerably shorten the lifetimes of photogenerated excited carriers, a detailed understanding about their origin and nature is required. In this report, we monitor the ultrafast charge carrier dynamics of CuInS2 (CIS), CuInSSe (CISSe), and CuInSe2 (CISe) nanocrystals, before and after ZnS shelling, using state-of-the-art time-resolved laser spectroscopy with broadband capabilities. The experimental results demonstrate the presence of both electron and hole trapping intra-bandgap states in the nanocrystals which can be removed significantly by ZnS shelling, and the carrier dynamics is slowed down. Another important observation remains the reduction of carrier lifetime in the presence of Se, and the shelling strategy is observed to be less effective at suppressing trap states. This study provides quantitative physical insights into the role of anion composition and shelling on the charge carrier dynamics in ternary CIS, CISSe, and CISe nanocrystals which are essential to improve their applicability for photovoltaics and optoelectronics.

  17. Combinatorial Discovery and Optimization of the Composition, Doping and Morphology of New Oxide Semiconductors for Efficient Photoelectrochemical Water Splitting

    Energy Technology Data Exchange (ETDEWEB)

    Parkinson, Bruce A. [Univ. of Wyoming, Laramie, WY (United States); Jianghua, He [Univ. of Wyoming, Laramie, WY (United States)

    2015-01-06

    The increasing need for carbon free energy has focused renewed attention on solar energy conversion. Although photovoltaic cells excel at directly converting of solar energy to electricity, they do not directly produce stored energy or fuels that account for more than 75% of current energy use. Direct photoelectrolysis of water has the advantage of converting solar energy directly to hydrogen, an ideal non-carbon and nonpolluting energy carrier, by replacing both a photovoltaic array and an electrolysis unit with one potentially inexpensive device. Unfortunately no materials are currently known to efficiently photoelectrolyze water that are, efficient, inexpensive and stable under illumination in electrolytes for many years. Nanostructured semiconducting metal oxides could potentially fulfill these requirements, making them the most promising materials for solar water photoelectrolysis, however no oxide semiconductor has yet been discovered with all the required properties. We have developed a simple, high-throughput combinatorial approach to prepare and screen many multi component metal oxides for water photoelectrolysis activity. The approach uses ink jet printing of overlapping patterns of soluble metal oxide precursors onto conductive glass substrates. Subsequent pyrolysis produces metal oxide phases that are screened for photoelectrolysis activity by measuring photocurrents produced by scanning a laser over the printed patterns in aqueous electrolytes. Several promising and unexpected compositions have been identified.

  18. Ultra-broadband and wide-angle perfect absorber based on composite metal-semiconductor grating

    Science.gov (United States)

    Li, Xu; Wang, Zongpeng; Hou, Yumin

    2018-01-01

    In this letter, we present an ultra-broadband and wide-angle perfect absorber based on composite Ge-Ni grating. Near perfect absorption above 90% is achieved in a wide frequency range from 150 nm to 4200 nm, which covers almost the full spectrum of solar radiation. The absorption keeps robust in a wide range of incident angle from 0º to 60º. The upper triangle Ge grating works as an antireflection coating. The lower Ni grating works as a reflector and an effective energy trapper. The guided modes inside Ge grating are excited due to reflection of the lower Ni grating surface. In longer wavelength band, gap surface plasmons (GSPs) in the Ni grating are excited and couple with the guided modes inside the Ge grating. The coupled modes extend the perfect absorption band to the near-infrared region (150 nm-4200 nm). This design has potential application in photovoltaic devices and thermal emitters.

  19. Composite metal oxide semiconductor based photodiodes for solar panel tracking applications

    Energy Technology Data Exchange (ETDEWEB)

    Al-Ghamdi, Ahmed A., E-mail: aghamdi90@hotmail.com [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Dere, A. [Department of Physics, Faculty of Science, Firat University, Elazig (Turkey); Tataroğlu, A. [Department of Physics, Faculty of Science, Gazi University, Ankara (Turkey); Arif, Bilal [Department of Physics, Faculty of Science, Firat University, Elazig (Turkey); Yakuphanoglu, F. [Department of Physics, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); Department of Physics, Faculty of Science, Firat University, Elazig (Turkey); El-Tantawy, Farid [Department of Physics, Faculty of Science, Suez Canal University, Ismailia (Egypt); Farooq, W.A. [Physics and Astronomy Department, College of Science, King Saud University, Riyadh (Saudi Arabia)

    2015-11-25

    The Zn{sub 1−x}Al{sub x}O:Cu{sub 2}O composite films were synthesized by the sol gel method to fabricate photodiodes. The transparent metal oxide Zn{sub 1−x}Al{sub x}O:Cu{sub 2}O thin films were grown on p-Si substrates by spin coating technique. Electrical characterization of the p-Si/AZO:Cu{sub 2}O photodiodes was performed by current–voltage and capacitance–conductance–voltage characteristics under dark and various illumination conditions. The transient photocurrent of the diodes increases with increase in illumination intensity. The photoconducting mechanism of the diodes is controlled by the continuous distribution of trap levels. The photocapacitance and photoconductivity of the diodes are decreased with increasing Cu{sub 2}O content. The series resistance–voltage behavior confirms the presence of the interface states in the interface of the diodes. The photoresponse properties of the diodes indicate that the p-Si/Zn{sub 1−x}Al{sub x}O–Cu{sub 2}O diodes can be used as a photosensor in solar panel tracking applications. - Highlights: • Zn{sub 1−x}Al{sub x}O:Cu{sub 2}O composite films were synthesized by the sol gel method. • p-Si/Zn{sub 1−x}Al{sub x}O–Cu{sub 2}O diodes were fabricated. • p-Si/Zn{sub 1−x}Al{sub x}O–Cu{sub 2}O diodes can be used in the optoelectronic applications.

  20. Gelcasting polycrystalline alumina

    Energy Technology Data Exchange (ETDEWEB)

    Janney, M.A. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    This work is being done as part of a CRADA with Osram-Sylvania, Inc. (OSI) OSI is a major U.S. manufacturer of high-intensity lighting. Among its products is the Lumalux{reg_sign} line of high-pressure sodium vapor arc lamps, which are used for industrial, highway, and street lighting. The key to the performance of these lamps is the polycrystalline alumina (PCA) tube that is used to contain the plasma that is formed in the electric arc. That plasma consists of ionized sodium, mercury, and xenon vapors. The key attributes of the PCA tubes are their transparency (95% total transmittance in the visible region), their refractoriness (inner wall temperature can reach 1400{degrees}C), and their chemical resistance (sodium and mercury vapor are extremely corrosive). The current efficiency of the lamps is very high, on the order of several hundred lumens / watt. (Compare - incandescent lamps -13 lumens/watt fluorescent lamps -30 lumens/watt.) Osram-Sylvania would like to explore using gelcasting to form PCA tubes for Lumalux{reg_sign} lamps, and eventually for metal halide lamps (known as quartz-halogen lamps). Osram-Sylvania, Inc. currently manufactures PCA tubes by isostatic pressing. This process works well for the shapes that they presently use. However, there are several types of tubes that are either difficult or impossible to make by isostatic pressing. It is the desire to make these new shapes and sizes of tubes that has prompted Osram-Sylvania`s interest in gelcasting. The purpose of the CRADA is to determine the feasibility of making PCA items having sufficient optical quality that they are useful in lighting applications using gelcasting.

  1. Direct femtosecond observation of charge carrier recombination in ternary semiconductor nanocrystals: The effect of composition and shelling

    KAUST Repository

    Bose, Riya; Ahmed, Ghada H.; Alarousu, Erkki; Parida, Manas R.; Abdelhady, Ahmed L.; Bakr, Osman; Mohammed, Omar F.

    2015-01-01

    Heavy-metal free ternary semiconductor nanocrystals are emerging as key materials in photoactive applications. However, the relative abundance of intra-bandgap defect states and lack of understanding of their origins within this class

  2. High-pressure-assisted synthesis of high-volume ZnGeP2 polycrystalline

    Science.gov (United States)

    Huang, Changbao; Wu, Haixin; Xiao, Ruichun; Chen, Shijing; Ma, Jiaren

    2018-06-01

    The pnictide and chalcogenide semiconductors are promising materials for the applications in the field of photoelectric. High-purity and high-volume polycrystalline required in the real-world applications is hard to be synthesized due to the high vapor pressure of phosphorus and sulfur components at high temperature. A new high-pressure-resisted method was used to investigate the synthesis of the nonlinear-optical semiconductor ZnGeP2. The high-purity ZnGeP2 polycrystalline material of approximately 500 g was synthesized in one run, which enables the preparation of nominally stoichiometric material. Since increasing internal pressure resistance of quartz crucible and reducing the reaction space, the high-pressure-resisted method can be used to rapidly synthesize other pnictide and chalcogenide semiconductors and control the components ratio.

  3. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1987-01-01

    In-depth exploration of the implications of carrier populations and Fermi energies examines distribution of electrons in energy bands and impurity levels of semiconductors. Also: kinetics of semiconductors containing excess carriers, particularly in terms of trapping, excitation, and recombination.

  4. Semiconductor physics

    CERN Document Server

    Böer, Karl W

    2018-01-01

    This handbook gives a complete survey of the important topics and results in semiconductor physics. It addresses every fundamental principle and most research topics and areas of application in the field of semiconductor physics. Comprehensive information is provided on crystalline bulk and low-dimensional as well as amporphous semiconductors, including optical, transport, and dynamic properties.

  5. A unique metal-semiconductor interface and resultant electron transfer phenomenon

    OpenAIRE

    Taft, S. L.

    2012-01-01

    An unusual electron transfer phenomenon has been identified from an n-type semiconductor to Schottky metal particles, the result of a unique metal semiconductor interface that results when the metal particles are grown from the semiconductor substrate. The unique interface acts as a one-way (rectifying) open gateway and was first identified in reduced rutile polycrystalline titanium dioxide (an n-type semiconductor) to Group VIII (noble) metal particles. The interface significantly affects th...

  6. Polycrystalline thin films : A review

    Energy Technology Data Exchange (ETDEWEB)

    Valvoda, V [Charles Univ., Prague (Czech Republic). Faculty of Mathematics and Physics

    1996-09-01

    Polycrystalline thin films can be described in terms of grain morphology and in terms of their packing by the Thornton`s zone model as a function of temperature of deposition and as a function of energy of deposited atoms. Grain size and preferred grain orientation (texture) can be determined by X-ray diffraction (XRD) methods. A review of XRD analytical methods of texture analysis is given with main attention paid to simple empirical functions used for texture description and for structure analysis by joint texture refinement. To illustrate the methods of detailed structure analysis of thin polycrystalline films, examples of multilayers are used with the aim to show experiments and data evaluation to determine layer thickness, periodicity, interface roughness, lattice spacing, strain and the size of diffraction coherent volumes. The methods of low angle and high angle XRD are described and discussed with respect to their complementary information content.

  7. Diffraction by disordered polycrystalline fibers

    International Nuclear Information System (INIS)

    Stroud, W.J.; Millane, R.P.

    1995-01-01

    X-ray diffraction patterns from some polycrystalline fibers show that the constituent microcrystallites are disordered. The relationship between the crystal structure and the diffracted intensities is then quite complicated and depends on the precise kind and degree of disorder present. The effects of disorder on diffracted intensities must be included in structure determinations using diffraction data from such specimens. Theory and algorithms are developed here that allow the full diffraction pattern to be calculated for a disordered polycrystalline fiber made up of helical molecules. The model accommodates various kinds of disorder and includes the effects of finite crystallite size and cylindrical averaging of the diffracted intensities from a fiber. Simulations using these methods show how different kinds, or components, of disorder produce particular diffraction effects. General properties of disordered arrays of helical molecules and their effects on diffraction patterns are described. Implications for structure determination are discussed. (orig.)

  8. Magnetostrictive properties of polycrystalline iron cobalt films

    International Nuclear Information System (INIS)

    Cooke, M.D.

    2000-10-01

    This thesis is concerned with the magnetic properties of magnetostrictive FeCo polycrystalline alloy films produced by RF magnetron sputter deposition. The bulk material is known to have highly magnetostrictive properties, coupled with the possibility of a low anisotropy with the correct thermal treatment to allow ordering. Significant reduction in the anisotropy was found by using post depostional thermal treatment in Ar/H. It has been demonstrated that it is possible to produce FeCo films with magnetostrictive properties similar to those found in the bulk. Detailed examination showed an increased peak in the magnetostriction with composition which had not been previously viewed in the bulk materials. Initial development was also made of a novel co-depositional technique to allow magnetostrictive determination as a function of composition in a single deposition. Development was made of a technique using the Daresbury Synchrotron research facility and the XRD equipment to allow determination of the magnetostriction coefficients of polycrystalline films. This is the first time this has been achieved for thin film materials and provides exciting new possibilities for the future. A critique was made of the optical cantilever technique for determining magnetostriction. Clear consideration has to be made of rotational and frequency effects. A new analytical theory was devised which allowing determination of the cantilever deflection for similar substrate and film thickness. This is essential for development of current trends in nanotechnology. The results were then optimised for use in sensor and actuator devices providing novel results. Finally investigation was made of the possible effects of surfaces on the magnetic properties. The magnetostriction of FeCo/Ag multilayers and Ag embedded in an FeCo matrix are compared. These clearly show the influence of surface and illustrate the importance of considering the technique used to determine the magnetostriction. (author)

  9. IMPEDANCE SPECTROSCOPY OF POLYCRYSTALLINE TIN DIOXIDE FILMS

    Directory of Open Access Journals (Sweden)

    D. V. Adamchuck

    2016-01-01

    Full Text Available The aim of this work is the analysis of the influence of annealing in an inert atmosphere on the electrical properties and structure of non-stoichiometric tin dioxide films by means of impedance spectroscopy method. Non-stoichiometric tin dioxide films were fabricated by two-step oxidation of metallic tin deposited on the polycrystalline Al2O3 substrates by DC magnetron sputtering. In order to modify the structure and stoichiometric composition, the films were subjected to the high temperature annealing in argon atmosphere in temperature range 300–800 °С. AC-conductivity measurements of the films in the frequency range 20 Hz – 2 MHz were carried out. Variation in the frequency dependencies of the real and imaginary parts of the impedance of tin dioxide films was found to occur as a result of high-temperature annealing. Equivalent circuits for describing the properties of films with various structure and stoichiometric composition were proposed. Possibility of conductivity variation of the polycrystalline tin dioxide films as a result of аnnealing in an inert atmosphere was demonstrated by utilizing impedance spectroscopy. Annealing induces the recrystallization of the films, changing in their stoichiometry as well as increase of the sizes of SnO2 crystallites. Variation of electrical conductivity and structure of tin dioxide films as a result of annealing in inert atmosphere was confirmed by X-ray diffraction analysis. Analysis of the impedance diagrams of tin dioxide films was found to be a powerful tool to study their electrical properties. 

  10. Semiconductor Manufacturing equipment introduction

    International Nuclear Information System (INIS)

    Im, Jong Sun

    2001-02-01

    This book deals with semiconductor manufacturing equipment. It is comprised of nine chapters, which are manufacturing process of semiconductor device, history of semiconductor manufacturing equipment, kinds and role of semiconductor manufacturing equipment, construction and method of semiconductor manufacturing equipment, introduction of various semiconductor manufacturing equipment, spots of semiconductor manufacturing, technical elements of semiconductor manufacturing equipment, road map of technology of semiconductor manufacturing equipment and semiconductor manufacturing equipment in the 21st century.

  11. Acoustic emission from polycrystalline graphites

    International Nuclear Information System (INIS)

    Ioka, I.; Yoda, S.; Oku, T.; Miyamoto, Y.

    1987-01-01

    Acoustic emission was monitored from polycrystalline graphites with different microstructure (pore size and pore volume) subjected to compressive loading. The graphites used in this study comprised five brands, that is, PGX, ISEM-1, IG-11, IG-15, and ISO-88. A root mean square (RMS) voltage and event counts of acoustic emission for graphites were measured during compressive loading. The acoustic emission was measured using a computed-based data acquisition and analysis system. The graphites were first deformed up to 80 % of the average fracture stress, then unloaded and reloaded again until the fracture occured. During the first loading, the change in RMS voltage for acoustic emission was detected from the initial stage. During the unloading, the RMS voltage became zero level as soon as the applied stress was released and then gradually rose to a peak and declined. The behavior indicated that the reversed plastic deformation occured in graphites. During the second loading, the RMS voltage gently increased until the applied stress exceeded the maximum stress of the first loading; there is no Kaiser effect in the graphites. A bicrystal model could give a reasonable explanation of this results. The empirical equation between the ratio of σ AE to σ f and σ f was obtained. It is considered that the detection of microfracture by the acoustic emission technique is effective in macrofracture prediction of polycrystalline graphites. (author)

  12. Semiconductor spintronics

    CERN Document Server

    Xia, Jianbai; Chang, Kai

    2012-01-01

    Semiconductor Spintronics, as an emerging research discipline and an important advanced field in physics, has developed quickly and obtained fruitful results in recent decades. This volume is the first monograph summarizing the physical foundation and the experimental results obtained in this field. With the culmination of the authors' extensive working experiences, this book presents the developing history of semiconductor spintronics, its basic concepts and theories, experimental results, and the prospected future development. This unique book intends to provide a systematic and modern foundation for semiconductor spintronics aimed at researchers, professors, post-doctorates, and graduate students, and to help them master the overall knowledge of spintronics.

  13. Metal/oxide/semiconductor interface investigated by monoenergetic positrons

    Science.gov (United States)

    Uedono, A.; Tanigawa, S.; Ohji, Y.

    1988-10-01

    Variable-energy positron-beam studies have been carried out for the first time on a metal/oxide/semiconductor (MOS) structure of polycrystalline Si/SiO 2/Si-substrate. We were successful in collecting injected positrons at the SiO 2/Si interface by the application of an electric field between the MOS electrodes.

  14. Process Research on Polycrystalline Silicon Material (PROPSM)

    Science.gov (United States)

    Culik, J. S.; Wrigley, C. Y.

    1985-01-01

    Results of hydrogen-passivated polycrysalline silicon solar cell research are summarized. The short-circuit current of solar cells fabricated from large-grain cast polycrystalline silicon is nearly equivalent to that of single-crystal cells, which indicates long bulk minority-carrier diffusion length. Treatments with molecular hydrogen showed no effect on large-grain cast polycrystalline silicon solar cells.

  15. Scattering amplitudes and static atomic correction factors for the composition-sensitive 002 reflection in sphalerite ternary III-V and II-VI semiconductors.

    Science.gov (United States)

    Schowalter, M; Müller, K; Rosenauer, A

    2012-01-01

    Modified atomic scattering amplitudes (MASAs), taking into account the redistribution of charge due to bonds, and the respective correction factors considering the effect of static atomic displacements were computed for the chemically sensitive 002 reflection for ternary III-V and II-VI semiconductors. MASAs were derived from computations within the density functional theory formalism. Binary eight-atom unit cells were strained according to each strain state s (thin, intermediate, thick and fully relaxed electron microscopic specimen) and each concentration (x = 0, …, 1 in 0.01 steps), where the lattice parameters for composition x in strain state s were calculated using continuum elasticity theory. The concentration dependence was derived by computing MASAs for each of these binary cells. Correction factors for static atomic displacements were computed from relaxed atom positions by generating 50 × 50 × 50 supercells using the lattice parameter of the eight-atom unit cells. Atoms were randomly distributed according to the required composition. Polynomials were fitted to the composition dependence of the MASAs and the correction factors for the different strain states. Fit parameters are given in the paper.

  16. Zero and low coefficient of thermal expansion polycrystalline oxides

    International Nuclear Information System (INIS)

    Skaggs, S.R.

    1977-09-01

    Polycrystalline oxide systems with zero to low coefficient of thermal expansion (CTE) investigated by the author include hafnia-titania and hafnia. The CTE for 30 to 40 mol% TiO 2 in HfO 2 is less than or equal to 1 x 10 -6 / 0 C, while for other compositions in the range 25 to 60 mol% it is approximately 4 x 10 -6 / 0 C. An investigation of the CTE of 99.999% HfO 2 yielded a value of 4.6 x 10 -6 / 0 C from room temperature to 1000 0 C. Correlation with data on HfO 2 by other investigators shows a definite relationship between the CTE and the amount of ZrO 2 present. Data are listed for comparison of the CTE of several other polycrystalline oxides investigated by Holcombe at Oak Ridge

  17. Zero and low coefficient of thermal expansion polycrystalline oxides

    International Nuclear Information System (INIS)

    Skaggs, S.R.

    1977-01-01

    Polycrystalline oxide systems with zero to low coefficient of thermal expansion (CTE) investigated by the author include hafnia-titania and hafnia. The CTE for 30 to 40 mol percent TiO 2 in HfO 2 is less than or equal to 1 x 10 -6 / 0 C, while for other compositions in the range 25 to 60 mol percent approximately 4 x 10 -6 / 0 C. An investigation of the CTE of 99.999 percent HfO 2 yielded a value of 4.6 x 10 -6 / 0 C from room temperature to 1000 0 C. Correlation with data on HfO 2 by other investigators shows a definite relationship between the CTE and the amount of ZrO 2 present. Data are listed for comparison of the CTE of several other polycrystalline oxides investigated by Holcombe at Oak Ridge

  18. Semiconductor spintronics

    International Nuclear Information System (INIS)

    Fabian, J.; Abiague, A.M.; Ertler, Ch.; Stano, P.; Zutic, I.

    2007-01-01

    Spintronics refers commonly to phenomena in which the spin of electrons in a solid state environment plays the determining role. In a more narrow sense spintronics is an emerging research field of electronics: spintronics devices are based on a spin control of electronics, or on an electrical and optical control of spin of magnetism. While metal spintronics has already found its niche in the computer industry - giant magnetoresistance systems are used as hard disk read heads - semiconductor spintronics is vet demonstrate its full potential. This review presents selected themes of semiconductor spintronics, introducing important concepts in spin transport, spin transport, spin injection. Silsbee-Johnson spin-charge coupling, and spin-dependent tunneling, as well as spin relaxation and spin dynamics. The most fundamental spin-dependent interaction in nonmagnetic semiconductors is spin-orbit coupling. Depending on the crystal symmetries of the material, as well as on the structural properties of semiconductor based heterostructures, the spin-orbit coupling takes on different functional forms, giving a nice playground of effective spin-orbit Hamiltonians. The effective Hamiltonians for the most relevant classes of materials and heterostructures are derived here from realistic electronic band structure descriptions. Most semiconductor device systems are still theoretical concepts, waiting for experimental demonstrations. A review of selected proposed, and a few demonstrated devices is presented, with detailed description of two important classes: magnetic resonant tunnel structures and bipolar magnetic diodes and transistors. In view of the importance of ferromagnetic semiconductor material, a brief discussion of diluted magnetic semiconductors is included. In most cases the presentation is of tutorial style, introducing the essential theoretical formalism at an accessible level, with case-study-like illustrations of actual experimental results, as well as with brief

  19. An investigation of impurity centers in semiconductors of variable composition. Part 1: General theory and some applications

    Science.gov (United States)

    Vonroos, O. H.

    1982-01-01

    A theory of deep point defects imbedded in otherwise perfect semiconductor crystals is developed with the aid of pseudopotentials. The dominant short-range forces engendered by the impurity are sufficiently weakened in all cases where the cancellation theorem of the pseudopotential formalism is operative. Thus, effective-mass-like equations exhibiting local effective potentials derived from nonlocal pseudopotentials are shown to be valid for a large class of defects. A two-band secular determinant for the energy eigenvalues of deep defects is also derived from the set of integral equations which corresponds to the set of differential equations of the effective-mass type. Subsequently, the theory in its simplest form, is applied to the system Al(x)Ga(1-x)As:Se. It is shown that the one-electron donor level of Se within the forbidden gap of Al(x)Ga(1-x)As as a function of the AlAs mole fraction x reaches its maximum of about 300 meV (as measured from the conduction band edge) at the cross-over from the direct to the indirect band-gap at x = 0.44 in agreement with experiments.

  20. Fabrication and Characterization of Electrospun Semiconductor Nanoparticle—Polyelectrolyte Ultra-Fine Fiber Composites for Sensing Applications

    Directory of Open Access Journals (Sweden)

    Caroline L. Schauer

    2011-10-01

    Full Text Available Fluorescent composite fibrous assembles of nanoparticle-polyelectrolyte fibers are useful multifunctional materials, utilized in filtration, sensing and tissue engineering applications, with the added benefits of improved mechanical, electrical or structural characteristics over the individual components. Composite fibrous mats were prepared by electrospinning aqueous solutions of 6 wt% poly(acrylic acid (PAA loaded with 0.15 and 0.20% v/v, carboxyl functionalized CdSe/ZnS nanoparticles (SNPs. The resulting fluorescent composite fibrous mats exhibits recoverable quenching when exposed to high humidity. The sensor response is sensitive to water concentration and is attributed to the change in the local charges around the SNPs due to deprotonation of the carboxylic acids on the SNPs and the surrounding polymer matrix.

  1. Oxide semiconductors

    CERN Document Server

    Svensson, Bengt G; Jagadish, Chennupati

    2013-01-01

    Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. Originally widely known as the ""Willardson and Beer"" Series, it has succeeded in publishing numerous landmark volumes and chapters. The series publishes timely, highly relevant volumes intended for long-term impact and reflecting the truly interdisciplinary nature of the field. The volumes in Semiconductors and Semimetals have been and will continue to be of great interest to physicists, chemists, materials scientists, and device engineers in academia, scient

  2. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1962-01-01

    Semiconductor Statistics presents statistics aimed at complementing existing books on the relationships between carrier densities and transport effects. The book is divided into two parts. Part I provides introductory material on the electron theory of solids, and then discusses carrier statistics for semiconductors in thermal equilibrium. Of course a solid cannot be in true thermodynamic equilibrium if any electrical current is passed; but when currents are reasonably small the distribution function is but little perturbed, and the carrier distribution for such a """"quasi-equilibrium"""" co

  3. Programmable and coherent crystallization of semiconductors

    KAUST Repository

    Yu, Liyang

    2017-03-04

    The functional properties and technological utility of polycrystalline materials are largely determined by the structure, geometry, and spatial distribution of their multitude of crystals. However, crystallization is seeded through stochastic and incoherent nucleation events, limiting the ability to control or pattern the microstructure, texture, and functional properties of polycrystalline materials. We present a universal approach that can program the microstructure of materials through the coherent seeding of otherwise stochastic homogeneous nucleation events. The method relies on creating topographic variations to seed nucleation and growth at designated locations while delaying nucleation elsewhere. Each seed can thus produce a coherent growth front of crystallization with a geometry designated by the shape and arrangement of seeds. Periodic and aperiodic crystalline arrays of functional materials, such as semiconductors, can thus be created on demand and with unprecedented sophistication and ease by patterning the location and shape of the seeds. This approach is used to demonstrate printed arrays of organic thin-film transistors with remarkable performance and reproducibility owing to their demonstrated spatial control over the microstructure of organic and inorganic polycrystalline semiconductors.

  4. High vacuum tribology of polycrystalline diamond coatings

    Indian Academy of Sciences (India)

    Polycrystalline diamond coatings; hot filament CVD; high vacuum tribology. 1. Introduction .... is a characteristic of graphite. We mark the (diamond ... coefficient of friction due to changes in substrate temperature. The average coefficient of.

  5. Semiconductor Detectors

    International Nuclear Information System (INIS)

    Cortina, E.

    2007-01-01

    Particle detectors based on semiconductor materials are among the few devices used for particle detection that are available to the public at large. In fact we are surrounded by them in our daily lives: they are used in photoelectric cells for opening doors, in digital photographic and video camera, and in bar code readers at supermarket cash registers. (Author)

  6. New Method for the Development of Plasmonic Metal-Semiconductor Interface Layer: Polymer Composites with Reduced Energy Band Gap

    Directory of Open Access Journals (Sweden)

    Shujahadeen B. Aziz

    2017-01-01

    Full Text Available Silver nanoparticles within a host polymer of chitosan were synthesized by using in situ method. Ultraviolet-visible spectroscopy was then carried out for the prepared chitosan : silver triflate (CS : AgTf samples, showing a surface plasmonic resonance (SPR peak at 420 nm. To prepare polymer composites with reduced energy band gap, different amounts of alumina nanoparticles were incorporated into the CS : AgTf solution. In the present work, the results showed that the reduced silver nanoparticles and their adsorption on wide band gap alumina (Al2O3 particles are an excellent approach for the preparation of polymer composites with small optical band gaps. The optical dielectric loss parameter has been used to determine the band gap experimentally. The physics behind the optical dielectric loss were interpreted from the viewpoint of quantum mechanics. From the quantum-mechanics viewpoint, optical dielectric loss was also found to be a complex equation and required lengthy numerical computation. From the TEM investigation, the adsorption of silver nanoparticles on alumina has been observed. The optical micrograph images showed white spots (silver specks with different sizes on the surface of the films. The second semicircle in impedance Cole-Cole plots was found and attributed to the silver particles.

  7. Control of a metalorganic chemical vapor deposition process for improved composition and thickness precision in compound semiconductors

    Science.gov (United States)

    Gaffney, Monique Suzanne

    1998-11-01

    Metalorganic chemical vapor deposition (MOCVD) is a process used to manufacture electronic and optoelectronic devices that has traditionally lacked real-time growth monitoring and control. Controlling the growth rate and composition using the existing sensors, as well as advanced monitoring systems developed in-house, is shown to improve device quality. Specific MOCVD growth objectives are transformed into controller performance goals. Group III bubbler concentration variations, which perturb both growth rate and composition precision, are identified to be the primary disturbances. First a feed forward control system was investigated, which used an ultrasonic concentration monitor, located upstream in the process. This control strategy resulted in improved regulation of the gallium delivery rate by cancelling the sensed gallium bubbler concentration disturbances via the injection mass flow controller. The controller performance is investigated by growing GaInAs/InP superlattices. Results of growths performed under normal operating conditions and also under large perturbations include X-ray diffraction from the samples as well as real-time sensor signal data. High quality superlattices that display up to eight orders of satellite peaks are obtained under the feed forward compensation scheme, demonstrating improved layer-to-layer reproducibility of thickness and composition. The success of the feed forward control demonstration led to the development of a more complex downstream feedback control system. An ultraviolet absorption monitor was fabricated and retrofitted as a feedback control signal. A control-oriented model of the downstream process was developed for the feedback controller synthesis. Although challenged with both the photolysis and multi-gas detection issues common to UV absorption monitors, closed loop control with the UV sensor was performed and proved to be an effective method of disturbance rejection. An InP/GaInAs test structure was grown under

  8. Semiconductor sensors

    International Nuclear Information System (INIS)

    Hartmann, Frank

    2011-01-01

    Semiconductor sensors have been around since the 1950s and today, every high energy physics experiment has one in its repertoire. In Lepton as well as Hadron colliders, silicon vertex and tracking detectors led to the most amazing physics and will continue doing so in the future. This contribution tries to depict the history of these devices exemplarily without being able to honor all important developments and installations. The current understanding of radiation damage mechanisms and recent R and D topics demonstrating the future challenges and possible technical solutions for the SLHC detectors are presented. Consequently semiconductor sensor candidates for an LHC upgrade and a future linear collider are also briefly introduced. The work presented here is a collage of the work of many individual silicon experts spread over several collaborations across the world.

  9. Semiconductor Optics

    CERN Document Server

    Klingshirn, Claus F

    2012-01-01

    This updated and enlarged new edition of Semiconductor Optics provides an introduction to and an overview of semiconductor optics from the IR through the visible to the UV, including linear and nonlinear optical properties, dynamics, magneto and electrooptics, high-excitation effects and laser processes, some applications, experimental techniques and group theory. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered extend from physics to materials science and optoelectronics. Significantly updated chapters add coverage of current topics such as electron hole plasma, Bose condensation of excitons and meta materials. Over 120 problems, chapter introductions and a detailed index make it the key textbook for graduate students in physics. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered ...

  10. Semiconductor annealing

    International Nuclear Information System (INIS)

    Young, J.M.; Scovell, P.D.

    1982-01-01

    A process for annealing crystal damage in ion implanted semiconductor devices in which the device is rapidly heated to a temperature between 450 and 900 0 C and allowed to cool. It has been found that such heating of the device to these relatively low temperatures results in rapid annealing. In one application the device may be heated on a graphite element mounted between electrodes in an inert atmosphere in a chamber. (author)

  11. A MONTÉ CARLO MODEL FOR SIMULATING THE NITROGEN DIFFUSION EFFECT INTO B-LPCVD-NIDOS POLYCRYSTALLINE THIN FILMS

    OpenAIRE

    S ALLAG; S MERABET; M BOUKEZZATA

    2012-01-01

    The principal objective of our current work, is to study the influence of different treatment from surface which makes it possible to improve the properties of materials by technique of beam of ions (diffusion – implantation), on the distribution of the particles in a semiconductor the prone polycrystalline Silicon of our study, largely used in micro-electronics.  The interest of this study is related to the ceaseless requirements in industry for increasingly reduced, powerful materials and w...

  12. The importance of stress percolation patterns in rocks and other polycrystalline materials.

    Science.gov (United States)

    Burnley, P C

    2013-01-01

    A new framework for thinking about the deformation behavior of rocks and other heterogeneous polycrystalline materials is proposed, based on understanding the patterns of stress transmission through these materials. Here, using finite element models, I show that stress percolates through polycrystalline materials that have heterogeneous elastic and plastic properties of the same order as those found in rocks. The pattern of stress percolation is related to the degree of heterogeneity in and statistical distribution of the elastic and plastic properties of the constituent grains in the aggregate. The development of these stress patterns leads directly to shear localization, and their existence provides insight into the formation of rhythmic features such as compositional banding and foliation in rocks that are reacting or dissolving while being deformed. In addition, this framework provides a foundation for understanding and predicting the macroscopic rheology of polycrystalline materials based on single-crystal elastic and plastic mechanical properties.

  13. PROPERTIES AND OPTICAL APPLICATION OF POLYCRYSTALLINE ZINC SELENIDE OBTAINED BY PHYSICAL VAPOR DEPOSITION

    Directory of Open Access Journals (Sweden)

    A. A. Dunaev

    2015-05-01

    Full Text Available Findings on production technology, mechanical and optical properties of polycrystalline zinc selenide are presented. The combination of its physicochemical properties provides wide application of ZnSe in IR optics. Production technology is based on the method of physical vapor deposition on a heated substrate (Physical Vapor Deposition - PVD. The structural features and heterogeneity of elemental composition for the growth surfaces of ZnSe polycrystalline blanks were investigated using CAMEBAX X-ray micro-analyzer. Characteristic pyramid-shaped crystallites were recorded for all growth surfaces. The measurements of the ratio for major elements concentrations show their compliance with the stoichiometry of the ZnSe compounds. Birefringence, optical homogeneity, thermal conductivity, mechanical and optical properties were measured. It is established that regardless of polycrystalline condensate columnar and texturing, the optical material is photomechanically isotropic and homogeneous. The actual performance of parts made of polycrystalline optical zinc selenide in the thermal spectral ranges from 3 to 5 μm and from 8 to 14 μm and in the CO2 laser processing plants with a power density of 500 W/cm2 is shown. The developed technology gives the possibility to produce polycrystalline optical material on an industrial scale.

  14. Semiconductor annealing

    International Nuclear Information System (INIS)

    Young, J.M.; Scovell, P.D.

    1981-01-01

    A process for annealing crystal damage in ion implanted semiconductor devices is described in which the device is rapidly heated to a temperature between 450 and 600 0 C and allowed to cool. It has been found that such heating of the device to these relatively low temperatures results in rapid annealing. In one application the device may be heated on a graphite element mounted between electrodes in an inert atmosphere in a chamber. The process may be enhanced by the application of optical radiation from a Xenon lamp. (author)

  15. Polycrystalline intrinsic zinc oxide to be used in transparent electronic devices

    International Nuclear Information System (INIS)

    Pimentel, A.; Fortunato, E.; Goncalves, A.; Marques, A.; Aguas, H.; Pereira, L.; Ferreira, I.; Martins, R.

    2005-01-01

    In this paper we present results of intrinsic/non-doped zinc oxide deposited at room temperature by radio frequency magnetron sputtering able to be used as a semiconductor material on electronic devices, like for example ozone gas sensors, ultra-violet detectors and thin film transistors. These films present a resistivity as high as 2.5x10 8 Ω cm with an optical transmittance of 90%. Concerning the structural properties, these films are polycrystalline presenting a uniform and very smooth surface

  16. Methods of removal of defects arising at liquid etching of polycrystalline silicon

    Directory of Open Access Journals (Sweden)

    Ivanchykou A. E.

    2008-02-01

    Full Text Available The paper presents a model of generation of defects having the form of spots on the surface of the polycrystalline silicon during processing of semiconductor wafers with hydrofluoric acid based etchant, and a model of removal of such defects in chemical solutions. The authors investigate how the centrifuge speed during drying and the relief of structures, produced on the plate, effect the number of defects. It is shown that there is a possibility to remove defects by chemical treatment in the peroxide-ammonia solutions (PAS and also by sequence of chemical cleaning in Karo mixture, SiO2 etching and treatment in PAS.

  17. Magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bihler, Christoph

    2009-04-15

    In this thesis we investigated in detail the properties of Ga{sub 1-x}Mn{sub x}As, Ga{sub 1-x}Mn{sub x}P, and Ga{sub 1-x}Mn{sub x}N dilute magnetic semiconductor thin films with a focus on the magnetic anisotropy and the changes of their properties upon hydrogenation. We applied two complementary spectroscopic techniques to address the position of H in magnetic semiconductors: (i) Electron paramagnetic resonance, which provides direct information on the symmetry of the crystal field of the Mn{sup 2+} atoms and (ii) x-ray absorption fine structure analysis which allows to probe the local crystallographic neighborhood of the absorbing Mn atom via analysing the fine structure at the Mn K absorption edge. Finally, we discussed the obstacles that have to be overcome to achieve Curie temperatures above the current maximum in Ga{sub 1-x}Mn{sub x}As of 185 K. Here, we outlined in detail the generic problem of the formation of precipitates at the example of Ge:MN. (orig.)

  18. Isotopically controlled semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Haller, Eugene E.

    2006-06-19

    The following article is an edited transcript based on the Turnbull Lecture given by Eugene E. Haller at the 2005 Materials Research Society Fall Meeting in Boston on November 29, 2005. The David Turnbull Lectureship is awarded to recognize the career of a scientist who has made outstanding contributions to understanding materials phenomena and properties through research, writing, and lecturing, as exemplified by the life work of David Turnbull. Haller was named the 2005 David Turnbull Lecturer for his 'pioneering achievements and leadership in establishing the field of isotopically engineered semiconductors; for outstanding contributions to materials growth, doping and diffusion; and for excellence in lecturing, writing, and fostering international collaborations'. The scientific interest, increased availability, and technological promise of highly enriched isotopes have led to a sharp rise in the number of experimental and theoretical studies with isotopically controlled semiconductor crystals. This article reviews results obtained with isotopically controlled semiconductor bulk and thin-film heterostructures. Isotopic composition affects several properties such as phonon energies, band structure, and lattice constant in subtle, but, for their physical understanding, significant ways. Large isotope-related effects are observed for thermal conductivity in local vibrational modes of impurities and after neutron transmutation doping. Spectacularly sharp photoluminescence lines have been observed in ultrapure, isotopically enriched silicon crystals. Isotope multilayer structures are especially well suited for simultaneous self- and dopant-diffusion studies. The absence of any chemical, mechanical, or electrical driving forces makes possible the study of an ideal random-walk problem. Isotopically controlled semiconductors may find applications in quantum computing, nanoscience, and spintronics.

  19. Semiconductor Laser Measurements Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Semiconductor Laser Measurements Laboratory is equipped to investigate and characterize the lasing properties of semiconductor diode lasers. Lasing features such...

  20. Extremal Overall Elastic Response of Polycrystalline Materials

    DEFF Research Database (Denmark)

    Bendsøe, Martin P; Lipton, Robert

    1997-01-01

    Polycrystalline materials comprised of grains obtained from a single anisotropic material are considered in the framework of linear elasticity. No assumptions on the symmetry of the polycrystal are made. We subject the material to independent external strain and stress fields with prescribed mean...

  1. Preparation and characterization of polycrystalline n-CdSe photoelectrode

    Energy Technology Data Exchange (ETDEWEB)

    Bandyopadhyay, T. K.

    1979-01-01

    Thin layers of polycrystalline p-CdSe were prepared by the simultaneous eletrodeposition of cadmium and selenium from cadmium sulfate and selenious acid in a sulfuric acid solution at pH 0-1 on a titanium substrate. The adherence of the layers to the substrate, stoichiometric ratio of Cd:Se and photovoltaic property of the film depend upon the molar ratio of CdSO/sub 4/ and H/sub 2/SeO/sub 3/ and current density as well as on the pH and temperature of the electrolysis bath. On increasing the current density or the ratio of CdSO/sub 4/:H/sub 2/SeO/sub 3/ in the electrolysis bath, the Cd:Se of the electrodeposit increased. The semiconductor films so prepared were annealed at 550/sup 0/C in a nitrogen atmosphere, followed by etching in an acid solution and then used to construct the photo-electrochemical cell, Ti/CdSe/Na/sub 2/S-Na/sub 2/S/sub x/(aq.)/Pt, and the current-voltage curves have been studied. 11 references.

  2. Near single-crystalline, high-carrier-mobility silicon thin film on a polycrystalline/amorphous substrate

    Science.gov (United States)

    Findikoglu, Alp T [Los Alamos, NM; Jia, Quanxi [Los Alamos, NM; Arendt, Paul N [Los Alamos, NM; Matias, Vladimir [Santa Fe, NM; Choi, Woong [Los Alamos, NM

    2009-10-27

    A template article including a base substrate including: (i) a base material selected from the group consisting of polycrystalline substrates and amorphous substrates, and (ii) at least one layer of a differing material upon the surface of the base material; and, a buffer material layer upon the base substrate, the buffer material layer characterized by: (a) low chemical reactivity with the base substrate, (b) stability at temperatures up to at least about 800.degree. C. under low vacuum conditions, and (c) a lattice crystal structure adapted for subsequent deposition of a semiconductor material; is provided, together with a semiconductor article including a base substrate including: (i) a base material selected from the group consisting of polycrystalline substrates and amorphous substrates, and (ii) at least one layer of a differing material upon the surface of the base material; and, a buffer material layer upon the base substrate, the buffer material layer characterized by: (a) low chemical reactivity with the base substrate, (b) stability at temperatures up to at least about 800.degree. C. under low vacuum conditions, and (c) a lattice crystal structure adapted for subsequent deposition of a semiconductor material, and, a top-layer of semiconductor material upon the buffer material layer.

  3. Fundamentals, progress, and future directions of nitride-based semiconductors and their composites in two-dimensional limit: A first-principles perspective to recent synthesis

    Science.gov (United States)

    Kecik, D.; Onen, A.; Konuk, M.; Gürbüz, E.; Ersan, F.; Cahangirov, S.; Aktürk, E.; Durgun, E.; Ciraci, S.

    2018-03-01

    Potential applications of bulk GaN and AlN crystals have made possible single and multilayer allotropes of these III-V compounds to be a focus of interest recently. As of 2005, the theoretical studies have predicted that GaN and AlN can form two-dimensional (2D) stable, single-layer (SL) structures being wide band gap semiconductors and showing electronic and optical properties different from those of their bulk parents. Research on these 2D structures have gained importance with recent experimental studies achieving the growth of ultrathin 2D GaN and AlN on substrates. It is expected that these two materials will open an active field of research like graphene, silicene, and transition metal dichalcogenides. This topical review aims at the evaluation of previous experimental and theoretical works until 2018 in order to provide input for further research attempts in this field. To this end, starting from three-dimensional (3D) GaN and AlN crystals, we review 2D SL and multilayer (ML) structures, which were predicted to be stable in free-standing states. These are planar hexagonal (or honeycomb), tetragonal, and square-octagon structures. First, we discuss earlier results on dynamical and thermal stability of these SL structures, as well as the predicted mechanical properties. Next, their electronic and optical properties with and without the effect of strain are reviewed and compared with those of the 3D parent crystals. The formation of multilayers, hence prediction of new periodic layered structures and also tuning their physical properties with the number of layers are other critical subjects that have been actively studied and discussed here. In particular, an extensive analysis pertaining to the nature of perpendicular interlayer bonds causing planar GaN and AlN to buckle is presented. In view of the fact that SL GaN and AlN can be fabricated only on a substrate, the question of how the properties of free-standing, SL structures are affected if they are grown

  4. Semiconductor laser shearing interferometer

    International Nuclear Information System (INIS)

    Ming Hai; Li Ming; Chen Nong; Xie Jiaping

    1988-03-01

    The application of semiconductor laser on grating shearing interferometry is studied experimentally in the present paper. The method measuring the coherence of semiconductor laser beam by ion etching double frequency grating is proposed. The experimental result of lens aberration with semiconductor laser shearing interferometer is given. Talbot shearing interferometry of semiconductor laser is also described. (author). 2 refs, 9 figs

  5. Introduction to cathodoluminescence in semiconductors

    International Nuclear Information System (INIS)

    Dussac, M.

    1985-01-01

    The use of cathodoluminescence in a scanning electron microscope leads to acquire a spectrum in a place of the sample surface, or to register the intensity profile of a special emission band along a scanning line, or also to realize a map of the irradiated sample. Composition variations can then, at ambient temperature, be determined, also defects can be shown, together with grain joints and dislocations, radiative and non radiative regions can be distinguished and, at low temperature, elementary processes of luminescence can be studied and impurities identified in semiconductors. Through this analysis method is applicable to every insulating or semiconductor material (that is to say to every material having a gap), in this article only crystalline semi-conductor will be studied [fr

  6. Ultrasensitive NO2 Sensor Based on Ohmic Metal-Semiconductor Interfaces of Electrolytically Exfoliated Graphene/Flame-Spray-Made SnO2 Nanoparticles Composite Operating at Low Temperatures.

    Science.gov (United States)

    Tammanoon, Nantikan; Wisitsoraat, Anurat; Sriprachuabwong, Chakrit; Phokharatkul, Ditsayut; Tuantranont, Adisorn; Phanichphant, Sukon; Liewhiran, Chaikarn

    2015-11-04

    In this work, flame-spray-made undoped SnO2 nanoparticles were loaded with 0.1-5 wt % electrolytically exfoliated graphene and systematically studied for NO2 sensing at low working temperatures. Characterizations by X-ray diffraction, transmission/scanning electron microscopy, and Raman and X-ray photoelectron spectroscopy indicated that high-quality multilayer graphene sheets with low oxygen content were widely distributed within spheriodal nanoparticles having polycrystalline tetragonal SnO2 phase. The 10-20 μm thick sensing films fabricated by spin coating on Au/Al2O3 substrates were tested toward NO2 at operating temperatures ranging from 25 to 350 °C in dry air. Gas-sensing results showed that the optimal graphene loading level of 0.5 wt % provided an ultrahigh response of 26,342 toward 5 ppm of NO2 with a short response time of 13 s and good recovery stabilization at a low optimal operating temperature of 150 °C. In addition, the optimal sensor also displayed high sensor response and relatively short response time of 171 and 7 min toward 5 ppm of NO2 at room temperature (25 °C). Furthermore, the sensors displayed very high NO2 selectivity against H2S, NH3, C2H5OH, H2, and H2O. Detailed mechanisms for the drastic NO2 response enhancement by graphene were proposed on the basis of the formation of graphene-undoped SnO2 ohmic metal-semiconductor junctions and accessible interfaces of graphene-SnO2 nanoparticles. Therefore, the electrolytically exfoliated graphene-loaded FSP-made SnO2 sensor is a highly promising candidate for fast, sensitive, and selective detection of NO2 at low operating temperatures.

  7. Creep behavior for advanced polycrystalline SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States); Kohyama, Akira [Kyoto Univ. (Japan)] [and others

    1997-04-01

    A bend stress relaxation (BSR) test has been utilized to examine irradiation enhanced creep in polycrystalline SiC fibers which are under development for use as fiber reinforcement in SiC/SiC composite. Qualitative, S-shaped 1hr BSR curves were compared for three selected advanced SiC fiber types and standard Nicalon CG fiber. The temperature corresponding to the middle of the S-curve (where the BSR parameter m = 0.5) is a measure of a fiber`s thermal stability as well as it creep resistance. In order of decreasing thermal creep resistance, the measured transition temperatures were Nicalon S (1450{degrees}C), Sylramic (1420{degrees}C), Hi-Nicalon (1230{degrees}C) and Nicalon CG (1110{degrees}C).

  8. Equilibrium shapes of polycrystalline silicon nanodots

    Energy Technology Data Exchange (ETDEWEB)

    Korzec, M. D., E-mail: korzec@math.tu-berlin.de; Wagner, B., E-mail: bwagner@math.tu-berlin.de [Department of Mathematics, Technische Universität Berlin, Straße des 17. Juni 136, 10623 Berlin (Germany); Roczen, M., E-mail: maurizio.roczen@physik.hu-berlin.de [Department of Physics, Humboldt-Universität zu Berlin, Newtonstraße 15, 12489 Berlin (Germany); Schade, M., E-mail: martin.schade@physik.uni-halle.de [Zentrum für Innovationskompetenz SiLi-nano, Martin-Luther-Universität Halle-Wittenberg, Karl-Freiherr-von-Fritsch-Straße 3, 06120 Halle (Germany); Rech, B., E-mail: bernd.rech@helmholtz-berlin.de [Helmholtz-Zentrum Berlin, Institute for Silicon Photovoltaics, Kekuléstraße 5, 12489 Berlin (Germany)

    2014-02-21

    This study is concerned with the topography of nanostructures consisting of arrays of polycrystalline nanodots. Guided by transmission electron microscopy (TEM) measurements of crystalline Si (c-Si) nanodots that evolved from a “dewetting” process of an amorphous Si (a-Si) layer from a SiO{sub 2} coated substrate, we investigate appropriate formulations for the surface energy density and transitions of energy density states at grain boundaries. We introduce a new numerical minimization formulation that allows to account for adhesion energy from an underlying substrate. We demonstrate our approach first for the free standing case, where the solutions can be compared to well-known Wulff constructions, before we treat the general case for interfacial energy settings that support “partial wetting” and grain boundaries for the polycrystalline case. We then use our method to predict the morphologies of silicon nanodots.

  9. Method for producing polycrystalline boron nitride

    International Nuclear Information System (INIS)

    Alexeevskii, V.P.; Bochko, A.V.; Dzhamarov, S.S.; Karpinos, D.M.; Karyuk, G.G.; Kolomiets, I.P.; Kurdyumov, A.V.; Pivovarov, M.S.; Frantsevich, I.N.; Yarosh, V.V.

    1975-01-01

    A mixture containing less than 50 percent of graphite-like boron nitride treated by a shock wave and highly defective wurtzite-like boron nitride obtained by a shock-wave method is compressed and heated at pressure and temperature values corresponding to the region of the phase diagram for boron nitride defined by the graphite-like compact modifications of boron nitride equilibrium line and the cubic wurtzite-like boron nitride equilibrium line. The resulting crystals of boron nitride exhibit a structure of wurtzite-like boron nitride or of both wurtzite-like and cubic boron nitride. The resulting material exhibits higher plasticity as compared with polycrystalline cubic boron nitride. Tools made of this compact polycrystalline material have a longer service life under impact loads in machining hardened steel and chilled iron. (U.S.)

  10. Effective polycrystalline sensor of ultraviolet radiation

    Directory of Open Access Journals (Sweden)

    S.Yu. Pavelets

    2017-10-01

    Full Text Available Deposition of special thin layers with high and low resistance in space charge region of surface barrier photoconverters based on the p-Cu1.8S/n-CdS structure leads to a sufficient increase in photosensitivity and decrease in dark tunneling-recombination current. Highly efficient and stable polycrystalline photoconverters of ultraviolet radiation based on polycrystalline CdS have been obtained. Electrical and photoelectric properties have been investigated, and the main operational parameters of ultraviolet sensors have been adduced. The reasons for high stability of the parameters inherent to the p-Cu1.8S/n-CdS sensors are as follows: the absence of impurity components additionally doped to the barrier structure and stability of the photocurrent photoemission component.

  11. Extremal Overall Elastic Response of Polycrystalline Materials

    DEFF Research Database (Denmark)

    Bendsøe, Martin P; Lipton, Robert

    1996-01-01

    Polycrystalline materials comprised of grains obtained froma single anisotropic material are considered in the frameworkof linear elasticity. No assumptions on the symmetry of thepolycrystal are made. We subject the material to independentexternal strain and stress fields with prescribed mean...... values.We show that the extremal overall elastic response is alwaysachieved by a configuration consisting of a single properlyoriented crystal. This result is compared to results for isotropicpolycrystals....

  12. Hydrogen solubility in polycrystalline - and nonocrystalline niobium

    International Nuclear Information System (INIS)

    Ishikawa, T.T.; Silva, J.R.G. da

    1981-01-01

    Hydrogen solubility in polycrystalline and monocrystalline niobium was measured in the range 400 0 C to 1000 0 C at one atmosphere hydrogen partial pressure. The experimental technique consists of saturation of the solvent metal with hydrogen, followed by quenching and analysis of the solid solution. It is presented solubility curves versus reciprocal of the absolute doping temperature, associated with their thermodynamical equation. (Author) [pt

  13. Characterization of electrochemically modified polycrystalline platinum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Krebs, L.C.; Ishida, Takanobu.

    1991-12-01

    The characterization of electrochemically modified polycrystalline platinum surfaces has been accomplished through the use of four major electrochemical techniques. These were chronoamperometry, chronopotentiommetry, cyclic voltammetry, and linear sweep voltammetry. A systematic study on the under-potential deposition of several transition metals has been performed. The most interesting of these were: Ag, Cu, Cd, and Pb. It was determined, by subjecting the platinum electrode surface to a single potential scan between {minus}0.24 and +1.25 V{sub SCE} while stirring the solution, that the electrocatalytic activity would be regenerated. As a consequence of this study, a much simpler method for producing ultra high purity water from acidic permanganate has been developed. This method results in water that surpasses the water produced by pyrocatalytic distillation. It has also been seen that the wettability of polycrystalline platinum surfaces is greatly dependent on the quantity of oxide present. Oxide-free platinum is hydrophobic and gives a contact angle in the range of 55 to 62 degrees. We have also modified polycrystalline platinum surface with the electrically conducting polymer poly-{rho}-phenylene. This polymer is very stable in dilute sulfuric acid solutions, even under applied oxidative potentials. It is also highly resistant to electrochemical hydrogenation. The wettability of the polymer modified platinum surface is severely dependent on the choice of supporting electrolyte chosen for the electrochemical polymerization. Tetraethylammonium tetrafluoroborate produces a film that is as hydrophobic as Teflon, whereas tetraethylammonium perchlorate produces a film that is more hydrophilic than oxide-free platinum.

  14. Characterization of electrochemically modified polycrystalline platinum surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Krebs, Leonard C. [State Univ. of New York (SUNY), Stony Brook, NY (United States); Ishida, Takanobu [State Univ. of New York (SUNY), Stony Brook, NY (United States)

    1991-12-01

    The characterization of electrochemically modified polycrystalline platinum surfaces has been accomplished through the use of four major electrochemical techniques. These were chronoamperometry, chronopotentiommetry, cyclic voltammetry, and linear sweep voltammetry. A systematic study on the under-potential deposition of several transition metals has been performed. The most interesting of these were: Ag, Cu, Cd, and Pb. It was determined, by subjecting the platinum electrode surface to a single potential scan between -0.24 and +1.25 VSCE while stirring the solution, that the electrocatalytic activity would be regenerated. As a consequence of this study, a much simpler method for producing ultra high purity water from acidic permanganate has been developed. This method results in water that surpasses the water produced by pyrocatalytic distillation. It has also been seen that the wettability of polycrystalline platinum surfaces is greatly dependent on the quantity of oxide present. Oxide-free platinum is hydrophobic and gives a contact angle in the range of 55 to 62 degrees. We have also modified polycrystalline platinum surface with the electrically conducting polymer poly-ρ-phenylene. This polymer is very stable in dilute sulfuric acid solutions, even under applied oxidative potentials. It is also highly resistant to electrochemical hydrogenation. The wettability of the polymer modified platinum surface is severely dependent on the choice of supporting electrolyte chosen for the electrochemical polymerization. Tetraethylammonium tetrafluoroborate produces a film that is as hydrophobic as Teflon, whereas tetraethylammonium perchlorate produces a film that is more hydrophilic than oxide-free platinum.

  15. Carrier Transport, Recombination, and the Effects of Grain Boundaries in Polycrystalline Cadmium Telluride Thin Films for Photovoltaics

    Science.gov (United States)

    Tuteja, Mohit

    Cadmium Telluride (CdTe), a chalcogenide semiconductor, is currently used as the absorber layer in one of the highest efficiency thin film solar cell technologies. Current efficiency records are over 22%. In 2011, CdTe solar cells accounted for 8% of all solar cells installed. This is because, in part, CdTe has a low degradation rate, high optical absorption coefficient, and high tolerance to intrinsic defects. Solar cells based on polycrystalline CdTe exhibit a higher short-circuit current, fill factor, and power conversion efficiency than their single crystal counterparts. This is despite the fact that polycrystalline CdTe devices exhibit lower open-circuit voltages. This is contrary to the observation for silicon and III-V semiconductors, where material defects cause a dramatic drop in device performance. For example, grain boundaries in covalently-bonded semiconductors (a) act as carrier recombination centers, and (b) lead to localized energy states, causing carrier trapping. Despite significant research to date, the mechanism responsible for the superior current collection properties of polycrystalline CdTe solar cells has not been conclusively answered. This dissertation focuses on the macro-scale electronic band structure, and micro scale electronic properties of grains and grain boundaries in device-grade CdTe thin films to answer this open question. My research utilized a variety of experimental techniques. Samples were obtained from leading groups fabricating the material and devices. A CdCl 2 anneal is commonly performed as part of this fabrication and its effects were also investigated. Photoluminescence (PL) spectroscopy was employed to study the band structure and defect states in CdTe polycrystals. Cadmium vacancy- and chlorine-related states lead to carrier recombination, as in CdTe films grown by other methods. Comparing polycrystalline and single crystal CdTe, showed that the key to explaining the improved performance of polycrystalline CdTe does

  16. Analysis and evaluation for practical application of photovoltaic power generation system. Analysis and evaluation for thin substrate polycrystalline solar cells (compound semiconductors and their fabrication technologies); Taiyoko hatsuden system jitsuyoka no tame no kaiseki hyoka. Usumaku taiyo denchi jitsuyoka no tame no kaiseki hyoka (kagobutsu taiyo denchi zairyo oyobi seisaku gijutsu no kaiseki hyoka)

    Energy Technology Data Exchange (ETDEWEB)

    Oyagi, H; Okada, Y; Yamaguchi, H; Shiota, T; Kuroda, S; Igarashi, O; Tanino, H; Makita, Y; Yamada, A; Kimura, S; Ohara, A; Niki, S; Shibata, H; Fons, P [Electrotechnical Laboratory, Tsukuba (Japan)

    1994-12-01

    Described herein are the results of the FY1994 research program for analysis and evaluation for thin-film compound semiconductor solar cells. The study on epitaxial growth and optical properties of the thin films of CuInSe2 and CuGaSe2 evaluates the thin epitaxial films grown under various conditions, showing morphology of the defects at the interface of heteroepitaxial growth. These results are used to set the growth conditions under which a thin film of high luminescence by exciter recombination is produced. The study also gives information of luminescence transition in the vicinity of the band ends and of energy level between the bands. The study on structural analysis of the epitaxially grown thin films of CuInSe2 investigates dependence of lattice constants of the MBE-grown CIS layer on film thickness by the X-ray diffractometry based on the bond method. The study on epitaxial growth by the Se(CH3)2-halogen transfer method tests epitaxial growth of the single-crystalline Mo on a substrate of single-crystalline sapphire. 5 figs.

  17. Semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Marstein Erik Stensrud

    2003-07-01

    This thesis presents a study of two material systems containing semiconductor nanocrystals, namely porous silicon (PSi) films and germanium (Ge) nanocrystals embedded in silicon dioxide (SiO2) films. The PSi films were made by anodic etching of silicon (Si) substrates in an electrolyte containing hydrofluoric acid. The PSi films were doped with erbium (Er) using two different doping methods. electrochemical doping and doping by immersing the PSi films in a solution containing Er. The resulting Er concentration profiles were investigated using scanning electron microscopy (SEN1) combined with energy dispersive X-ray analysis (EDS). The main subject of the work on PSi presented in this thesis was investigating and comparing these two doping methods. Ge nanocrystals were made by implanting Ge ions into Si02 films that were subsequently annealed. However. nanocrystal formation occurred only for certain sets of processing parameters. The dependence of the microstructure of the Ge implanted Si02 films on the processing parameters were therefore investigated. A range of methods were employed for these investigations, including transmission electron microscopy (TEM) combined with EDS, X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). The observed structures, ranging from Ge nanocrystals to voids with diameters of several tens of nanometers and Ge rich Si02 films without any nanocrystals is described. A model explaining the void formation is also presented. For certain sets of processing parameters. An accumulation of Ge at the Si-Si02 interface was observed. The effect of this accumulation on the electrical properties of MOS structures made from Ge implanted SiO2 films was investigated using CV-measurements. (Author)

  18. Photoelectrochemical cell including Ga(Sb.sub.x)N.sub.1-x semiconductor electrode

    Science.gov (United States)

    Menon, Madhu; Sheetz, Michael; Sunkara, Mahendra Kumar; Pendyala, Chandrashekhar; Sunkara, Swathi; Jasinski, Jacek B.

    2017-09-05

    The composition of matter comprising Ga(Sb.sub.x)N.sub.1-x where x=0.01 to 0.06 is characterized by a band gap between 2.4 and 1.7 eV. A semiconductor device includes a semiconductor layer of that composition. A photoelectric cell includes that semiconductor device.

  19. Methods of producing free-standing semiconductors using sacrificial buffer layers and recyclable substrates

    Science.gov (United States)

    Ptak, Aaron Joseph; Lin, Yong; Norman, Andrew; Alberi, Kirstin

    2015-05-26

    A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a spinel substrate using a sacrificial buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The sacrificial buffer material and semiconductor materials may be deposited using lattice-matching epitaxy or coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The sacrificial buffer layer may be dissolved using an epitaxial liftoff technique in order to separate the semiconductor device from the spinel substrate, and the spinel substrate may be reused in the subsequent fabrication of other semiconductor devices. The low-defect density semiconductor materials produced using this method result in the enhanced performance of the semiconductor devices that incorporate the semiconductor materials.

  20. Semiconductor radiation detector

    Science.gov (United States)

    Bell, Zane W.; Burger, Arnold

    2010-03-30

    A semiconductor detector for ionizing electromagnetic radiation, neutrons, and energetic charged particles. The detecting element is comprised of a compound having the composition I-III-VI.sub.2 or II-IV-V.sub.2 where the "I" component is from column 1A or 1B of the periodic table, the "II" component is from column 2B, the "III" component is from column 3A, the "IV" component is from column 4A, the "V" component is from column 5A, and the "VI" component is from column 6A. The detecting element detects ionizing radiation by generating a signal proportional to the energy deposited in the element, and detects neutrons by virtue of the ionizing radiation emitted by one or more of the constituent materials subsequent to capture. The detector may contain more than one neutron-sensitive component.

  1. Organic Semiconductor Photovoltaics

    Science.gov (United States)

    Sariciftci, Niyazi Serdar

    2005-03-01

    Recent developments on organic photovoltaic elements are reviewed. Semiconducting conjugated polymers and molecules as well as nanocrystalline inorganic semiconductors are used in composite thin films. The photophysics of such photoactive devices is based on the photoinduced charge transfer from donor type semiconducting molecules onto acceptor type molecules such as Buckminsterfullerene, C60 and/or nanoparticles. Similar to the first steps in natural photosynthesis, this photoinduced electron transfer leads to a number of potentially interesting applications which include sensitization of the photoconductivity and photovoltaic phenomena. Examples of photovoltaic architectures are discussed with their potential in terrestrial solar energy conversion. Several materials are introduced and discussed for their photovoltaic activities. Furthermore, nanomorphology has been investigated with AFM, SEM and TEM. The morphology/property relationship for a given photoactive system is found to be a major effect.

  2. Amorphous and Polycrystalline Photoconductors for Direct Conversion Flat Panel X-Ray Image Sensors

    Directory of Open Access Journals (Sweden)

    Karim S. Karim

    2011-05-01

    Full Text Available In the last ten to fifteen years there has been much research in using amorphous and polycrystalline semiconductors as x-ray photoconductors in various x-ray image sensor applications, most notably in flat panel x-ray imagers (FPXIs. We first outline the essential requirements for an ideal large area photoconductor for use in a FPXI, and discuss how some of the current amorphous and polycrystalline semiconductors fulfill these requirements. At present, only stabilized amorphous selenium (doped and alloyed a-Se has been commercialized, and FPXIs based on a-Se are particularly suitable for mammography, operating at the ideal limit of high detective quantum efficiency (DQE. Further, these FPXIs can also be used in real-time, and have already been used in such applications as tomosynthesis. We discuss some of the important attributes of amorphous and polycrystalline x-ray photoconductors such as their large area deposition ability, charge collection efficiency, x-ray sensitivity, DQE, modulation transfer function (MTF and the importance of the dark current. We show the importance of charge trapping in limiting not only the sensitivity but also the resolution of these detectors. Limitations on the maximum acceptable dark current and the corresponding charge collection efficiency jointly impose a practical constraint that many photoconductors fail to satisfy. We discuss the case of a-Se in which the dark current was brought down by three orders of magnitude by the use of special blocking layers to satisfy the dark current constraint. There are also a number of polycrystalline photoconductors, HgI2 and PbO being good examples, that show potential for commercialization in the same way that multilayer stabilized a-Se x-ray photoconductors were developed for commercial applications. We highlight the unique nature of avalanche multiplication in a-Se and how it has led to the development of the commercial HARP video-tube. An all solid state version of the

  3. Discrete Tomography and Imaging of Polycrystalline Structures

    DEFF Research Database (Denmark)

    Alpers, Andreas

    High resolution transmission electron microscopy is commonly considered as the standard application for discrete tomography. While this has yet to be technically realized, new applications with a similar flavor have emerged in materials science. In our group at Ris� DTU (Denmark's National...... Laboratory for Sustainable Energy), for instance, we study polycrystalline materials via synchrotron X-ray diffraction. Several reconstruction problems arise, most of them exhibit inherently discrete aspects. In this talk I want to give a concise mathematical introduction to some of these reconstruction...... problems. Special focus is on their relationship to classical discrete tomography. Several open mathematical questions will be mentioned along the way....

  4. Hydrogenation of polycrystalline silicon thin films

    Czech Academy of Sciences Publication Activity Database

    Honda, Shinya; Mates, Tomáš; Knížek, Karel; Ledinský, Martin; Fejfar, Antonín; Kočka, Jan; Yamazaki, T.; Uraoka, Y.; Fuyuki, T.

    2006-01-01

    Roč. 501, - (2006), s. 144-148 ISSN 0040-6090 R&D Projects: GA MŠk ME 537; GA MŽP(CZ) SM/300/1/03; GA AV ČR(CZ) IAA1010316; GA AV ČR(CZ) IAA1010413; GA ČR(CZ) GA202/03/0789 Institutional research plan: CEZ:AV0Z1010914 Keywords : polycrystalline silicon * atmospheric pressure chemical vapour deposition * hydrogen passivation * photoluminescence * Raman spectroscopy * Si-H 2 bonding * hydrogen molecules Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.666, year: 2006

  5. Field performance of a polycrystalline silicon module

    International Nuclear Information System (INIS)

    Adegboyega, G.A.; Kuku, T.A.; Salau, A.A.M.

    1985-12-01

    The field performance of a polycrystalline silicon module is reported. The recorded data include the ambient temperature, solar insolation and the module output power. The module has given efficiencies in the range of 2-4% and has demonstrated good stability over a ten month period. From the field data, equations that could be used to predict performance for various seasons of the year for this location have been developed and the fit between predicted and actual performance has been found to be quite good. (author)

  6. Numerical simulation of large deformation polycrystalline plasticity

    International Nuclear Information System (INIS)

    Inal, K.; Neale, K.W.; Wu, P.D.; MacEwen, S.R.

    2000-01-01

    A finite element model based on crystal plasticity has been developed to simulate the stress-strain response of sheet metal specimens in uniaxial tension. Each material point in the sheet is considered to be a polycrystalline aggregate of FCC grains. The Taylor theory of crystal plasticity is assumed. The numerical analysis incorporates parallel computing features enabling simulations of realistic models with large number of grains. Simulations have been carried out for the AA3004-H19 aluminium alloy and the results are compared with experimental data. (author)

  7. Creep cavitation effects in polycrystalline alumina

    International Nuclear Information System (INIS)

    Porter, J.R.; Blumenthal, W.; Evans, A.G.

    1981-01-01

    Fine grained polycrystalline alumina has been deformed in creep at high temperatures, to examine the evolution of cavities at grain boundaries. Cavities with equilibrium and crack-like morphologies have been observed, distributed nonuniformly throughout the material. The role of these cavities during creep has been described. A transition from equilibrium to crack-like morphology has been observed and correlated with a model based on the influence of the surface to boundary diffusivity ratio and the local tensile stress. The contribution of cavitation to the creep rate and total creep strain has been analyzed and excluded as the principal cause of the observed non-linear creep rate

  8. Anomalous Hall effect in polycrystalline Ni films

    KAUST Repository

    Guo, Zaibing

    2012-02-01

    We systematically studied the anomalous Hall effect in a series of polycrystalline Ni films with thickness ranging from 4 to 200 nm. It is found that both the longitudinal and anomalous Hall resistivity increased greatly as film thickness decreased. This enhancement should be related to the surface scattering. In the ultrathin films (46 nm thick), weak localization corrections to anomalous Hall conductivity were studied. The granular model, taking into account the dominated intergranular tunneling, has been employed to explain this phenomenon, which can explain the weak dependence of anomalous Hall resistivity on longitudinal resistivity as well. © 2011 Elsevier Ltd. All rights reserved.

  9. Solid spectroscopy: semiconductors

    International Nuclear Information System (INIS)

    Silva, C.E.T.G. da

    1983-01-01

    Photoemission as technique of study of the semiconductor electronic structure is shortly discussed. Homogeneous and heterogeneous semiconductors, where volume and surface electronic structure, core levels and O and H chemisorption in GaAs, Schottky barrier are treated, respectively. Amorphous semiconductors are also discussed. (L.C.) [pt

  10. CVD polycrystalline diamond. A novel neutron detector and applications

    International Nuclear Information System (INIS)

    Mongkolnavin, R.

    1998-01-01

    Chemical Vapour Deposition (CVD) Polycrystalline Diamond film has been investigated as a low noise sensor for beta particles, gammas and neutrons using High Energy Physics technologies. Its advantages and disadvantages have been explored in comparison with other particle detectors such as silicon detector and other plastic scintillators. The performance and characteristic of the diamond detector have been fully studied and discussed. These studies will lead to a better understanding of how CVD diamonds perform as a detector and how to improve their performance under various conditions. A CVD diamond detector model has been proposed which is an attempt to explain the behaviour of such an extreme detector material. A novel neutron detector is introduced as a result of these studies. A good thermal and fast neutron detector can be fabricated with CVD diamond with new topologies. This detector will perform well without degradation in a high neutron radiation environment, as diamond is known to be radiation hard. It also offers better neutrons and gammas discrimination for high gamma background applications compared to other semiconductor detectors. A full simulation of the detector has also been done using GEANT, a Monte-Carlo simulation program for particle detectors. Simulation results show that CVD diamond detectors with this novel topology can detect neutrons with great directionality. Experimental work has been done on this detector in a nuclear reactor environment and accelerator source. A novel neutron source which offers a fast pulse high-energy neutrons has also been studied. With this detector, applications in neutron spectrometer for low-Z material have been pursued with various neutron detection techniques. One of these is a low-Z material identification system. The system has been designed and simulated for contraband luggage interrogation using the detector and the novel neutron source. Also other neutron related applications have been suggested. (author)

  11. CVD polycrystalline diamond. A novel neutron detector and applications

    International Nuclear Information System (INIS)

    Mongkolnavin, R.

    1998-07-01

    Chemical Vapour Deposition (CVD) Polycrystalline Diamond film has been investigated as a low noise sensor for beta particles, gammas and neutrons using High Energy Physics technologies. Its advantages and disadvantages have been explored in comparison with other particle detectors such as silicon detector and other plastic scintillators. The performance and characteristic of the diamond detector have been fully studied and discussed. These studies will lead to a better understanding of how CVD diamonds perform as a detector and how to improve their performance under various conditions. A CVD diamond detector model has been proposed which is an attempt to explain the behaviour of such an extreme detector material. A novel neutron detector is introduced as a result of these studies. A good thermal and fast neutron detector can be fabricated with CVD diamond with new topologies. This detector will perform well without degradation in a high neutron radiation environment, as diamond is known to be radiation-hard. It also offers better neutrons and gammas discrimination for high gamma background applications compared to other semiconductor detectors. A full simulation of the detector has also been done using GEANT, a Monte Carlo simulation program for particle detectors. Simulation results show that CVD diamond detectors with this novel topology can detect neutrons with great directionality. Experimental work has been done on this detector in a nuclear reactor environment and accelerator source. A novel neutron source which offers a fast pulse high-energy neutrons has also been studied. With this detector, applications in neutron spectrometry for low-Z material have been pursued with various neutron detection techniques. One of these is a low-Z material identification system. The system has been designed and simulated for contraband luggage interrogation using the detector and the novel neutron source. (author)

  12. Physics with isotopically controlled semiconductors

    International Nuclear Information System (INIS)

    Haller, E.E.

    1994-08-01

    Control of the isotopic composition of semiconductors offers a wide range of new scientific opportunities. In this paper a number of recent results obtained with isotopically pure as well as deliberately mixed diamond and Ge bulk single crystals and Ge isotope superlattices will be reviewed. Isotopic composition affects several properties such as phonon energies, bandstructure and lattice constant in subtle but theoretically well understood ways. Large effects are observed for thermal conductivity, local vibrational modes of impurities and after neutron transmutation doping (NTD). Several experiments which could profit greatly from isotope control are proposed

  13. Giant 1/f noise in two-dimensional polycrystalline media

    International Nuclear Information System (INIS)

    Snarskii, A.; Bezsudnov, I.

    2008-01-01

    The behaviour of excess (1/f noise) in two-dimensional polycrystalline media is investigated. On the base of current trap model, it is shown that there exists a certain anisotropy value of conductivity tensor for polycrystalline media when the amplitude of 1/f noise becomes giant

  14. Construction of High-Performance, Low-Cost Photoelectrodes with Controlled Polycrystalline Architectures

    Energy Technology Data Exchange (ETDEWEB)

    Kyoung-Shin Choi

    2013-06-30

    The major goal of our research was to gain the ability in electrochemical synthesis to precisely control compositions and morphologies of various oxide-based polycrystalline photoelectrodes in order to establish the composition-morphology-photoelectrochemical property relationships while discovering highly efficient photoelectrode systems for use in solar energy conversion. Major achievements include: development of porous n-type BiVO{sub 4} photoanode for efficient and stable solar water oxidation; development of p-type CuFeO{sub 2} photocathode for solar hydrogen production; and junction studies on electrochemically fabricated p-n Cu{sub 2}O homojunction solar cells for efficiency enhancement.

  15. Polycrystalline Diamond Schottky Diodes and Their Applications.

    Science.gov (United States)

    Zhao, Ganming

    In this work, four-hot-filament CVD techniques for in situ boron doped diamond synthesis on silicon substrates were extensively studied. A novel tungsten filament shape and arrangement used to obtain large-area, uniform, boron doped polycrystalline diamond thin films. Both the experimental results and radiative heat transfer analysis showed that this technique improved the uniformity of the substrate temperature. XRD, Raman and SEM studies indicate that large area, uniform, high quality polycrystalline diamond films were obtained. Schottky diodes were fabricated by either sputter deposition of silver or thermal evaporation of aluminum or gold, on boron doped diamond thin films. High forward current density and a high forward-to-reverse current ratio were exhibited by silver on diamond Schottky diodes. Schottky barrier heights and the majority carrier concentrations of both aluminum and gold contacted diodes were determined from the C-V measurements. Furthermore, a novel theoretical C-V-f analysis of deep level boron doped diamond Schottky diodes was performed. The analytical results agree well with the experimental results. Compressive stress was found to have a large effect on the forward biased I-V characteristics of the diamond Schottky diodes, whereas the effect on the reverse biased characteristics was relatively small. The stress effect on the forward biased diamond Schottky diode was attributed to piezojunction and piezoresistance effects. The measured force sensitivity of the diode was as high as 0.75 V/N at 1 mA forward bias. This result shows that CVD diamond device has potential for mechanical transducer applications. The quantitative photoresponse characteristics of the diodes were studied in the spectral range of 300 -1050 nm. Semi-transparent gold contacts were used for better photoresponse. Quantum efficiency as high as 50% was obtained at 500 nm, when a reverse bias of over 1 volt was applied. The Schottky barrier heights between either gold or

  16. Hypersonic modes in nanophononic semiconductors.

    Science.gov (United States)

    Hepplestone, S P; Srivastava, G P

    2008-09-05

    Frequency gaps and negative group velocities of hypersonic phonon modes in periodically arranged composite semiconductors are presented. Trends and criteria for phononic gaps are discussed using a variety of atomic-level theoretical approaches. From our calculations, the possibility of achieving semiconductor-based one-dimensional phononic structures is established. We present results of the location and size of gaps, as well as negative group velocities of phonon modes in such structures. In addition to reproducing the results of recent measurements of the locations of the band gaps in the nanosized Si/Si{0.4}Ge{0.6} superlattice, we show that such a system is a true one-dimensional hypersonic phononic crystal.

  17. Effect of composition on SILAR deposited CdxZn1-xS thin films

    Science.gov (United States)

    Ashith V., K.; Gowrish Rao, K.

    2018-04-01

    In the group of II-VI compound semiconductor, cadmium zinc sulphide (CdxZn1-xS) thin films have broad application in photovoltaic, optoelectronic devices etc. For heterojunction aspects, CdxZn1-xS thin film can be used as heterojunction partner for CdTe as the absorber layer. In this work, CdZnS thin films prepared on glass substrates by Successive Ion Layer Adsorption and Reaction (SILAR) method by varying the composition. The XRD patterns of deposited films showed polycrystalline with the hexagonal phase. The crystallite size of the films was estimated from W-H plot. The bond length of the film varied w.r.to the composition of the CdxZn1-xS films. The urbach energy of the films was calcualted from absorbance data.

  18. Large negative magnetoresistance in reactive sputtered polycrystalline GdNx films

    KAUST Repository

    Mi, W. B.; Guo, Z. B.; Duan, X. F.; Zhang, X. J.; Bai, H. L.

    2013-01-01

    Polycrystalline ferromagnetic GdN x films were fabricated at different N2 flow rates ( fN2 ) to modify N-vacancy concentration so as to study its influence on electrotransport. Metal-semiconductor transition appears at Curie temperature (TC ) of ∼40 K. Temperature-dependent magnetoresistance (MR) shows a peak at T C. The films at fN2  = 5, 10, 15, and 20 sccm show MR of −38%, −42%, −46%, and −86% at 5 K and 50 kOe, respectively. Above 15 K, MR is from colossal MR and from both colossal and tunneling MR below 15 K. The enhanced MR at fN2  = 20 sccm is attributed to large spin polarization of half-metallicity in GdN x with low N vacancies.

  19. Polycrystalline diamond RF MOSFET with MoO3 gate dielectric

    Directory of Open Access Journals (Sweden)

    Zeyang Ren

    2017-12-01

    Full Text Available We report the radio frequency characteristics of the diamond metal-oxide-semiconductor field effect transistor with MoO3 gate dielectric for the first time. The device with 2-μm gate length was fabricated on high quality polycrystalline diamond. The maximum drain current of 150 mA/mm at VGS = -5 V and the maximum transconductance of 27 mS/mm were achieved. The extrinsic cutoff frequency of 1.2 GHz and the maximum oscillation frequency of 1.9 GHz have been measured. The moderate frequency characteristics are attributed to the moderate transconductance limited by the series resistance along the channel. We expect that the frequency characteristics of the device can be improved by increasing the magnitude of gm, or fundamentally decreasing the gate-controlled channel resistance and series resistance along the channel, and down-scaling the gate length.

  20. Large negative magnetoresistance in reactive sputtered polycrystalline GdNx films

    KAUST Repository

    Mi, W. B.

    2013-06-07

    Polycrystalline ferromagnetic GdN x films were fabricated at different N2 flow rates ( fN2 ) to modify N-vacancy concentration so as to study its influence on electrotransport. Metal-semiconductor transition appears at Curie temperature (TC ) of ∼40 K. Temperature-dependent magnetoresistance (MR) shows a peak at T C. The films at fN2  = 5, 10, 15, and 20 sccm show MR of −38%, −42%, −46%, and −86% at 5 K and 50 kOe, respectively. Above 15 K, MR is from colossal MR and from both colossal and tunneling MR below 15 K. The enhanced MR at fN2  = 20 sccm is attributed to large spin polarization of half-metallicity in GdN x with low N vacancies.

  1. Improved contact metallization for high efficiency EFG polycrystalline silicon solar cells

    International Nuclear Information System (INIS)

    Dube, C.E.; Gonsiorawski, R.C.

    1990-01-01

    Improvements in the performance of polycrystalline silicon solar cells based on a novel, laser patterned contact process are described. Small lots of cells having an average conversion efficiency of 14 + %, with several cells approaching 15%, are reported for cells of 45 cm 2 area. The high efficiency contact design is based on YAG laser patterning of the silicon nitride anti-reflection coating. The Cu metallization is done using light-induced plating, with the cell providing the driving voltage for the plating process. The Cu electrodeposits into the laser defined windows in the AR coating for reduced contact area, following which the Cu bridges on top of the Ar coating to form a continuous finger pattern. The higher cell conversion efficiency is attributed to reduced shadow loss, higher junction quality, and reduced metal-semiconductor interfacial area

  2. Composition and Electrical Property Relationships in Polycrystalline Inorganic Materials.

    Science.gov (United States)

    1983-02-01

    have the ilmenite structure (32). Moreover, neutron diffraction studies on ilmenite itself, FeTiO3 , are best fit by a 10% disordering of the cation... FeTiO3 , and might also be useful for LiNbO3. 3 30. 14 r ’ + " ’ " _ "i i I "i . . I n m ~ ~ l ’ == h ao ’ ’ ’ + ’ - ’ a ’ ’ ’ - B. Anomalously high

  3. Considerations for improved polycrystalline cuprate superconductors

    International Nuclear Information System (INIS)

    Shinde, S.L.; Shaw, T.M.

    1990-01-01

    Polycrystalline cuprate superconductors exhibit two-stage superconducting transitions, that are characteristic of granular systems. This behaviour suggests approaches involving improvements in intra and inter-grain properties in order to improve the technologically important superconducting properties such as the magnetic remanent moment and transport critical current density. This paper reports results of our studies on oxygenation, twin density control through grain size and changes in flux pinning within the YBa 2 Cu 3 O 7-δ matrix with Ag substitution under the heading of intra-grain properties and the detrimental effect of grain boundary phases and the effect of Ag substitution on grain boundary pinning under the heading of inter-grain properties

  4. Process Research of Polycrystalline Silicon Material (PROPSM)

    Science.gov (United States)

    Culik, J. S.

    1984-01-01

    An investigation was begun into the usefulness of molecular hydrogen annealing on polycrystalline solar cells. No improvement was realized even after twenty hours of hydrogenation. Thus, samples were chosen on the basis of: (1) low open circuit voltage; (2) low shunt conductance; and (3) high light generated current. These cells were hydrogenated in molecular hydrogen at 300 C. The differences between the before and after hydrogenation values are so slight as to be negligible. These cells have light generated current densities that indicate long minority carrier diffusion lengths. The open circuit voltage appears to be degraded, and quasi-neutral recombination current enhanced. Therefore, molecular hydrogen is not usful for passivating electrically active defects.

  5. Mechanical properties of porous PNZT polycrystalline ceramics

    International Nuclear Information System (INIS)

    Biswas, D.R.; Fulrath, R.M.

    1977-08-01

    Niobium-doped lead zirconate-titanate (PNZT) was used to investigate the effect of porosity on the mechanical properties of a polycrystalline ceramic. Spherical pores (110 to 150 μm diameter) were introduced by using organic materials in the initial specimen fabrication. The matrix grain size (2 to 5 μm) was kept constant. Small pores (2 to 3 μm diameter) of the order of the grain size were formed by varying the sintering conditions. The effect of porosity on strength was predicted quite well by Weibull's probabilistic approach. The Young's modulus showed a linear relationship with increase in porosity. A decrease in fracture toughness with increase in porosity was also observed. It was found that at equivalent porosities, small pore specimens gave higher strength, Young's modulus and fracture toughness compared to specimens containing large pores. Fracture surface analysis, by scanning electron microscopy, showed fracture originated either at the tensile surface or at the edge of the specimen

  6. Semiconductor apparatus and method of fabrication for a semiconductor apparatus

    NARCIS (Netherlands)

    2010-01-01

    The invention relates to a semiconductor apparatus (1) and a method of fabrication for a semiconductor apparatus (1), wherein the semiconductor apparatus (1) comprises a semiconductor layer (2) and a passivation layer (3), arranged on a surface of the semiconductor layer (2), for passivating the

  7. The features of modelling semiconductor lasers with a wide contact

    Directory of Open Access Journals (Sweden)

    Rzhanov Alexey

    2017-01-01

    Full Text Available The aspects of calculating the dynamics and statics of powerful semiconductor laser diodes radiation are investigated. It takes into account the main physical mechanisms influencing power, spectral composition, far and near field of laser radiation. It outlines a dynamic distributed model of a semiconductor laser with a wide contact and possible algorithms for its implementation.

  8. Semiconductor Physical Electronics

    CERN Document Server

    Li, Sheng

    2006-01-01

    Semiconductor Physical Electronics, Second Edition, provides comprehensive coverage of fundamental semiconductor physics that is essential to an understanding of the physical and operational principles of a wide variety of semiconductor electronic and optoelectronic devices. This text presents a unified and balanced treatment of the physics, characterization, and applications of semiconductor materials and devices for physicists and material scientists who need further exposure to semiconductor and photonic devices, and for device engineers who need additional background on the underlying physical principles. This updated and revised second edition reflects advances in semicondutor technologies over the past decade, including many new semiconductor devices that have emerged and entered into the marketplace. It is suitable for graduate students in electrical engineering, materials science, physics, and chemical engineering, and as a general reference for processing and device engineers working in the semicondi...

  9. Semiconductor neutron detectors based on new types of materials

    International Nuclear Information System (INIS)

    Pochet, T.; Foulon, F.

    1993-01-01

    Neutron detection in hostile environments such as nuclear reactors has been performed using a new kind of semiconductor detector. So far, crystalline semiconductor detectors are not used in nuclear reactor instrumentation because of their sensitivity to radiation damage. For doses in excess of a few tens of kilo rads, radiation induced lattice defects produce a strong loss in the standard semiconductor detector performances. In the last few years, new semiconductor materials having amorphous or polycrystalline structures such as silicon, silicon carbide or CVD diamond, became available. These semiconductors, produced by Chemical Vapor Deposition, come in the form of thin layers being typically a few tens of micron thick. Their crystalline structure is particularly resistant to radiation damage up to a few Mrads but prevent the material use in spectrometry measurements. Nevertheless, these detectors, working in a counting mode, are suitable for the detection of alpha particles produced by the neutron capture reaction with boron. Such thin film detectors have a very poor sensitivity to γ-ray background. Furthermore, they are easier and cheaper to implement than current neutron gas counters. Preliminary results obtained with diamond and amorphous silicon diodes exposed to α particles are presented. (authors). 7 figs., 3 tabs., 11 refs

  10. Arsenic implantation into polycrystalline silicon and diffusion to silicon substrate

    International Nuclear Information System (INIS)

    Tsukamoto, K.; Akasaka, Y.; Horie, K.

    1977-01-01

    Arsenic implantation into polycrystalline silicon and drive-in diffusion to silicon substrate have been investigated by MeV He + backscattering analysis and also by electrical measurements. The range distributions of arsenic implanted into polycrystalline silicon are well fitted to Gaussian distributions over the energy range 60--350 keV. The measured values of R/sub P/ and ΔR/sub P/ are about 10 and 20% larger than the theoretical predictions, respectively. The effective diffusion coefficient of arsenic implanted into polycrystalline silicon is expressed as D=0.63 exp[(-3.22 eV/kT)] and is independent of the arsenic concentration. The drive-in diffusion of arsenic from the implanted polycrystalline silicon layer into the silicon substrate is significantly affected by the diffusion atmosphere. In the N 2 atmosphere, a considerable amount of arsenic atoms diffuses outward to the ambient. The outdiffusion can be suppressed by encapsulation with Si 3 N 4 . In the oxidizing atmosphere, arsenic atoms are driven inward by growing SiO 2 due to the segregation between SiO 2 and polycrystalline silicon, and consequently the drive-in diffusion of arsenic is enhanced. At the interface between the polycrystalline silicon layer and the silicon substrate, arsenic atoms are likely to segregate at the polycrystalline silicon side

  11. Contacts to semiconductors

    International Nuclear Information System (INIS)

    Tove, P.A.

    1975-08-01

    Contacts to semiconductors play an important role in most semiconductor devices. These devices range from microelectronics to power components, from high-sensitivity light or radiation detectors to light-emitting of microwave-generating components. Silicon is the dominating material but compound semiconductors are increasing in importance. The following survey is an attempt to classify contact properties and the physical mechanisms involved, as well as fabrication methods and methods of investigation. The main interest is in metal-semiconductor type contacts where a few basic concepts are dealt with in some detail. (Auth.)

  12. Semiconductor Electrical Measurements Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Semiconductor Electrical Measurements Laboratory is a research laboratory which complements the Optical Measurements Laboratory. The laboratory provides for Hall...

  13. Creep behavior for advanced polycrystalline SiC fibers

    International Nuclear Information System (INIS)

    Youngblood, G.E.; Jones, R.H.; Kohyama, Akira

    1997-01-01

    A bend stress relaxation (BSR) test is planned to examine irradiation enhanced creep in polycrystalline SiC fibers which are under development for use as fiber reinforcement in SiC/SiC composite. Baseline 1 hr and 100 hr BSR thermal creep open-quotes mclose quotes curves have been obtained for five selected advanced SiC fiber types and for standard Nicalon CG fiber. The transition temperature, that temperature where the S-shaped m-curve has a value 0.5, is a measure of fiber creep resistance. In order of decreasing thermal creep resistance, with the 100 hr BSR transition temperature given in parenthesis, the fibers ranked: Sylramic (1261 degrees C), Nicalon S (1256 degrees C), annealed Hi Nicalon (1215 degrees C), Hi Nicalon (1078 degrees C), Nicalon CG (1003 degrees C) and Tyranno E (932 degrees C). The thermal creep for Sylramic, Nicalon S, Hi Nicalon and Nicalon CG fibers in a 5000 hr irradiation creep BSR test is projected from the temperature dependence of the m-curves determined during 1 and 100 hr BSR control tests

  14. Creep behavior for advanced polycrystalline SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States); Kohyama, Akira [Kyoto Univ. (Japan)] [and others

    1997-08-01

    A bend stress relaxation (BSR) test is planned to examine irradiation enhanced creep in polycrystalline SiC fibers which are under development for use as fiber reinforcement in SiC/SiC composite. Baseline 1 hr and 100 hr BSR thermal creep {open_quotes}m{close_quotes} curves have been obtained for five selected advanced SiC fiber types and for standard Nicalon CG fiber. The transition temperature, that temperature where the S-shaped m-curve has a value 0.5, is a measure of fiber creep resistance. In order of decreasing thermal creep resistance, with the 100 hr BSR transition temperature given in parenthesis, the fibers ranked: Sylramic (1261{degrees}C), Nicalon S (1256{degrees}C), annealed Hi Nicalon (1215{degrees}C), Hi Nicalon (1078{degrees}C), Nicalon CG (1003{degrees}C) and Tyranno E (932{degrees}C). The thermal creep for Sylramic, Nicalon S, Hi Nicalon and Nicalon CG fibers in a 5000 hr irradiation creep BSR test is projected from the temperature dependence of the m-curves determined during 1 and 100 hr BSR control tests.

  15. Synthesis, characterization and structural refinement of polycrystalline uranium substituted zirconolite

    International Nuclear Information System (INIS)

    Shrivastava, O.P.; Narendra Kumar; Sharma, I.B.

    2005-01-01

    Ceramic precursors of Zirconolite (CaZrTi 2 O 7 ) family have a remarkable property of substitution Zr 4+ cationic sites. This makes them potential material for nuclear waste management in 'synroc' technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a solid phase of composition CaZr 0.95 U 0.5 Ti 2 O 7 has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium respectively. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050 degC. The polycrystalline solid phase has been characterized by its typical powder diffraction pattern. Step analysis data has been used for ab initio calculation of structural parameters. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (15). The following unit cell parameters have been calculated: a =12.4883(15), b =7.2448(5), c 11.3973(10) and β = 100.615(9)0. The structure was refined to satisfactory completion. The Rp and Rwp are found to be 7.48% and 9.74% respectively. (author)

  16. Internal friction and elastic softening in polycrystalline Nb3Sn

    International Nuclear Information System (INIS)

    Bussiere, J.F.; Faucher, B.; Snead, C.L. Jr.; Welch, D.O.

    1981-01-01

    The vibrating-reed technique was used to measure internal friction and Young's modulus of polycrystalline Nb 3 Sn in the form of composite Nb/Nb 3 Sn tapes from 6 to 300 K. In tapes with only small residual strain in the A15 layers, a dramatic increase in internal friction with decreasing temperature is observed with an abrupt onset at approx.48 K. The internal friction Q -1 between 6 and 48 K is believed to be associated with stress-induced motion of martensitic-domain walls. In this temperature range, Q -1 is approximately proportional to the square of the tetragonal strain of the martensitic phase; Q -1 α (c/a-1) 2 . With residual compressive strains of approx.0.2%, the internal friction associated with domain-wall motion is considerably reduced. This is attributed to a biasing of domain-wall orientation with residual stress, which reduces wall motion induced by the (much smaller) applied stress. The transformation temperature, however, is unchanged (within +- 1 K) by residual strains of up to 0.2%. Young's modulus exhibits substantial softening on cooling from 300 to 6 K. This softening, is substantially reduced in the presence of small residual compressive strains, indicating a highly nonlinear stress-strain relationship as previously reported for V 3 Si

  17. Self-oriented Ag-based polycrystalline cubic nanostructures through polymer stabilization

    Science.gov (United States)

    Alonso, Amanda; Vigués, Núria; Rodríguez-Rodríguez, Rosalía; Borrisé, Xavier; Muñoz, María; Muraviev, Dmitri N.; Mas, Jordi; Muñoz-Berbel, Xavier

    2016-10-01

    This paper presents the study of the dynamics of the formation of polymer-assisted highly-orientated polycrystalline cubic structures (CS) by a fractal-mediated mechanism. This mechanism involves the formation of seed Ag@Co nanoparticles by InterMatrix Synthesis and subsequent overgrowth after incubation at a low temperature in chloride and phosphate solutions. These ions promote the dissolution and recrystallization in an ordered configuration of pre-synthetized nanoparticles initially embedded in negatively-charged polymeric matrices. During recrystallization, silver ions aggregate in AgCl@Co fractal-like structures, then evolve into regular polycrystalline solid nanostructures (e.g. CS) in a single crystallization step on specific regions of the ion exchange resin (IER) which maintain the integrity of polycrystalline nanocubes. Here, we study the essential role of the IER in the formation of these CS for the maintenance of their integrity and stability. Thus, this synthesis protocol may be easily expanded to the composition of other nanoparticles providing an interesting, cheap and simple alternative for cubic structure formation and isolation.

  18. Composites

    International Nuclear Information System (INIS)

    Kasen, M.B.

    1983-01-01

    This chapter discusses the roles of composite laminates and aggregates in cryogenic technology. Filamentary-reinforced composites are emphasized because they are the most widely used composite materials. Topics considered include composite systems and terminology, design and fabrication, composite failure, high-pressure reinforced plastic laminates, low-pressure reinforced plastics, reinforced metals, selectively reinforced structures, the effect of cryogenic temperatures, woven-fabric and random-mat composites, uniaxial fiber-reinforced composites, composite joints in cryogenic structures, joining techniques at room temperature, radiation effects, testing laminates at cryogenic temperatures, static and cyclic tensile testing, static and cyclic compression testing, interlaminar shear testing, secondary property tests, and concrete aggregates. It is suggested that cryogenic composite technology would benefit from the development of a fracture mechanics model for predicting the fitness-for-purpose of polymer-matrix composite structures

  19. LaF3 thin films as chemically sensitive material for semiconductor sensors

    International Nuclear Information System (INIS)

    Szeponik, J.; Moritz, W.; Sellam, F.

    1991-01-01

    A new kind of semiconductor based fluoride sensor was prepared by growing thin polycrystalline LaF 3 films directly on silicon substrates using vacuum vapour deposition technique. The EICS (Electrolyte Ion Conductor Semiconductor) structure was investigated by means of impedance spectroscopy, C-V measurements and exchange measurements with labeled ions ( 18 F). Whereas charge and potential conditions at the LaF 3 /electrolyte interface are governed by the fast fluoride exchange the LaF 3 bulk and the blocked Si/LaF 3 interface determine the electrical behavior. Although the Si/LaF 3 contact is not reversible the potential stability of the EICS structure is surprisingly high. Additional results at epitaxial LaF 3 layers, prepared by MBE, were taken into account for comparision with those at polycrystalline layers. (orig.)

  20. Semiconductors data handbook

    CERN Document Server

    Madelung, Otfried

    2004-01-01

    This volume Semiconductors: Data Handbook contains frequently used data from the corresponding larger Landolt-Börnstein handbooks in a low price book for the individual scientist working in the laboratory. The Handbook contain important information about a large number of semiconductors

  1. Semiconductor radiation detection systems

    CERN Document Server

    2010-01-01

    Covers research in semiconductor detector and integrated circuit design in the context of medical imaging using ionizing radiation. This book explores other applications of semiconductor radiation detection systems in security applications such as luggage scanning, dirty bomb detection and border control.

  2. Spin physics in semiconductors

    CERN Document Server

    Dyakonov, Mikhail I

    2008-01-01

    This book describes beautiful optical and transport phenomena related to the electron and nuclear spins in semiconductors with emphasis on a clear presentation of the physics involved. Recent results on quantum wells and quantum dots are reviewed. The book is intended for students and researchers in the fields of semiconductor physics and nanoelectronics.

  3. Loss of shear strength in polycrystalline tungsten under shock compression

    International Nuclear Information System (INIS)

    Dandekar, D.P.

    1976-01-01

    A reexamination of existing data on shock compression of polycrystalline tungsten at room temperature indicates that tungsten may be an exception to the common belief that metals do not behave like elastic-isotropic solids under shock compression

  4. Compound Semiconductor Radiation Detectors

    CERN Document Server

    Owens, Alan

    2012-01-01

    Although elemental semiconductors such as silicon and germanium are standard for energy dispersive spectroscopy in the laboratory, their use for an increasing range of applications is becoming marginalized by their physical limitations, namely the need for ancillary cooling, their modest stopping powers, and radiation intolerance. Compound semiconductors, on the other hand, encompass such a wide range of physical and electronic properties that they have become viable competitors in a number of applications. Compound Semiconductor Radiation Detectors is a consolidated source of information on all aspects of the use of compound semiconductors for radiation detection and measurement. Serious Competitors to Germanium and Silicon Radiation Detectors Wide-gap compound semiconductors offer the ability to operate in a range of hostile thermal and radiation environments while still maintaining sub-keV spectral resolution at X-ray wavelengths. Narrow-gap materials offer the potential of exceeding the spectral resolutio...

  5. Terahertz semiconductor nonlinear optics

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias

    2013-01-01

    In this proceedings we describe our recent results on semiconductor nonlinear optics, investigated using single-cycle THz pulses. We demonstrate the nonlinear absorption and self-phase modulation of strong-field THz pulses in doped semiconductors, using n-GaAs as a model system. The THz...... nonlinearity in doped semiconductors originates from the near-instantaneous heating of free electrons in the ponderomotive potential created by electric field of the THz pulse, leading to ultrafast increase of electron effective mass by intervalley scattering. Modification of effective mass in turn leads...... to a decrease of plasma frequency in semiconductor and produces a substantial modification of THz-range material dielectric function, described by the Drude model. As a result, the nonlinearity of both absorption coefficient and refractive index of the semiconductor is observed. In particular we demonstrate...

  6. Organic semiconductor crystals.

    Science.gov (United States)

    Wang, Chengliang; Dong, Huanli; Jiang, Lang; Hu, Wenping

    2018-01-22

    Organic semiconductors have attracted a lot of attention since the discovery of highly doped conductive polymers, due to the potential application in field-effect transistors (OFETs), light-emitting diodes (OLEDs) and photovoltaic cells (OPVs). Single crystals of organic semiconductors are particularly intriguing because they are free of grain boundaries and have long-range periodic order as well as minimal traps and defects. Hence, organic semiconductor crystals provide a powerful tool for revealing the intrinsic properties, examining the structure-property relationships, demonstrating the important factors for high performance devices and uncovering fundamental physics in organic semiconductors. This review provides a comprehensive overview of the molecular packing, morphology and charge transport features of organic semiconductor crystals, the control of crystallization for achieving high quality crystals and the device physics in the three main applications. We hope that this comprehensive summary can give a clear picture of the state-of-art status and guide future work in this area.

  7. Deuterium transport and trapping in polycrystalline tungsten

    International Nuclear Information System (INIS)

    Anderl, R.A.; Holland, D.F.; Longhurst, G.R.; Pawelko, R.J.; Trybus, C.L.; Sellers, C.H.

    1992-01-01

    This paper reports that deuterium permeation studies for polycrystalline tungsten foil have been conducted to provide data for estimating tritium transport and trapping in tungsten-clad divertors proposed for advanced fusion-reactor concepts. Based on a detailed transmission electron microscopy (TEM) microstructural characterization of the specimen material and on analyses of permeation data measured at temperatures ranging form 610 to 823 K for unannealed and annealed tungsten foil (25 μm thick), the authors note the following key results: deuterium transport in tungsten foil is dominated by extensive trapping that varies inversely with prior anneal temperatures of the foil material, the reduction in the trapped fraction correlates with a corresponding elimination of a high density of dislocations in cell-wall structures introduced during the foil fabrication process, trapping behavior in these foils can be modelled using trap energies between 1.3 eV and 1.5 eV and trap densities ranging from 1 x 10 -5 atom fraction

  8. Thermomechanical characterization of pure polycrystalline tantalum

    International Nuclear Information System (INIS)

    Rittel, D.; Bhattacharyya, A.; Poon, B.; Zhao, J.; Ravichandran, G.

    2007-01-01

    The thermomechanical behavior of pure polycrystalline tantalum has been characterized over a wide range of strain rates, using the recently developed shear compression specimen [D. Rittel, S. Lee, G. Ravichandran, Experimental Mechanics 42 (2002) 58-64]. Dynamic experiments were carried out using a split Hopkinson pressure bar, and the specimen's temperature was monitored throughout the tests using an infrared radiometer. The results of the mechanical tests confirm previous results on pure Ta. Specifically, in addition to its significant strain rate sensitivity, it was observed that pure Ta exhibits very little strain hardening at high strain rates. The measured temperature rise in the specimen's gauge was compared to theoretical predictions which assume a total conversion of the mechanical energy into heat (β = 1) [G.I. Taylor, H. Quinney, Proceedings of the Royal Society of London, vol. A, 1934, pp. 307-326], and an excellent agreement was obtained. This result confirms the previous result of Kapoor and Nemat-Nasser [R. Kapoor, S. Nemat-Nasser, Mech. Mater. 27 (1998) 1-12], while a different experimental approach was adopted here. The assumption that β = 1 is found to be justified in this specific case by the lack of dynamic strain hardening of pure Ta. However, this assumption should be limited to non-hardening materials, to reflect the fact that strain hardening implies that part of the mechanical energy is stored into the material's microstructure

  9. Tritium diffusion in polycrystalline lithium tungstate

    International Nuclear Information System (INIS)

    Krutyakov, A.N.; Shadrin, A.A.; Saunin, E.I.; Gromov, V.V.; Shafiev, A.I.

    1984-01-01

    Using radiometric method the investigation of tritium separation from neutron irradiated (neutron flux density 1.2x10 13 n/cm 2 xs) polycrystalline Li 2 WO 4 in the temperature range 200-680 deg C has been carried out. It is established that the use of helium as gas-carrier of flow-type gas-discharge counter permits to conduct continuous stable measurements of concentrations of tritium extracted depending on its chemical state. It is shown that volume diffusion is the process, limiting tritiated particle separation rate from Li 2 WO 4 . It is found that the process of tritium volume diffusion in Li 2 WO 4 corresponds to two different mechanisms respectively in low- (200-300 deg C) and high-temperature (350-680 deg C) ranges. A supposition is made that in the low-temperature range the process of diffusion is conditioned by the dissociation of the radiation defect-tritiated particle complex, which is confirmed by the data on radiation defect annealing in Li 2 WO 4 . The value of activation energy of tritium separation process in the range 350-680 deg C, proved to be equal to 13.3 kJ/mol. Possible role of crystal structure peculiarities of Li 2 WO 4 for diffusion process is pointed out

  10. Deformation localization and cyclic strength in polycrystalline molybdenum

    Energy Technology Data Exchange (ETDEWEB)

    Sidorov, O.T.; Rakshin, A.F.; Fenyuk, M.I.

    1983-06-01

    Conditions of deformation localization and its interrelation with cyclic strength in polycrystalline molybdenum were investigated. A fatigue failure of polycrystalline molybdenum after rolling and in an embrittled state reached by recrystallization annealing under cyclic bending at room temperature takes place under nonuniform distribution of microplastic strain resulting in a temperature rise in separate sections of more than 314 K. More intensive structural changes take place in molybdenum after rolling than in recrystallized state.

  11. Selection of efficient etchants for nondestructive treatment of semiconductors

    International Nuclear Information System (INIS)

    Tomashik, V.N.; Fomin, A.V.; Tomashik, Z.F.

    1996-01-01

    The scheme for studying etching processes of semiconductor materials and developing new etchants for different semiconductors is proposed. The scheme includes the experiment mathematical planning, computerized physicochemical modeling, kinetic studies, investigation of surface layers, formed by etching. Such on approach makes it possible to optimize the etchant composition in every concrete cage. The scheme is tested in the course of developing optimal methodologies of preepitaxial treatment and selection of etchants composition for semiconductor compounds of the A 1 B 6 and A 3 B 5 type. 13 refs., 4 figs

  12. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2011-01-01

    Strategies are open compositions to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them in full...

  13. Composition

    DEFF Research Database (Denmark)

    2014-01-01

    Memory Pieces are open compositions to be realised solo by an improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them...

  14. Technique for measuring irradiation creep in polycrystalline SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Hamilton, M.L.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    A bend stress relaxation (BSR) test has been designed to examine irradiation enhanced creep in polycrystalline SiC fibers being considered for fiber reinforcement in SiC/SiC composite. Thermal creep results on Nicalon-CG and Hi-Nicalon were shown to be consistent with previously published data with Hi-Nicalon showing about a 100{degrees}C improvement in creep resistance. Preliminary data was also obtained on Nicalon-S that demonstrated that its creep resistance is greater than that of Hi-Nicalon.

  15. Laser vapor phase deposition of semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Karlov, N.V.; Luk' ianchuk, B.S.; Sisakian, E.V.; Shafeev, G.A.

    1987-06-01

    The pyrolytic effect of IR laser radiation is investigated with reference to the initiation and control of the vapor phase deposition of semiconductor films. By selecting the gas mixture composition and laser emission parameters, it is possible to control the deposition and crystal formation processes on the surface of semiconductors, with the main control action achieved due to the nonadiabatic kinetics of reactions in the gas phase and high temperatures in the laser heating zone. This control mechanism is demonstrated experimentally during the laser vapor deposition of germanium and silicon films from tetrachlorides on single-crystal Si and Ge substrates. 5 references.

  16. Magnetic susceptibility of semiconductor melts

    International Nuclear Information System (INIS)

    Kutvitskij, V.A.; Shurygin, P.M.

    1975-01-01

    The temperature dependences chi of various alloys confirm the existence of cluster formations in molten semiconductors, the stability of these formations in melts being considerably affected by the anion nature. The concentrational dependences of the magnetic susceptibility for all the investigated systems exhibit the diamagnetism maxima corresponding to the compound compositions. Heating the melt causes ''smearing'' the maxima, which is related with the cluster structure dissociation. The existence of the maxima concentrational dependence chi corresponding to BiTe and BiSe is found in the isotherms. The non-linear dependence of chi on the composition shows the absence of a single-valued relation between the phase diagram and the chi-diagram for melts

  17. Defects in semiconductors

    International Nuclear Information System (INIS)

    Pimentel, C.A.F.

    1983-01-01

    Some problems openned in the study of defects in semiconductors are presented. In particular, a review is made of the more important problems in Si monocrystals of basic and technological interest: microdefects and the presence of oxigen and carbon. The techniques usually utilized in the semiconductor material characterization are emphatized according its potentialities. Some applications of x-ray techniques in the epitaxial shell characterization in heterostructures, importants in electronic optics, are shown. The increase in the efficiency of these defect analysis methods in semiconductor materials with the use of synchrotron x-ray sources is shown. (L.C.) [pt

  18. Introduction to Semiconductor Devices

    Science.gov (United States)

    Brennan, Kevin F.

    2005-03-01

    This volume offers a solid foundation for understanding the most important devices used in the hottest areas of electronic engineering today, from semiconductor fundamentals to state-of-the-art semiconductor devices in the telecommunications and computing industries. Kevin Brennan describes future approaches to computing hardware and RF power amplifiers, and explains how emerging trends and system demands of computing and telecommunications systems influence the choice, design and operation of semiconductor devices. In addition, he covers MODFETs and MOSFETs, short channel effects, and the challenges faced by continuing miniaturization. His book is both an excellent senior/graduate text and a valuable reference for practicing engineers and researchers.

  19. Spin physics in semiconductors

    CERN Document Server

    2017-01-01

    This book offers an extensive introduction to the extremely rich and intriguing field of spin-related phenomena in semiconductors. In this second edition, all chapters have been updated to include the latest experimental and theoretical research. Furthermore, it covers the entire field: bulk semiconductors, two-dimensional semiconductor structures, quantum dots, optical and electric effects, spin-related effects, electron-nuclei spin interactions, Spin Hall effect, spin torques, etc. Thanks to its self-contained style, the book is ideally suited for graduate students and researchers new to the field.

  20. Physics of semiconductor lasers

    CERN Document Server

    Mroziewicz, B; Nakwaski, W

    2013-01-01

    Written for readers who have some background in solid state physics but do not necessarily possess any knowledge of semiconductor lasers, this book provides a comprehensive and concise account of fundamental semiconductor laser physics, technology and properties. The principles of operation of these lasers are therefore discussed in detail with the interrelations between their design and optical, electrical and thermal properties. The relative merits of a large number of laser structures and their parameters are described to acquaint the reader with the various aspects of the semiconductor l

  1. Semiconductors bonds and bands

    CERN Document Server

    Ferry, David K

    2013-01-01

    As we settle into this second decade of the twenty-first century, it is evident that the advances in micro-electronics have truly revolutionized our day-to-day lifestyle. The technology is built upon semiconductors, materials in which the band gap has been engineered for special values suitable to the particular application. This book, written specifically for a one semester course for graduate students, provides a thorough understanding of the key solid state physics of semiconductors. It describes how quantum mechanics gives semiconductors unique properties that enabled the micro-electronics revolution, and sustain the ever-growing importance of this revolution.

  2. Defects in semiconductors

    CERN Document Server

    Romano, Lucia; Jagadish, Chennupati

    2015-01-01

    This volume, number 91 in the Semiconductor and Semimetals series, focuses on defects in semiconductors. Defects in semiconductors help to explain several phenomena, from diffusion to getter, and to draw theories on materials' behavior in response to electrical or mechanical fields. The volume includes chapters focusing specifically on electron and proton irradiation of silicon, point defects in zinc oxide and gallium nitride, ion implantation defects and shallow junctions in silicon and germanium, and much more. It will help support students and scientists in their experimental and theoret

  3. A new electrode design for ambipolar injection in organic semiconductors.

    Science.gov (United States)

    Kanagasekaran, Thangavel; Shimotani, Hidekazu; Shimizu, Ryota; Hitosugi, Taro; Tanigaki, Katsumi

    2017-10-17

    Organic semiconductors have attracted much attention for low-cost, flexible and human-friendly optoelectronics. However, achieving high electron-injection efficiency is difficult from air-stable electrodes and cannot be equivalent to that of holes. Here, we present a novel concept of electrode composed of a bilayer of tetratetracontane (TTC) and polycrystalline organic semiconductors (pc-OSC) covered by a metal layer. Field-effect transistors of single-crystal organic semiconductors with the new electrodes of M/pc-OSC/TTC (M: Ca or Au) show both highly efficient electron and hole injection. Contact resistance for electron injection from Au/pc-OSC/TTC and hole injection from Ca/pc-OSC/TTC are comparable to those for electron injection from Ca and hole injection from Au, respectively. Furthermore, the highest field-effect mobilities of holes (22 cm 2  V -1  s -1 ) and electrons (5.0 cm 2  V -1  s -1 ) are observed in rubrene among field-effect transistors with electrodes so far proposed by employing Ca/pc-OSC/TTC and Au/pc-OSC/TTC electrodes for electron and hole injection, respectively.One of technological challenges building organic electronics is efficient injection of electrons at metal-semiconductor interfaces compared to that of holes. The authors show an air-stable electrode design with induced gap states, which support Fermi level pinning and thus ambipolar carrier injection.

  4. Optical Biosensors Based on Semiconductor Nanostructures

    Directory of Open Access Journals (Sweden)

    Raúl J. Martín-Palma

    2009-06-01

    Full Text Available The increasing availability of semiconductor-based nanostructures with novel and unique properties has sparked widespread interest in their use in the field of biosensing. The precise control over the size, shape and composition of these nanostructures leads to the accurate control of their physico-chemical properties and overall behavior. Furthermore, modifications can be made to the nanostructures to better suit their integration with biological systems, leading to such interesting properties as enhanced aqueous solubility, biocompatibility or bio-recognition. In the present work, the most significant applications of semiconductor nanostructures in the field of optical biosensing will be reviewed. In particular, the use of quantum dots as fluorescent bioprobes, which is the most widely used application, will be discussed. In addition, the use of some other nanometric structures in the field of biosensing, including porous semiconductors and photonic crystals, will be presented.

  5. Biggest semiconductor installed

    CERN Multimedia

    2008-01-01

    Scientists and technicians at the European Laboratory for Particle Physics, commonly known by its French acronym CERN (Centre Europen pour la Recherche Nuclaire), have completed the installation of the largest semiconductor silicon detector.

  6. Compact semiconductor lasers

    CERN Document Server

    Yu, Siyuan; Lourtioz, Jean-Michel

    2014-01-01

    This book brings together in a single volume a unique contribution by the top experts around the world in the field of compact semiconductor lasers to provide a comprehensive description and analysis of the current status as well as future directions in the field of micro- and nano-scale semiconductor lasers. It is organized according to the various forms of micro- or nano-laser cavity configurations with each chapter discussing key technical issues, including semiconductor carrier recombination processes and optical gain dynamics, photonic confinement behavior and output coupling mechanisms, carrier transport considerations relevant to the injection process, and emission mode control. Required reading for those working in and researching the area of semiconductors lasers and micro-electronics.

  7. Polycrystalline apatite synthesized by hydrothermal replacement of calcium carbonates

    Science.gov (United States)

    Kasioptas, Argyrios; Geisler, Thorsten; Perdikouri, Christina; Trepmann, Claudia; Gussone, Nikolaus; Putnis, Andrew

    2011-06-01

    Aragonite and calcite single crystals can be readily transformed into polycrystalline hydroxyapatite pseudomorphs by hydrothermal treatment in a (NH 4) 2HPO 4 solution. Scanning electron microscopy of the reaction products showed that the transformation of aragonite to apatite is characterised by the formation of a sharp interface between the two phases and by the development of intracrystalline porosity in the hydroxyapatite phase. In addition, electron backscattered diffraction (EBSD) imaging showed that the c-axis of apatite is predominantly oriented perpendicular to the reaction front with no crystallographic relationship to the aragonite lattice. However, the Ca isotopic composition of the parent aragonite, measured by thermal ionization mass spectrometry was inherited by the apatite product. Hydrothermal experiments conducted with use of phosphate solutions prepared with water enriched in 18O (97%) further revealed that the 18O from the solution is incorporated in the product apatite, as measured by micro-Raman spectroscopy. Monitoring the distribution of 18O with Raman spectroscopy was possible because the incorporation of 18O in the PO 4 group of apatite generates four new Raman bands at 945.8, 932, 919.7 and 908.8 cm -1, in addition to the ν1(PO 4) symmetric stretching band of apatite located at 962 cm -1, which can be assigned to four 18O-bearing PO 4 species. The relative intensities of these bands reflect the 18O content in the PO 4 group of the apatite product. By using equilibrated and non-equilibrated solutions, with respect to the 18O distribution between aqueous phosphate and water, we could show that the concentration of 18O in the apatite product is linked to the degree of 18O equilibration in the solution. The textural and chemical observations are indicative of a coupled mechanism of aragonite dissolution and apatite precipitation taking place at a moving reaction interface.

  8. Radiation effects in semiconductors

    CERN Document Server

    2011-01-01

    There is a need to understand and combat potential radiation damage problems in semiconductor devices and circuits. Written by international experts, this book explains the effects of radiation on semiconductor devices, radiation detectors, and electronic devices and components. These contributors explore emerging applications, detector technologies, circuit design techniques, new materials, and innovative system approaches. The text focuses on how the technology is being used rather than the mathematical foundations behind it. It covers CMOS radiation-tolerant circuit implementations, CMOS pr

  9. Market survey of semiconductors

    International Nuclear Information System (INIS)

    Mackintosh, I.M.; Diegel, D.; Brown, A.; Brinker, C.S. den

    1977-06-01

    Examination of technology and product trends over the range of current and future products in integrated circuits and optoelectronic displays. Analysis and forecast of major economic influences that affect the production costs of integrated circuits and optoelectronic displays. Forecast of the applications and markets for integrated circuits up to 1985 in West Europe, the USA and Japan. Historic development of the semiconductor industry and the prevailing tendencies - factors which influence success in the semiconductor industry. (orig.) [de

  10. Electronic properties of semiconductor heterostructures

    International Nuclear Information System (INIS)

    Einevoll, G.T.

    1991-02-01

    Ten papers on the electronic properties of semiconductors and semiconductor heterostructures constitute the backbone of this thesis. Four papers address the form and validity of the single-band effective mass approximation for semiconductor heterostructures. In four other papers properties of acceptor states in bulk semiconductors and semiconductor heterostructures are studied using the novel effective bond-orbital model. The last two papers deal with localized excitions. 122 refs

  11. Direct observation of nanometer-scale amorphous layers and oxide crystallites at grain boundaries in polycrystalline Sr1−xKxFe2As2 superconductors

    KAUST Repository

    Wang, Lei; Ma, Yanwei; Wang, Qingxiao; Li, Kun; Zhang, Xixiang; Qi, Yanpeng; Gao, Zhaoshun; Zhang, Xianping; Wang, Dongliang; Yao, Chao; Wang, Chunlei

    2011-01-01

    We report here an atomic resolution study of the structure and composition of the grain boundaries in polycrystallineSr0.6K0.4Fe2As2superconductor. A large fraction of grain boundaries contain amorphous layers larger than the coherence length, while

  12. Nanoscale Metal Oxide Semiconductors for Gas Sensing

    Science.gov (United States)

    Hunter, Gary W.; Evans, Laura; Xu, Jennifer C.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Michael J.

    2011-01-01

    A report describes the fabrication and testing of nanoscale metal oxide semiconductors (MOSs) for gas and chemical sensing. This document examines the relationship between processing approaches and resulting sensor behavior. This is a core question related to a range of applications of nanotechnology and a number of different synthesis methods are discussed: thermal evaporation- condensation (TEC), controlled oxidation, and electrospinning. Advantages and limitations of each technique are listed, providing a processing overview to developers of nanotechnology- based systems. The results of a significant amount of testing and comparison are also described. A comparison is made between SnO2, ZnO, and TiO2 single-crystal nanowires and SnO2 polycrystalline nanofibers for gas sensing. The TECsynthesized single-crystal nanowires offer uniform crystal surfaces, resistance to sintering, and their synthesis may be done apart from the substrate. The TECproduced nanowire response is very low, even at the operating temperature of 200 C. In contrast, the electrospun polycrystalline nanofiber response is high, suggesting that junction potentials are superior to a continuous surface depletion layer as a transduction mechanism for chemisorption. Using a catalyst deposited upon the surface in the form of nanoparticles yields dramatic gains in sensitivity for both nanostructured, one-dimensional forms. For the nanowire materials, the response magnitude and response rate uniformly increase with increasing operating temperature. Such changes are interpreted in terms of accelerated surface diffusional processes, yielding greater access to chemisorbed oxygen species and faster dissociative chemisorption, respectively. Regardless of operating temperature, sensitivity of the nanofibers is a factor of 10 to 100 greater than that of nanowires with the same catalyst for the same test condition. In summary, nanostructure appears critical to governing the reactivity, as measured by electrical

  13. Direct observation of nanometer-scale amorphous layers and oxide crystallites at grain boundaries in polycrystalline Sr1−xKxFe2As2 superconductors

    KAUST Repository

    Wang, Lei

    2011-06-01

    We report here an atomic resolution study of the structure and composition of the grain boundaries in polycrystallineSr0.6K0.4Fe2As2superconductor. A large fraction of grain boundaries contain amorphous layers larger than the coherence length, while some others contain nanometer-scale crystallites sandwiched in between amorphous layers. We also find that there is significant oxygen enrichment at the grain boundaries. Such results explain the relatively low transport critical current density (Jc) of polycrystalline samples with respect to that of bicrystal films.

  14. Ultrafast laser-semiconductor interactions

    International Nuclear Information System (INIS)

    Schile, L.A.

    1996-01-01

    Studies of the ultrafast (< 100 fs) interactions of infrared, sub-100 fs laser pulses with IR, photosensitive semiconductor materials InGaAs, InSb, and HgCdTe are reported. Both the carrier dynamics and the associated Terahertz radiation from these materials are discussed. The most recent developments of femtosecond (< 100 fs) Optical Parametric Oscillators (OPO) has extended the wavelength range from the visible to 5.2 μm. The photogenerated semiconductor free carrier dynamics are determined in the 77 to 300 degrees K temperature range using the Transmission Correlation Peak (TCP) method. The electron-phonon scattering times are typically 200 - 600 fs. Depending upon the material composition and substrate on which the IR crystalline materials are deposited, the nonlinear TCP absorption gives recombination rates as fast as 10's of picoseconds. For the HgCdTe, there exists a 400 fs electron-phonon scattering process along with a much longer 3600 fs loss process. Studies of the interactions of these ultrashort laser pulses with semiconductors produce Terahertz (Thz) radiative pulses. With undoped InSb, there is a substantial change in the spectral content of this THz radiation between 80 - 260 degrees K while the spectrum of Te-doped InSb remains nearly unchanged, an effect attributed to its mobility being dominated by impurity scattering. At 80 degrees K, the terahertz radiation from undoped InSb is dependent on wavelength, with both a higher frequency spectrum and much larger amplitudes generated at longer wavelengths. No such effect is observed at 260 degrees K. Finally, new results on the dependence of the emitted THz radiation on the InSb crystal's orientation is presented

  15. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2014-01-01

    Cue Rondo is an open composition to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound/video files will in some cases only provide a few minutes' sample, or the visuals will not appear at all....... Please DOWNLOAD them to see/hear them in full length! This work is licensed under a Creative Commons "by-nc" License. You may for non-commercial purposes use and distribute it, performance instructions as well as specially designated recordings, as long as the author is mentioned. Please see http...

  16. Atomistic modeling of mechanical properties of polycrystalline graphene

    International Nuclear Information System (INIS)

    Mortazavi, Bohayra; Cuniberti, Gianaurelio

    2014-01-01

    We performed molecular dynamics (MD) simulations to investigate the mechanical properties of polycrystalline graphene. By constructing molecular models of ultra-fine-grained graphene structures, we studied the effect of different grain sizes of 1–10 nm on the mechanical response of graphene. We found that the elastic modulus and tensile strength of polycrystalline graphene decrease with decreasing grain size. The calculated mechanical proprieties for pristine and polycrystalline graphene sheets are found to be in agreement with experimental results in the literature. Our MD results suggest that the ultra-fine-grained graphene structures can show ultrahigh tensile strength and elastic modulus values that are very close to those of pristine graphene sheets. (papers)

  17. Polycrystalline Materials as a Cold Neutron and Gamma Radiation Filter

    International Nuclear Information System (INIS)

    Habib, N.

    2009-01-01

    The total neutron cross-section of polycrystalline beryllium, graphite and iron has been calculated beyond their cut-off wavelength using a general formula. The computer Cold Filter code was developed in order to provide the required calculations. The code also permits the calculation of attenuation of reactor gamma radiation, The calculated neutron transmissions through polycrystalline Be graphite and iron at different temperatures were compared with the experimental data measured at the ETRR-1 reactor using two TOF spectrometers. An overall agreement is obtained between the formula fits and experimental data at different temperatures. A feasibility study is carried on using polycrystalline Be, graphite and iron an efficient filter for cold neutrons and gamma radiation.

  18. Atomistic modeling of mechanical properties of polycrystalline graphene.

    Science.gov (United States)

    Mortazavi, Bohayra; Cuniberti, Gianaurelio

    2014-05-30

    We performed molecular dynamics (MD) simulations to investigate the mechanical properties of polycrystalline graphene. By constructing molecular models of ultra-fine-grained graphene structures, we studied the effect of different grain sizes of 1-10 nm on the mechanical response of graphene. We found that the elastic modulus and tensile strength of polycrystalline graphene decrease with decreasing grain size. The calculated mechanical proprieties for pristine and polycrystalline graphene sheets are found to be in agreement with experimental results in the literature. Our MD results suggest that the ultra-fine-grained graphene structures can show ultrahigh tensile strength and elastic modulus values that are very close to those of pristine graphene sheets.

  19. Band Engineering Small Bandgap p-Type Semiconductors: Investigations of their Optical and Photoelectrochemical Properties

    Science.gov (United States)

    Zoellner, Brandon

    Mixed-metal oxides containing Mn(II), Cu(I), Ta(V), Nb(V), and V(V) were investigated for their structures and properties as new p-type semiconductors and in the potential applications involving the photocatalytic conversion of water into hydrogen and oxygen. Engineering of the bandgaps was achieved by combining metal cations that have halffilled (Mn 3d5) or filled (Cu 3d10) d-orbitals together with metal cations that have empty (V/Nb/Ta 3/4/5 d0) d-orbitals. The research described herein focuses on the synthesis, optical, electronic, and photocatalytic properties of the metal-oxide semiconductors MnV2O6, Cu3VO 4, CuNb1-xTaxO3, and Cu5(Ta1-xNbx)11O30. Powder X-ray diffraction was used to probe their phase purity as well as atomic-level crystallographic details, i.e. shifts of lattice parameters, chemical compositions, and changes in local bonding environments. Optical measurements revealed visible-light bandgap sizes of ˜1.17 eV (Cu3VO4), ˜1.45 eV (MnV2O6), ˜1.89-1.97 eV (CuNb1-xTa xO3), and ˜1.97-2.50 eV (Cu5(Ta1-xNb x)11O30). The latter two were found to systematically vary as a function of composition. Electrochemical impedance spectroscopy measurements of MnV2O6 and Cu3VO 4 provided the first experimental characterization of the energetic positions of the valence and conduction bands with respect to the water oxidation and reduction potentials, as well as confirmed the p-type nature of each semiconductor. The valence and conduction band energies were found to be suitable for driving either one or both of the water-splitting half reaction (i.e. 2H+ → H2 and 2H2O → O2 + 4H+). Photoelectrochemical measurements on polycrystalline films of the Cu(I)-based semiconductors under visible-light irradiation produced cathodic currents indicative of p-type semiconductor character and chemical reduction at their surfaces in the electrolyte solution. The stability of the photocurrents was increased by the addition of CuO oxide particles either externally deposited or

  20. The ATLAS semiconductor tracker (SCT)

    International Nuclear Information System (INIS)

    Jackson, J.N.

    2005-01-01

    The ATLAS detector (CERN,LHCC,94-43 (1994)) is designed to study a wide range of physics at the CERN Large Hadron Collider (LHC) at luminosities up to 10 34 cm -2 s -1 with a bunch-crossing rate of 40 MHz. The Semiconductor Tracker (SCT) forms a key component of the Inner Detector (vol. 1, ATLAS TDR 4, CERN,LHCC 97-16 (1997); vol. 2, ATLAS TDR 5, CERN,LHCC 97-17 (1997)) which is situated inside a 2 T solenoid field. The ATLAS Semiconductor Tracker (SCT) utilises 4088 silicon modules with binary readout mounted on carbon fibre composite structures arranged in the forms of barrels in the central region and discs in the forward region. The construction of the SCT is now well advanced. The design of the SCT modules, services and support structures will be briefly outlined. A description of the various stages in the construction process will be presented with examples of the performance achieved and the main difficulties encountered. Finally, the current status of the construction is reviewed

  1. Nucleation and growth of polycrystalline SiC

    DEFF Research Database (Denmark)

    Kaiser, M.; Schimmel, S.; Jokubavicius, V.

    2014-01-01

    The nucleation and bulk growth of polycrystalline SiC in a 2 inch PVT setup using isostatic and pyrolytic graphite as substrates was studied. Textured nucleation occurs under near-thermal equilibrium conditions at the initial growth stage with hexagonal platelet shaped crystallites of 4H, 6H and 15......R polytypes. It is found that pyrolytic graphite results in enhanced texturing of the nucleating gas species. Reducing the pressure leads to growth of the crystallites until a closed polycrystalline SiC layer containing voids with a rough surface is developed. Bulk growth was conducted at 35 mbar Ar...

  2. Hall measurements and grain-size effects in polycrystalline silicon

    International Nuclear Information System (INIS)

    Ghosh, A.K.; Rose, A.; Maruska, H.P.; Eustace, D.J.; Feng, T.

    1980-01-01

    The effects of grain size on Hall measurements in polycrystalline silicon are analyzed and interpreted, with some modifications, using the model proposed by Bube. This modified model predicts that the measured effective Hall voltage is composed of components originating from the bulk and space-charge regions. For materials with large grain sizes, the carrier concentration is independent of the intergrain boundary barrier, whereas the mobility is dependent on it. However, for small grains, both the carrier density and mobility depend on the barrier. These predictions are consistent with experimental results of mm-size Wacker and μm-size neutron-transmutation-doped polycrystalline silicon

  3. Spectral response of a polycrystalline silicon solar cell

    International Nuclear Information System (INIS)

    Ba, B.; Kane, M.

    1994-10-01

    A theoretical study of the spectral response of a polycrystalline silicon n-p junction solar cell is presented. The case of a fibrously oriented grain structure, involving grain boundary recombination velocity and grain size effects is discussed. The contribution of the base region on the internal quantum efficiency Q int is computed for different grain sizes and grain boundary recombination velocities in order to examine their influence. Suggestions are also made for the determination of base diffusion length in polycrystalline silicon solar cells using the spectral response method. (author). 15 refs, 4 figs

  4. Software optimization for electrical conductivity imaging in polycrystalline diamond cutters

    Energy Technology Data Exchange (ETDEWEB)

    Bogdanov, G.; Ludwig, R. [Department of Electrical and Computer Engineering, Worcester Polytechnic Institute, 100 Institute Rd, Worcester, MA 01609 (United States); Wiggins, J.; Bertagnolli, K. [US Synthetic, 1260 South 1600 West, Orem, UT 84058 (United States)

    2014-02-18

    We previously reported on an electrical conductivity imaging instrument developed for measurements on polycrystalline diamond cutters. These cylindrical cutters for oil and gas drilling feature a thick polycrystalline diamond layer on a tungsten carbide substrate. The instrument uses electrical impedance tomography to profile the conductivity in the diamond table. Conductivity images must be acquired quickly, on the order of 5 sec per cutter, to be useful in the manufacturing process. This paper reports on successful efforts to optimize the conductivity reconstruction routine, porting major portions of it to NVIDIA GPUs, including a custom CUDA kernel for Jacobian computation.

  5. Development of surface relief on polycrystalline metals due to sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Voitsenya, V.S. [IPP NSC KIPT, 61108 Kharkov (Ukraine); Balden, M. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, Garching (Germany); Bardamid, A.F. [Taras Shevchenko National University, 01033 Kiev (Ukraine); Bondarenko, V.N. [IPP NSC KIPT, 61108 Kharkov (Ukraine); Davis, J.W., E-mail: jwdavis@starfire.utias.utoronto.ca [University of Toronto Institute for Aerospace Studies, 4925 Dufferin St., Toronto, ON, Canada M3H5T6 (Canada); Konovalov, V.G.; Ryzhkov, I.V.; Skoryk, O.O.; Solodovchenko, S.I. [IPP NSC KIPT, 61108 Kharkov (Ukraine); Zhang-jian, Zhou [University of Science and Technology Beijing, Beijing 100 083 (China)

    2013-05-01

    The characteristics of surface microrelief that appear in sputtering experiments with polycrystalline metals of various grain sizes have been studied. Specimens with grain sizes varying from 30–70 nm in the case of crystallized amorphous alloys, to 1–3 μm for technical tungsten grade and 10–100 μm for recrystallized tungsten were investigated. A model is proposed for the development of roughness on polycrystalline metals which is based on the dependence of sputtering rate on crystal orientation. The results of the modeling are in good agreement with experiments showing that the length scale of roughness is much larger than the grain size.

  6. Laser induced single-crystal transition in polycrystalline silicon

    International Nuclear Information System (INIS)

    Vitali, G.; Bertolotti, M.; Foti, G.; Rimini, E.

    1978-01-01

    Transition to single crystal of polycrystalline Si material underlying a Si crystal substrate of 100 orientation was obtained via laser irradiation. The changes in the structure were analyzed by reflection high energy electron diffraction and by channeling effect technique using 2.0 MeV He Rutherford scattering. The power density required to induce the transition in a 4500 A thick polycrystalline layer is about 70 MW/cm 2 (50ns). The corresponding amorphous to single transition has a threshold of about 45 MW/cm 2 . (orig.) 891 HPOE [de

  7. Method of doping a semiconductor

    International Nuclear Information System (INIS)

    Yang, C.Y.; Rapp, R.A.

    1983-01-01

    A method is disclosed for doping semiconductor material. An interface is established between a solid electrolyte and a semiconductor to be doped. The electrolyte is chosen to be an ionic conductor of the selected impurity and the semiconductor material and electrolyte are jointly chosen so that any compound formed from the impurity and the semiconductor will have a free energy no lower than the electrolyte. A potential is then established across the interface so as to allow the impurity ions to diffuse into the semiconductor. In one embodiment the semiconductor and electrolyte may be heated so as to increase the diffusion coefficient

  8. Printable semiconductor structures and related methods of making and assembling

    Science.gov (United States)

    Nuzzo, Ralph G.; Rogers, John A.; Menard, Etienne; Lee, Keon Jae; Khang; , Dahl-Young; Sun, Yugang; Meitl, Matthew; Zhu, Zhengtao; Ko, Heung Cho; Mack, Shawn

    2013-03-12

    The present invention provides a high yield pathway for the fabrication, transfer and assembly of high quality printable semiconductor elements having selected physical dimensions, shapes, compositions and spatial orientations. The compositions and methods of the present invention provide high precision registered transfer and integration of arrays of microsized and/or nanosized semiconductor structures onto substrates, including large area substrates and/or flexible substrates. In addition, the present invention provides methods of making printable semiconductor elements from low cost bulk materials, such as bulk silicon wafers, and smart-materials processing strategies that enable a versatile and commercially attractive printing-based fabrication platform for making a broad range of functional semiconductor devices.

  9. Structure refinement of polycrystalline orthorhombic yttrium ...

    Indian Academy of Sciences (India)

    The perovskite ceramic phases with composition Ca1−YTiO3+ (where = 0.1, 0.2 and 0.3; hereafter CYT-10, CYT-20 and CYT-30) have been synthesized by solid state reaction at 1050°C. The structure refinement using general structure analysis system (GSAS) software converges to satisfactory profile indicators ...

  10. Metal-semiconductor interface in extreme temperature conditions

    International Nuclear Information System (INIS)

    Bulat, L.P.; Erofeeva, I.A.; Vorobiev, Yu.V.; Gonzalez-Hernandez, J.

    2008-01-01

    We present an investigation of electrons' and phonons' temperatures in the volume of a semiconductor (or metal) sample and at the interface between metal and semiconductor. Two types of mismatch between electrons' and phonons' temperatures take place: at metal-semiconductor interfaces and in the volume of the sample. The temperature mismatch leads to nonlinear terms in expressions for heat and electricity transport. The nonlinear effects should be taken into consideration in the study of electrical and heat transport in composites and in electronic chips

  11. Metal-doped semiconductor nanoparticles and methods of synthesis thereof

    Science.gov (United States)

    Ren, Zhifeng (Inventor); Chen, Gang (Inventor); Poudel, Bed (Inventor); Kumar, Shankar (Inventor); Wang, Wenzhong (Inventor); Dresselhaus, Mildred (Inventor)

    2009-01-01

    The present invention generally relates to binary or higher order semiconductor nanoparticles doped with a metallic element, and thermoelectric compositions incorporating such nanoparticles. In one aspect, the present invention provides a thermoelectric composition comprising a plurality of nanoparticles each of which includes an alloy matrix formed of a Group IV element and Group VI element and a metallic dopant distributed within the matrix.

  12. Industrial application of atom probe tomography to semiconductor devices

    NARCIS (Netherlands)

    Giddings, A.D.; Koelling, S.; Shimizu, Y.; Estivill, R.; Inoue, K.; Vandervorst, W.; Yeoh, W.K.

    2018-01-01

    Advanced semiconductor devices offer a metrology challenge due to their small feature size, diverse composition and intricate structure. Atom probe tomography (APT) is an emerging technique that provides 3D compositional analysis at the atomic-scale; as such, it seems uniquely suited to meet these

  13. Fundamentals of semiconductor lasers

    CERN Document Server

    Numai, Takahiro

    2015-01-01

    This book explains physics under the operating principles of semiconductor lasers in detail based on the experience of the author, dealing with the first manufacturing of phase-shifted DFB-LDs and recent research on transverse modes.   The book also bridges a wide gap between journal papers and textbooks, requiring only an undergraduate-level knowledge of electromagnetism and quantum mechanics, and helps readers to understand journal papers where definitions of some technical terms vary, depending on the paper. Two definitions of the photon density in the rate equations and two definitions of the phase-shift in the phase-shifted DFB-LD are explained, and differences in the calculated results are indicated, depending on the definitions.    Readers can understand the physics of semiconductor lasers and analytical tools for Fabry-Perot LDs, DFB-LDs, and VCSELs and will be stimulated to develop semiconductor lasers themselves.

  14. Coherent dynamics in semiconductors

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher

    1998-01-01

    enhanced in quantum confined lower-dimensional systems, where exciton and biexciton effects dominate the spectra even at room temperature. The coherent dynamics of excitons are at modest densities well described by the optical Bloch equations and a number of the dynamical effects known from atomic......Ultrafast nonlinear optical spectroscopy is used to study the coherent dynamics of optically excited electron-hole pairs in semiconductors. Coulomb interaction implies that the optical inter-band transitions are dominated, at least at low temperatures, by excitonic effects. They are further...... and molecular systems are found and studied in the exciton-biexciton system of semiconductors. At densities where strong exciton interactions, or many-body effects, become dominant, the semiconductor Bloch equations present a more rigorous treatment of the phenomena Ultrafast degenerate four-wave mixing is used...

  15. Hydrogen in semiconductors II

    CERN Document Server

    Nickel, Norbert H; Weber, Eicke R; Nickel, Norbert H

    1999-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The "Willardson and Beer" Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices, Oxygen in Silicon, and others promise that this tradition ...

  16. Photoelectronic properties of semiconductors

    CERN Document Server

    Bube, Richard H

    1992-01-01

    The interaction between light and electrons in semiconductors forms the basis for many interesting and practically significant properties. This book examines the fundamental physics underlying this rich complexity of photoelectronic properties of semiconductors, and will familiarise the reader with the relatively simple models that are useful in describing these fundamentals. The basic physics is also illustrated with typical recent examples of experimental data and observations. Following introductory material on the basic concepts, the book moves on to consider a wide range of phenomena, including photoconductivity, recombination effects, photoelectronic methods of defect analysis, photoeffects at grain boundaries, amorphous semiconductors, photovoltaic effects and photoeffects in quantum wells and superlattices. The author is Professor of Materials Science and Electrical Engineering at Stanford University, and has taught this material for many years. He is an experienced author, his earlier books having fo...

  17. Semiconductor optoelectronic infrared spectroscopy

    International Nuclear Information System (INIS)

    Hollingworth, A.R.

    2001-08-01

    We use spectroscopy to study infrared optoelectronic inter and intraband semiconductor carrier dynamics. The overall aim of this thesis was to study both III-V and Pb chalcogenide material systems in order to show their future potential use in infrared emitters. The effects of bandstructure engineering have been studied in the output characteristics of mid-IR III-V laser diodes to show which processes (defects, radiative, Auger and phonon) dominate and whether non-radiative processes can be suppressed. A new three-beam pump probe experiment was used to investigate interband recombination directly in passive materials. Experiments on PbSe and theory for non-parabolic near-mirror bands and non-degenerate statistics were in good agreement. Comparisons with HgCdTe showed a reduction in the Auger coefficient of 1-2 orders of magnitude in the PbSe. Using Landau confinement to model spatial confinement in quantum dots (QDs) 'phonon bottlenecking' was studied. The results obtained from pump probe and cyclotron resonance saturation measurements showed a clear suppression in the cooling of carriers when Landau level separation was not resonant with LO phonon energy. When a bulk laser diode was placed in a magnetic field to produce a quasi quantum wire device the resulting enhanced differential gain and reduced Auger recombination lowered I th by 30%. This result showed many peaks in the light output which occurred when the LO phonon energy was a multiple of the Landau level separation. This showed for the first time evidence of the phonon bottleneck in a working laser device. A new technique called time resolved optically detected cyclotron resonance, was used as a precursor to finding the carrier dynamics within a spatially confined quantum dot. By moving to the case of a spatial QD using an optically detected intraband resonance it was possible to measure the energy separation interband levels and conduction and valence sublevels within the dot simultaneously. Furthermore

  18. The three-dimensional microstructure of polycrystalline materials unravelled by synchrotron light

    DEFF Research Database (Denmark)

    Ludwig, W.; King, A.; Herbig, M.

    2011-01-01

    The three-dimensional microstructure of polycrystalline materials unravelled by synchrotron light Synchrotron radiation X-ray imaging and diffraction techniques offer new possibilities for non-destructive bulk characterization of polycrystalline materials. Minute changes in electron density (diff...

  19. Metastable states in amorphous chalcogenide semiconductors

    CERN Document Server

    Mikla, Victor I

    2009-01-01

    This book addresses an interesting and technologically important class of materials, the amorphous chalcogenide semiconductors. Experimental results on the structural and electronic metastable states in Se-rich chalcogenides are presented. Special attention is paid to the states in the mobility gap and their sensitivity to various factors such as irradiation, annealing and composition. Photoinduced changes of structure and physical properties are also considered and structural transformation at photocrystallization is studied in detail. Finally, the authors discuss potential applications of th

  20. Effect of barrier height on friction behavior of the semiconductors silicon and gallium arsenide in contact with pure metals

    Science.gov (United States)

    Mishina, H.; Buckley, D. H.

    1984-01-01

    Friction experiments were conducted for the semiconductors silicon and gallium arsenide in contact with pure metals. Polycrystalline titanium, tantalum, nickel, palladium, and platinum were made to contact a single crystal silicon (111) surface. Indium, nickel, copper, and silver were made to contact a single crystal gallium arsenide (100) surface. Sliding was conducted both in room air and in a vacuum of 10 to the minus 9th power torr. The friction of semiconductors in contact with metals depended on a Schottky barrier height formed at the metal semiconductor interface. Metals with a higher barrier height on semiconductors gave lower friction. The effect of the barrier height on friction behavior for argon sputtered cleaned surfaces in vacuum was more specific than that for the surfaces containing films in room air. With a silicon surface sliding on titanium, many silicon particles back transferred. In contrast, a large quantity of indium transferred to the gallium arsenide surface.

  1. Advances in semiconductor lasers

    CERN Document Server

    Coleman, James J; Jagadish, Chennupati

    2012-01-01

    Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. Originally widely known as the ""Willardson and Beer"" Series, it has succeeded in publishing numerous landmark volumes and chapters. The series publishes timely, highly relevant volumes intended for long-term impact and reflecting the truly interdisciplinary nature of the field. The volumes in Semiconductors and Semimetals have been and will continue to be of great interest to physicists, chemists, materials scientists, and device engineers in academia, scien

  2. Superconductivity in doped semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bustarret, E., E-mail: Etienne.bustarret@neel.cnrs.fr

    2015-07-15

    A historical survey of the main normal and superconducting state properties of several semiconductors doped into superconductivity is proposed. This class of materials includes selenides, tellurides, oxides and column-IV semiconductors. Most of the experimental data point to a weak coupling pairing mechanism, probably phonon-mediated in the case of diamond, but probably not in the case of strontium titanate, these being the most intensively studied materials over the last decade. Despite promising theoretical predictions based on a conventional mechanism, the occurrence of critical temperatures significantly higher than 10 K has not been yet verified. However, the class provides an enticing playground for testing theories and devices alike.

  3. Semiconductor opto-electronics

    CERN Document Server

    Moss, TS; Ellis, B

    1972-01-01

    Semiconductor Opto-Electronics focuses on opto-electronics, covering the basic physical phenomena and device behavior that arise from the interaction between electromagnetic radiation and electrons in a solid. The first nine chapters of this book are devoted to theoretical topics, discussing the interaction of electromagnetic waves with solids, dispersion theory and absorption processes, magneto-optical effects, and non-linear phenomena. Theories of photo-effects and photo-detectors are treated in detail, including the theories of radiation generation and the behavior of semiconductor lasers a

  4. Ternary chalcopyrite semiconductors

    CERN Document Server

    Shay, J L; Pamplin, B R

    2013-01-01

    Ternary Chalcopyrite Semiconductors: Growth, Electronic Properties, and Applications covers the developments of work in the I-III-VI2 and II-IV-V2 ternary chalcopyrite compounds. This book is composed of eight chapters that focus on the crystal growth, characterization, and applications of these compounds to optical communications systems. After briefly dealing with the status of ternary chalcopyrite compounds, this book goes on describing the crystal growth of II-IV-V2 and I-III-VI2 single crystals. Chapters 3 and 4 examine the energy band structure of these semiconductor compounds, illustrat

  5. Compound semiconductor device physics

    CERN Document Server

    Tiwari, Sandip

    2013-01-01

    This book provides one of the most rigorous treatments of compound semiconductor device physics yet published. A complete understanding of modern devices requires a working knowledge of low-dimensional physics, the use of statistical methods, and the use of one-, two-, and three-dimensional analytical and numerical analysis techniques. With its systematic and detailed**discussion of these topics, this book is ideal for both the researcher and the student. Although the emphasis of this text is on compound semiconductor devices, many of the principles discussed will also be useful to those inter

  6. Introductory semiconductor device physics

    CERN Document Server

    Parker, Greg

    2004-01-01

    ATOMS AND BONDINGThe Periodic TableIonic BondingCovalent BondingMetallic bondingvan der Waals BondingStart a DatabaseENERGY BANDS AND EFFECTIVE MASSSemiconductors, Insulators and MetalsSemiconductorsInsulatorsMetalsThe Concept of Effective MassCARRIER CONCENTRATIONS IN SEMICONDUCTORSDonors and AcceptorsFermi-LevelCarrier Concentration EquationsDonors and Acceptors Both PresentCONDUCTION IN SEMICONDUCTORSCarrier DriftCarrier MobilitySaturated Drift VelocityMobility Variation with TemperatureA Derivation of Ohm's LawDrift Current EquationsSemiconductor Band Diagrams with an Electric Field Presen

  7. Tunable radiation emitting semiconductor device

    NARCIS (Netherlands)

    2009-01-01

    A tunable radiation emitting semiconductor device includes at least one elongated structure at least partially fabricated from one or more semiconductor materials exhibiting a bandgap characteristic including one or more energy transitions whose energies correspond to photon energies of light

  8. Photoemission studies of semiconductor nanocrystals

    International Nuclear Information System (INIS)

    Hamad, K.S.; Roth, R.; Alivisatos, A.P.

    1997-01-01

    Semiconductor nanocrystals have been the focus of much attention in the last ten years due predominantly to their size dependent optical properties. Namely, the band gap of nanocrystals exhibits a shift to higher energy with decreasing size due to quantum confinement effects. Research in this field has employed primarily optical techniques to study nanocrystals, and in this respect this system has been investigated extensively. In addition, one is able to synthesize monodisperse, crystalline particles of CdS, CdSe, Si, InP, InAs, as well as CdS/HgS/CdS and CdSe/CdS composites. However, optical spectroscopies have proven ambiguous in determining the degree to which electronic excitations are interior or surface admixtures or giving a complete picture of the density of states. Photoemission is a useful technique for understanding the electronic structure of nanocrystals and the effects of quantum confinement, chemical environments of the nanocrystals, and surface coverages. Of particular interest to the authors is the surface composition and structure of these particles, for they have found that much of the behavior of nanocrystals is governed by their surface. Previously, the authors had performed x-ray photoelectron spectroscopy (XPS) on CdSe nanocrystals. XPS has proven to be a powerful tool in that it allows one to determine the composition of the nanocrystal surface

  9. A Statistical Learning Framework for Materials Science: Application to Elastic Moduli of k-nary Inorganic Polycrystalline Compounds.

    Science.gov (United States)

    de Jong, Maarten; Chen, Wei; Notestine, Randy; Persson, Kristin; Ceder, Gerbrand; Jain, Anubhav; Asta, Mark; Gamst, Anthony

    2016-10-03

    Materials scientists increasingly employ machine or statistical learning (SL) techniques to accelerate materials discovery and design. Such pursuits benefit from pooling training data across, and thus being able to generalize predictions over, k-nary compounds of diverse chemistries and structures. This work presents a SL framework that addresses challenges in materials science applications, where datasets are diverse but of modest size, and extreme values are often of interest. Our advances include the application of power or Hölder means to construct descriptors that generalize over chemistry and crystal structure, and the incorporation of multivariate local regression within a gradient boosting framework. The approach is demonstrated by developing SL models to predict bulk and shear moduli (K and G, respectively) for polycrystalline inorganic compounds, using 1,940 compounds from a growing database of calculated elastic moduli for metals, semiconductors and insulators. The usefulness of the models is illustrated by screening for superhard materials.

  10. Fabrication of poly-crystalline Si-based Mie resonators via amorphous Si on SiO2 dewetting.

    Science.gov (United States)

    Naffouti, Meher; David, Thomas; Benkouider, Abdelmalek; Favre, Luc; Ronda, Antoine; Berbezier, Isabelle; Bidault, Sebastien; Bonod, Nicolas; Abbarchi, Marco

    2016-02-07

    We report the fabrication of Si-based dielectric Mie resonators via a low cost process based on solid-state dewetting of ultra-thin amorphous Si on SiO2. We investigate the dewetting dynamics of a few nanometer sized layers annealed at high temperature to form submicrometric Si-particles. Morphological and structural characterization reveal the polycrystalline nature of the semiconductor matrix as well as rather irregular morphologies of the dewetted islands. Optical dark field imaging and spectroscopy measurements of the single islands reveal pronounced resonant scattering at visible frequencies. The linewidth of the low-order modes can be ∼20 nm in full width at half maximum, leading to a quality factor Q exceeding 25. These values reach the state-of-the-art ones obtained for monocrystalline Mie resonators. The simplicity of the dewetting process and its cost-effectiveness opens the route to exploiting it over large scales for applications in silicon-based photonics.

  11. Electrical Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide

    Science.gov (United States)

    2014-07-14

    Lou, Sina Najmaei, Matin Amani, Matthew L. Chin, Zheng Se. TASK NUMBER Liu Sf. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAMES AND ADDRESSES 8...Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide Sina Najmaei,t.§ Matin Ama ni,M Matthew L. Chin,* Zhe ng liu/ ·"·v: A. Gle n

  12. Electroreduction of CO on Polycrystalline Copper at Low Overpotentials

    DEFF Research Database (Denmark)

    Bertheussen, Erlend; Vagn Hogg, Thomas; Abghoui, Younes

    2018-01-01

    C uis the only monometallic electrocatalyst to produce highly reduced products from CO2 selectively because of its intermediate binding of CO. We investigate the performance of polycrystalline Cu for the electroreduction of CO in alkaline media (0.1 M KOH) at low overpotentials (−0.4 to −0.6 V vs...

  13. A study of ultrasonic velocity and attenuation on polycrystalline Ni ...

    Indian Academy of Sciences (India)

    Unknown

    tion of Fe3O4 particles at 800°C. Industrial grade particles of Ni and Zn oxides were ..... domain wall movements, which leads to electronic migrations: this can ... properties of polycrystalline Mn–Zn Ferrites, Ph.D. Thesis,. Osmania University ...

  14. Influence of hydrogen on high cycle fatigue of polycrystalline vanadium

    International Nuclear Information System (INIS)

    Chung, D.W.; Lee, K.S.; Stoloff, N.S.

    1977-02-01

    The room temperature fatigue behavior of several polycrystalline V-H 2 alloys is described. Hydrogen extends the life of unnotched vanadium but has a deleterious effect in notched materials. Crack propagation data are correlated with tensile yield stress and cyclic strain hardening data

  15. A MONTÉ CARLO MODEL FOR SIMULATING THE NITROGEN DIFFUSION EFFECT INTO B-LPCVD-NIDOS POLYCRYSTALLINE THIN FILMS

    Directory of Open Access Journals (Sweden)

    S ALLAG

    2012-06-01

    Full Text Available The principal objective of our current work, is to study the influence of different treatment from surface which makes it possible to improve the properties of materials by technique of beam of ions (diffusion – implantation, on the distribution of the particles in a semiconductor the prone polycrystalline Silicon of our study, largely used in micro-electronics.  The interest of this study is related to the ceaseless requirements in industry for increasingly reduced, powerful materials and with the weakest possible cost price.       We thus have, makes a nitriding in gas phase during the phase of deposit LPCVD of polycrystalline Silicon, then one made an ionic implantation with the Bore ions.  The results obtained, starting from a simulation based on the Monte Carlo method, although they are carried out with amounts much lower than the really introduced amounts, being given the limitation of the machine used, satisfied the predictions established at the beginning and encourage us to continue this study from the point of view of the use of this material in particular in varied fields.

  16. Physical principles of semiconductor detectors

    International Nuclear Information System (INIS)

    Micek, S.L.

    1979-01-01

    The general properties of semiconductors with respect to the possibilities of their use as the ionization radiation detectors are discussed. Some chosen types of semiconductor junctions and their characteristics are briefly presented. There are also discussed the physical phenomena connected with the formation of barriers in various types of semiconductor counters. Finally, the basic properties of three main types of semiconductor detectors are given. (author)

  17. Metal semiconductor contacts and devices

    CERN Document Server

    Cohen, Simon S; Einspruch, Norman G

    1986-01-01

    VLSI Electronics Microstructure Science, Volume 13: Metal-Semiconductor Contacts and Devices presents the physics, technology, and applications of metal-semiconductor barriers in digital integrated circuits. The emphasis is placed on the interplay among the theory, processing, and characterization techniques in the development of practical metal-semiconductor contacts and devices.This volume contains chapters that are devoted to the discussion of the physics of metal-semiconductor interfaces and its basic phenomena; fabrication procedures; and interface characterization techniques, particularl

  18. Handbook of luminescent semiconductor materials

    CERN Document Server

    Bergman, Leah

    2011-01-01

    Photoluminescence spectroscopy is an important approach for examining the optical interactions in semiconductors and optical devices with the goal of gaining insight into material properties. With contributions from researchers at the forefront of this field, Handbook of Luminescent Semiconductor Materials explores the use of this technique to study semiconductor materials in a variety of applications, including solid-state lighting, solar energy conversion, optical devices, and biological imaging. After introducing basic semiconductor theory and photoluminescence principles, the book focuses

  19. Depletion field focusing in semiconductors

    NARCIS (Netherlands)

    Prins, M.W.J.; Gelder, Van A.P.

    1996-01-01

    We calculate the three-dimensional depletion field profile in a semiconductor, for a planar semiconductor material with a spatially varying potential upon the surface, and for a tip-shaped semiconductor with a constant surface potential. The nonuniform electric field gives rise to focusing or

  20. Nonlinear Elasticity of Doped Semiconductors

    Science.gov (United States)

    2017-02-01

    AFRL-RY-WP-TR-2016-0206 NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS Mark Dykman and Kirill Moskovtsev Michigan State University...2016 4. TITLE AND SUBTITLE NONLINEAR ELASTICITY OF DOPED SEMICONDUCTORS 5a. CONTRACT NUMBER FA8650-16-1-7600 5b. GRANT NUMBER 5c. PROGRAM...vibration amplitude. 15. SUBJECT TERMS semiconductors , microresonators, microelectromechanical 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

  1. Semi-conductor rectifiers

    International Nuclear Information System (INIS)

    1981-01-01

    A method is described for treating a semiconductor rectifier, comprising: heating the rectifier to a temperature in the range of 100 0 C to 500 0 C, irradiating the rectifier while maintaining its temperature within the said range, and then annealing the rectifier at a temperature of between 280 0 C and 350 0 C for between two and ten hours. (author)

  2. Semiconductor detector physics

    International Nuclear Information System (INIS)

    Equer, B.

    1987-01-01

    Comprehension of semiconductor detectors follows comprehension of some elements of solid state physics. They are recalled here, limited to the necessary physical principles, that is to say the conductivity. P-n and MIS junctions are discussed in view of their use in detection. Material and structure (MOS, p-n, multilayer, ..) are also reviewed [fr

  3. Protein patterning on polycrystalline silicon-germanium via standard UV lithography for bioMEMS applications

    Energy Technology Data Exchange (ETDEWEB)

    Lenci, S., E-mail: silvia.lenci@gmail.com [Dipartimento di Ingegneria dell' Informazione, University of Pisa, Via G. Caruso 16, I-56122 Pisa (Italy); imec, Kapeldreef 75, Leuven B-3001 (Belgium); Tedeschi, L.; Domenici, C.; Lande, C. [Istituto di Fisiologia Clinica, CNR, via G. Moruzzi 1, Pisa I-56124 (Italy); Nannini, A.; Pennelli, G.; Pieri, F. [Dipartimento di Ingegneria dell' Informazione, University of Pisa, Via G. Caruso 16, I-56122 Pisa (Italy); Severi, S. [imec, Kapeldreef 75, Leuven B-3001 (Belgium)

    2010-10-12

    Polycrystalline silicon-germanium (poly-SiGe) is a promising structural material for the post-processing of micro electro-mechanical systems (MEMS) on top of complementary metal-oxide-semiconductor (CMOS) substrates. Combining MEMS and CMOS allows for the development of high-performance devices. We present for the first time selective protein immobilization on top of poly-SiGe surfaces, an enabling technique for the development of novel poly-SiGe based MEMS biosensors. Active regions made of 3-aminopropyl-triethoxysilane (APTES) were defined using silane deposition onto photoresist patterns followed by lift-off in organic solvents. Subsequently, proteins were covalently bound on the created APTES patterns. Fluorescein-labeled human serum albumin (HSA) was used to verify the immobilization procedure while the binding capability of the protein layer was tested by an antigen-labeled antibody pair. Inspection by fluorescence microscopy showed protein immobilization inside the desired bioactive areas and low non-specific adsorption outside the APTES pattern. Furthermore, the quality of the silane patches was investigated by treatment with 30 nm-diameter gold nanoparticles and scanning electron microscope observation. The developed technique is therefore a promising first step towards the realization of poly-SiGe based biosensors.

  4. Disposal of metal fragments released during polycrystalline slicing by multi-wire saw

    Science.gov (United States)

    Boutouchent-Guerfi, N.; Drouiche, N.; Medjahed, S.; Ould-Hamou, M.; Sahraoui, F.

    2016-08-01

    The environmental and economic impacts linked with solar systems are largely based on discharges of slurry generated during the various stages of sawing and cutting ingots. These discharges into the environment are subject to the general regulations on hazardous and special industrial waste disposal. Therefore, they should not be abandoned or burned in open air. The cutting of Silicon ingots leads to the production of Silicon wafers additional costs, losing more than 30% of Silicon material. Abrasive grains (Silicon Carbide) trapped between the wire and the block of Silicon need to be removed by various mechanisms to be later evacuated by slurry fragments. In the interest of decreasing operational costs during polycrystalline ingot slicing at Semiconductors Research Center, and, avoid environmental problems; it is necessary to recover the solar grade Silicon from the Silicon sawing waste. For this reason, the removal of metal fragments has become a preliminary requirement to regenerate the slurry; in addition, the solid phase needs to be separated from the liquid phase after the dissolution PEG with the solvent. In the present study, magnetic separation and centrifugation methods were adopted for metals removal, followed by the analysis of some operating parameters such as: washing time, pH, and initial concentration of Silicon. Finally, analytical, morphological and basic methods were performed in order to evaluate the efficiency of the process undertaken.

  5. X-ray beam penetration in TXRF measurement of polycrystalline and amorphous surfaces

    International Nuclear Information System (INIS)

    Ghatak-Roy, A.R.; Hossain, T.Z.

    2000-01-01

    For TXRF measurement on single crystal silicon surface, it is generally agreed that the x-ray beam penetration is of the order of a few hundred Angstroms from the surface. However, for polycrystalline and amorphous surfaces - frequently used in semiconductor manufacturing there are evidences that x-rays penetrate much deeper revealing underlying layers. The evidences come from various measurements done with films such as silicon dioxide, silicon nitride and metal films such as aluminum, titanium and cobalt. A systematic study was carried out to help understand the issue further. Four sets of samples (on 8 inch wafers) were prepared to create layers buried under various deposited metal and non-metal layers. The metal layers created were aluminum, titanium and cobalt and the non-metal layers were silicon dioxide and silicon nitride. These samples were analyzed by TXRF under various angles and energies and the data were analyzed for signals from various buried layers along with their angular dependence. The results indicated deep penetration of x-ray beams. The samples were further analyzed by SIMS (Secondary Ion Mass Spectrometry) and some of them by ICP-MS (Inductively Coupled Plasma - Mass Spectrometry) to obtain information about their depth profiles. This was done in order to rule out the possibility of intermixing of layers during deposition. (author)

  6. Origin of colossal dielectric permittivity of rutile Ti₀.₉In₀.₀₅Nb₀.₀₅O₂: single crystal and polycrystalline.

    Science.gov (United States)

    Song, Yongli; Wang, Xianjie; Sui, Yu; Liu, Ziyi; Zhang, Yu; Zhan, Hongsheng; Song, Bingqian; Liu, Zhiguo; Lv, Zhe; Tao, Lei; Tang, Jinke

    2016-02-12

    In this paper, we investigated the dielectric properties of (In + Nb) co-doped rutile TiO2 single crystal and polycrystalline ceramics. Both of them showed colossal, up to 10(4), dielectric permittivity at room temperature. The single crystal sample showed one dielectric relaxation process with a large dielectric loss. The voltage-dependence of dielectric permittivity and the impedance spectrum suggest that the high dielectric permittivity of single crystal originated from the surface barrier layer capacitor (SBLC). The impedance spectroscopy at different temperature confirmed that the (In + Nb) co-doped rutile TiO2 polycrystalline ceramic had semiconductor grains and insulating grain boundaries, and that the activation energies were calculated to be 0.052 eV and 0.35 eV for grain and grain boundary, respectively. The dielectric behavior and impedance spectrum of the polycrystalline ceramic sample indicated that the internal barrier layer capacitor (IBLC) mode made a major contribution to the high ceramic dielectric permittivity, instead of the electron-pinned defect-dipoles.

  7. Multiband semiconductor compositions for photovoltaic devices

    Science.gov (United States)

    Walukiewicz, Wladyslaw; Yu, Kin Man; Wu, Junqiao

    2010-05-04

    The highly mismatched alloy Zn.sub.1-yMn.sub.yO.sub.xTe.sub.1-x, 0.ltoreq.ysolar energy spectrum, Zn.sub.1-yMn.sub.yO.sub.xTe.sub.1-x is a material perfectly satisfying the conditions for single-junction photovoltaics with the potential for power conversion efficiencies surpassing 50%.

  8. Interfacial effects in organic semiconductor heterojunctions

    International Nuclear Information System (INIS)

    Stadler, P.

    2011-01-01

    The field of organic electronics has systematically gained interest in recent years, technologically and scientifically advances have been made leading to practical applications such as organic light emitting diodes, organic field-effect transistors and organic photo-voltaic cells. In this thesis a fundamental study on organic molecules is presented targeting on interfacial effects at organic heterojunctions. Generally in organic electronic devices interfaces are considered as key parameters for achieving high performance applications. Therefore in this work the emphasis is to investigate layer-by-layer heterojunctions of organic molecules. Defined heterojunctions at inorganic III-V semiconductors form superlattices and quantum-wells, which lead to interfacial effects summarized as quantum confinement and two-dimensional electron gases. Although organic molecules differ in many aspects from their inorganic counterparts, similar effects can be theoretically expected at organic heterojunctions as well. Organic molecules form van-der-Waals type crystals and domains which are macroscopically anisotropic and polycrystalline or amorphous. Organic molecules are intrinsic semiconductors and at interfaces dipoles are formed, which control the energy level alignment. In order to characterize such structures and compare them to inorganic superlattices and quantum-wells it is necessary to induce charge carriers. In this work this is established either by interfacial doping using high-performance dielectrics in a field-effect transistor structure or by photo-doping by exciting a donor-acceptor bilayer. In both cases C 60 was chosen as organic semiconductor exhibiting good acceptor properties and an electron mobility in the range of 0.5 cm 2 V -1 s -1 . The fabrication of well-defined few-molecular layers allows probing directly at the interface. Spectroscopic methods and transport measurements are applied for characterization: Photoemission spectroscopy, absorption and photo

  9. Positron annihilation in a metal-oxide semiconductor studied by using a pulsed monoenergetic positron beam

    Science.gov (United States)

    Uedono, A.; Wei, L.; Tanigawa, S.; Suzuki, R.; Ohgaki, H.; Mikado, T.; Ohji, Y.

    1993-12-01

    The positron annihilation in a metal-oxide semiconductor was studied by using a pulsed monoenergetic positron beam. Lifetime spectra of positrons were measured as a function of incident positron energy for a polycrystalline Si(100 nm)/SiO2(400 nm)/Si specimen. Applying a gate voltage between the polycrystalline Si film and the Si substrate, positrons implanted into the specimen were accumulated at the SiO2/Si interface. From the measurements, it was found that the annihilation probability of ortho-positronium (ortho-Ps) drastically decreased at the SiO2/Si interface. The observed inhibition of the Ps formation was attributed to an interaction between positrons and defects at the SiO2/Si interface.

  10. Crystallization of II-VI semiconductor compounds forming long microcrystalline linear assemblies

    Directory of Open Access Journals (Sweden)

    Marcelino Becerril

    2013-04-01

    Full Text Available In this work we report the formation of long microcrystalline linear self-assemblies observed during the thin film growth of several II-VI compounds. Polycrystalline CdTe, CdS, CdCO3, and nanocrystalline CdTe:Al thin films were prepared on glass substrates by different deposition techniques. In order to observe these crystalline formations in the polycrystalline materials, the thin film growth was suspended before the grains reached to form a continuous layer. The chains of semiconductor crystals were observed among many isolated and randomly distributed grains. Since CdTe, CdTe:Al, CdS and CdCO3 are not ferroelectric and/or ferromagnetic materials, the relevant problem would be to explain what is the mechanism through which the grains are held together to form linear chains. It is well known that some nanocrystalline materials form rods and wires by means of electrostatic forces. This occurs in polar semiconductors, where it is assumed that the attraction forces between surface polar faces of the small crystals are the responsible for the chains formation. Since there are not too many mechanisms responsible for the attraction we assume that a dipolar interaction is the force that originates the formation of chain-like grain clusters. The study of this property can be useful for the understanding of nucleation processes in the growth of semiconductor thin films.

  11. Optical cavity cooling of mechanical modes of a semiconductor nanomembrane

    DEFF Research Database (Denmark)

    Usami, Koji; Naesby, A.; Bagci, Tolga

    2012-01-01

    Mechanical oscillators can be optically cooled using a technique known as optical-cavity back-action. Cooling of composite metal–semiconductor mirrors, dielectric mirrors and dielectric membranes has been demonstrated. Here we report cavity cooling of mechanical modes in a high-quality-factor and......Mechanical oscillators can be optically cooled using a technique known as optical-cavity back-action. Cooling of composite metal–semiconductor mirrors, dielectric mirrors and dielectric membranes has been demonstrated. Here we report cavity cooling of mechanical modes in a high...

  12. Single frequency semiconductor lasers

    CERN Document Server

    Fang, Zujie; Chen, Gaoting; Qu, Ronghui

    2017-01-01

    This book systematically introduces the single frequency semiconductor laser, which is widely used in many vital advanced technologies, such as the laser cooling of atoms and atomic clock, high-precision measurements and spectroscopy, coherent optical communications, and advanced optical sensors. It presents both the fundamentals and characteristics of semiconductor lasers, including basic F-P structure and monolithic integrated structures; interprets laser noises and their measurements; and explains mechanisms and technologies relating to the main aspects of single frequency lasers, including external cavity lasers, frequency stabilization technologies, frequency sweeping, optical phase locked loops, and so on. It paints a clear, physical picture of related technologies and reviews new developments in the field as well. It will be a useful reference to graduate students, researchers, and engineers in the field.

  13. Basic semiconductor physics

    CERN Document Server

    Hamaguchi, Chihiro

    2017-01-01

    This book presents a detailed description of basic semiconductor physics. The text covers a wide range of important phenomena in semiconductors, from the simple to the advanced. Four different methods of energy band calculations in the full band region are explained: local empirical pseudopotential, non-local pseudopotential, KP perturbation and tight-binding methods. The effective mass approximation and electron motion in a periodic potential, Boltzmann transport equation and deformation potentials used for analysis of transport properties are discussed. Further, the book examines experiments and theoretical analyses of cyclotron resonance in detail. Optical and transport properties, magneto-transport, two-dimensional electron gas transport (HEMT and MOSFET) and quantum transport are reviewed, while optical transition, electron-phonon interaction and electron mobility are also addressed. Energy and electronic structure of a quantum dot (artificial atom) are explained with the help of Slater determinants. The...

  14. Semiconductor physics an introduction

    CERN Document Server

    Seeger, Karlheinz

    1999-01-01

    Semiconductor Physics - An Introduction - is suitable for the senior undergraduate or new graduate student majoring in electrical engineering or physics. It will also be useful to solid-state scientists and device engineers involved in semiconductor design and technology. The text provides a lucid account of charge transport, energy transport and optical processes, and a detailed description of many devices. It includes sections on superlattices and quantum well structures, the effects of deep-level impurities on transport, the quantum Hall effect and the calculation of the influence of a magnetic field on the carrier distribution function. This 6th edition has been revised and corrected, and new sections have been added to different chapters.

  15. Three dimensional strained semiconductors

    Science.gov (United States)

    Voss, Lars; Conway, Adam; Nikolic, Rebecca J.; Leao, Cedric Rocha; Shao, Qinghui

    2016-11-08

    In one embodiment, an apparatus includes a three dimensional structure comprising a semiconductor material, and at least one thin film in contact with at least one exterior surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the three dimensional structure. In another embodiment, a method includes forming a three dimensional structure comprising a semiconductor material, and depositing at least one thin film on at least one surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the structure.

  16. Compound semiconductor device modelling

    CERN Document Server

    Miles, Robert

    1993-01-01

    Compound semiconductor devices form the foundation of solid-state microwave and optoelectronic technologies used in many modern communication systems. In common with their low frequency counterparts, these devices are often represented using equivalent circuit models, but it is often necessary to resort to physical models in order to gain insight into the detailed operation of compound semiconductor devices. Many of the earliest physical models were indeed developed to understand the 'unusual' phenomena which occur at high frequencies. Such was the case with the Gunn and IMPATI diodes, which led to an increased interest in using numerical simulation methods. Contemporary devices often have feature sizes so small that they no longer operate within the familiar traditional framework, and hot electron or even quantum­ mechanical models are required. The need for accurate and efficient models suitable for computer aided design has increased with the demand for a wider range of integrated devices for operation at...

  17. Optically coupled semiconductor device

    Energy Technology Data Exchange (ETDEWEB)

    Kumagaya, Naoki

    1988-11-18

    This invention concerns an optically coupled semiconductor device using the light as input signal and a MOS transistor for the output side in order to control on-off of the output side by the input signal which is insulated from the output. Concerning this sort of element, when a MOS transistor and a load resistance are planned to be accumulated on the same chip, a resistor and control of impurity concentration of the channel, etc. become necessary despite that the only formation of a simple P-N junction is enough, for a solar cell, hence cost reduction thereof cannot be done. In order to remove this defect, this invention offers an optically coupled semiconductor device featuring that two solar cells are connected in reverse parallel between the gate sources of the output MOS transistors and an operational light emitting element is individually set facing a respective solar cell. 4 figs.

  18. Behaviour of polycrystalline fluoride-selective membrane electrode in aqueous-organic media

    International Nuclear Information System (INIS)

    Manakova, L.I.; Bausova, N.V.; Moiseev, V.E.; Bamburov, V.G.; Sivoplyas, A.P.

    1978-01-01

    The behaviour of polycrystalline fluoride membrane electrode (RFME) in aqueous-organic media has been studied when the content of the organic component (methanol, ethanol, acetone, dioxane) has been changed from 20 to 80 mass%. Since LaF 3 is the base of the membrane, its solubility has been studied depending on the organic component content in the solution. It has been established that LaF 3 solubility decreases with increasing content of of the organic component. This explains the effect of the composition of an aqueous-organic solvent on the electrode sensitivity. The electrode sensitivity rises with increasing content of the organic component in an aqueous-organic solvent. A greater decrease of LaF 3 solubility in aqueous-organic solvents as compared with that of LaCl 3 , La(NO 3 ) 3 , and La 2 (SO 4 ) 3 causes a higher selectivity of RFME with respect to the anions under study

  19. Phase evolution during CuInSe{sub 2} electrodeposition on polycrystalline Mo

    Energy Technology Data Exchange (ETDEWEB)

    Saucedo, E., E-mail: edgardo.saucedo@hotmail.co [Institut de Recherche et Developement sur l' Energie Photovoltaique (IRDEP), 6 Quai Watier-BP 49, 78401 Chatou cedex (France); Ruiz, C.M.; Chassaing, E.; Jaime-Ferrer, J.S.; Grand, P.P.; Savidand, G.; Bermudez, V. [Institut de Recherche et Developement sur l' Energie Photovoltaique (IRDEP), 6 Quai Watier-BP 49, 78401 Chatou cedex (France)

    2010-05-03

    Using structural analyses means of ex-situ Raman spectroscopy and X-ray diffraction combined with electrical measurements, we study the phase evolution in the growth by electrodeposition technique of CuInSe{sub 2} on polycrystalline Mo. For this purpose the growth was stopped at different stages, and then the different layers were analysed. First growth steps seem to be controlled by the deposition of secondary phases, like elemental Se and Cu{sub 2}Se binary. After the deposition of approximately 300 nm of material, CuInSe{sub 2} ternary and ordered vacancy compounds start to adequately form. At a thickness close to 2000 nm, the formation of binary Cu{sub x}Se is observed, remaining up to the final growth process (4350 nm). All these results are compared with the kinetic model of the system under the consideration of the experimental composition evolution.

  20. Properties of polycrystalline indium oxide in open air and in vacuum

    International Nuclear Information System (INIS)

    Solov'eva, A.E.; Zhdanov, V.A.; Markov, V.L.; Shvangiradze, R.R.

    1982-01-01

    Properties of polycrystalline indium oxide according to annealing temperature in open air and in vacuum are investigated. It is established that the indium oxide begins to change its chemical composition during the annealing in the open air from 1200 deg C, and in the vacuum - form 800 deg C. During the annealing of the samples in ths open air in the temperature range of 1200-1450 deg C the lattice of the indium oxide loses probably, only oxygen; this process is accompanied by change of the samples color, electrophysical properties, lattice parameter density. Cation sublattice is disturbed in the vacuum beginning from 900 deg C, which is accompanied by destruction of the color centers. X-ray density and the activation energy of the reduction accounting the formation of the color centers are calculated on the base of the X-ray data and the deviation from stoichiometry of the indium oxide depending on the annealing temperature in the open air

  1. Controlled nanostructuration of polycrystalline tungsten thin films

    Energy Technology Data Exchange (ETDEWEB)

    Girault, B. [Institut P' (UPR 3346 CNRS), Universite de Poitiers, ENSMA, Bd Pierre et Marie Curie, 86962 Futuroscope Cedex (France); Institut de Recherche en Genie Civil et Mecanique (UMR CNRS 6183), LUNAM Universite, Universite de Nantes, Centrale Nantes, CRTT, 37 Bd de l' Universite, BP 406, 44602 Saint-Nazaire Cedex (France); Eyidi, D.; Goudeau, P.; Guerin, P.; Bourhis, E. Le; Renault, P.-O. [Institut P' (UPR 3346 CNRS), Universite de Poitiers, ENSMA, Bd Pierre et Marie Curie, 86962 Futuroscope Cedex (France); Sauvage, T. [CEMHTI/CNRS (UPR 3079 CNRS), Universite d' Orleans, 3A rue de la Ferollerie, 45071 Orleans Cedex 2 (France)

    2013-05-07

    Nanostructured tungsten thin films have been obtained by ion beam sputtering technique stopping periodically the growing. The total thickness was maintained constant while nanostructure control was obtained using different stopping periods in order to induce film stratification. The effect of tungsten sublayers' thicknesses on film composition, residual stresses, and crystalline texture evolution has been established. Our study reveals that tungsten crystallizes in both stable {alpha}- and metastable {beta}-phases and that volume proportions evolve with deposited sublayers' thicknesses. {alpha}-W phase shows original fiber texture development with two major preferential crystallographic orientations, namely, {alpha}-W<110> and unexpectedly {alpha}-W<111> texture components. The partial pressure of oxygen and presence of carbon have been identified as critical parameters for the growth of metastable {beta}-W phase. Moreover, the texture development of {alpha}-W phase with two texture components is shown to be the result of a competition between crystallographic planes energy minimization and crystallographic orientation channeling effect maximization. Controlled grain size can be achieved for the {alpha}-W phase structure over 3 nm stratification step. Below, the {beta}-W phase structure becomes predominant.

  2. Anomalous normal mode oscillations in semiconductor microcavities

    Energy Technology Data Exchange (ETDEWEB)

    Wang, H. [Univ. of Oregon, Eugene, OR (United States). Dept. of Physics; Hou, H.Q.; Hammons, B.E. [Sandia National Labs., Albuquerque, NM (United States)

    1997-04-01

    Semiconductor microcavities as a composite exciton-cavity system can be characterized by two normal modes. Under an impulsive excitation by a short laser pulse, optical polarizations associated with the two normal modes have a {pi} phase difference. The total induced optical polarization is then expected to exhibit a sin{sup 2}({Omega}t)-like oscillation where 2{Omega} is the normal mode splitting, reflecting a coherent energy exchange between the exciton and cavity. In this paper the authors present experimental studies of normal mode oscillations using three-pulse transient four wave mixing (FWM). The result reveals surprisingly that when the cavity is tuned far below the exciton resonance, normal mode oscillation in the polarization is cos{sup 2}({Omega}t)-like, in contrast to what is expected form the simple normal mode model. This anomalous normal mode oscillation reflects the important role of virtual excitation of electronic states in semiconductor microcavities.

  3. Doping of organic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Luessem, B.; Riede, M.; Leo, K. [Institut fuer Angewandte Photophysik, TU Dresden (Germany)

    2013-01-15

    The understanding and applications of organic semiconductors have shown remarkable progress in recent years. This material class has been developed from being a lab curiosity to the basis of first successful products as small organic LED (OLED) displays; other areas of application such as OLED lighting and organic photovoltaics are on the verge of broad commercialization. Organic semiconductors are superior to inorganic ones for low-cost and large-area optoelectronics due to their flexibility, easy deposition, and broad variety, making tailor-made materials possible. However, electrical doping of organic semiconductors, i.e. the controlled adjustment of Fermi level that has been extremely important to the success of inorganic semiconductors, is still in its infancy. This review will discuss recent work on both fundamental principles and applications of doping, focused primarily to doping of evaporated organic layers with molecular dopants. Recently, both p- and n-type molecular dopants have been developed that lead to efficient and stable doping of organic thin films. Due to doping, the conductivity of the doped layers increases several orders of magnitude and allows for quasi-Ohmic contacts between organic layers and metal electrodes. Besides reducing voltage losses, doping thus also gives design freedom in terms of transport layer thickness and electrode choice. The use of doping in applications like OLEDs and organic solar cells is highlighted in this review. Overall, controlled molecular doping can be considered as key enabling technology for many different organic device types that can lead to significant improvements in efficiencies and lifetimes. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Images through semiconductors

    International Nuclear Information System (INIS)

    Anon.

    1986-01-01

    Improved image processing techniques are constantly being developed for television and for scanners using X-rays or other radiation for industrial or medical applications, etc. As Erik Heijne of CERN explains here, particle physics too has its own special requirements for image processing. The increasing use of semiconductor techniques for handling measurements down to the level of a few microns provides another example of the close interplay between scientific research and technological development. (orig.).

  5. Muonium states in semiconductors

    International Nuclear Information System (INIS)

    Patterson, B.D.

    1987-01-01

    There is a brief summary of what is known about the muonium states isotropic, anisotropic and diamagnetic in diamond and zincblende semiconductors. The report deals with muonium spectroscopy, including the formation probabilities, hyperfine parameters and electronic g-factors of the states. The dynamics of the states is treated including a discussion of the transition from isotropic Mu to anisotropic Mu in diamond, temperature-dependent linewidthes in silicon and germanium and effects of daping and radiation damage

  6. Nonradiative recombination in semiconductors

    CERN Document Server

    Abakumov, VN; Yassievich, IN

    1991-01-01

    In recent years, great progress has been made in the understandingof recombination processes controlling the number of excessfree carriers in semiconductors under nonequilibrium conditions. As a result, it is now possible to give a comprehensivetheoretical description of these processes. The authors haveselected a number of experimental results which elucidate theunderlying physical problems and enable a test of theoreticalmodels. The following topics are dealt with: phenomenological theory ofrecombination, theoretical models of shallow and deep localizedstates, cascade model of carrier captu

  7. Doping of organic semiconductors

    International Nuclear Information System (INIS)

    Luessem, B.; Riede, M.; Leo, K.

    2013-01-01

    The understanding and applications of organic semiconductors have shown remarkable progress in recent years. This material class has been developed from being a lab curiosity to the basis of first successful products as small organic LED (OLED) displays; other areas of application such as OLED lighting and organic photovoltaics are on the verge of broad commercialization. Organic semiconductors are superior to inorganic ones for low-cost and large-area optoelectronics due to their flexibility, easy deposition, and broad variety, making tailor-made materials possible. However, electrical doping of organic semiconductors, i.e. the controlled adjustment of Fermi level that has been extremely important to the success of inorganic semiconductors, is still in its infancy. This review will discuss recent work on both fundamental principles and applications of doping, focused primarily to doping of evaporated organic layers with molecular dopants. Recently, both p- and n-type molecular dopants have been developed that lead to efficient and stable doping of organic thin films. Due to doping, the conductivity of the doped layers increases several orders of magnitude and allows for quasi-Ohmic contacts between organic layers and metal electrodes. Besides reducing voltage losses, doping thus also gives design freedom in terms of transport layer thickness and electrode choice. The use of doping in applications like OLEDs and organic solar cells is highlighted in this review. Overall, controlled molecular doping can be considered as key enabling technology for many different organic device types that can lead to significant improvements in efficiencies and lifetimes. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Surface Potential of Polycrystalline Hematite in Aqueous Medium

    Directory of Open Access Journals (Sweden)

    Tajana Preočanin

    2011-01-01

    Full Text Available The surface potential of polycrystalline hematite in aqueous sodium perchlorate environment as a function of pH was examined. Surface potential of hematite was obtained from measured electrode potential of a nonporous polycrystalline hematite electrode. Acidic solution was titrated with base, and the backward titration with acid was performed. Substantial hysteresis was obtained which enabled location of the point of zero potential and equilibrium values of surface potentials. The theoretical interpretation of the equilibrium data was performed by applying the surface complexation model and the thermodynamic equilibrium constants for the first and the second step of surface protonation was obtained as logK1∘=11.3;logK2∘=2.8.

  9. Inelastic x-ray scattering from polycrystalline materials

    International Nuclear Information System (INIS)

    Fischer, I.

    2008-09-01

    Inelastic X-ray scattering (IXS) is a tool to determine the phonon dispersion along high symmetry directions in single crystals. However, novel materials and crystals under extreme conditions are often only available in form of polycrystalline samples. Thus the investigation is limited to orientation-averaged properties. To overcome these limitations, a methodology to extract the single crystal phonon dispersion from polycrystalline materials was developed. The approach consists of recording IXS spectra over a large momentum transfer region and confront them with a Born - von Karman model calculation. A least-square refinement of the model IXS spectra then provides the single crystal dispersion scheme. In this work the method is developed on the test case Be. Further studies were performed on more and more complex systems, in order to explore the limitations. This novel application of IXS promises to be a valuable tool in cases where single crystalline materials are not available. (author)

  10. Ultrathin polycrystalline 6,13-Bis(triisopropylsilylethynyl)-pentacene films

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Min-Cherl; Zhang, Dongrong; Nikiforov, Gueorgui O.; Lee, Michael V.; Qi, Yabing, E-mail: Yabing.Qi@oist.jp [Energy Materials and Surface Sciences Unit (EMSS), Okinawa Institute of Science and Technology Graduate University (OIST), 1919-1 Tancha, Onna-son, Okinawa 904-0495 (Japan); Joo Shin, Tae; Ahn, Docheon; Lee, Han-Koo; Baik, Jaeyoon; Shin, Hyun-Joon [Pohang Accelerator Laboratory, POSTECH, Pohang 790-784 (Korea, Republic of)

    2015-03-15

    Ultrathin (<6 nm) polycrystalline films of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-P) are deposited with a two-step spin-coating process. The influence of spin-coating conditions on morphology of the resulting film was examined by atomic force microscopy. Film thickness and RMS surface roughness were in the range of 4.0–6.1 and 0.6–1.1 nm, respectively, except for small holes. Polycrystalline structure was confirmed by grazing incidence x-ray diffraction measurements. Near-edge x-ray absorption fine structure measurements suggested that the plane through aromatic rings of TIPS-P molecules was perpendicular to the substrate surface.

  11. Survey of semiconductor physics

    CERN Document Server

    Böer, Karl W

    1992-01-01

    Any book that covers a large variety of subjects and is written by one author lacks by necessity the depth provided by an expert in his or her own field of specialization. This book is no exception. It has been written with the encouragement of my students and colleagues, who felt that an extensive card file I had accumulated over the years of teaching solid state and semiconductor physics would be helpful to more than just a few of us. This file, updated from time to time, contained lecture notes and other entries that were useful in my research and permitted me to give to my students a broader spectrum of information than is available in typical textbooks. When assembling this material into a book, I divided the top­ ics into material dealing with the homogeneous semiconductor, the subject of the previously published Volume 1, and the inhomoge­ neous semiconductor, the subject of this Volume 2. In order to keep the book to a manageable size, sections of tutorial character which can be used as text for a g...

  12. Semiconductor Ion Implanters

    International Nuclear Information System (INIS)

    MacKinnon, Barry A.; Ruffell, John P.

    2011-01-01

    In 1953 the Raytheon CK722 transistor was priced at $7.60. Based upon this, an Intel Xeon Quad Core processor containing 820,000,000 transistors should list at $6.2 billion! Particle accelerator technology plays an important part in the remarkable story of why that Intel product can be purchased today for a few hundred dollars. Most people of the mid twentieth century would be astonished at the ubiquity of semiconductors in the products we now buy and use every day. Though relatively expensive in the nineteen fifties they now exist in a wide range of items from high-end multicore microprocessors like the Intel product to disposable items containing 'only' hundreds or thousands like RFID chips and talking greeting cards. This historical development has been fueled by continuous advancement of the several individual technologies involved in the production of semiconductor devices including Ion Implantation and the charged particle beamlines at the heart of implant machines. In the course of its 40 year development, the worldwide implanter industry has reached annual sales levels around $2B, installed thousands of dedicated machines and directly employs thousands of workers. It represents in all these measures, as much and possibly more than any other industrial application of particle accelerator technology. This presentation discusses the history of implanter development. It touches on some of the people involved and on some of the developmental changes and challenges imposed as the requirements of the semiconductor industry evolved.

  13. The Physics of Semiconductors

    Science.gov (United States)

    Brennan, Kevin F.

    1999-02-01

    Modern fabrication techniques have made it possible to produce semiconductor devices whose dimensions are so small that quantum mechanical effects dominate their behavior. This book describes the key elements of quantum mechanics, statistical mechanics, and solid-state physics that are necessary in understanding these modern semiconductor devices. The author begins with a review of elementary quantum mechanics, and then describes more advanced topics, such as multiple quantum wells. He then disusses equilibrium and nonequilibrium statistical mechanics. Following this introduction, he provides a thorough treatment of solid-state physics, covering electron motion in periodic potentials, electron-phonon interaction, and recombination processes. The final four chapters deal exclusively with real devices, such as semiconductor lasers, photodiodes, flat panel displays, and MOSFETs. The book contains many homework exercises and is suitable as a textbook for electrical engineering, materials science, or physics students taking courses in solid-state device physics. It will also be a valuable reference for practicing engineers in optoelectronics and related areas.

  14. Effect of hydrogen passivation on polycrystalline silicon thin films

    Czech Academy of Sciences Publication Activity Database

    Honda, Shinya; Mates, Tomáš; Ledinský, Martin; Oswald, Jiří; Fejfar, Antonín; Kočka, Jan; Yamazaki, T.; Uraoka, Y.; Fuyuki, T.

    2005-01-01

    Roč. 487, - (2005), s. 152-156 ISSN 0040-6090 R&D Projects: GA AV ČR(CZ) IAA1010316; GA AV ČR(CZ) IAA1010413; GA ČR(CZ) GD202/05/H003 Institutional research plan: CEZ:AV0Z10100521 Keywords : hydrogen passivation * polycrystalline silicon * photoluminescence * Raman spectroscopy * Si-H 2 * hydrogen molecules Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.569, year: 2005

  15. Formation of photovoltaic modules based on polycrystalline solar cells

    OpenAIRE

    L. A. Dobrzański; A. Drygała; A. Januszka

    2009-01-01

    Purpose: The main aim of the paper is formation of photovoltaic modules and analysis of their main electric parameters.Design/methodology/approach: Photovoltaic modules were produced from four polycrystalline silicon solar cells, that were cut and next joined in series. Soft soldering technique and copper-tin strip were used for joining cells.Findings: In order to provide useful power for any application, the individual solar cells must be connected together to give the appropriate current an...

  16. Ferromagnetic clusters in polycrystalline BaCoO3

    International Nuclear Information System (INIS)

    Botta, P.M.; Pardo, V.; Calle, C. de la; Baldomir, D.; Alonso, J.A.; Rivas, J.

    2007-01-01

    Polycrystalline BaCoO 3 was synthesized by a citrate technique using thermal treatments at high oxygen pressure. Magnetic susceptibility measurements on the compound were carried out under AC conditions. The magnetic properties of the material at low temperatures were found to be determined by the appearance of nanoscale ferromagnetic (FM) regions and not by a true magnetic phase transition. These clusters have a mean size of about 1 nm in diameter and obey an Arrhenius-like thermal relaxation

  17. Mesoscopic approach to modeling elastic-plastic polycrystalline material behaviour

    International Nuclear Information System (INIS)

    Kovac, M.; Cizelj, L.

    2001-01-01

    Extreme loadings during severe accident conditions might cause failure or rupture of the pressure boundary of a reactor coolant system. Reliable estimation of the extreme deformations can be crucial to determine the consequences of such an accident. One of important drawbacks of classical continuum mechanics is idealization of inhomogenous microstructure of materials. This paper discusses the mesoscopic approach to modeling the elastic-plastic behavior of a polycrystalline material. The main idea is to divide the continuum (e.g., polycrystalline aggregate) into a set of sub-continua (grains). The overall properties of the polycrystalline aggregate are therefore determined by the number of grains in the aggregate and properties of randomly shaped and oriented grains. The random grain structure is modeled with Voronoi tessellation and random orientations of crystal lattices are assumed. The elastic behavior of monocrystal grains is assumed to be anisotropic. Crystal plasticity is used to describe plastic response of monocrystal grains. Finite element method is used to obtain numerical solutions of strain and stress fields. The analysis is limited to two-dimensional models.(author)

  18. Polycrystalline diamond detectors with three-dimensional electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Lagomarsino, S., E-mail: lagomarsino@fi.infn.it [University of Florence, Department of Physics, Via Sansone 1, 50019 Sesto Fiorentino (Italy); INFN Firenze, Via B. Rossi 1, 50019 Sesto Fiorentino (Italy); Bellini, M. [INO-CNR Firenze, Largo E. Fermi 6, 50125 Firenze (Italy); Brianzi, M. [INFN Firenze, Via B. Rossi 1, 50019 Sesto Fiorentino (Italy); Carzino, R. [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia, Genova, Via Morego 30, 16163 Genova (Italy); Cindro, V. [Joseph Stefan Institute, Jamova Cesta 39, 1000 Ljubljana (Slovenia); Corsi, C. [University of Florence, Department of Physics, Via Sansone 1, 50019 Sesto Fiorentino (Italy); LENS Firenze, Via N. Carrara 1, 50019 Sesto Fiorentino (Italy); Morozzi, A.; Passeri, D. [INFN Perugia, Perugia (Italy); Università degli Studi di Perugia, Dipartimento di Ingegneria, via G. Duranti 93, 06125 Perugia (Italy); Sciortino, S. [University of Florence, Department of Physics, Via Sansone 1, 50019 Sesto Fiorentino (Italy); INFN Firenze, Via B. Rossi 1, 50019 Sesto Fiorentino (Italy); Servoli, L. [INFN Perugia, Perugia (Italy)

    2015-10-01

    The three-dimensional concept in diamond detectors has been applied, so far, to high quality single-crystal material, in order to test this technology in the best available conditions. However, its application to polycrystalline chemical vapor deposited diamond could be desirable for two reasons: first, the short inter-electrode distance of three-dimensional detectors should improve the intrinsically lower collection efficiency of polycrystalline diamond, and second, at high levels of radiation damage the performances of the poly-crystal material are not expected to be much lower than those of the single crystal one. We report on the fabrication and test of three-dimensional polycrystalline diamond detectors with several inter-electrode distances, and we demonstrate that their collection efficiency is equal or higher than that obtained with conventional planar detectors fabricated with the same material. - Highlights: • Pulsed laser fabrication of polycristalline diamond detectors with 3D electrodes. • Measurement of the charge collection efficiency (CCE) under beta irradiation. • Comparation between the CCE of 3D and conventional planar diamond sensors. • A rationale for the behavior of three-dimensional and planar sensors is given.

  19. Ag-based semiconductor photocatalysts in environmental purification

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jiade; Fang, Wen [School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi Province (China); Yu, Changlin, E-mail: yuchanglinjx@163.com [School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi Province (China); School of Environment Engineering and biology Engineering, Guangdong University of Petrochemical Technology, Maoming, 525000 Guangdong Province (China); Zhou, Wanqin [School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi Province (China); State Key Laboratory of Photocatalysis on Energy and Environment, Fuzhou University, Fuzhou, 350002 (China); Zhu, Lihua [School of Metallurgy and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi Province (China); Xie, Yu, E-mail: xieyu_121@163.com [College of Environment and Chemical Engineering, Nanchang Hangkong University, Nanchang 330063, Jiangxi (China)

    2015-12-15

    -based semiconductor could produce high efficient composite photocatalyts.

  20. Ag-based semiconductor photocatalysts in environmental purification

    International Nuclear Information System (INIS)

    Li, Jiade; Fang, Wen; Yu, Changlin; Zhou, Wanqin; Zhu, Lihua; Xie, Yu

    2015-01-01

    -based semiconductor could produce high efficient composite photocatalyts.

  1. Structural, optical, and magnetic properties of polycrystalline Co-doped TiO2 synthesized by solid-state method

    International Nuclear Information System (INIS)

    Bouaine, Abdelhamid; Schmerber, G.; Ihiawakrim, D.; Derory, A.

    2012-01-01

    Highlights: ► Influence of Co doping on the TiO 2 tetragonal structure. ► Decrease of the energy band gap after doping with Co atoms. ► Appearance of ferromagnetism in Co-doped TiO 2 diluted magnetic semiconductors. - Abstract: We have used a solid-state method to synthesize polycrystalline Co-doped TiO 2 diluted magnetic semiconductors (DMSs) with Co concentrations of 0, and 0.5 at.%. X-ray diffraction patterns reveal that Co doped TiO 2 crystallizes in the rutile tetragonal structure with no additional peaks. Transmission electron microscopy (TEM) did not indicate the presence of magnetic parasitic phases and confirmed that Co ions are uniformly distributed inside the samples. Optical absorbance measurements showed an energy band gap which decreases after doping with the Co atoms into the TiO 2 matrix. Magnetization measurements revealed a paramagnetic behavior for the as-prepared Co-doped TiO 2 and a ferromagnetic behavior for the same samples after annealed under a mixture of H 2 /N 2 atmosphere.

  2. Thin polycrystalline diamond films protecting zirconium alloys surfaces: from technology to layer analysis and application in nuclear facilities

    Czech Academy of Sciences Publication Activity Database

    Ashcheulov, Petr; Škoda, R.; Škarohlíd, J.; Taylor, Andrew; Fekete, Ladislav; Fendrych, František; Vega, R.; Shao, L.; Kalvoda, L.; Vratislav, S.; Cháb, Vladimír; Horáková, K.; Kůsová, Kateřina; Klimša, Ladislav; Kopeček, Jaromír; Sajdl, P.; Macák, J.; Johnson, S.; Kratochvílová, Irena

    2015-01-01

    Roč. 359, Dec (2015), s. 621-628 ISSN 0169-4332 R&D Projects: GA ČR(CZ) GA15-05095S; GA TA ČR TA04020156; GA MŠk LO1409; GA MŠk(CZ) LM2011029 Grant - others:SAFMAT(XE) CZ.2.16/3.1.00/22132 Institutional support: RVO:68378271 Keywords : metal coatings * thin polycrystalline diamond film * impedance spectroscopy * Raman spectroscopy * XPS Subject RIV: JI - Composite Materials Impact factor: 3.150, year: 2015

  3. High Performance High Temperature Thermoelectric Composites with Metallic Inclusions

    Science.gov (United States)

    Ma, James M. (Inventor); Bux, Sabah K. (Inventor); Fleurial, Jean-Pierre (Inventor); Ravi, Vilupanur A. (Inventor); Firdosy, Samad A. (Inventor); Star, Kurt (Inventor); Kaner, Richard B. (Inventor)

    2017-01-01

    The present invention provides a composite thermoelectric material. The composite thermoelectric material can include a semiconductor material comprising a rare earth metal. The atomic percent of the rare earth metal in the semiconductor material can be at least about 20%. The composite thermoelectric material can further include a metal forming metallic inclusions distributed throughout the semiconductor material. The present invention also provides a method of forming this composite thermoelectric material.

  4. Study of non-stoichiometric BaSrTiFeO3 oxide dedicated to semiconductor gas sensors

    International Nuclear Information System (INIS)

    Fasquelle, D.; Verbrugghe, N.; Deputier, S.

    2016-01-01

    Developing instrumentation systems compatible with the European RoHS directive (restriction of hazardous substances) to monitor our environment is of great interest for our society. Our research therefore aims at developing innovating integrated systems of detection dedicated to the characterization of various environmental exposures. These systems, which integrate new gas sensors containing lead-free oxides, are dedicated to the detection of flammable and toxic gases. We have firstly chosen to study semiconductor gas sensors implemented with lead-free oxides in view to develop RoHS devices. Therefore thick films deposited by spin-coating and screen-printing have been chosen for their robustness, ease to realize and ease to finally obtain cost-effective sensors. As crystalline defects and ionic vacancies are of great interest for gas detection, we have decided to study a non-stoichiometric composition of the BaSrTiFeO 3 sensible oxide. Nonstoichiometric BaSrTiFeO 3 lead-free oxide thick films were deposited by screen-printing on polycrystalline AFO 3 substrates covered by a layer of Ag-Pd acting as bottom electrode. The physical characterizations have revealed a crystalline structure mainly composed of BaTiO 3 pseudo-cubic phase and Ba 4 Ti 12 O 27 monoclinic phase for the powder, and a porous microstructure for the thick films. When compared to a BSTF thick film with a stoichiometric composition, a notable increase in the BSTF dielectric constant value was observed when taking into account of a similar microstructure and grain size. The loss tangent mean value varies more softly for the non-stoichiometric BaSrTiFeO 3 films than for the perovskite BSTF film as tanδ decreases from 0.45 to 0.04 when the frequency increases from 100 Hz to 1 MHz. (paper)

  5. Electrodes for Semiconductor Gas Sensors

    Science.gov (United States)

    Lee, Sung Pil

    2017-01-01

    The electrodes of semiconductor gas sensors are important in characterizing sensors based on their sensitivity, selectivity, reversibility, response time, and long-term stability. The types and materials of electrodes used for semiconductor gas sensors are analyzed. In addition, the effect of interfacial zones and surface states of electrode–semiconductor interfaces on their characteristics is studied. This study describes that the gas interaction mechanism of the electrode–semiconductor interfaces should take into account the interfacial zone, surface states, image force, and tunneling effect. PMID:28346349

  6. Development of semiconductor electronics

    International Nuclear Information System (INIS)

    Bardeen, John.

    1977-01-01

    In 1931, Wilson applied Block's theory about the energy bands for the motion of electrons in a crystal lattice to semiconductors and showed that conduction can take place in two different ways, by electrons and by holes. Not long afterwards Frenkel showed that these carriers can flow by diffusion in a concentration gradient as well as under the influence of an electric field and wrote down equations for the current flow. The third major contribution, in the late 1930's was the explanation of rectification at a metalsemiconductor contact by Mott and more completely by Schottky. In late 1947 the first transistor of the point contact type was invented by Brattin, Shockley and Bardeen. Then after single crystals of Ge were grown, the junction transistor was developed by the same group. The first silicon transistors appeared in 1954. Then an important step was discovery of the planar transistor by Hoenri in 1960 which led to development of integrated circuits by 1962. Many transistors are produced by batch processing on a slice of silicon. Then in 1965 Mos (Metal-Oxide Semiconductor) transistor and in 1968 LSI (Large Scale Intergration circuits) were developed. Aside from electronic circuits, there are many other applications of semiconductors, including junction power rectifiers, junction luminescence (including lasers), solar batteries, radiation detectors, microwave oscillators and charged-coupled devices for computer memories and devices. One of the latest developments is a microprocessor with thousands of transistors and associated circuitry on a single small chip of silicon. It can be programmed to provide a variety of circuit functions, thus it is not necessary to go through the great expense of LSI's for each desired function, but to use standard microprocessors and program to do the job

  7. Comparison of polycrystalline Cu(In,Ga)Se2 device efficiency with junction depth and interfacial structure

    International Nuclear Information System (INIS)

    Nelson, A.J.; Gabor, A.M.; Contreras, M.A.; Tuttle, J.R.; Noufi, R.; Sobol, P.E.; Asoka-Kumar, P.; Lynn, K.G.

    1995-01-01

    X-ray photoemission spectroscopy (XPS) and positron annihilation spectroscopy (PAS) have been used to characterize the surface versus bulk composition, electronic, and physical structure of polycrystalline Cu(In,Ga)Se 2 thin-film interfaces. Angle-resolved high-resolution photoemission measurements on the valence-band electronic structure and Cu 2p, In 3d, Ga 2p, and Se 3d core lines were used to evaluate the surface and near surface chemistry of CuInSe 2 and Cu(In,Ga)Se 2 device grade thin films. XPS compositional depth profiles were also acquired from the near surface region. PAS was used as a nondestructive, depth-sensitive probe for open-volume-type defects. Results of these measurements are related to device efficiencies to show the effects of compositional variations and defect concentrations in the near surface region on device performance. copyright 1995 American Institute of Physics

  8. Layered semiconductor neutron detectors

    Science.gov (United States)

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  9. Basic properties of semiconductors

    CERN Document Server

    Landsberg, PT

    2013-01-01

    Since Volume 1 was published in 1982, the centres of interest in the basic physics of semiconductors have shifted. Volume 1 was called Band Theory and Transport Properties in the first edition, but the subject has broadened to such an extent that Basic Properties is now a more suitable title. Seven chapters have been rewritten by the original authors. However, twelve chapters are essentially new, with the bulk of this work being devoted to important current topics which give this volume an almost encyclopaedic form. The first three chapters discuss various aspects of modern band theory and the

  10. Electrowetting on semiconductors

    Science.gov (United States)

    Palma, Cesar; Deegan, Robert

    2015-01-01

    Applying a voltage difference between a conductor and a sessile droplet sitting on a thin dielectric film separating it from the conductor will cause the drop to spread. When the conductor is a good metal, the change of the drop's contact angle due to the voltage is given by the Young-Lippmann (YL) equation. Here, we report experiments with lightly doped, single crystal silicon as the conductive electrode. We derive a modified YL equation that includes effects due to the semiconductor and contact line pinning. We show that light induces a non-reversible wetting transition, and that our model agrees well with our experimental results.

  11. Semiconductor ionizino. radiation detectors

    International Nuclear Information System (INIS)

    1982-01-01

    Spectrometric semiconductor detectors of ionizing radiation with the electron-hole junction, based on silicon and germanium are presented. The following parameters are given for the individual types of germanium detectors: energy range of detected radiation, energy resolution given as full width at half maximum (FWHM) and full width at one tenth of maximum (FWTM) for 57 Co and 60 Co, detection sensitivity, optimal voltage, and electric capacitance at optimal voltage. For silicon detectors the value of FWHM for 239 Pu is given, the sensitive area and the depth of the sensitive area. (E.S.)

  12. Band structure of semiconductors

    CERN Document Server

    Tsidilkovski, I M

    2013-01-01

    Band Structure of Semiconductors provides a review of the theoretical and experimental methods of investigating band structure and an analysis of the results of the developments in this field. The book presents the problems, methods, and applications in the study of band structure. Topics on the computational methods of band structure; band structures of important semiconducting materials; behavior of an electron in a perturbed periodic field; effective masses and g-factors for the most commonly encountered band structures; and the treatment of cyclotron resonance, Shubnikov-de Haas oscillatio

  13. Defects in Cu(In,Ga)Se{sub 2} chalcopyrite semiconductors: a comparative study of material properties, defect states, and photovoltaic performance

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Qing; Gunawan, Oki; Copel, Matthew; Reuter, Kathleen B; Chey, S Jay; Mitzi, David B [IBM T.J. Watson Research Center, Yorktown Heights, NY (United States); Deline, Vaughn R [IBM Almaden Resesarch Center, San Jose, CA (United States)

    2011-10-15

    Understanding defects in Cu(In,Ga)(Se,S){sub 2} (CIGS), especially correlating changes in the film formation process with differences in material properties, photovoltaic (PV) device performance, and defect levels extracted from admittance spectroscopy, is a critical but challenging undertaking due to the complex nature of this polycrystalline compound semiconductor. Here we present a systematic comparative study wherein varying defect density levels in CIGS films were intentionally induced by growing CIGS grains using different selenium activity levels. Material characterization results by techniques including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and medium energy ion scattering indicate that this process variation, although not significantly affecting CIGS grain structure, crystal orientation, or bulk composition, leads to enhanced formation of a defective chalcopyrite layer with high density of indium or gallium at copper antisite defects ((In, Ga){sub Cu}) near the CIGS surface, for CIGS films grown with insufficient selenium supply. This defective layer or the film growth conditions associated with it is further linked with observed current-voltage characteristics, including rollover and crossover behavior, and a defect state at around 110 meV (generally denoted as the N1 defect) commonly observed in admittance spectroscopy. The impact of the (In, Ga){sub Cu} defects on device PV performance is also established. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. Effects of ion sputtering on semiconductor surfaces

    International Nuclear Information System (INIS)

    McGuire, G.E.

    1978-01-01

    Ion beam sputtering has been combined with Auger spectroscopy to study the effects of ion beams on semiconductor surfaces. Observations on the mass dependence of ion selective sputtering of two component systems are presented. The effects of ion implantation are explained in terms of atomic dilution. Experimental data are presented that illustrate the super-position of selective sputtering and implantation effects on the surface composition. Sample reduction from electron and ion beam interaction is illustrated. Apparent sample changes which one might observe from the effects of residual gas contamination and electric fields are also discussed. (Auth.)

  15. Defects and diffusion in semiconductors XIV

    CERN Document Server

    Fisher, David J

    2012-01-01

    This 14th volume in the series covers the latest results in the field of Defects and Diffusion in Semiconductor. The issue also includes some original papers: An Experimental Study of the Thermal Properties of Modified 9Cr-1Mo Steel; Physico-Mechanical Properties of Sintered Iron-Silica Sand Nanoparticle Composites: A Preliminary Study; Defect and Dislocation Density Parameters of 5251 Al Alloy Using Positron Annihilation Lifetime Technique; A Novel Computational Strategy to Enhance the Ability of Elaborate Search by Entire Swarm to Find the Best Solution in Optimization of AMCs; Synthesis and

  16. Organic Semiconductor-Containing Supramolecules: Effect of Small Molecule Crystallization and Molecular Packing

    KAUST Repository

    Rancatore, Benjamin J.; Kim, BongSoo; Mauldin, Clayton E.; Frechet, Jean; Xu, Ting

    2016-01-01

    on these highly crystalline molecules differs from their less crystalline counterparts. Here, two families of organic semiconductor SMs are investigated, where the composition of the crystalline core, the location (side- vs end-functionalization) of the alkyl

  17. Single filament semiconductor laser

    International Nuclear Information System (INIS)

    Botez, D.

    1980-01-01

    A semiconductor laser comprising: a body of semiconductor material including a substrate having a surface and a pair of spaced, substantially parallel dove-tailed shaped grooves in said surface, said body having a pair of end surfaces between which said grooves extend, said end surfaces being reflective to light with at least one of said end surfaces being partially transparent to light a first epitaxial layer over said surface of the substrate and the surfaces of the grooves, said first epitaxial layer having a flat surface portion over the portion of the substrate surface between the grooves, a thin second epitaxial layer over said first epitaxial layer, a third epitaxial layer over said second epitaxial layer, said first and third epitaxial layers being of opposite conductivity types and the second epitaxial layer being the active recombination region of the laser with the light being generated therein in the vicinity of the portion which is over the flat surface portion of the first epitaxial layer, and a pair of contacts on said body with one contact being over said third epitaxial body and the other being on said substrate

  18. Disorder phenomena in covalent semiconductors

    International Nuclear Information System (INIS)

    Popescu, M.A.

    1975-01-01

    The structure of the amorphous semiconductors has been investigated by means of X-ray diffraction and by computer simulation of random network models. Amorphous germanium contains mainly five and six-membered rings of atoms. In glassy state, the ternary compounds A 2 B 4 C 2 5 , such as CdGeAs 2 contain only even rings of atoms (six-membered and eight-membered rings). In the memory glasses of the type A 2 B 4 C 2 5 , such as GeAs 2 Te 7 , the valency state of every element is that from the crystal and important van der Waals forces are effective in the network. No Ge-Ge, Ge-As and As-As bonds are formed. The high pressure forms of the germanium have been simulated by computer. The force constants of the covalent bonds in Ge III and Ge IV differ from those in Ge I. The bond bending force constant decreases rapidly when the density of the crystal increases, a fact which has been imparted to a reduction of the sp 3 hybridization. The compressibility curve of the Ge I has been explained. The effect of the radial and uniaxial deformation on the non-crystalline networks has been studied. The compressibility of the amorphous germanium is by 1.5 per cent greater than that of crystalline germanium. The Poisson coefficient for a-Ge network is 0.233. The structure of the As 2 S 3 glass doped with different amounts of germanium (up to 40 at. per cent) and silver (up to 12 at. per cent) has been investigated. The As 2 S 3 Gesub(x) compositions are constituted from a disordered packing of structural units whose chemical composition and relative proportion in the glass essentially depends on the germanium content. (author)

  19. Electronic and optical properties of diamond/organic semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Gajewski, Wojciech; Garrido, Jose; Niedermeier, Martin; Stutzmann, Martin [Walter Schottky Institute, TU Muenchen, Am Coulombwall 3, 85748 Garching (Germany); Williams, Oliver; Haenen, Ken [Institute for Materials Research, University of Hasselt, Wetenschapspark 1, BE-3590 Diepenbeek (Belgium)

    2007-07-01

    Different diamond substrates (single crystalline: SCD, poly-crystalline: PCD and nano-crystalline: NCD) were used to investigate the electronic and optical properties of the diamond/organic semiconductor heterostructures. Layers of a poly[ethynyl-(2-decyloxy-5methoxy)benzene] - PEB, pentacene and 4-nitro-biphenyl-4-diazonium cations - Ph-Ph-NO{sub 2} were prepared by spin coating, thermal evaporation and grafting, respectively. The measurements of the electronic transport along the organic layer were performed using a Hg probe as well as Hall effect measurements in the temperature range 70-400 K. The I-V characteristics of the B-doped diamond/organic semiconductor heterostructures were measured at room temperature by means of the Hg probe. Undoped IIa and undoped PCD films were used for a study of the optical and optoelectronic properties of prepared heterostructures. The influence of the organic layer homogeneity and layer thickness on the optical properties will be discussed. Furthermore, preliminary data on perpendicular and parallel transport in the heterostructures layer will be reported.

  20. Efficiency limitations of polycrystalline thin film solar cells: case of Cu(In,Ga)Se2

    International Nuclear Information System (INIS)

    Werner, Juergen H.; Mattheis, Julian; Rau, Uwe

    2005-01-01

    Small-area Cu(In,Ga)Se 2 thin film solar cells have reached more than 19% efficiencies. Compared to other polycrystalline materials this efficiency value is remarkable. Nevertheless, the 19% for Cu(In,Ga)Se 2 range more than 6% (absolute) below the world's best single-crystalline Si cells and almost 14% below the upper theoretical limit of 33% for an ideal black body cell with infinitely large mobility and radiative recombination only. About 4% out of the 14% are of optical nature, additional 3% stem from the limited mobility/diffusion length and from band gap fluctuations with a standard deviation no. sigmano. g no. approxno. 50 meV due to spatial variations of composition and stoichiometry of the quaternary compound Cu(In,Ga)Se 2 . Thus, about 26% efficiency would be possible if there were only these band gap fluctuations. Additional, voltage-dependent electrostatic potential fluctuations push down the efficiency further to 19%: The polycrystalline Cu(In,Ga)Se 2 which is unavoidably structurally inhomogeneous due to dislocations, grain boundaries, point defects, etc. is also electrostatically inhomogeneous because of charged defects. Electrostatic potential fluctuations at the valence and conduction band edge may be not only responsible for a high saturation current density but also for the ideality factor in the current/voltage curve. The band gap and electrostatic potential fluctuations make the effective band gap which controls the intrinsic carrier density smaller than the average optical gap. The (zero bias) electrostatic potential fluctuations are here derived from the ideality factors of the current/voltage curve. The ideality factor reflects the voltage-induced electrostatic homogenization of the sample. For the world's best Cu(In,Ga)Se 2 cells with an ideality factor of n id =1.5, we estimate zero bias electrostatic potential fluctuations with a standard deviation no. sigmano. elec no. approxno. 140 meV

  1. Conduit for high temperature transfer of molten semiconductor crystalline material

    Science.gov (United States)

    Fiegl, George (Inventor); Torbet, Walter (Inventor)

    1983-01-01

    A conduit for high temperature transfer of molten semiconductor crystalline material consists of a composite structure incorporating a quartz transfer tube as the innermost member, with an outer thermally insulating layer designed to serve the dual purposes of minimizing heat losses from the quartz tube and maintaining mechanical strength and rigidity of the conduit at the elevated temperatures encountered. The composite structure ensures that the molten semiconductor material only comes in contact with a material (quartz) with which it is compatible, while the outer layer structure reinforces the quartz tube, which becomes somewhat soft at molten semiconductor temperatures. To further aid in preventing cooling of the molten semiconductor, a distributed, electric resistance heater is in contact with the surface of the quartz tube over most of its length. The quartz tube has short end portions which extend through the surface of the semiconductor melt and which are lef bare of the thermal insulation. The heater is designed to provide an increased heat input per unit area in the region adjacent these end portions.

  2. II-VI semiconductor compounds

    CERN Document Server

    1993-01-01

    For condensed matter physicists and electronic engineers, this volume deals with aspects of II-VI semiconductor compounds. Areas covered include devices and applications of II-VI compounds; Co-based II-IV semi-magnetic semiconductors; and electronic structure of strained II-VI superlattices.

  3. Electronic structure of semiconductor interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Herman, F

    1983-02-01

    The study of semiconductor interfaces is one of the most active and exciting areas of current semiconductor research. Because interfaces play a vital role in modern semiconductor technology (integrated circuits, heterojunction lasers, solar cells, infrared detectors, etc.), there is a strong incentive to understand interface properties at a fundamental level and advance existing technology thereby. At the same time, technological advances such as molecular beam epitaxy have paved the way for the fabrication of semiconductor heterojunctions and superlattices of novel design which exhibit unusual electronic, optical, and magnetic properties and offer unique opportunities for fundamental scientific research. A general perspective on this subject is offered treating such topics as the atomic and electronic structure of semiconductor surfaces and interfaces; oxidation and oxide layers; semiconductor heterojunctions and superlattices; rectifying metal-semiconductor contacts; and interface reactions. Recent progress is emphasized and some future directions are indicated. In addition, the role that large-scale scientific computation has played in furthering our theoretical understanding of semiconductor surfaces and interfaces is discussed. Finally, the nature of theoretical models, and the role they play in describing the physical world is considered.

  4. Quantum transport in semiconductor nanowires

    NARCIS (Netherlands)

    Van Dam, J.

    2006-01-01

    This thesis describes a series of experiments aimed at understanding the low-temperature electrical transport properties of semiconductor nanowires. The semiconductor nanowires (1-100 nm in diameter) are grown from nanoscale gold particles via a chemical process called vapor-liquid-solid (VLS)

  5. Semiconductor photocatalysis principles and applications

    CERN Document Server

    Kisch, Horst

    2014-01-01

    Focusing on the basic principles of semiconductor photocatalysis, this book also gives a brief introduction to photochemistry, photoelectrochemistry, and homogeneous photocatalysis. In addition, the author - one of the leading authorities in the field - presents important environmental and practical aspects. A valuable, one-stop source for all chemists, material scientists, and physicists working in this area, as well as novice researchers entering semiconductor photocatalysis.

  6. Progress in semiconductor drift detectors

    International Nuclear Information System (INIS)

    Rehak, P.; Walton, J.; Gatti, E.

    1985-01-01

    Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements

  7. Semiconductor materials and their properties

    NARCIS (Netherlands)

    Reinders, Angelina H.M.E.; Verlinden, Pierre; van Sark, Wilfried; Freundlich, Alexandre; Reinders, Angele; Verlinden, Pierre; van Sark, Wilfried; Freundlich, Alexandre

    2017-01-01

    Semiconductor materials are the basic materials which are used in photovoltaic (PV) devices. This chapter introduces solid-state physics and semiconductor properties that are relevant to photovoltaics without spending too much time on unnecessary information. Usually atoms in the group of

  8. Optical coherent control in semiconductors

    DEFF Research Database (Denmark)

    Østergaard, John Erland; Vadim, Lyssenko; Hvam, Jørn Märcher

    2001-01-01

    of quantum control including the recent applications to semiconductors and nanostructures. We study the influence of inhomogeneous broadening in semiconductors on CC results. Photoluminescence (PL) and the coherent emission in four-wave mixing (FWM) is recorded after resonant excitation with phase...

  9. Terahertz Nonlinear Optics in Semiconductors

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias C.

    2013-01-01

    We demonstrate the nonlinear optical effects – selfphase modulation and saturable absorption of a single-cycle THz pulse in a semiconductor. Resulting from THz-induced modulation of Drude plasma, these nonlinear optical effects, in particular, lead to self-shortening and nonlinear spectral...... breathing of a single-cycle THz pulse in a semiconductor....

  10. Electronic structure of semiconductor interfaces

    International Nuclear Information System (INIS)

    Herman, F.

    1983-01-01

    The study of semiconductor interfaces is one of the most active and exciting areas of current semiconductor research. Because interfaces play a vital role in modern semiconductor technology (integrated circuits, heterojunction lasers, solar cells, infrared detectors, etc.), there is a strong incentive to understand interface properties at a fundamental level and advance existing technology thereby. At the same time, technological advances such as molecular beam epitaxy have paved the way for the fabrication of semiconductor heterojunctions and superlattices of novel design which exhibit unusual electronic, optical, and magnetic properties and offer unique opportunities for fundamental scientific research. A general perspective on this subject is offered treating such topics as the atomic and electronic structure of semiconductor surfaces and interfaces; oxidation and oxide layers; semiconductor heterojunctions and superlattices; rectifying metal-semiconductor contacts; and interface reactions. Recent progress is emphasized and some future directions are indicated. In addition, the role that large-scale scientific computation has played in furthering our theoretical understanding of semiconductor surfaces and interfaces is discussed. Finally, the nature of theoretical models, and the role they play in describing the physical world is considered. (Author) [pt

  11. Palladium assisted silver transport in polycrystalline SiC

    Energy Technology Data Exchange (ETDEWEB)

    Neethling, J.H., E-mail: Jan.Neethling@nmmu.ac.za [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa); O' Connell, J.H.; Olivier, E.J. [Physics Department, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031 (South Africa)

    2012-10-15

    The transport of silver in polycrystalline 3C-SiC and hexagonal 6H-SiC has been investigated by annealing the SiC samples in contact with a Pd-Ag compound at temperatures of 800 and 1000 Degree-Sign C and times of 24 and 67 h. The Pd was added in an attempt to improve the low wetting of SiC by Ag and further because Pd is produced in measurable concentrations in coated particles during reactor operation. Pd is also known to coalesce at the IPyC-SiC interface and to chemically attack the SiC layer. SEM, TEM and EDS were used to show that the Ag penetrates polycrystalline SiC along grain boundaries together with Pd. It is suggested that Ag transport in SiC takes place along grain boundaries in the form of moving nodules consisting of a Ag-Pd mixture. It is assumed that the nodules move along grain boundaries by dissolving the SiC at the leading edge followed by the reprecipitation of SiC at the trailing edge. Since the solubility of Cs in Ag and Pd is extremely low, it is unlikely that Cs will penetrate the SiC together with the Ag-Pd compound if present at the IPyC-SiC interface. If it is assumed that the dominant transport mechanism of Ag in intact polycrystalline SiC is indeed the Pd assisted mechanism, then the stabilization of Pd (and other metallic fission products) in the kernel could be a way of mitigating Ag release from TRISO-coated particles.

  12. Palladium assisted silver transport in polycrystalline SiC

    International Nuclear Information System (INIS)

    Neethling, J.H.; O’Connell, J.H.; Olivier, E.J.

    2012-01-01

    The transport of silver in polycrystalline 3C-SiC and hexagonal 6H-SiC has been investigated by annealing the SiC samples in contact with a Pd–Ag compound at temperatures of 800 and 1000 °C and times of 24 and 67 h. The Pd was added in an attempt to improve the low wetting of SiC by Ag and further because Pd is produced in measurable concentrations in coated particles during reactor operation. Pd is also known to coalesce at the IPyC–SiC interface and to chemically attack the SiC layer. SEM, TEM and EDS were used to show that the Ag penetrates polycrystalline SiC along grain boundaries together with Pd. It is suggested that Ag transport in SiC takes place along grain boundaries in the form of moving nodules consisting of a Ag–Pd mixture. It is assumed that the nodules move along grain boundaries by dissolving the SiC at the leading edge followed by the reprecipitation of SiC at the trailing edge. Since the solubility of Cs in Ag and Pd is extremely low, it is unlikely that Cs will penetrate the SiC together with the Ag–Pd compound if present at the IPyC–SiC interface. If it is assumed that the dominant transport mechanism of Ag in intact polycrystalline SiC is indeed the Pd assisted mechanism, then the stabilization of Pd (and other metallic fission products) in the kernel could be a way of mitigating Ag release from TRISO-coated particles.

  13. Influence of copper foil polycrystalline structure on graphene anisotropic etching

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Kamal P. [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Mahyavanshi, Rakesh D. [Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Tanemura, Masaki [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)

    2017-01-30

    Graphical abstract: Hexagonal hole formation with anisotropic etching independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. - Highlights: • Reveal the influence of copper polycrystalline structure on anisotropic etching of graphene. • Hexagonal hole formation with etching is observed to be independent of stripes and wrinkles in graphene. • Variation in etched pattern of graphene depending on the base Cu grain is confirmed. • This finding will help to understand the nature of microscopic etched pattern in graphene. - Abstract: Anisotropic etching of graphene and other two dimensional materials is an important tool to understand the growth process as well as enabling fabrication of various well-defined structures. Here, we reveal the influence of copper foil polycrystalline structure on anisotropic etching process of as-synthesized graphene. Graphene crystals were synthesized on the polycrystalline Cu foil by a low-pressure chemical vapor deposition (LPCVD) system. Microscopic analysis shows difference in shape, size and stripes alignment of graphene crystals with dissimilar nucleation within closure vicinity of neighboring Cu grains. Post-growth etching of such graphene crystals also significantly affected by the crystallographic nature of Cu grains as observed by the field emission scanning electron microscope (FE-SEM) and electron back scattered diffraction (EBSD) analysis. Hexagonal hole formation with anisotropic etching is observed to be independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. The findings can facilitate to understand the nature of microscopic etched pattern depending on metal

  14. Influence of copper foil polycrystalline structure on graphene anisotropic etching

    International Nuclear Information System (INIS)

    Sharma, Kamal P.; Mahyavanshi, Rakesh D.; Kalita, Golap; Tanemura, Masaki

    2017-01-01

    Graphical abstract: Hexagonal hole formation with anisotropic etching independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. - Highlights: • Reveal the influence of copper polycrystalline structure on anisotropic etching of graphene. • Hexagonal hole formation with etching is observed to be independent of stripes and wrinkles in graphene. • Variation in etched pattern of graphene depending on the base Cu grain is confirmed. • This finding will help to understand the nature of microscopic etched pattern in graphene. - Abstract: Anisotropic etching of graphene and other two dimensional materials is an important tool to understand the growth process as well as enabling fabrication of various well-defined structures. Here, we reveal the influence of copper foil polycrystalline structure on anisotropic etching process of as-synthesized graphene. Graphene crystals were synthesized on the polycrystalline Cu foil by a low-pressure chemical vapor deposition (LPCVD) system. Microscopic analysis shows difference in shape, size and stripes alignment of graphene crystals with dissimilar nucleation within closure vicinity of neighboring Cu grains. Post-growth etching of such graphene crystals also significantly affected by the crystallographic nature of Cu grains as observed by the field emission scanning electron microscope (FE-SEM) and electron back scattered diffraction (EBSD) analysis. Hexagonal hole formation with anisotropic etching is observed to be independent of the stripes and wrinkles in the synthesized graphene. We also observed variation in etched pattern of the graphene depending on the base Cu grain orientations, attributing to difference in nucleation and growth process. The findings can facilitate to understand the nature of microscopic etched pattern depending on metal

  15. Hydrogen retention properties of polycrystalline tungsten and helium irradiated tungsten

    International Nuclear Information System (INIS)

    Hino, T.; Koyama, K.; Yamauchi, Y.; Hirohata, Y.

    1998-01-01

    The hydrogen retention properties of a polycrystalline tungsten and tungsten irradiated by helium ions with an energy of 5 keV were examined by using an ECR ion irradiation apparatus and a technique of thermal desorption spectroscopy, TDS. The polycrystalline tungsten was irradiated at RT with energetic hydrogen ions, with a flux of 10 15 H cm -2 and an energy of 1.7 keV up to a fluence of 5 x 10 18 H cm -2 . Subsequently, the amount of retained hydrogen was measured by TDS. The heating temperature was increased from RT to 1000 C, and the heating rate was 50 C min -1 . Below 1000 C, two distinct hydrogen desorption peaks were observed at 200 C and 400 C. The retained amount of hydrogen was observed to be five times smaller than that of graphite, but the concentration in the implantation layer was comparable with that of graphite. Also, the polycrystalline tungsten was irradiated with 5 keV helium ions up to a fluence of 1.4 x 10 18 He cm -2 , and then re-irradiated with 1.7 keV hydrogen ions. The amount of retained hydrogen in this later experiment was close to the value in the case without prior helium ion irradiation. However, the amount of hydrogen which desorbed around the low temperature peak, 200 C, was largely enhanced. The desorption amount at 200 C saturated for the helium fluence of more than 5 x 10 17 He cm -2 . The present data shows that the trapping state of hydrogen is largely changed by the helium ion irradiation. Additionally, 5 keV helium ion irradiation was conducted on a sample pre-implanted with hydrogen ions to simulate a helium ion impact desorption of hydrogen retained in tungsten. The amount of the hydrogen was reduced as much as 50%. (orig.)

  16. Trace diffusion of different nuclear reactions products in polycrystalline tantalum

    International Nuclear Information System (INIS)

    Beyer, G.J.; Fromm, W.D.; Novgorodov, A.F.

    1976-07-01

    Measurements of the lattice diffusion coefficients for carrier free isotopes of Hf, Lu, Yb, Tm, Tb, Gd, Eu, Ba, Cs, Y, Sr, Rb and As in polycrystalline tantalum were made over the temperature range 1700 Fsub(As)>Fsub(lanthanides)>Fsub(Sr)>Fsub(Ba)>Fsub(Hf)>Fsub(Rb)>Fsub(Cs). The data indicate, that the Arrhenius relation was obeyed over the entire temperature range. Within the lanthanide-group no differences in the diffusion velocities could be detected, this fact points to a diffusion mechanism of Me 3+ -ions of lanthanides, Me 2+ -ions of earth alkaline elements and Me + -ions of alkaline elements. (author)

  17. Progress and issues in polycrystalline thin-film PV technologies

    Energy Technology Data Exchange (ETDEWEB)

    Zweibel, K.; Ullal, H.S.; Roedern, B. von [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    Substantial progress has occurred in polycrystalline thin-film photovoltaic technologies in the past 18 months. However, the transition to first-time manufacturing is still under way, and technical problems continue. This paper focuses on the promise and the problems of the copper indium diselenide and cadmium telluride technologies, with an emphasis on continued R&D needs for the near-term transition to manufacturing and for next-generation improvements. In addition, it highlights the joint R&D efforts being performed in the U.S. Department of Energy/National Renewable Energy Laboratory Thin-Film Photovoltaic Partnership Program.

  18. Compensation for thermally induced birefringence in polycrystalline ceramic active elements

    International Nuclear Information System (INIS)

    Kagan, M A; Khazanov, E A

    2003-01-01

    Polycrystalline ceramics differ significantly from single crystals in that the crystallographic axes (and hence of the axes of thermally induced birefringence) are oriented randomly in each granule of the ceramic. The quaternion formalism is employed to calculate the depolarisation in the ceramics and the efficiency of its compensation. The obtained analytic expressions are in good agreement with the numerical relations. It is shown that the larger the ratio of the sample length to the granule size, the closer the properties of the ceramics to those of a single crystal with the [111] orientation (in particular, the uncompensated depolarisation is inversely proportional to this ratio). (active media)

  19. Modeling chemisorption kinetics of carbon monoxide on polycrystalline platinum

    Energy Technology Data Exchange (ETDEWEB)

    Donnelly, R.G.; Modell, M.; Baddour, R.F.

    1978-04-01

    Seven distinct desorption surface states of carbon monoxide on polycrystalline platinum were detected by deconvoluting temperature-programed desorption spectra of 4-100% carbon monoxide monolayer coverage. The adstates had fixed activation energies of desorption (22.5-32.6 kcal/mole) over the entire coverage range. Rates of formation and populations were derived. The chemisorption was modeled by a Hinshelwood-type expression which allowed for site creation and suggested that adsorbed molecules are sufficiently mobile during desorption heating to fill ordered states of minimum energy and that chemisorption into these states is noncompetitive and determined by the surface. Spectra, diagrams, graphs, tables, and 49 references.

  20. Laser beam machining of polycrystalline diamond for cutting tool manufacturing

    Science.gov (United States)

    Wyszyński, Dominik; Ostrowski, Robert; Zwolak, Marek; Bryk, Witold

    2017-10-01

    The paper concerns application of DPSS Nd: YAG 532nm pulse laser source for machining of polycrystalline WC based diamond inserts (PCD). The goal of the research was to determine optimal laser cutting parameters for cutting tool shaping. Basic criteria to reach the goal was cutting edge quality (minimalization of finishing operations), material removal rate (time and cost efficiency), choice of laser beam characteristics (polarization, power, focused beam diameter). The research was planned and realised and analysed according to design of experiment rules (DOE). The analysis of the cutting edge was prepared with use of Alicona Infinite Focus measurement system.

  1. Rotary Ultrasonic Machining of Poly-Crystalline Cubic Boron Nitride

    Directory of Open Access Journals (Sweden)

    Kuruc Marcel

    2014-12-01

    Full Text Available Poly-crystalline cubic boron nitride (PCBN is one of the hardest material. Generally, so hard materials could not be machined by conventional machining methods. Therefore, for this purpose, advanced machining methods have been designed. Rotary ultrasonic machining (RUM is included among them. RUM is based on abrasive removing mechanism of ultrasonic vibrating diamond particles, which are bonded on active part of rotating tool. It is suitable especially for machining hard and brittle materials (such as glass and ceramics. This contribution investigates this advanced machining method during machining of PCBN.

  2. New deformation model of grain boundary strengthening in polycrystalline metals

    International Nuclear Information System (INIS)

    Trefilov, V.I.; Moiseev, V.F.; Pechkovskij, Eh.P.

    1988-01-01

    A new model explaining grain boundary strengthening in polycrystalline metals and alloys by strain hardening due to localization of plastic deformation in narrow bands near grain boundaries is suggested. Occurrence of localized deformation is caused by different flow stresses in grains of different orientation. A new model takes into account the active role of stress concentrator, independence of the strengthening coefficient on deformation, influence of segregations. Successful use of the model suggested for explanation of rhenium effect in molybdenum and tungsten is alloys pointed out

  3. An acoustic emission study of plastic deformation in polycrystalline aluminium

    Science.gov (United States)

    Bill, R. C.; Frederick, J. R.; Felbeck, D. K.

    1979-01-01

    Acoustic emission experiments were performed on polycrystalline and single crystal 99.99% aluminum while undergoing tensile deformation. It was found that acoustic emission counts as a function of grain size showed a maximum value at a particular grain size. Furthermore, the slip area associated with this particular grain size corresponded to the threshold level of detectability of single dislocation slip events. The rate of decline in acoustic emission activity as grain size is increased beyond the peak value suggests that grain boundary associated dislocation sources are giving rise to the bulk of the detected acoustic emissions.

  4. An electrical conductivity inspection methodology of polycrystalline diamond cutters

    Science.gov (United States)

    Bogdanov, G.; Wiggins, J.; Bertagnolli, K.; Ludwig, R.

    2012-05-01

    The polycrystalline diamond cutter (PDC) is widely used in oil and gas drilling operations. It is manufactured by sintering diamond powder onto a tungsten carbide substrate at 6 GPa and 1500 C. During sintering, molten cobalt from the substrate infiltrates the diamond table. The residual metal content correlates with cutter performance. We present an instrument that employs electrical impedance tomography capable of imaging the 3D metal content distribution in the diamond table. These images can be used to predict cutter performance as well as detect flaws.

  5. High energy argon ion irradiations of polycrystalline iron

    International Nuclear Information System (INIS)

    Dunlop, A.; Lesueur, D.; Lorenzelli, N.; Boulanger, L.

    1986-09-01

    We present here the results of our recent irradiations of polycrystalline iron targets with very energetic (1.76 GeV) Ar ions. The targets consist of piles of thin iron samples, the total thickness of each target being somewhat greater than the theoretical range (450 μm) of the ions. We can thus separate the phenomena which occur at different average energies of the ions and study during the slowing-down process: the different types of induced nuclear reactions. They allow us to determine the experimental range of the ions, the defect profiles in the targets, the structure of the displacement cascades (electron microscopy) and their stability

  6. Complex strain paths in polycrystalline copper: microstructural aspects

    Directory of Open Access Journals (Sweden)

    M.F. Vieira

    1999-07-01

    Full Text Available Microstructural aspects of polycrystalline copper sheets subjected to complex strain paths were analysed in this work. Dislocation structures developed during the strain paths (rolling and tension and the evolution of this microstructure during reloading have been studied. The active slip systems developed in each strain path were used to explain the microstructural evolution. The heterogeneous surface deformation observed on polished tensile specimens prestrained in rolling was also analysed. The structural aspects are related with the mechanical behaviour of the material, namely with the increase in yield stress in reloading, the work hardening evolution and the premature occurrence of plastic instability for some prestrain values.

  7. Organic semiconductors in a spin

    CERN Document Server

    Samuel, I

    2002-01-01

    A little palladium can go a long way in polymer-based light-emitting diodes. Inorganic semiconductors such as silicon and gallium arsenide are essential for countless applications in everyday life, ranging from PCs to CD players. However, while they offer unrivalled computational speed, inorganic semiconductors are also rigid and brittle, which means that they are less suited to applications such as displays and flexible electronics. A completely different class of materials - organic semiconductors - are being developed for these applications. Organic semiconductors have many attractive features: they are easy to make, they can emit visible light, and there is tremendous scope for tailoring their properties to specific applications by changing their chemical structure. Research groups and companies around the world have developed a wide range of organic-semiconductor devices, including transistors, light-emitting diodes (LEDs), solar cells and lasers. (U.K.)

  8. Ion implantation for semiconductors

    International Nuclear Information System (INIS)

    Grey-Morgan, T.

    1995-01-01

    Full text: Over the past two decades, thousands of particle accelerators have been used to implant foreign atoms like boron, phosphorus and arsenic into silicon crystal wafers to produce special embedded layers for manufacturing semiconductor devices. Depending on the device required, the atomic species, the depth of implant and doping levels are the main parameters for the implantation process; the selection and parameter control is totally automated. The depth of the implant, usually less than 1 micron, is determined by the ion energy, which can be varied between 2 and 600 keV. The ion beam is extracted from a Freeman or Bernas type ion source and accelerated to 60 keV before mass analysis. For higher beam energies postacceleration is applied up to 200 keV and even higher energies can be achieved by mass selecting multiplycharged ions, but with a corresponding reduction in beam output. Depending on the device to be manufactured, doping levels can range from 10 10 to 10 15 atoms/cm 2 and are controlled by implanter beam currents in the range up to 30mA; continuous process monitoring ensures uniformity across the wafer of better than 1 % . As semiconductor devices get smaller, additional sophistication is required in the design of the implanter. The silicon wafers charge electrically during implantation and this charge must be dissipated continuously to reduce the electrical stress in the device and avoid destructive electrical breakdown. Electron flood guns produce low energy electrons (below 10 electronvolts) to neutralize positive charge buildup and implanter design must ensure minimum contamination by other isotopic species and ensure low internal sputter rates. The pace of technology in the semiconductor industry is such that implanters are being built now for 256 Megabit circuits but which are only likely to be widely available five years from now. Several specialist companies manufacture implanter systems, each costing around US$5 million, depending on the

  9. Semiconductor testing method

    International Nuclear Information System (INIS)

    Brown, Stephen.

    1992-01-01

    In a method of avoiding use of nuclear radiation, eg gamma rays, X-rays, electron beams, for testing semiconductor components for resistance to hard radiation, which hard radiation causes data corruption in some memory devices and 'latch-up' in others, similar fault effects can be achieved using a xenon or other 'light' flash gun even though the penetration of light is significantly less than that of gamma rays. The method involves treating a device with gamma radiation, measuring a particular fault current at the onset of a fault event, repeating the test with light to confirm the occurrence of the fault event at the same measured fault current, and using the fault current value as a reference for future tests using light on similar devices. (author)

  10. Radial semiconductor drift chambers

    International Nuclear Information System (INIS)

    Rawlings, K.J.

    1987-01-01

    The conditions under which the energy resolution of a radial semiconductor drift chamber based detector system becomes dominated by the step noise from the detector dark current have been investigated. To minimise the drift chamber dark current attention should be paid to carrier generation at Si/SiO 2 interfaces. This consideration conflicts with the desire to reduce the signal risetime: a higher drift field for shorter signal pulses requires a larger area of SiO 2 . Calculations for the single shaping and pseudo Gaussian passive filters indicate that for the same degree of signal risetime sensitivity in a system dominated by the step noise from the detector dark current, the pseudo Gaussian filter gives only a 3% improvement in signal/noise and 12% improvement in rate capability compared with the single shaper performance. (orig.)

  11. Energy distribution in semiconductors

    International Nuclear Information System (INIS)

    Ance, C.

    1979-01-01

    For various semiconductors the dispersive energy Esub(d) defined in the Wemple-Didomenico model is connected with the covalent and ionic energies Esub(h) and C. A continuous curve of ionicity against the ratio of the two energies Esub(A) and Esub(B), connected to Esub(h) and C is reported. Afromowitz's model is applied to the ternary compounds Gasub(1-x)Alsub(x)Sb using optical decomposition. From these results the average energy gap Esub(g) is given by Esub(g) = D 0 M 0 sup((IB))/(epsilon 1 (0)-1) where M 0 sup((IB)) is the interband transition contribution to the optical moment M 0 . (author)

  12. Parameterization of the dielectric function of semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Petrik, P., E-mail: petrik@mfa.kfki.hu

    2014-11-15

    Optical methods like spectroscopic ellipsometry are sensitive to the structural properties of semiconductor films such as crystallinity or grain size. The imaginary part of the dielectric function is proportional to the joint density of electronic states. Consequently, the analysis of the dielectric function around the critical point energies provides useful information about the electron band structure and all related parameters like the grain structure, band gap, temperature, composition, phase structure, and carrier mobility. In this work an attempt is made to present a selection of the approaches to parameterize and analyze the dielectric function of semiconductors, as well as some applications.

  13. The role of rare earths in narrow energy gap semiconductors

    International Nuclear Information System (INIS)

    Partin, D.L.; Heremans, J.; Morelli, D.T.; Thrush, C.M.

    1991-01-01

    Narrow energy band gap semiconductors are potentially useful for various devices, including infrared detectors and diode lasers. Rare earth elements have been introduced into lead chalcogenide semiconductors using the molecular beam epitaxy growth process. Europium and ytterbium increase the energy band gap, and nearly lattice-matched heterojunctions have been grown. In some cases, valence changes in the rare earth element cause doping of the alloy. In this paper some initial investigations of the addition of europium to indium antimonide are reported, including the variation of lattice parameter and optical transmission with composition and a negative magnetoresistance effect

  14. Fracture properties of polycrystalline YBa2Cu3Ox

    International Nuclear Information System (INIS)

    Cook, R.F.; Shaw, T.M.; Duncombe, P.R.

    1987-01-01

    Polycrystalline YBa 2 Cu 3 O x has been prepared by sintering pre-reacted powder in oxygen to yield a material with 15 μm grain size, 86% relative density and which superconducts above liquid nitrogen temperatures. Indentation crack length measurements give a toughness K c = 1.3 ± 0.2 MPa m 1/2 , above a threshold contact load for radial crack initiation of approximately 5 N (compared with 1.1 MPa m 1/2 and < 0.1 N, respectively, for single crystals). The increased toughness and threshold contact load are controlled by the deviation of cracks from the plane of maximum driving force for fracture by weak grain boundaries and preferred fracture planes within grains. Optical microscopy of indentation cracks and scanning electron microscopy of fracture surfaces reveals approximately 50% intergranular fracture. The hardness of the polycrystal was H = 2.0 ± 0.5 GPa (compared with 8.7 GPa for single crystals). The decreased hardness arises from the porosity of the polycrystalline material and grain boundary sliding under the indentation contact. Time dependent growth of lateral cracks at the indentation contacts suggests that these materials are susceptible to moisture controlled non-equilibrium crack growth

  15. Spray Pyrolyzed Polycrystalline Tin Oxide Thin Film as Hydrogen Sensor

    Directory of Open Access Journals (Sweden)

    Ganesh E. Patil

    2010-09-01

    Full Text Available Polycrystalline tin oxide (SnO2 thin film was prepared by using simple and inexpensive spray pyrolysis technique (SPT. The film was characterized for their phase and morphology by X-ray diffraction (XRD and scanning electron microscopy (SEM, respectively. The crystallite size calculated from the XRD pattern is 84 nm. Conductance responses of the polycrystalline SnO2 were measured towards gases like hydrogen (H2, liquefied petroleum gas (LPG, ethanol vapors (C2H5OH, NH3, CO, CO2, Cl2 and O2. The gas sensing characteristics were obtained by measuring the sensor response as a function of various controlling factors like operating temperature, operating voltages (1 V, 5 V, 10 V 15 V, 20 V and 25 V and concentration of gases. The sensor response measurement showed that the SnO2 has maximum response to hydrogen. Furthermore; the SnO2 based sensor exhibited fast response and good recovery towards hydrogen at temperature 150 oC. The result of response towards H2 reveals that SnO2 thin film prepared by SPT would be a suitable material for the fabrication of the hydrogen sensor.

  16. Microdamage in polycrystalline ceramics under dynamic compression and tension

    International Nuclear Information System (INIS)

    Zhang, K.S.; Zhang, D.; Feng, R.; Wu, M.S.

    2005-01-01

    In-grain microplasticity and intergranular microdamage in polycrystalline hexagonal-structure ceramics subjected to a sequence of dynamic compression and tension are studied computationally using the Voronoi polycrystal model, by which the topological heterogeneity and material anisotropy of the crystals are simulated explicitly. The constitutive modeling considers crystal plasticity by basal slip, intergranular shear damage during compression, and intergranular mode-I cracking during tension. The model parameters are calibrated with the available shock compression and spall strength data on polycrystalline α-6H silicon carbide. The numerical results show that microplasticity is a more plausible micromechanism for the inelastic response of the material under shock compression. On the other hand, the spallation behavior of the shocked material can be well predicted by intergranular mode-I microcracking during load reversal from dynamic compression to tension. The failure process and the resulting spall strength are, however, affected strongly by the intensity of local release heterogeneity induced by heterogeneous microplasticity, and by the grain-boundary shear damage during compression

  17. Electrostrain in excess of 1% in polycrystalline piezoelectrics

    Science.gov (United States)

    Narayan, Bastola; Malhotra, Jaskaran Singh; Pandey, Rishikesh; Yaddanapudi, Krishna; Nukala, Pavan; Dkhil, Brahim; Senyshyn, Anatoliy; Ranjan, Rajeev

    2018-05-01

    Piezoelectric actuators transform electrical energy into mechanical energy, and because of their compactness, quick response time and accurate displacement, they are sought after in many applications. Polycrystalline piezoelectric ceramics are technologically more appealing than single crystals due to their simpler and less expensive processing, but have yet to display electrostrain values that exceed 1%. Here we report a material design strategy wherein the efficient switching of ferroelectric-ferroelastic domains by an electric field is exploited to achieve a high electrostrain value of 1.3% in a pseudo-ternary ferroelectric alloy system, BiFeO3-PbTiO3-LaFeO3. Detailed structural investigations reveal that this electrostrain is associated with a combination of several factors: a large spontaneous lattice strain of the piezoelectric phase, domain miniaturization, a low-symmetry ferroelectric phase and a very large reverse switching of the non-180° domains. This insight for the design of a new class of polycrystalline piezoceramics with high electrostrains may be useful to develop alternatives to costly single-crystal actuators.

  18. Semantic modeling of plastic deformation of polycrystalline rock

    Science.gov (United States)

    Babaie, Hassan A.; Davarpanah, Armita

    2018-02-01

    We have developed the first iteration of the Plastic Rock Deformation (PRD) ontology by modeling the semantics of a selected set of deformational processes and mechanisms that produce, reconfigure, displace, and/or consume the material components of inhomogeneous polycrystalline rocks. The PRD knowledge model also classifies and formalizes the properties (relations) that hold between instances of the dynamic physical and chemical processes and the rock components, the complex physio-chemical, mathematical, and informational concepts of the plastic rock deformation system, the measured or calculated laboratory testing conditions, experimental procedures and protocols, the state and system variables, and the empirical flow laws that define the inter-relationships among the variables. The ontology reuses classes and properties from several existing ontologies that are built for physics, chemistry, biology, and mathematics. With its flexible design, the PRD ontology is well positioned to incrementally develop into a model that more fully represents the knowledge of plastic deformation of polycrystalline rocks in the future. The domain ontology will be used to consistently annotate varied data and information related to the microstructures and the physical and chemical processes that produce them at different spatial and temporal scales in the laboratory and in the solid Earth. The PRDKB knowledge base, when built based on the ontology, will help the community of experimental structural geologists and metamorphic petrologists to coherently and uniformly distribute, discover, access, share, and use their data through automated reasoning and integration and query of heterogeneous experimental deformation data that originate from autonomous rock testing laboratories.

  19. Dielectric and conducting behaviour of polycrystalline holmium octa-molybdate

    International Nuclear Information System (INIS)

    Want, Basharat; Zahoor Ahmad, Bhat; Hamid Bhat, Bilal

    2014-01-01

    Polycrystalline holmium octa-molybdate spherulites have been obtained by using gel diffusion technique and characterized by different physio-chemical techniques. The surfaces of these spherulites are composed of nano-rod with an average diameter of about 80 nm. At room temperature the initial crystal structure is triclinic, space group P1. Thermal studies suggested a phase transition occurring in holmium octa-molybdate crystals at about 793 K. The electrical properties of the system have been studied as a function of frequency and temperature in the ranges of 20 Hz–3 MHz and 290–570 K, respectively. A giant dielectric constant and two loss peaks have been observed in the permittivity formalism. The conducting behaviour of the material is also discussed. The conductivity was found to be 1572 μ Ω −1 m −1 at room temperature and 3 MHz frequency. The conductivity of the polycrystalline material was attributed to the fact that it arises due to the migration of defects on the oxygen sub-lattice. Impedance studies were also performed in the frequency domain to infer the bulk and grain boundary contributions to the overall electric response of the material. The electrical responses have been attributed to the grain, grain-boundary, and interfacial effects. (paper)

  20. Shear strength of shock-loaded polycrystalline tungsten

    International Nuclear Information System (INIS)

    Asay, J.R.; Chhabildas, L.C.; Dandekar, D.P.

    1980-01-01

    Previous experiments have suggested that tungsten undergoes a significant loss of shear strength when shock loaded to stresses greater than 7 GPa. In order to investigate this effect in more detail, a series of experiments was conducted in which polycrystalline tungsten was first shock loaded to approximately 10 GPa and then either unloaded or reloaded from the shocked state. Analysis of measured time-resolved wave profiles indicates that during initial compression to 9.7 GPa, the shear stress in polycrystalline tungsten increases to a maximum value of 1.1 GPA near a longitudinal stress of 5 GPa, but decreases to a final value of 0.8 GPa for stresses approaching 10 GPa. During reloading from a longitudinal stress of 9.7 GPa to a final value of approx.14 GPa, the shear stress increases to a peak value of 1.2 GPa and softens to 1.0 GPa in the final state. During unloading from the shocked state, the initial response is elastic with a strong Baushinger effect. Examination of a recovered sample shows evidence for both deformation slipping and twinning, which may be responsible for the observed softening

  1. Three dimensional grain boundary modeling in polycrystalline plasticity

    Science.gov (United States)

    Yalçinkaya, Tuncay; Özdemir, Izzet; Fırat, Ali Osman

    2018-05-01

    At grain scale, polycrystalline materials develop heterogeneous plastic deformation fields, localizations and stress concentrations due to variation of grain orientations, geometries and defects. Development of inter-granular stresses due to misorientation are crucial for a range of grain boundary (GB) related failure mechanisms, such as stress corrosion cracking (SCC) and fatigue cracking. Local crystal plasticity finite element modelling of polycrystalline metals at micron scale results in stress jumps at the grain boundaries. Moreover, the concepts such as the transmission of dislocations between grains and strength of the grain boundaries are not included in the modelling. The higher order strain gradient crystal plasticity modelling approaches offer the possibility of defining grain boundary conditions. However, these conditions are mostly not dependent on misorientation of grains and can define only extreme cases. For a proper definition of grain boundary behavior in plasticity, a model for grain boundary behavior should be incorporated into the plasticity framework. In this context, a particular grain boundary model ([l]) is incorporated into a strain gradient crystal plasticity framework ([2]). In a 3-D setting, both bulk and grain boundary models are implemented as user-defined elements in Abaqus. The strain gradient crystal plasticity model works in the bulk elements and considers displacements and plastic slips as degree of freedoms. Interface elements model the plastic slip behavior, yet they do not possess any kind of mechanical cohesive behavior. The physical aspects of grain boundaries and the performance of the model are addressed through numerical examples.

  2. The fabrication of YBCO superconductor polycrystalline powder by CCSO

    International Nuclear Information System (INIS)

    Martirosyan, K S; Luss, D; Galstyan, E; Xue, Y Y

    2008-01-01

    We present a novel, cost-effective and simple method to produce polycrystalline superconductor YBa 2 Cu 3 O 7-δ (YBCO) powder by a self-sustaining one-step process called carbon combustion synthesis of oxides (CCSO). In this process the exothermic oxidation of carbon nanoparticles generates a thermal wave that propagates at a velocity of about 1 mm s -1 through the solid yttrium, barium, and copper precursors, converting them rapidly (in the order of seconds) to polycrystalline YBCO. The carbon is not incorporated in the product and is emitted as carbon dioxide (CO 2 ) from the sample, generating a highly porous (∼70%) and friable product. Most of the grains have a plate-like shape, are well connected, and have a size of between 1 and 3 μm. The concentration of the residual carbon was less than 0.06 wt%. The magnetization of as-synthesized samples (without external post-annealing in oxygen), as determined by a SQUID magnetometer, showed an onset of the superconducting (SC) transition at ∼91 K, with a 44% shielding fraction of the -1/(4π) value

  3. Grain-boundary unzipping by oxidation in polycrystalline graphene

    Science.gov (United States)

    Alexandre, Simone; Lucio, Aline; Nunes, Ricardo

    2011-03-01

    The need for large-scale production of graphene will inevitably lead to synthesis of the polycrystalline material [1,2]. Understanding the chemical, mechanical, and electronic properties of grain boundaries in graphene polycrystals will be crucial for the development of graphene-based electronics. Oxidation of this material has been suggested to lead to graphene ribbons, by the oxygen-driven unzipping mechanism. A cooperative-strain mechanism, based on the formation of epoxy groups along lines of parallel bonds in the hexagons of graphene's honeycomb lattice, was proposed to explain the unzipping effect in bulk graphene In this work we employ ab initio calculations to study the oxidation of polycrystalline graphene by chemisorption of oxygen at the grain boundaries. Our results indicate that oxygen tends to segregate at the boundaries, and that the unzipping mechanism is also operative along the grain boundaries, despite the lack of the parallel bonds due to the presence of fivefold and sevenfold carbon rings along the boundary core. We acknowledge support from the Brazilian agencies: CNPq, Fapemig, and INCT-Materiais de Carbono.

  4. Growth and characterization of polycrystalline Ge1-xCx by reactive pulsed laser deposition

    International Nuclear Information System (INIS)

    Hernandez, M.P.; Farias, M.H.; Castillon, F.F.; Diaz, Jesus A.; Avalos, M.; Ulloa, L.; Gallegos, J.A.; Yee-Madeiros, H.

    2011-01-01

    Polycrystalline thin films of Ge-C were grown on Si (1 1 1) substrates by means of reactive pulsed laser deposition with methane pressure of 100 mTorr. Effect substrate temperature, T s , on C incorporation to substitutional sites (x) in Ge 1-x C x was investigated systematically by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyzes. The substrate temperatures were ranging from 250 to 400 deg. C. The substitutional C composition x in the films by XRD were estimated using the Vegard's linear law. The maximum value of x calculated by XRD was 0.032 for T s of 350 deg. C. The position of the C 1s peak at 283.4 eV in the XPS spectrum confirmed the germanium-carbon alloys. XRD measurements indicated that x increased with T s from 250 deg. C to 350 deg. C. At T s = 400 deg. C, the estimation of x was lowered. However, the C content calculated by XPS analyzes increased with T s being more these values than substitutional C composition x. XPS and XRD analyzes demonstrate that the remaining C atoms are incorporated to interstitial sites. The use of the T s plays important roles in the incorporation of substitutional C and in restraining C-cluster formation in the reactive pulsed laser deposition growth of Ge-C/Si.

  5. Fluorocarbon polymer formation, characterization, and reduction in polycrystalline-silicon etching with CF4-added plasma

    International Nuclear Information System (INIS)

    Xu Songlin; Sun Zhiwen; Chen Arthur; Qian Xueyu; Podlesnik, Dragan

    2001-01-01

    Addition of CF 4 into HBr-based plasma for polycrystalline-silicon gate etching reduces the deposition of an etch byproduct, silicon oxide, onto the chamber wall but tends to generate organic polymer. In this work, a detailed study has been carried out to analyze the mechanism of polymerization and to characterize the polymer composition and quantity. The study has shown that the polymer formation is due to the F-radical depletion by H atoms dissociated from HBr. The composition of the polymer changes significantly with CF 4 concentration in the gas feed, and the polymer deposition rate depends on CF 4 % and other process conditions such as source power, bias power, and pressure. Surface temperature also affects the polymer deposition rate. Adding O 2 into the plasma can clean the organic polymer, but the O 2 amount has to be well controlled in order to prevent the formation of silicon oxide. Based on a series of tests to evaluate polymer deposition and oxide cleaning with O 2 addition, an optimized process regime in terms of O 2 -to-CF 4 ratio has been identified to simultaneously suppress the polymer and oxide deposition so that the etch process becomes self-cleaning

  6. Impact of energy filtering and carrier localization on the thermoelectric properties of granular semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Narducci, Dario, E-mail: dario.narducci@unimib.it [Department of Materials Science, University of Milano Bicocca, via Cozzi 53, 20125 Milano (Italy); Consorzio DeltaTi Research (Italy); Selezneva, Ekaterina [Department of Materials Science, University of Milano Bicocca, via Cozzi 53, 20125 Milano (Italy); Cerofolini, Gianfranco [Department of Materials Science, University of Milano Bicocca, via Cozzi 53, 20125 Milano (Italy); Consorzio DeltaTi Research (Italy); Frabboni, Stefano; Ottaviani, Giampiero [Department of Physics, University of Modena and Reggio Emilia, via Campi 213, 41100 Modena (Italy)

    2012-09-15

    Energy filtering has been widely considered as a suitable tool to increase the thermoelectric performances of several classes of materials. In its essence, energy filtering provides a way to increase the Seebeck coefficient by introducing a strongly energy-dependent scattering mechanism. Under certain conditions, however, potential barriers may lead to carrier localization, that may also affect the thermoelectric properties of a material. A model is proposed, actually showing that randomly distributed potential barriers (as those found, e.g., in polycrystalline films) may lead to the simultaneous occurrence of energy filtering and carrier localization. Localization is shown to cause a decrease of the actual carrier density that, along with the quantum tunneling of carriers, may result in an unexpected increase of the power factor with the doping level. The model is corroborated toward experimental data gathered by several authors on degenerate polycrystalline silicon and lead telluride. - Graphical abstract: In heavily doped semiconductors potential barriers may lead to both carrier energy filtering and localization. This may lead to an enhancement of the thermoelectric properties of the material, resulting in an unexpected increase of the power factor with the doping level. Highlights: Black-Right-Pointing-Pointer Potential barriers are shown to lead to carrier localization in thermoelectric materials. Black-Right-Pointing-Pointer Evidence is put forward of the formation of a mobility edge. Black-Right-Pointing-Pointer Energy filtering and localization may explain the enhancement of power factor in degenerate semiconductors.

  7. Magnetic excitations in ferromagnetic semiconductors

    International Nuclear Information System (INIS)

    Furdyna, J.K.; Liu, X.; Zhou, Y.Y.

    2009-01-01

    Magnetic excitations in a series of GaMnAs ferromagnetic semiconductor films were studied by ferromagnetic resonance (FMR). Using the FMR approach, multi-mode spin wave resonance spectra have been observed, whose analysis provides information on magnetic anisotropy (including surface anisotropy), distribution of magnetization precession within the GaMnAs film, dynamic surface spin pinning (derived from surface anisotropy), and the value of exchange stiffness constant D. These studies illustrate a combination of magnetism and semiconductor physics that is unique to magnetic semiconductors

  8. Semiconductor Nanocrystals for Biological Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Aihua; Gu, Weiwei; Larabell, Carolyn; Alivisatos, A. Paul

    2005-06-28

    Conventional organic fluorophores suffer from poor photo stability, narrow absorption spectra and broad emission feature. Semiconductor nanocrystals, on the other hand, are highly photo-stable with broad absorption spectra and narrow size-tunable emission spectra. Recent advances in the synthesis of these materials have resulted in bright, sensitive, extremely photo-stable and biocompatible semiconductor fluorophores. Commercial availability facilitates their application in a variety of unprecedented biological experiments, including multiplexed cellular imaging, long-term in vitro and in vivo labeling, deep tissue structure mapping and single particle investigation of dynamic cellular processes. Semiconductor nanocrystals are one of the first examples of nanotechnology enabling a new class of biomedical applications.

  9. Electromechanical Response of Polycrystalline Barium Titanate Resolved at the Grain Scale

    DEFF Research Database (Denmark)

    Majkut, Marta; Daniels, John E.; Wright, Jonathan P.

    2017-01-01

    critical for understanding bulk polycrystalline ferroic behavior. Here, three-dimensional X-ray diffraction is used to reconstruct a 3D grain map (grain orientations and neighborhoods) of a polycrystalline barium titanate sample and track the grain-scale non-180° ferroelectric domain switching strains...

  10. Friction and dynamically dissipated energy dependence on temperature in polycrystalline silicon MEMS devices

    NARCIS (Netherlands)

    Gkouzou, A.; Kokorian, J.; Janssen, G.C.A.M.; van Spengen, W.M.

    2017-01-01

    In this paper, we report on the influence of capillary condensation on the sliding friction of sidewall surfaces in polycrystalline silicon micro-electromechanical
    systems (MEMS). We developed a polycrystalline silicon MEMS tribometer, which is a microscale test device with two components

  11. Approximate bilateral symmetry in evaporation-induced polycrystalline structures from droplets of wheat grain leakages and fluctuating asymmetry as quality indicator

    Science.gov (United States)

    Kokornaczyk, Maria Olga; Dinelli, Giovanni; Betti, Lucietta

    2013-01-01

    The present paper reports on an observation that dendrite-like polycrystalline structures from evaporating droplets of wheat grain leakages exhibit bilateral symmetry. The exactness of this symmetry, measured by means of fluctuating asymmetry, varies depending on the cultivar and stress factor influence, and seems to correspond to the seed germination rate. In the bodies of plants, animals, and humans, the exactness of bilateral symmetry is known to reflect the environmental conditions of an organism's growth, its health, and its success in sexual selection. In polycrystalline structures, formed under the same conditions, the symmetry exactness depends on the properties of the crystallizing solution such as the composition and viscosity; however, it has never been associated with sample quality. We hypothesize here that, as in living nature, the exactness of approximate bilateral symmetry might be considered a quality indicator also in crystallographic methods applied to food quality analysis.

  12. State of the art in semiconductor detectors

    International Nuclear Information System (INIS)

    Rehak, P.; Gatti, E.

    1990-01-01

    The state of the art in semiconductor detectors for elementary particle physics and X-ray astronomy is briefly reviewed. Semiconductor detectors are divided into two groups; i) classical semiconductor diode detectors and ii) semiconductor memory detectors. Principles of signal formation for both groups of detectors are described and their performance is compared. New developments of silicon detectors are reported here. (orig.)

  13. State of the art in semiconductor detectors

    International Nuclear Information System (INIS)

    Rehak, P.; Gatti, E.

    1989-01-01

    The state of the art in semiconductor detectors for elementary particle physics and x-ray astronomy is briefly reviewed. Semiconductor detectors are divided into two groups; classical semiconductor diode detectors; and semiconductor memory detectors. Principles of signal formation for both groups of detectors are described and their performance is compared. New developments of silicon detectors are reported here. 13 refs., 8 figs

  14. Semiconductor device comprising a pn-heterojunction

    NARCIS (Netherlands)

    2007-01-01

    An electric device is disclosed comprising a pn-heterojunction ( 4 ) formed by a nanowire ( 3 ) of 111 -V semiconductor material and a semiconductor body ( 1 ) comprising a group IV semiconductor material. The nanowire ( 3 ) is positioned in direct contact with the surface ( 2 ) of the semiconductor

  15. Toward designing semiconductor-semiconductor heterojunctions for photocatalytic applications

    Science.gov (United States)

    Zhang, Liping; Jaroniec, Mietek

    2018-02-01

    Semiconductor photocatalysts show a great potential for environmental and energy-related applications, however one of the major disadvantages is their relatively low photocatalytic performance due to the recombination of electron-hole pairs. Therefore, intensive research is being conducted toward design of heterojunctions, which have been shown to be effective for improving the charge-transfer properties and efficiency of photocatalysts. According to the type of band alignment and direction of internal electric field, heterojunctions are categorized into five different types, each of which is associated with its own charge transfer characteristics. Since the design of heterojunctions requires the knowledge of band edge positions of component semiconductors, the commonly used techniques for the assessment of band edge positions are reviewed. Among them the electronegativity-based calculation method is applied for a large number of popular visible-light-active semiconductors, including some widely investigated bismuth-containing semiconductors. On basis of the calculated band edge positions and the type of component semiconductors reported, heterojunctions composed of the selected bismuth-containing semiconductors are proposed. Finally, the most popular synthetic techniques for the fabrication of heterojunctions are briefly discussed.

  16. Mechanisms limiting the performance of large grain polycrystalline silicon solar cells

    Science.gov (United States)

    Culik, J. S.; Alexander, P.; Dumas, K. A.; Wohlgemuth, J. W.

    1984-01-01

    The open-circuit voltage and short-circuit current of large-grain (1 to 10 mm grain diameter) polycrystalline silicon solar cells is determined by the minority-carrier diffusion length within the bulk of the grains. This was demonstrated by irradiating polycrystalline and single-crystal (Czochralski) silicon solar cells with 1 MeV electrons to reduce their bulk lifetime. The variation of short-circuit current with minority-carrier diffusion length for the polycrystalline solar cells is identical to that of the single-crystal solar cells. The open-circuit voltage versus short-circuit current characteristic of the polycrystalline solar cells for reduced diffusion lengths is also identical to that of the single-crystal solar cells. The open-circuit voltage of the polycrystalline solar cells is a strong function of quasi-neutral (bulk) recombination, and is reduced only slightly, if at all, by grain-boundary recombination.

  17. Method of manufacturing a semiconductor device and semiconductor device obtained with such a method

    NARCIS (Netherlands)

    2008-01-01

    The invention relates to a method of manufacturing a semiconductor device (10) with a semiconductor body (1) which is provided with at least one semiconductor element, wherein on the surface of the semiconductor body (1) a mesa- shaped semiconductor region (2) is formed, a masking layer (3) is

  18. Selective, electrochemical etching of a semiconductor

    Science.gov (United States)

    Dahal, Rajendra P.; Bhat, Ishwara B.; Chow, Tat-Sing

    2018-03-20

    Methods for facilitating fabricating semiconductor structures are provided which include: providing a multilayer structure including a semiconductor layer, the semiconductor layer including a dopant and having an increased conductivity; selectively increasing, using electrochemical processing, porosity of the semiconductor layer, at least in part, the selectively increasing porosity utilizing the increased conductivity of the semiconductor layer; and removing, at least in part, the semiconductor layer with the selectively increased porosity from the multilayer structure. By way of example, the selectively increasing porosity may include selectively, anodically oxidizing, at least in part, the semiconductor layer of the multilayer structure.

  19. Metal-insulator-semiconductor photodetectors.

    Science.gov (United States)

    Lin, Chu-Hsuan; Liu, Chee Wee

    2010-01-01

    The major radiation of the sun can be roughly divided into three regions: ultraviolet, visible, and infrared light. Detection in these three regions is important to human beings. The metal-insulator-semiconductor photodetector, with a simpler process than the pn-junction photodetector and a lower dark current than the MSM photodetector, has been developed for light detection in these three regions. Ideal UV photodetectors with high UV-to-visible rejection ratio could be demonstrated with III-V metal-insulator-semiconductor UV photodetectors. The visible-light detection and near-infrared optical communications have been implemented with Si and Ge metal-insulator-semiconductor photodetectors. For mid- and long-wavelength infrared detection, metal-insulator-semiconductor SiGe/Si quantum dot infrared photodetectors have been developed, and the detection spectrum covers atmospheric transmission windows.

  20. Metal-Insulator-Semiconductor Photodetectors

    Directory of Open Access Journals (Sweden)

    Chu-Hsuan Lin

    2010-09-01

    Full Text Available The major radiation of the Sun can be roughly divided into three regions: ultraviolet, visible, and infrared light. Detection in these three regions is important to human beings. The metal-insulator-semiconductor photodetector, with a simpler process than the pn-junction photodetector and a lower dark current than the MSM photodetector, has been developed for light detection in these three regions. Ideal UV photodetectors with high UV-to-visible rejection ratio could be demonstrated with III-V metal-insulator-semiconductor UV photodetectors. The visible-light detection and near-infrared optical communications have been implemented with Si and Ge metal-insulator-semiconductor photodetectors. For mid- and long-wavelength infrared detection, metal-insulator-semiconductor SiGe/Si quantum dot infrared photodetectors have been developed, and the detection spectrum covers atmospheric transmission windows.

  1. Quantum optics with semiconductor nanostructures

    CERN Document Server

    Jahnke, Frank

    2012-01-01

    A guide to the theory, application and potential of semiconductor nanostructures in the exploration of quantum optics. It offers an overview of resonance fluorescence emission.$bAn understanding of the interaction between light and matter on a quantum level is of fundamental interest and has many applications in optical technologies. The quantum nature of the interaction has recently attracted great attention for applications of semiconductor nanostructures in quantum information processing. Quantum optics with semiconductor nanostructures is a key guide to the theory, experimental realisation, and future potential of semiconductor nanostructures in the exploration of quantum optics. Part one provides a comprehensive overview of single quantum dot systems, beginning with a look at resonance fluorescence emission. Quantum optics with single quantum dots in photonic crystal and micro cavities are explored in detail, before part two goes on to review nanolasers with quantum dot emitters. Light-matter interaction...

  2. Atomic layer deposition for semiconductors

    CERN Document Server

    Hwang, Cheol Seong

    2014-01-01

    This edited volume discusses atomic layer deposition (ALD) for all modern semiconductor devices, moving from the basic chemistry of ALD and modeling of ALD processes to sections on ALD for memories, logic devices, and machines.

  3. Semiconductor technology program. Progress briefs

    Science.gov (United States)

    Bullis, W. M.

    1980-01-01

    Measurement technology for semiconductor materials, process control, and devices is reviewed. Activities include: optical linewidth and thermal resistance measurements; device modeling; dopant density profiles; resonance ionization spectroscopy; and deep level measurements. Standardized oxide charge terminology is also described.

  4. Semiconductor radiation detectors. Device physics

    International Nuclear Information System (INIS)

    Lutz, G.

    2007-01-01

    Starting from basic principles, the author, whose own contributions to these developments have been significant, describes the rapidly growing field of modern semiconductor detectors used for energy and position measurement radiation. This development was stimulated by requirements in elementary particle physics where it has led to important scientific discoveries. It has now spread to many other fields of science and technology. The book is written in a didactic way and includes an introduction to semiconductor physics. The working principles of semiconductor radiation detectors are explained in an intuitive way, followed by formal quantitative analysis. Broad coverage is also given to electronic signal readout and to the subject of radiation damage. The book is the first to comprehensively cover the semiconductor radiation detectors currently in use. It is useful as a teaching guide and as a reference work for research and applications. (orig.)

  5. Self-assembling peptide semiconductors

    Science.gov (United States)

    Tao, Kai; Makam, Pandeeswar; Aizen, Ruth; Gazit, Ehud

    2017-01-01

    Semiconductors are central to the modern electronics and optics industries. Conventional semiconductive materials bear inherent limitations, especially in emerging fields such as interfacing with biological systems and bottom-up fabrication. A promising candidate for bioinspired and durable nanoscale semiconductors is the family of self-assembled nanostructures comprising short peptides. The highly ordered and directional intermolecular π-π interactions and hydrogen-bonding network allow the formation of quantum confined structures within the peptide self-assemblies, thus decreasing the band gaps of the superstructures into semiconductor regions. As a result of the diverse architectures and ease of modification of peptide self-assemblies, their semiconductivity can be readily tuned, doped, and functionalized. Therefore, this family of electroactive supramolecular materials may bridge the gap between the inorganic semiconductor world and biological systems. PMID:29146781

  6. Temperature controller of semiconductor laser

    Czech Academy of Sciences Publication Activity Database

    Matoušek, Vít; Číp, Ondřej

    2003-01-01

    Roč. 73, č. 3 (2003), s. 10 - 12 ISSN 0928-5008 Institutional research plan: CEZ:AV0Z2065902 Keywords : temperature controller * semiconductor laser * laser diode Subject RIV: BH - Optics, Masers, Lasers

  7. Wake fields in semiconductor plasmas

    International Nuclear Information System (INIS)

    Berezhiani, V.I.; Mahajan, S.M.

    1994-05-01

    It is shown that an intense short laser pulse propagating through a semiconductor plasma will generated longitudinal Langmuir waves in its wake. The measurable wake field can be used as a diagnostic to study nonlinear optical phenomena. For narrow gap semiconductors (for examples InSb) with Kane-type dispersion relation, the system can simulate, at currently available laser powers, the physics underlying wake-field accelerators. (author). 9 refs, 1 fig

  8. Semiconductor research with reactor neutrons

    International Nuclear Information System (INIS)

    Kimura, Itsuro

    1992-01-01

    Reactor neutrons play an important role for characterization of semiconductor materials as same as other advanced materials. On the other hand reactor neutrons bring about not only malignant irradiation effects called radiation damage, but also useful effects such as neutron transmutation doping and defect formation for opto-electronics. Research works on semiconductor materials with the reactor neutrons of the Kyoto University Reactor (KUR) are briefly reviewed. In this review, a stress is laid on the present author's works. (author)

  9. Semiconductor crystal high resolution imager

    Science.gov (United States)

    Levin, Craig S. (Inventor); Matteson, James (Inventor)

    2011-01-01

    A radiation imaging device (10). The radiation image device (10) comprises a subject radiation station (12) producing photon emissions (14), and at least one semiconductor crystal detector (16) arranged in an edge-on orientation with respect to the emitted photons (14) to directly receive the emitted photons (14) and produce a signal. The semiconductor crystal detector (16) comprises at least one anode and at least one cathode that produces the signal in response to the emitted photons (14).

  10. Dissipative chaos in semiconductor superlattices

    Directory of Open Access Journals (Sweden)

    F. Moghadam

    2008-03-01

    Full Text Available In this paper the motion of electron in a miniband of a semiconductor superlattice (SSL under the influence of external electric and magnetic fields is investigated. The electric field is applied in a direction perpendicular to the layers of the semiconductor superlattice, and the magnetic field is applied in different direction Numerical calculations show conditions led to the possibility of chaotic behaviors.

  11. Reducing leakage current in semiconductor devices

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Bin; Matioli, Elison de Nazareth; Palacios, Tomas Apostol

    2018-03-06

    A semiconductor device includes a first region having a first semiconductor material and a second region having a second semiconductor material. The second region is formed over the first region. The semiconductor device also includes a current blocking structure formed in the first region between first and second terminals of the semiconductor device. The current blocking structure is configured to reduce current flow in the first region between the first and second terminals.

  12. Optical orientation in ferromagnet/semiconductor hybrids

    International Nuclear Information System (INIS)

    Korenev, V L

    2008-01-01

    The physics of optical pumping of semiconductor electrons in ferromagnet/semiconductor hybrids is discussed. Optically oriented semiconductor electrons detect the magnetic state of a ferromagnetic film. In turn, the ferromagnetism of the hybrid can be controlled optically with the help of a semiconductor. Spin–spin interactions near the ferromagnet/semiconductor interface play a crucial role in the optical readout and the manipulation of ferromagnetism

  13. Optical orientation in ferromagnet/semiconductor hybrids

    Science.gov (United States)

    Korenev, V. L.

    2008-11-01

    The physics of optical pumping of semiconductor electrons in ferromagnet/semiconductor hybrids is discussed. Optically oriented semiconductor electrons detect the magnetic state of a ferromagnetic film. In turn, the ferromagnetism of the hybrid can be controlled optically with the help of a semiconductor. Spin-spin interactions near the ferromagnet/semiconductor interface play a crucial role in the optical readout and the manipulation of ferromagnetism.

  14. Optical Orientation in Ferromagnet/Semiconductor Hybrids

    OpenAIRE

    Korenev, V. L.

    2008-01-01

    The physics of optical pumping of semiconductor electrons in the ferromagnet/semiconductor hybrids is discussed. Optically oriented semiconductor electrons detect the magnetic state of the ferromagnetic film. In turn, the ferromagnetism of the hybrid can be controlled optically with the help of the semiconductor. Spin-spin interactions near the interface ferromagnet/semiconductor play crucial role in the optical readout and the manipulation of ferromagnetism.

  15. Semiconductors for plasmonics and metamaterials

    DEFF Research Database (Denmark)

    Naik, G.V.; Boltasseva, Alexandra

    2010-01-01

    Plasmonics has conventionally been in the realm of metal-optics. However, conventional metals as plasmonic elements in the near-infrared (NIR) and visible spectral ranges suffer from problems such as large losses and incompatibility with semiconductor technology. Replacing metals with semiconduct......Plasmonics has conventionally been in the realm of metal-optics. However, conventional metals as plasmonic elements in the near-infrared (NIR) and visible spectral ranges suffer from problems such as large losses and incompatibility with semiconductor technology. Replacing metals...... with semiconductors can alleviate these problems if only semiconductors could exhibit negative real permittivity. Aluminum doped zinc oxide (AZO) is a low loss semiconductor that can show negative real permittivity in the NIR. A comparative assessment of AZO-based plasmonic devices such as superlens and hyperlens...... with their metal-based counterparts shows that AZO-based devices significantly outperform at a wavelength of 1.55 µm. This provides a strong stimulus in turning to semiconductor plasmonics at the telecommunication wavelengths. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)....

  16. Ripening of Semiconductor Nanoplatelets.

    Science.gov (United States)

    Ott, Florian D; Riedinger, Andreas; Ochsenbein, David R; Knüsel, Philippe N; Erwin, Steven C; Mazzotti, Marco; Norris, David J

    2017-11-08

    Ostwald ripening describes how the size distribution of colloidal particles evolves with time due to thermodynamic driving forces. Typically, small particles shrink and provide material to larger particles, which leads to size defocusing. Semiconductor nanoplatelets, thin quasi-two-dimensional (2D) particles with thicknesses of only a few atomic layers but larger lateral dimensions, offer a unique system to investigate this phenomenon. Experiments show that the distribution of nanoplatelet thicknesses does not defocus during ripening, but instead jumps sequentially from m to (m + 1) monolayers, allowing precise thickness control. We investigate how this counterintuitive process occurs in CdSe nanoplatelets. We develop a microscopic model that treats the kinetics and thermodynamics of attachment and detachment of monomers as a function of their concentration. We then simulate the growth process from nucleation through ripening. For a given thickness, we observe Ostwald ripening in the lateral direction, but none perpendicular. Thicker populations arise instead from nuclei that capture material from thinner nanoplatelets as they dissolve laterally. Optical experiments that attempt to track the thickness and lateral extent of nanoplatelets during ripening appear consistent with these conclusions. Understanding such effects can lead to better synthetic control, enabling further exploration of quasi-2D nanomaterials.

  17. A semiconductor laser device

    Energy Technology Data Exchange (ETDEWEB)

    Takaro, K.; Naoki, T.; Satosi, K.; Yasutosi, K.

    1984-03-17

    A device is proposed which makes it possible to obtain single vertical mode emission in the absence of noise. Noise suppression is achieved by a method which determines the relationship between the donor densities in the second and third layers of an n type semiconductor laser, and the total output optical emission of layers with respect to the emission from the entire laser. The device consists of a photoresist film with a window applied to a 100 GaAs n type conductivity substrate using a standard method. Chemical etching through this window in the substrate is used to generate a slot approximately 1 micrometer in size. After the photoresist film is removed, the following layers are deposited from the liquid phase onto the substrate in the sequence indicated: a telurium doped protective layer of n type AlxGa(1-x) As; 2) an undoped active p type AlyGa(1-6) As layer and a tellurium doped upper protective n type conductivity GaAs layer.

  18. Semiconductor integrated circuits

    International Nuclear Information System (INIS)

    Michel, A.E.; Schwenker, R.O.; Ziegler, J.F.

    1979-01-01

    An improved method involving ion implantation to form non-epitaxial semiconductor integrated circuits. These are made by forming a silicon substrate of one conductivity type with a recessed silicon dioxide region extending into the substrate and enclosing a portion of the silicon substrate. A beam of ions of opposite conductivity type impurity is directed at the substrate at an energy and dosage level sufficient to form a first region of opposite conductivity within the silicon dioxide region. This impurity having a concentration peak below the surface of the substrate forms a region of the one conductivity type which extends from the substrate surface into the first opposite type region to a depth between the concentration peak and the surface and forms a second region of opposite conductivity type. The method, materials and ion beam conditions are detailed. Vertical bipolar integrated circuits can be made this way when the first opposite type conductivity region will function as a collector. Also circuits with inverted bipolar devices when this first region functions as a 'buried'' emitter region. (U.K.)

  19. Impurity gettering in semiconductors

    Science.gov (United States)

    Sopori, Bhushan L.

    1995-01-01

    A process for impurity gettering in a semiconductor substrate or device such as a silicon substrate or device. The process comprises hydrogenating the substrate or device at the back side thereof with sufficient intensity and for a time period sufficient to produce a damaged back side. Thereafter, the substrate or device is illuminated with electromagnetic radiation at an intensity and for a time period sufficient to cause the impurities to diffuse to the back side and alloy with a metal there present to form a contact and capture the impurities. The impurity gettering process also can function to simultaneously passivate defects within the substrate or device, with the defects likewise diffusing to the back side for simultaneous passivation. Simultaneously, substantially all hydrogen-induced damage on the back side of the substrate or device is likewise annihilated. Also taught is an alternate process comprising thermal treatment after hydrogenation of the substrate or device at a temperature of from about 500.degree. C. to about 700.degree. C. for a time period sufficient to cause the impurities to diffuse to the damaged back side thereof for subsequent capture by an alloying metal.

  20. Semiconductor acceleration sensor

    Science.gov (United States)

    Ueyanagi, Katsumichi; Kobayashi, Mitsuo; Goto, Tomoaki

    1996-09-01

    This paper reports a practical semiconductor acceleration sensor especially suited for automotive air bag systems. The acceleration sensor includes four beams arranged in a swastika structure. Two piezoresistors are formed on each beam. These eight piezoresistors constitute a Wheatstone bridge. The swastika structure of the sensing elements, an upper glass plate and a lower glass plate exhibit the squeeze film effect which enhances air dumping, by which the constituent silicon is prevented from breakdown. The present acceleration sensor has the following features. The acceleration force component perpendicular to the sensing direction can be cancelled. The cross-axis sensitivity is less than 3 percent. And, the erroneous offset caused by the differences between the thermal expansion coefficients of the constituent materials can be canceled. The high aspect ratio configuration realized by plasma etching facilitates reducing the dimensions and improving the sensitivity of the acceleration sensor. The present acceleration sensor is 3.9 mm by 3.9 mm in area and 1.2 mm in thickness. The present acceleration sensor can measure from -50 to +50 G with sensitivity of 0.275 mV/G and with non-linearity of less than 1 percent. The acceleration sensor withstands shock of 3000 G.

  1. Resistive switching in polycrystalline YMnO3 thin films

    Directory of Open Access Journals (Sweden)

    A. Bogusz

    2014-10-01

    Full Text Available We report a unipolar, nonvolatile resistive switching in polycrystalline YMnO3 thin films grown by pulsed laser deposition and sandwiched between Au top and Ti/Pt bottom electrodes. The ratio of the resistance in the OFF and ON state is larger than 103. The observed phenomena can be attributed to the formation and rupture of conductive filaments within the multiferroic YMnO3 film. The generation of conductive paths under applied electric field is discussed in terms of the presence of grain boundaries and charged domain walls inherently formed in hexagonal YMnO3. Our findings suggest that engineering of the ferroelectric domains might be a promising route for designing and fabrication of novel resistive switching devices.

  2. Mueller matrix mapping of biological polycrystalline layers using reference wave

    Science.gov (United States)

    Dubolazov, A.; Ushenko, O. G.; Ushenko, Yu. O.; Pidkamin, L. Y.; Sidor, M. I.; Grytsyuk, M.; Prysyazhnyuk, P. V.

    2018-01-01

    The paper consists of two parts. The first part is devoted to the short theoretical basics of the method of differential Mueller-matrix description of properties of partially depolarizing layers. It was provided the experimentally measured maps of differential matrix of the 1st order of polycrystalline structure of the histological section of brain tissue. It was defined the statistical moments of the 1st-4th orders, which characterize the distribution of matrix elements. In the second part of the paper it was provided the data of statistic analysis of birefringence and dichroism of the histological sections of mice liver tissue (normal and with diabetes). It were defined the objective criteria of differential diagnostics of diabetes.

  3. Analysis of Operating Temperature of the Polycrystalline Solar Cell

    Directory of Open Access Journals (Sweden)

    Vladimír GÁLL

    2017-12-01

    Full Text Available This work deals with the solar cells with orientation on the calculation of operating temperature of the polycrystalline solar cell, which is under actual load. Operating conditions have a significant effect on the efficiency of solar cells. In the summer with increasing temperature, the efficiency decreases. In the winter, efficiency and output voltage are rising. The operating temperature is determined by intensity of solar radiation, the types of materials used by construction and operating condition. The aim of this work was simplify of the calculation of operating temperature of solar cells. The result of this work is a derived equation that allows a more accurate and faster calculation this temperature with using Matlab software.

  4. Microcracking in polycrystalline YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Smith, D.S.; Suasmoro, S.; Huger, M.; Gault, C.

    1991-01-01

    The presence of microcracks can have a significant role for the electrical properties of polycrystalline YBa 2 Cu 3 O 7-δ due to the reduction of the effective current carrying cross section. This results in an increase of the normal state resistivity and a decrease of the critical current density, j c . Shaw et.al have reported an onset of microcracking for grain sizes greater than 1-2 μm. In this work we focus attention on the geometrical aspects of the microstructure by using ultrasonic measurements to characterize the mechanical properties of the ceramic for comparison to the electrical data. The studies have been extended with experiments as a function of temperature and atmosphere in order to investigate the origins of the microcracks. (orig./BHO)

  5. Characterization of CdSe polycrystalline films by photoluminescence spectroscopy

    International Nuclear Information System (INIS)

    Brasil, M.J.S.P.

    1985-01-01

    The characterization of CdSe polycristalline films were done by photoluminescence spectroscopy, X-ray diffraction analysis, diagrams IxV, and efficiency of solar energy conversion for cells done by these films. The experimental data shown strong temperature dependence of annealing, and the optimum temperature around 650 0 C was determined. The films did not present photoluminescence before heat treatment, but the annealed sample spectrum showed fine structures in the excitonic region, crystal phase transformation, enhancement of grain size, and better efficiency of the cell. Measurements of photoluminescence between 2 and 300 K, showed two bands of infrared emission, width and intense enough. The shape, at half-width, and the integrated intensity of one these bands were described by a configuration coordinate model for deep centers. Based on obtained results, some hypothesis about the origin of these bands and its correlation with efficiency of cells done with CdSe polycrystalline films, are proposed. (M.C.K.) [pt

  6. Mechanical properties of amorphous and polycrystalline multilayer systems

    International Nuclear Information System (INIS)

    Barzen, I.; Edinger, M.; Scherer, J.; Ulrich, S.; Jung, K.; Ehrhardt, H.

    1993-01-01

    Amorphous and polycrystalline multilayer structures containing materials with metallic (Cr, Cr 3 C 2 ), ionic (Al 2 O 3 ) and covalent (SiC) bonding have been prepared by magnetron sputtering and ion plating in a dual-source apparatus. Up to 1000 layers have been deposited with a constant total thickness of 2.3 μm. Below a single-layer thickness of 10-30 nm the mechanical properties stress and hardness show strong variations. On one hand it is possible that below a certain thickness the mechanical properties of a single layer change. On the other hand electrical resistance and electron spin density measurements indicate that electronic effects may be involved. An attempt is made to explain the observed correlations by transport mechanisms of the electrons, by saturation of dangling bonds with delocalized electrons and by changes in the electronic band structure. (orig.)

  7. Polycrystalline Diamond Coating of Additively Manufactured Titanium for Biomedical Applications.

    Science.gov (United States)

    Rifai, Aaqil; Tran, Nhiem; Lau, Desmond W; Elbourne, Aaron; Zhan, Hualin; Stacey, Alastair D; Mayes, Edwin L H; Sarker, Avik; Ivanova, Elena P; Crawford, Russell J; Tran, Phong A; Gibson, Brant C; Greentree, Andrew D; Pirogova, Elena; Fox, Kate

    2018-03-14

    Additive manufacturing using selective laser melted titanium (SLM-Ti) is used to create bespoke items across many diverse fields such as medicine, defense, and aerospace. Despite great progress in orthopedic implant applications, such as for "just in time" implants, significant challenges remain with regards to material osseointegration and the susceptibility to bacterial colonization on the implant. Here, we show that polycrystalline diamond coatings on these titanium samples can enhance biological scaffold interaction improving medical implant applicability. The highly conformable coating exhibited excellent bonding to the substrate. Relative to uncoated SLM-Ti, the diamond coated samples showed enhanced mammalian cell growth, enriched apatite deposition, and reduced microbial S. aureus activity. These results open new opportunities for novel coatings on SLM-Ti devices in general and especially show promise for improved biomedical implants.

  8. Structural Evolution and Mechanisms of Fatigue in Polycrystalline Brass

    DEFF Research Database (Denmark)

    Carstensen, Jesper Vejlø

    The plastic strain controlled fatigue behaviour of polycrystalline Cu-15%Zn and Cu-30%Zn has been investigated with the aim of studying the effect of slip mode modification by the addition of zinc to copper. It has been clearly demonstrated, that true cyclic saturation does not occur in the plastic...... type single slip. This behaviour has been described by the self-consistent Sachs-Eshelby model, which provides estimates of the CSS curve for brass polycrystals. Successive stages of primary hardening, softening and secondary hardening has been observed in the plastic strain controlled fatigue of brass....... It has been found that the primary hardening is attributed to an increase of intergranular stresses whereas the sec-ondary hardening apparently is attributed to an increase of friction stresses. Investigations of the structural evolution show that the softening behaviour can be explained by the presence...

  9. X-ray stress analysis in textured polycrystalline materials

    International Nuclear Information System (INIS)

    Yokoyama, Ryouichi; Harada, Jimpei

    2010-01-01

    The relationship between stress and strain in polycrystalline materials with fibre texture is examined on the basis of the strain analysis in the constituent crystallites within the Reuss approximation. By introducing the symmetry of reciprocal lattices for the constituent crystallites, the physical meaning of taking an average of the strains observed by X-ray diffraction (XRD) is made clear. By using formulae obtained by the present treatment for the stress-strain relation in cubic specimens with fibre texture in the Laue classes m3-bar m hkl Bragg reflections with h≠k≠l split into doublets owing to the existence of crystallites with two different orientations under the stress field. This technique was confirmed by the profile analysis in XRD data observed for reflections of 222 and 420 in a cubic TiN thin film sputtered on a polyimide film. The technique of the stress analysis and its confirmation are introduced. (author)

  10. Polycrystalline Silicon Gettered by Porous Silicon and Heavy Phosphorous Diffusion

    Institute of Scientific and Technical Information of China (English)

    LIU Zuming(刘祖明); Souleymane K Traore; ZHANG Zhongwen(张忠文); LUO Yi(罗毅)

    2004-01-01

    The biggest barrier for photovoltaic (PV) utilization is its high cost, so the key for scale PV utilization is to further decrease the cost of solar cells. One way to improve the efficiency, and therefore lower the cost, is to increase the minority carrier lifetime by controlling the material defects. The main defects in grain boundaries of polycrystalline silicon gettered by porous silicon and heavy phosphorous diffusion have been studied. The porous silicon was formed on the two surfaces of wafers by chemical etching. Phosphorous was then diffused into the wafers at high temperature (900℃). After the porous silicon and diffusion layers were removed, the minority carrier lifetime was measured by photo-conductor decay. The results show that the lifetime's minority carriers are increased greatly after such treatment.

  11. Wavelet analysis of polarization maps of polycrystalline biological fluids networks

    Science.gov (United States)

    Ushenko, Y. A.

    2011-12-01

    The optical model of human joints synovial fluid is proposed. The statistic (statistic moments), correlation (autocorrelation function) and self-similar (Log-Log dependencies of power spectrum) structure of polarization two-dimensional distributions (polarization maps) of synovial fluid has been analyzed. It has been shown that differentiation of polarization maps of joint synovial fluid with different physiological state samples is expected of scale-discriminative analysis. To mark out of small-scale domain structure of synovial fluid polarization maps, the wavelet analysis has been used. The set of parameters, which characterize statistic, correlation and self-similar structure of wavelet coefficients' distributions of different scales of polarization domains for diagnostics and differentiation of polycrystalline network transformation connected with the pathological processes, has been determined.

  12. Effect of localized polycrystalline silicon properties on solar cell performance

    Science.gov (United States)

    Leung, D.; Iles, P. A.; Hyland, S.; Kachare, A.

    1984-01-01

    Several forms of polycrystalline silicon, mostly from cast ingots, (including UCP, SILSO and HEM) were studied. On typical slices, localized properties were studied in two ways. Small area (about 2.5 sq mm) mesa diodes were formed, and localized photovoltaic properties were measured. Also a small area (about .015 sq mm) light spot was scanned across the cells; the light spot response was calibrated to measure local diffusion length directly. Using these methods, the effects of grain boundaries, or of intragrain imperfections were correlated with cell performance. Except for the fine grain portion of SILSO, grain boundaries played only a secondary role in determining cell performance. The major factor was intra-grain material quality and it varied with position in ingots and probably related to solidification procedure.

  13. Dislocation structures around crack tips of fatigued polycrystalline copper

    International Nuclear Information System (INIS)

    Kaneko, Yoshihisa; Ishikawa, Masao; Hashimoto, Satoshi

    2005-01-01

    Dislocation structures near fatigue cracks of polycrystalline copper specimens were analyzed using the electron channelling contrast imaging (ECCI) technique. Prior to the ECCI observations, optical microscopy was conducted to classify the fatigue crack morphologies into several kinds. It was found that the dislocation structures were correlated with the slip morphologies observed using the optical microscope. The cell structure almost corresponded to the severely deformed plastic zone where the individual slip bands could not be identified. The labyrinth dislocation structure was detected at the double-slip region. Ladder-like dislocation structure was detected ahead of the Stage I type fatigue crack. Hence, it can be said that the persistent slip band (PSB) was a favorable crack path. However, the microscopic route of the crack growth was not along the PSB but along the cell structure, which was developed locally in the vicinity of the crack tip

  14. Slip activity of persistent slip bands in polycrystalline nickel

    International Nuclear Information System (INIS)

    Weidner, A.; Beyer, R.; Blochwitz, C.; Holste, C.; Schwab, A.; Tirschler, W.

    2006-01-01

    The appearance of glide localizations after cyclic deformation in the saturation stage was investigated for polycrystalline nickel. It was shown that persistent slip bands (PSBs) are formed in a wide range of grain orientations. Concerning the grain size it was found, that the probability for the appearance of PSBs is higher for larger grains. The local slip activity of the formed PSBs was studied after half-cycle deformation using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The fraction of grains with glide-active PSBs and the glide-active PSB volume itself is very small after the half-cycle loading. The obtained local shear strain amplitudes are quite high and vary in the range of 0.2-5%. They are comparable with those found in nickel single crystals at the same loading procedure

  15. Surface roughness effects on blister formation in polycrystalline molybdenum

    International Nuclear Information System (INIS)

    Saidoh, Masahiro; Sone, Kazuho; Yamada, Rayji; Ohtsuka, Hidewo; Murakami, Yoshio

    1977-07-01

    Polycrystalline molybdenum targets with electropolished and roughened surfaces were bombarded with 100 keV He + and 200 keV H 2 + ions at room temperature. It has been demonstrated that the blister formation is largely or completely suppressed by roughening the electropolished surface with emery paper of No. 1200, No. 400 and No. 100. Up to a He + fluence of 1.0 x 10 19 particles/cm 2 , no blisters are observed in the targets with the two roughest surfaces, while on the smooth surface blisters begin to occur at a fluence of 7.5 x 10 17 particles/cm 2 . The surface roughness effect on blister suppression is discussed in relation to the projected range of incident particles. (auth.)

  16. Sputtering mechanisms of polycrystalline platinum by low energy ions

    International Nuclear Information System (INIS)

    Chernysh, V.S.; Eckstein, W.; Haidarov, A.A.; Kulikauskas, V.S.; Mashkova, E.S.; Molchanov, V.A.

    1999-01-01

    The results of an experimental study and a computer simulation with the TRIM.SP code of the angular distributions of atoms sputtered from polycrystalline platinum under 1.5-9 keV He + bombardment at the normal ion incidence are presented. It has been found that angular distributions of sputtered atoms are overcosine and that their shape is practically independent of the bombarding ion species and ion energy. Good agreement between experimental results and computer simulation data was found. Computer simulations of the partial angular distributions of Pt atoms ejected due to various sputtering mechanisms for He and Ar bombardments were performed. The role of different mechanisms in the formation of angular distributions of sputtered atoms has been analyzed

  17. Incorporation, diffusion and segregation of impurities in polycrystalline silicon

    Energy Technology Data Exchange (ETDEWEB)

    Deville, J.P.; Soltani, M.L. (Universite Louis Pasteur, 67 - Strasbourg (France)); Quesada, J. (Laboratoire de Metallurgie-Chimie des Materiaux, E.N.S.A.I.S., 67 - Strasbourg (France))

    1982-01-01

    We studied by means of X-Ray photoelectron Spectroscopy the nature, distribution and, when possible, the chemical bond of impurities at the surface of polycrystalline silicon samples grown on a carbon ribbon. Besides main impurities (carbon and oxygen), always present at concentrations around their limit of solubility in silicon, metal impurities have been found: their nature varies from one sample to another. Their spatial distribution is not random: some are strictly confined at the surface (sodium), whereas others are in the superficial oxidized layer (calcium, magnesium) or localized at the oxide-bulk silicon interface (iron). Metal impurities are coming from the carbon ribbon and are incorporated to silicon during the growth process. It is not yet possible to give a model of diffusion processes of impurities since they are too numerous and interact one with the other. However oxygen seems to play a leading role in the spatial distribution of metal impurities.

  18. Polycrystalline CdTe solar cells on elastic substrates

    International Nuclear Information System (INIS)

    Sibinski, M.; Lisik, Z.

    2007-01-01

    The presented article is a report on progress in photovoltaic devices and material processing. A cadmium telluride solar cell as one of the most attractive option for thin-film polycrystalline cell constructions is presented. All typical manufacturing steps of this device, including recrystallisation and junction activation are explained. A new potential field of application for this kind of device - the BIPV (Building Integrated Photovoltaic) is named and discussed. All possible configuration options for this application, according to material properties and exploitation demands are considered. The experimental part of the presented paper is focused on practical implementation of the high - temperature polymer foil as the substrate of the newly designed device by the help of ICSVT (Isothermal Close Space Vapour Transport) technique. The evaluation of the polyester and polyamide foils according to the ICSVT/CSS manufacturing process parameters is described and discussed. A final conclusion on practical verification of these materials is also given. (authors)

  19. Electronic properties of polycrystalline graphene under large local strain

    International Nuclear Information System (INIS)

    He, Xin; Tang, Ning; Duan, Junxi; Mei, Fuhong; Meng, Hu; Lu, Fangchao; Xu, Fujun; Yang, Xuelin; Gao, Li; Wang, Xinqiang; Shen, Bo; Ge, Weikun

    2014-01-01

    To explore the transport properties of polycrystalline graphene under large tensile strain, a strain device has been fabricated using piezocrystal to load local strain onto graphene, up to 22.5%. Ionic liquid gate whose capability of tuning carrier density being much higher than that of a solid gate is used to survey the transfer characteristics of the deformed graphene. The conductance of the Dirac point and field effect mobility of electrons and holes is found to decrease with increasing strain, which is attributed to the scattering of the graphene grain boundaries, the strain induced change of band structure, and defects. However, the transport gap is still not opened. Our study is helpful to evaluate the application of graphene in stretchable electronics.

  20. Improved orientation sampling for indexing diffraction patterns of polycrystalline materials

    DEFF Research Database (Denmark)

    Larsen, Peter Mahler; Schmidt, Søren

    2017-01-01

    to that of optimally distributing points on a four‐dimensional sphere. In doing so, the number of orientation samples needed to achieve a desired indexing accuracy is significantly reduced. Orientation sets at a range of sizes are generated in this way for all Laue groups and are made available online for easy use.......Orientation mapping is a widely used technique for revealing the microstructure of a polycrystalline sample. The crystalline orientation at each point in the sample is determined by analysis of the diffraction pattern, a process known as pattern indexing. A recent development in pattern indexing...... in the presence of noise, it has very high computational requirements. In this article, the computational burden is reduced by developing a method for nearly optimal sampling of orientations. By using the quaternion representation of orientations, it is shown that the optimal sampling problem is equivalent...

  1. Nanomembrane structures having mixed crystalline orientations and compositions

    Science.gov (United States)

    Lagally, Max G.; Scott, Shelley A.; Savage, Donald E.

    2014-08-12

    The present nanomembrane structures include a multilayer film comprising a single-crystalline layer of semiconductor material disposed between two other single-crystalline layers of semiconductor material. A plurality of holes extending through the nanomembrane are at least partially, and preferably entirely, filled with a filler material which is also a semiconductor, but which differs from the nanomembrane semiconductor materials in composition, crystal orientation, or both.

  2. Polycrystalline CVD diamond device level modeling for particle detection applications

    Science.gov (United States)

    Morozzi, A.; Passeri, D.; Kanxheri, K.; Servoli, L.; Lagomarsino, S.; Sciortino, S.

    2016-12-01

    Diamond is a promising material whose excellent physical properties foster its use for radiation detection applications, in particular in those hostile operating environments where the silicon-based detectors behavior is limited due to the high radiation fluence. Within this framework, the application of Technology Computer Aided Design (TCAD) simulation tools is highly envisaged for the study, the optimization and the predictive analysis of sensing devices. Since the novelty of using diamond in electronics, this material is not included in the library of commercial, state-of-the-art TCAD software tools. In this work, we propose the development, the application and the validation of numerical models to simulate the electrical behavior of polycrystalline (pc)CVD diamond conceived for diamond sensors for particle detection. The model focuses on the characterization of a physically-based pcCVD diamond bandgap taking into account deep-level defects acting as recombination centers and/or trap states. While a definite picture of the polycrystalline diamond band-gap is still debated, the effect of the main parameters (e.g. trap densities, capture cross-sections, etc.) can be deeply investigated thanks to the simulated approach. The charge collection efficiency due to β -particle irradiation of diamond materials provided by different vendors and with different electrode configurations has been selected as figure of merit for the model validation. The good agreement between measurements and simulation findings, keeping the traps density as the only one fitting parameter, assesses the suitability of the TCAD modeling approach as a predictive tool for the design and the optimization of diamond-based radiation detectors.

  3. Brine migration in hot-pressed polycrystalline sodium chloride

    International Nuclear Information System (INIS)

    Biggers, J.V.; Dayton, G.O.

    1982-12-01

    This report describes experiments designed to provide data on brine migration in polycrystalline salt. Polycrystalling samples of various grain sizes, density, and purity were prepared from several commercial-grade salts by hot-pressing. Three distinct experimental set-ups were used to place salt billets in an induced thermal gradient in contact with brine source. The test designs varied primarily in the way in which the thermal gradient was applied and monitored and the way in which brine migration was determined. All migration was in enclosed vessels which precluded visual observation of brine movement through the microstructure. Migration velocities were estimated either by the timed appearance of brine at the hot face of the sample, or by determination of the penetration distance of migration artifacts in the microstructure after tests of fixed duration. For various reasons both of these methods were subject to a large degree of error. Our results suggest, however, that the migration velocity in dense polycrystalline salt may be at least an order of magnitude greater than that suggested by single-crystal experiments. Microstructural analysis shows that brine prefers to migrate along paths of high crystalline activity such as grain and subgrain boundaries and is dispersed rather quickly in the microstructure. A series of tests were performed using various types of tracers in brine in order to flag migration paths and locate brine in the microstructure more decisively. These attempts failed and it appears that only the aqueous portion of the brine moves through the microstructure with the dissolved ions being lost and replaced rather quickly. This suggests the use of deuterium as a tracer in future work

  4. Polycrystalline CVD diamond device level modeling for particle detection applications

    International Nuclear Information System (INIS)

    Morozzi, A.; Passeri, D.; Kanxheri, K.; Servoli, L.; Lagomarsino, S.; Sciortino, S.

    2016-01-01

    Diamond is a promising material whose excellent physical properties foster its use for radiation detection applications, in particular in those hostile operating environments where the silicon-based detectors behavior is limited due to the high radiation fluence. Within this framework, the application of Technology Computer Aided Design (TCAD) simulation tools is highly envisaged for the study, the optimization and the predictive analysis of sensing devices. Since the novelty of using diamond in electronics, this material is not included in the library of commercial, state-of-the-art TCAD software tools. In this work, we propose the development, the application and the validation of numerical models to simulate the electrical behavior of polycrystalline (pc)CVD diamond conceived for diamond sensors for particle detection. The model focuses on the characterization of a physically-based pcCVD diamond bandgap taking into account deep-level defects acting as recombination centers and/or trap states. While a definite picture of the polycrystalline diamond band-gap is still debated, the effect of the main parameters (e.g. trap densities, capture cross-sections, etc.) can be deeply investigated thanks to the simulated approach. The charge collection efficiency due to β -particle irradiation of diamond materials provided by different vendors and with different electrode configurations has been selected as figure of merit for the model validation. The good agreement between measurements and simulation findings, keeping the traps density as the only one fitting parameter, assesses the suitability of the TCAD modeling approach as a predictive tool for the design and the optimization of diamond-based radiation detectors.

  5. Semiconductor nanocrystals for novel optical applications

    Science.gov (United States)

    Moon, Jong-Sik

    Inspired by the promise of enhanced spectral response, photorefractive polymeric composites photosensitized with semiconductor nanocrystals have emerged as an important class of materials. Here, we report on the photosensitization of photorefractive polymeric composites at visible wavelengths through the inclusion of narrow band-gap semiconductor nanocrystals composed of PbS. Through this approach, internal diffraction efficiencies in excess of 82%, two-beam-coupling gain coefficients in excess of 211 cm-1, and response times 34 ms have been observed, representing some of the best figures-of-merit reported on this class of materials. In addition to providing efficient photosensitization, however, extensive studies of these hybrid composites have indicated that the inclusion of nanocrystals also provides an enhancement in the charge-carrier mobility and subsequent reduction in the photorefractive response time. Through this approach with PbS as charge-carrier, unprecedented response times of 399 micros were observed, opening the door for video and other high-speed applications. It is further demonstrated that this improvement in response time occurs with little sacrifice in photorefractive efficiency and with internal diffraction efficiencies of 72% and two- beam-coupling gain coefficients of 500 cm-1 being measured. A thorough analysis of the experimental data is presented, supporting the hypothesized mechanism of the enhanced charge mobility without the accompaniment of superfluous traps. Finally, water soluble InP/ZnS and CdSe/ZnS quantum dots interacted with CPP and Herceptin to apply them as a bio-maker. Both of quantum dots showed the excellent potential for use in biomedical imaging and drug delivery applications. It is anticipated that these approaches can play a significant role in the eventual commercialization of these classes of materials.

  6. Semiconductor lasers stability, instability and chaos

    CERN Document Server

    Ohtsubo, Junji

    2017-01-01

    This book describes the fascinating recent advances made concerning the chaos, stability and instability of semiconductor lasers, and discusses their applications and future prospects in detail. It emphasizes the dynamics in semiconductor lasers by optical and electronic feedback, optical injection, and injection current modulation. Applications of semiconductor laser chaos, control and noise, and semiconductor lasers are also demonstrated. Semiconductor lasers with new structures, such as vertical-cavity surface-emitting lasers and broad-area semiconductor lasers, are intriguing and promising devices. Current topics include fast physical number generation using chaotic semiconductor lasers for secure communication, development of chaos, quantum-dot semiconductor lasers and quantum-cascade semiconductor lasers, and vertical-cavity surface-emitting lasers. This fourth edition has been significantly expanded to reflect the latest developments. The fundamental theory of laser chaos and the chaotic dynamics in se...

  7. Crystal Structure, Optical, and Electrical Properties of SnSe and SnS Semiconductor Thin Films Prepared by Vacuum Evaporation Techniques for Solar Cell Applications

    Science.gov (United States)

    Ariswan; Sutrisno, H.; Prasetyawati, R.

    2017-05-01

    Thin films of SnSe and SnS semiconductors had been prepared by vacuum evaporation techniques. All prepared samples were characterized on their structure, optical, and electrical properties in order to know their application in technology. The crystal structure of SnSe and SnS was determined by X-Ray Diffraction (XRD) instrument. The morphology and chemical composition were obtained by Scanning Electron Microscopy (SEM) coupled with Energy Dispersive of X-Ray Analysis (EDAX). The optical property such as band gap was determined by DR-UV-Vis (Diffuse Reflectance-Ultra Violet-Visible) spectroscopy, while the electrical properties were determined by measuring the conductivity by four probes method. The characterization results indicated that both SnSe and SnS thin films were polycrystalline. SnSe crystallized in an orthorhombic crystal system with the lattice parameters of a = 11.47 Å, b = 4.152 Å and c = 4.439 Å, while SnS had an orthorhombic crystal system with lattice parameters of a = 4.317 Å, b = 11.647 Å and c = 3.981 Å. Band gaps (Eg) of SnSe and SnS were 1.63 eV and 1.35 eV, respectively. Chemical compositions of both thin films were non-stoichiometric. Molar ratio of Sn : S was close to ideal which was 1 : 0.96, while molar ratio of Sn : S was 1 : 0.84. The surface morphology described the arrangement of the grains on the surface of the thin film with sizes ranging from 0.2 to 0.5 microns. Color similarity on the surface of the SEM images proved a homogenous thin layer.

  8. Initial steps toward the realization of large area arrays of single photon counting pixels based on polycrystalline silicon TFTs

    Science.gov (United States)

    Liang, Albert K.; Koniczek, Martin; Antonuk, Larry E.; El-Mohri, Youcef; Zhao, Qihua; Jiang, Hao; Street, Robert A.; Lu, Jeng Ping

    2014-03-01

    The thin-film semiconductor processing methods that enabled creation of inexpensive liquid crystal displays based on amorphous silicon transistors for cell phones and televisions, as well as desktop, laptop and mobile computers, also facilitated the development of devices that have become ubiquitous in medical x-ray imaging environments. These devices, called active matrix flat-panel imagers (AMFPIs), measure the integrated signal generated by incident X rays and offer detection areas as large as ~43×43 cm2. In recent years, there has been growing interest in medical x-ray imagers that record information from X ray photons on an individual basis. However, such photon counting devices have generally been based on crystalline silicon, a material not inherently suited to the cost-effective manufacture of monolithic devices of a size comparable to that of AMFPIs. Motivated by these considerations, we have developed an initial set of small area prototype arrays using thin-film processing methods and polycrystalline silicon transistors. These prototypes were developed in the spirit of exploring the possibility of creating large area arrays offering single photon counting capabilities and, to our knowledge, are the first photon counting arrays fabricated using thin film techniques. In this paper, the architecture of the prototype pixels is presented and considerations that influenced the design of the pixel circuits, including amplifier noise, TFT performance variations, and minimum feature size, are discussed.

  9. Additional compound semiconductor nanowires for photonics

    Science.gov (United States)

    Ishikawa, F.

    2016-02-01

    GaAs related compound semiconductor heterostructures are one of the most developed materials for photonics. Those have realized various photonic devices with high efficiency, e. g., lasers, electro-optical modulators, and solar cells. To extend the functions of the materials system, diluted nitride and bismide has been paid attention over the past decade. They can largely decrease the band gap of the alloys, providing the greater tunability of band gap and strain status, eventually suppressing the non-radiative Auger recombinations. On the other hand, selective oxidation for AlGaAs is a vital technique for vertical surface emitting lasers. That enables precisely controlled oxides in the system, enabling the optical and electrical confinement, heat transfer, and mechanical robustness. We introduce the above functions into GaAs nanowires. GaAs/GaAsN core-shell nanowires showed clear redshift of the emitting wavelength toward infrared regime. Further, the introduction of N elongated the carrier lifetime at room temperature indicating the passivation of non-radiative surface recombinations. GaAs/GaAsBi nanowire shows the redshift with metamorphic surface morphology. Selective and whole oxidations of GaAs/AlGaAs core-shell nanowires produce semiconductor/oxide composite GaAs/AlGaOx and oxide GaOx/AlGaOx core-shell nanowires, respectively. Possibly sourced from nano-particle species, the oxide shell shows white luminescence. Those property should extend the functions of the nanowires for their application to photonics.

  10. Hydrogen-related effects in crystalline semiconductors

    International Nuclear Information System (INIS)

    Haller, E.E.

    1988-08-01

    Recent experimental and theoretical information regarding the states of hydrogen in crystalline semiconductors is reviewed. The abundance of results illustrates that hydrogen does not preferentially occupy a few specific lattice sites but that it binds to native defects and impurities, forming a large variety of neutral and electrically active complexes. The study of hydrogen passivated shallow acceptors and donors and of partially passivated multivalent acceptors has yielded information on the electronic and real space structure and on the chemical composition of these complexes. Infrared spectroscopy, ion channeling, hydrogen isotope substitution and electric field drift experiments have shown that both static trigonal complexes as well as centers with tunneling hydrogen exist. Total energy calculations indicate that the charge state of the hydrogen ion which leads to passivation dominates, i.e., H + in p-type and H/sup /minus// in n-type crystals. Recent theoretical calculations indicate that is unlikely for a large fraction of the atomic hydrogen to exist in its neutral state, a result which is consistent with the total absence of any Electron Paramagnetic Resonance (EPR) signal. An alternative explanation for this result is the formation of H 2 . Despite the numerous experimental and theoretical results on hydrogen-related effects in Ge and Si there remains a wealth of interesting physics to be explored, especially in compound and alloy semiconductors. 6 refs., 6 figs

  11. Polycrystalline thin films of antimony selenide via chemical bath deposition and post deposition treatments

    International Nuclear Information System (INIS)

    Rodriguez-Lazcano, Y.; Pena, Yolanda; Nair, M.T.S.; Nair, P.K.

    2005-01-01

    We report a method for obtaining thin films of polycrystalline antimony selenide via chemical bath deposition followed by heating the thin films at 573 K in selenium vapor. The thin films deposited from chemical baths containing one or more soluble complexes of antimony, and selenosulfate initially did not show X-ray diffraction (XRD) patterns corresponding to crystalline antimony selenide. Composition of the films, studied by energy dispersive X-ray analyses indicated selenium deficiency. Heating these films in presence of selenium vapor at 573 K under nitrogen (2000 mTorr) resulted in an enrichment of Se in the films. XRD peaks of such films matched Sb 2 Se 3 . Evaluation of band gap from optical spectra of such films shows absorption due to indirect transition occurring in the range of 1-1.2 eV. The films are photosensitive, with dark conductivity of about 2 x 10 -8 (Ω cm) -1 and photoconductivity, about 10 -6 (Ω cm) -1 under tungsten halogen lamp illumination with intensity of 700 W m -2 . An estimate for the mobility life time product for the film is 4 x 10 -9 cm 2 V -1

  12. Lattice misfit during ageing of a polycrystalline nickel-base superalloy

    International Nuclear Information System (INIS)

    Collins, D.M.; Yan, L.; Marquis, E.A.; Connor, L.D.; Ciardiello, J.J.; Evans, A.D.; Stone, H.J.

    2013-01-01

    The temporal evolution of the lattice parameters and lattice misfit of an advanced polycrystalline nickel-base superalloy have been studied in situ during an ageing heat treatment using synchrotron X-ray diffraction. During ageing, the γ and γ′ lattice parameters were both observed to decrease, a trend that cannot be attributed to a loss of coherency alone. Phase-extracted γ′ replicated this behaviour. Atom probe tomography was used to measure the compositional changes between the start and end of the ageing heat treatment. Using these data, a thermodynamic assessment was made using the software ThermoCalc of the structural change across the interface between γ and γ′. Subsequently, the unconstrained lattice parameters were estimated and were shown to be in good agreement with the X-ray diffraction measurements. Thus, the observed anomalous lattice misfit behaviour was concluded to be dominated by elemental exchange between the γ and γ′ phases during ageing

  13. A mesomechanical analysis of the deformation and fracture in polycrystalline materials with ceramic porous coatings

    Science.gov (United States)

    Balokhonov, R. R.; Zinoviev, A. V.; Romanova, V. A.; Batukhtina, E. E.

    2015-10-01

    The special features inherent in the mesoscale mechanical behavior of a porous ceramic coating-steel substrate composite are investigated. Microstructure of the coated material is accounted for explicitly as initial conditions of a plane strain dynamic boundary-value problem solved by the finite difference method. Using a mechanical analogy method, a procedure for generating a uniform curvilinear finite difference computational mesh is developed to provide a more accurate description of the complex grain boundary geometry. A modified algorithm for generation of polycrystalline microstructure of the substrate is designed on the basis of the cellular automata method. The constitutive equations for a steel matrix incorporate an elastic-plastic model for a material subjected to isotropic hardening. The Hall-Petch relation is used to account for the effect of the grain size on the yield stress and strain hardening history. A brittle fracture model for a ceramic coating relying on the Huber criterion is employed. The model allows for crack nucleation in the regions of triaxial tension. The complex inhomogeneous stress and plastic strain patterns are shown to be due to the presence of interfaces of three types: coating-substrate interface, grain boundaries, and pore surfaces.

  14. Near-infrared light absorption by polycrystalline SiSn alloys grown on insulating layers

    Energy Technology Data Exchange (ETDEWEB)

    Kurosawa, Masashi, E-mail: kurosawa@alice.xtal.nagoya-u.ac.jp [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); JSPS, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo 102-0083 (Japan); Kato, Motohiro; Yamaha, Takashi; Taoka, Noriyuki; Nakatsuka, Osamu [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Zaima, Shigeaki [Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2015-04-27

    High-Sn-content SiSn alloys are strongly desired for the next-generation near-infrared optoelectronics. A polycrystalline growth study has been conducted on amorphous SiSn layers with a Sn-content of 2%–30% deposited on either a substrate of SiO{sub 2} or SiN. Incorporating 30% Sn into Si permits the crystallization of the amorphous layers at annealing temperatures below the melting point of Sn (231.9 °C). Composition analyses indicate that approximately 20% of the Sn atoms are substituted into the Si lattice after solid-phase crystallization at 150–220 °C for 5 h. Correspondingly, the optical absorption edge is red-shifted from 1.12 eV (Si) to 0.83 eV (Si{sub 1−x}Sn{sub x} (x ≈ 0.18 ± 0.04)), and the difference between the indirect and direct band gap is significantly reduced from 3.1 eV (Si) to 0.22 eV (Si{sub 1−x}Sn{sub x} (x ≈ 0.18 ± 0.04)). These results suggest that with higher substitutional Sn content the SiSn alloys could become a direct band-gap material, which would provide benefits for Si photonics.

  15. Comparative investigation of smooth polycrystalline diamond films on dental burs by chemical vapor deposition

    Science.gov (United States)

    Sein, Htet; Ahmed, Waqar; Rego, Christopher; Jackson, Mark; Polini, Riccardo

    2006-04-01

    Depositions of hot filament chemical vapor-deposited diamond on cobalt-cemented tungsten carbide (WC-Co) rotary cutting dental burs are presented. Conventional dental tools made of sintered polycrystalline diamond have a number of problems associated with the heterogeneity of the crystallite, decreased cutting efficiency, and short life. A preferential (111) faceted diamond was obtained after 15 h of deposition at a growth rate of 1.1 µm/h. Diamond-coated WC-Co dental burs and conventional sintered burs are mainly used in turning, milling, and drilling operations for machining metal ceramic hard alloys such as CoCr, composite teeth, and aluminum alloy in the dental laboratory. The influence of structure, the mechanical characteristics of both diamond grains and hard alloys on the wear behavior, as well as the regimen of grinding on diamond wear are considered. Erosion wear properties are also investigated under air-sand erosion testing. After machining with excessive cutting performance, calculations can be made on flank and crater wear areas. Diamond-coated WC-Co dental burs offered significantly better erosion and wear resistance compared with uncoated WC-Co tools and sintered burs.

  16. Impact of graphene polycrystallinity on the performance of graphene field-effect transistors

    International Nuclear Information System (INIS)

    Jiménez, David; Chaves, Ferney; Cummings, Aron W.; Van Tuan, Dinh; Kotakoski, Jani; Roche, Stephan

    2014-01-01

    We have used a multi-scale physics-based model to predict how the grain size and different grain boundary morphologies of polycrystalline graphene will impact the performance metrics of graphene field-effect transistors. We show that polycrystallinity has a negative impact on the transconductance, which translates to a severe degradation of the maximum and cutoff frequencies. On the other hand, polycrystallinity has a positive impact on current saturation, and a negligible effect on the intrinsic gain. These results reveal the complex role played by graphene grain boundaries and can be used to guide the further development and optimization of graphene-based electronic devices

  17. Impact of graphene polycrystallinity on the performance of graphene field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Jiménez, David; Chaves, Ferney [Departament d' Enginyeria Electrònica, Escola d' Enginyeria, Universitat Autònoma de Barcelona, 08193-Bellaterra (Spain); Cummings, Aron W.; Van Tuan, Dinh [ICN2, Institut Català de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain); Kotakoski, Jani [Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Wien (Austria); Department of Physics, University of Helsinki, P.O. Box 43, 00014 University of Helsinki (Finland); Roche, Stephan [ICN2, Institut Català de Nanociencia i Nanotecnologia, Campus UAB, 08193 Bellaterra (Barcelona) (Spain); ICREA, Institució Catalana de Recerca i Estudis Avançats, 08070 Barcelona (Spain)

    2014-01-27

    We have used a multi-scale physics-based model to predict how the grain size and different grain boundary morphologies of polycrystalline graphene will impact the performance metrics of graphene field-effect transistors. We show that polycrystallinity has a negative impact on the transconductance, which translates to a severe degradation of the maximum and cutoff frequencies. On the other hand, polycrystallinity has a positive impact on current saturation, and a negligible effect on the intrinsic gain. These results reveal the complex role played by graphene grain boundaries and can be used to guide the further development and optimization of graphene-based electronic devices.

  18. Hydrogen-induced structural changes in polycrystalline silicon as revealed by positron lifetime spectroscopy

    International Nuclear Information System (INIS)

    Arole, V.M.; Takwale, M.G.; Bhide, V.G.

    1989-01-01

    Hydrogen passivation of polycrystalline silicon wafer is carried out in order to reduce the deleterious effects of grain boundaries. A systematic variation is made in the process parameters implemented during hydrogen passivation and the results of room temperature resistivity measurements are reported. As an efficient tool to study the structure change, positron lifetime spectroscopic measurements are performed on original and hydrogenated polycrystalline silicon wafers and a systematic correlation is sought between the changes that take place in the electrical and structural properties of polycrystalline silicon wafer, brought about by hydrogen passivation. (author)

  19. Exciton fission in monolayer transition metal dichalcogenide semiconductors.

    Science.gov (United States)

    Steinhoff, A; Florian, M; Rösner, M; Schönhoff, G; Wehling, T O; Jahnke, F

    2017-10-27

    When electron-hole pairs are excited in a semiconductor, it is a priori not clear if they form a plasma of unbound fermionic particles or a gas of composite bosons called excitons. Usually, the exciton phase is associated with low temperatures. In atomically thin transition metal dichalcogenide semiconductors, excitons are particularly important even at room temperature due to strong Coulomb interaction and a large exciton density of states. Using state-of-the-art many-body theory, we show that the thermodynamic fission-fusion balance of excitons and electron-hole plasma can be efficiently tuned via the dielectric environment as well as charge carrier doping. We propose the observation of these effects by studying exciton satellites in photoemission and tunneling spectroscopy, which present direct solid-state counterparts of high-energy collider experiments on the induced fission of composite particles.

  20. Engineering charge transport by heterostructuring solution-processed semiconductors

    Science.gov (United States)

    Voznyy, Oleksandr; Sutherland, Brandon R.; Ip, Alexander H.; Zhitomirsky, David; Sargent, Edward H.

    2017-06-01

    Solution-processed semiconductor devices are increasingly exploiting heterostructuring — an approach in which two or more materials with different energy landscapes are integrated into a composite system. Heterostructured materials offer an additional degree of freedom to control charge transport and recombination for more efficient optoelectronic devices. By exploiting energetic asymmetry, rationally engineered heterostructured materials can overcome weaknesses, augment strengths and introduce emergent physical phenomena that are otherwise inaccessible to single-material systems. These systems see benefit and application in two distinct branches of charge-carrier manipulation. First, they influence the balance between excitons and free charges to enhance electron extraction in solar cells and photodetectors. Second, they promote radiative recombination by spatially confining electrons and holes, which increases the quantum efficiency of light-emitting diodes. In this Review, we discuss advances in the design and composition of heterostructured materials, consider their implementation in semiconductor devices and examine unexplored paths for future advancement in the field.

  1. Multi-analytical study of historical semiconductor pigments

    International Nuclear Information System (INIS)

    Caporosso, V.

    2015-01-01

    This work is focused on the study of semiconductor-based pigments, which substituted traditional pigments in the second half of the 19. century. Synthetic semiconductor pigments may be chemically unstable due to the presence of many impurities unintentionally introduced during manufacturing. The aim of this work is to provide an insight on the application of X-ray Fluorescence (XRF) for the analysis of these painting materials, including both Cd- and Zn-based pigments. Three different approaches have been followed: the semi-quantitative analysis of samples with similar elemental composition, the complementary use of XRF and Raman spectroscopy for the analysis of elemental and molecular composition and the synchrotron-based XRF and XANES for the detection of impurities. The synergetic combination of different techniques provides information useful for the definition of specific markers for future analysis of paint-samples with implications for the conservation and treatment of late 19. and early 20. century paintings.

  2. Simulation of semiconductor devices

    International Nuclear Information System (INIS)

    Oriato, D.

    2001-09-01

    In this thesis a drift diffusion model coupled with self-consistent solutions of Poisson's and Schroedinger's equations, is developed and used to investigate the operation of Gunn diodes and GaN-based LEDs. The model also includes parameters derived from Monte Carlo calculations of the simulated devices. In this way the characteristics of a Monte Carlo approach and of a quantum solver are built into a fast and flexible drift-diffusion model that can be used for testing a large number of heterostructure designs in a time-effective way. The full model and its numerical implementation are described in chapter 2. In chapter 3 the theory of Gunn diodes is presented. A basic model of the dynamics of domain formation and domain transport is described with particular regard to accumulation and dipole domains. Several modes of operation of the Gunn device are described, varying from the resonance mode to the quenched mode. Details about transferred electron devices and negative differential resistance in semiconductor materials are given. In chapter 4 results from the simulation of a simple conventional gunn device confirm the importance of the doping condition at the cathode. Accumulation or dipole domains are achieved respectively with high and low doping densities. The limits of a conventional Gunn diode are explained and solved by introducing the heterostructure Gunn diode. This new design consists of a conventional GaAs transit region coupled with an electron launcher at the cathode, made using an AIGaAs heterostructure step. Simulations show the importance of the insertion of a thin highly-doped layer between the transit region and the electron launcher in order to improve device operation. Chapter 5 is an introduction to Ill-nitrides, in particular GaN and its alloy ln-GaN. We outline the discrepancy in the elastic and piezoelectric parameters found in the literature. Strain, dislocations and piezoelectricity are presented as the main features of a InGaN/GaN system

  3. Programmable and coherent crystallization of semiconductors

    KAUST Repository

    Yu, Liyang; Niazi, Muhammad Rizwan; Ngongang Ndjawa, Guy Olivier; Li, Ruipeng; Kirmani, Ahmad R.; Munir, Rahim; Balawi, Ahmed H.; Laquai, Fré dé ric; Amassian, Aram

    2017-01-01

    and incoherent nucleation events, limiting the ability to control or pattern the microstructure, texture, and functional properties of polycrystalline materials. We present a universal approach that can program the microstructure of materials through the coherent

  4. N-doping of organic semiconductors by bis-metallosandwich compounds

    Science.gov (United States)

    Barlow, Stephen; Qi, Yabing; Kahn, Antoine; Marder, Seth; Kim, Sang Bok; Mohapatra, Swagat K.; Guo, Song

    2016-01-05

    The various inventions disclosed, described, and/or claimed herein relate to the field of methods for n-doping organic semiconductors with certain bis-metallosandwich compounds, the doped compositions produced, and the uses of the doped compositions in organic electronic devices. Metals can be manganese, rhenium, iron, ruthenium, osmium, rhodium, or iridium. Stable and efficient doping can be achieved.

  5. High pressure semiconductor physics I

    CERN Document Server

    Willardson, R K; Paul, William; Suski, Tadeusz

    1998-01-01

    Since its inception in 1966, the series of numbered volumes known as Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. The "Willardson and Beer" Series, as it is widely known, has succeeded in publishing numerous landmark volumes and chapters. Not only did many of these volumes make an impact at the time of their publication, but they continue to be well-cited years after their original release. Recently, Professor Eicke R. Weber of the University of California at Berkeley joined as a co-editor of the series. Professor Weber, a well-known expert in the field of semiconductor materials, will further contribute to continuing the series' tradition of publishing timely, highly relevant, and long-impacting volumes. Some of the recent volumes, such as Hydrogen in Semiconductors, Imperfections in III/V Materials, Epitaxial Microstructures, High-Speed Heterostructure Devices, Oxygen in Silicon, and others promise indeed that this tra...

  6. Catalysts, Protection Layers, and Semiconductors

    DEFF Research Database (Denmark)

    Chorkendorff, Ib

    2015-01-01

    Hydrogen is the simplest solar fuel to produce and in this presentation we shall give a short overview of the pros and cons of various tandem devices [1]. The large band gap semiconductor needs to be in front, but apart from that we can chose to have either the anode in front or back using either...... acid or alkaline conditions. Since most relevant semiconductors are very prone to corrosion the advantage of using buried junctions and using protection layers offering shall be discussed [2-4]. Next we shall discuss the availability of various catalysts for being coupled to these protections layers...... and how their stability may be evaluated [5, 6]. Examples of half-cell reaction using protection layers for both cathode and anode will be discussed though some of recent examples under both alkaline and acidic conditions. Si is a very good low band gap semiconductor and by using TiO2 as a protection...

  7. High mobility emissive organic semiconductor

    Science.gov (United States)

    Liu, Jie; Zhang, Hantang; Dong, Huanli; Meng, Lingqiang; Jiang, Longfeng; Jiang, Lang; Wang, Ying; Yu, Junsheng; Sun, Yanming; Hu, Wenping; Heeger, Alan J.

    2015-01-01

    The integration of high charge carrier mobility and high luminescence in an organic semiconductor is challenging. However, there is need of such materials for organic light-emitting transistors and organic electrically pumped lasers. Here we show a novel organic semiconductor, 2,6-diphenylanthracene (DPA), which exhibits not only high emission with single crystal absolute florescence quantum yield of 41.2% but also high charge carrier mobility with single crystal mobility of 34 cm2 V−1 s−1. Organic light-emitting diodes (OLEDs) based on DPA give pure blue emission with brightness up to 6,627 cd m−2 and turn-on voltage of 2.8 V. 2,6-Diphenylanthracene OLED arrays are successfully driven by DPA field-effect transistor arrays, demonstrating that DPA is a high mobility emissive organic semiconductor with potential in organic optoelectronics. PMID:26620323

  8. Thiophene-Based Organic Semiconductors.

    Science.gov (United States)

    Turkoglu, Gulsen; Cinar, M Emin; Ozturk, Turan

    2017-10-24

    Thiophene-based π-conjugated organic small molecules and polymers are the research subject of significant current interest owing to their potential use as organic semiconductors in material chemistry. Despite simple and similar molecular structures, the hitherto reported properties of thiophene-based organic semiconductors are rather diverse. Design of high performance organic semiconducting materials requires a thorough understanding of inter- and intra-molecular interactions, solid-state packing, and the influence of both factors on the charge carrier transport. In this chapter, thiophene-based organic semiconductors, which are classified in terms of their chemical structures and their structure-property relationships, are addressed for the potential applications as organic photovoltaics (OPVs), organic field-effect transistors (OFETs) and organic light emitting diodes (OLEDs).

  9. Use of semiconductor detectors for radioactive waste account and control

    CERN Document Server

    Davydov, L N; Zakharchenko, A A

    2002-01-01

    The possibilities and development status of the contemporary semiconductor detectors and detecting devices intended for radiation monitoring at nuclear industry enterprises, including Chernobyl Shelter and depositories of nuclear wastes are shown. Such devices,created in the last years, can be successfully used for measurements of the gamma-radiation dose rate as well as for the isotope composition evaluation of nuclear materials and wastes, both during the work cycles and in emergency situations.

  10. Singlet exciton fission in polycrystalline pentacene: from photophysics toward devices.

    Science.gov (United States)

    Wilson, Mark W B; Rao, Akshay; Ehrler, Bruno; Friend, Richard H

    2013-06-18

    Singlet exciton fission is the process in conjugated organic molecules bywhich a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers first reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These investigations used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest has been recently rekindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating additional photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chemistry, and small-molecule device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycrystalline thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, we review the results of our recent transient absorption and device-based studies of polycrystalline pentacene. We address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins our conclusion that singlet fission in pentacene is extraordinarily rapid (∼80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, we discuss our demonstration that triplet excitons

  11. Thermal processing of polycrystalline NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Frick, Carl P.; Ortega, Alicia M.; Tyber, Jeffrey; Maksound, A.El.M.; Maier, Hans J.; Liu Yinong; Gall, Ken

    2005-01-01

    The objective of this study is to examine the effect of heat treatment on polycrystalline Ti-50.9 at.% Ni in hot-rolled and cold-drawn states. In particular, we examine microstructure, transformation temperatures as well as mechanical behavior in terms of both uniaxial monotonic testing and instrumented Vickers micro-indentation. The results constitute a fundamental understanding of the effect of heat treatment on thermal/stress-induced martensite and resistance to plastic flow in NiTi, all of which are critical for optimizing the mechanical properties. The high temperature of the hot-rolling process caused recrystallization, recovery, and hindered precipitate formation, essentially solutionizing the NiTi. The subsequent cold-drawing-induced a high density of dislocations and martensite. Heat treatments were carried out on hot-rolled, as well as, hot-rolled then cold-drawn materials at various temperatures for 1.5 h. Transmission Electron Microscopy observations revealed that Ti 3 Ni 4 precipitates progressively increased in size and changed their interface with the matrix from being coherent to incoherent with increasing heat treatment temperature. Accompanying the changes in precipitate size and interface coherency, transformation temperatures were observed to systematically shift, leading to the occurrence of the R-phase and multiple-stage transformations. Room temperature stress-strain tests illustrated a variety of mechanical responses for the various heat treatments, from pseudoelasticity to shape memory. The changes in stress-strain behavior are interpreted in terms of shifts in the primary martensite transformation temperatures, rather then the occurrence of the R-phase transformation. The results confirm that Ti 3 Ni 4 precipitates can be used to elicit a desired isothermal stress-strain behavior in polycrystalline NiTi. Instrumented micro-indention tests revealed that Martens (Universal) Hardness values are more dependent on the resistance to dislocation

  12. Organic semiconductors in sensor applications

    CERN Document Server

    Malliaras, George; Owens, Róisín

    2008-01-01

    Organic semiconductors offer unique characteristics such as tunability of electronic properties via chemical synthesis, compatibility with mechanically flexible substrates, low-cost manufacturing, and facile integration with chemical and biological functionalities. These characteristics have prompted the application of organic semiconductors and their devices in physical, chemical, and biological sensors. This book covers this rapidly emerging field by discussing both optical and electrical sensor concepts. Novel transducers based on organic light-emitting diodes and organic thin-film transistors, as well as systems-on-a-chip architectures are presented. Functionalization techniques to enhance specificity are outlined, and models for the sensor response are described.

  13. Semiconductors and semimetals epitaxial microstructures

    CERN Document Server

    Willardson, Robert K; Beer, Albert C; Gossard, Arthur C

    1994-01-01

    Newly developed semiconductor microstructures can now guide light and electrons resulting in important consequences for state-of-the-art electronic and photonic devices. This volume introduces a new generation of epitaxial microstructures. Special emphasis has been given to atomic control during growth and the interrelationship between the atomic arrangements and the properties of the structures.Key Features* Atomic-level control of semiconductor microstructures* Molecular beam epitaxy, metal-organic chemical vapor deposition* Quantum wells and quantum wires* Lasers, photon(IR)detectors, heterostructure transistors

  14. Introduction to semiconductor manufacturing technology

    CERN Document Server

    2012-01-01

    IC chip manufacturing processes, such as photolithography, etch, CVD, PVD, CMP, ion implantation, RTP, inspection, and metrology, are complex methods that draw upon many disciplines. [i]Introduction to Semiconductor Manufacturing Technologies, Second Edition[/i] thoroughly describes the complicated processes with minimal mathematics, chemistry, and physics; it covers advanced concepts while keeping the contents accessible to readers without advanced degrees. Designed as a textbook for college students, this book provides a realistic picture of the semiconductor industry and an in-depth discuss

  15. Wide gap semiconductor microwave devices

    International Nuclear Information System (INIS)

    Buniatyan, V V; Aroutiounian, V M

    2007-01-01

    A review of properties of wide gap semiconductor materials such as diamond, diamond-like carbon films, SiC, GaP, GaN and AlGaN/GaN that are relevant to electronic, optoelectronic and microwave applications is presented. We discuss the latest situation and perspectives based on experimental and theoretical results obtained for wide gap semiconductor devices. Parameters are taken from the literature and from some of our theoretical works. The correspondence between theoretical results and parameters of devices is critically analysed. (review article)

  16. Detection of radioactivity by semiconductors

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    The class of detectors discussed in this chapter has a responsive component involving a diode, a junction between two types of semiconductor materials. Although diode detectors are not particularly efficient in counting radioactive emissions, they are superior to other commercially available detectors in spectroscopy. Consequently, diode detectors are used extensively for quanlitative purposes and for quantitative purposes when mixtures of radionuclides are present, not the usual situation with biological or medical research. Topics addressed in this chapter are as follows: Band Theory; Semiconductors and Junctions; and Radiation Detectors. 6 refs., 14 figs

  17. Modeling of semiconductor optical amplifiers

    DEFF Research Database (Denmark)

    Mørk, Jesper; Bischoff, Svend; Berg, Tommy Winther

    We discuss the modelling of semiconductor optical amplifiers with emphasis on their high-speed properties. Applications in linear amplification as well as ultrafast optical signal processing are reviewed. Finally, the possible role of quantum-dot based optical amplifiers is discussed.......We discuss the modelling of semiconductor optical amplifiers with emphasis on their high-speed properties. Applications in linear amplification as well as ultrafast optical signal processing are reviewed. Finally, the possible role of quantum-dot based optical amplifiers is discussed....

  18. Semiconductor X-ray spectrometers

    International Nuclear Information System (INIS)

    Muggleton, A.H.F.

    1978-02-01

    An outline is given of recent developments in particle and photon induced x-ray fluorescence (XRF) analysis. Following a brief description of the basic mechanism of semiconductor detector operation a comparison is made between semiconductor detectors, scintillators and gas filled proportional devices. Detector fabrication and cryostat design are described in more detail and the effects of various device parameters on system performance, such as energy resolution, count rate capability, efficiency, microphony, etc. are discussed. The main applications of these detectors in x-ray fluorescence analysis, electron microprobe analysis, medical and pollution studies are reviewed

  19. Integrating magnetism into semiconductor electronics

    Energy Technology Data Exchange (ETDEWEB)

    Zakharchenya, Boris P; Korenev, Vladimir L [A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg (Russian Federation)

    2005-06-30

    The view of a ferromagnetic-semiconducting hybrid structure as a single tunable system is presented. Based on an analysis of existing experiments it is shown that, contrary to a 'common sense', a nonmagnetic semiconductor is capable of playing an important role in controlling ferromagnetism. Magnetic properties of a hybrid (the hysteresis loop and the spatial orientation of magnetization) can be tuned both optically and electrically by utilizing semiconductor-making the hybrid an electronic-write-in and electronic-read-out elementary storage unit. (methodological notes)

  20. Integrating magnetism into semiconductor electronics

    International Nuclear Information System (INIS)

    Zakharchenya, Boris P; Korenev, Vladimir L

    2005-01-01

    The view of a ferromagnetic-semiconducting hybrid structure as a single tunable system is presented. Based on an analysis of existing experiments it is shown that, contrary to a 'common sense', a nonmagnetic semiconductor is capable of playing an important role in controlling ferromagnetism. Magnetic properties of a hybrid (the hysteresis loop and the spatial orientation of magnetization) can be tuned both optically and electrically by utilizing semiconductor-making the hybrid an electronic-write-in and electronic-read-out elementary storage unit. (methodological notes)

  1. Semiconductor lasers and herterojunction leds

    CERN Document Server

    Kressel, Henry

    2012-01-01

    Semiconductor Lasers and Heterojunction LEDs presents an introduction to the subject of semiconductor lasers and heterojunction LEDs. The book reviews relevant basic solid-state and electromagnetic principles; the relevant concepts in solid state physics; and the p-n junctions and heterojunctions. The text also describes stimulated emission and gain; the relevant concepts in electromagnetic field theory; and the modes in laser structures. The relation between electrical and optical properties of laser diodes; epitaxial technology; binary III-V compounds; and diode fabrication are also consider

  2. Laser action on rare earth doped nitride semiconductor thin layers

    International Nuclear Information System (INIS)

    Oussif, A.; Diaf, M.

    2010-01-01

    Complete text of publication follows. The structure, chemical composition, properties, and their relationships in solids lay the foundation of materials science. Recently, great interest in rare-earth (RE)-doped wide-bandgap semiconductors, which combine the electronic properties of semiconductors with the unique luminescence features of RE ions, is from the fundamental standpoint of structure-composition-properties of solids. At first, a significant amount of work has been reported on the study of infrared emissions from Er 3+- doped semiconductors because Er 3+ exhibits luminescence at 1.54 μm, a wavelength used in optical communications. Since Steckl and Birkhahn first reported visible emission associated with Er from GaN:Er films, the RE-doped semiconductors have received considerable interest for possible application in light emitting devices. Molecular-beam epitaxy (MBE) and metalorganic chemical vapour deposition (MOCVD) have been used mainly to grow GaN host films. The RE dopants were typically incorporated into the host films by in situ doping during the growth or by ion implantation after the growth. GaN doped with rare-earth elements (RE) hold significant potential for applications in optical devices, since they show sharp intense luminescence which is only minimally affected by temperature variations. Among the various RE dopants, Eu seems to be the most interesting, since it yields red luminescence 622 nm which has not been realized in commercially available light emitting devices (LEDs) that use InGaN active layers. We have earlier reported single crystalline growth of Eu-doped GaN and nearly temperature independent red luminescence at 622 nm originating from the intra-4f-4f transition of the Eu 3+ ion. The red luminescence was analyzed and determined to be generated through trap-level-mediated energy transfer from the semiconductor host.

  3. Blending crystalline/liquid crystalline small molecule semiconductors: A strategy towards high performance organic thin film transistors

    Science.gov (United States)

    He, Chao; He, Yaowu; Li, Aiyuan; Zhang, Dongwei; Meng, Hong

    2016-10-01

    Solution processed small molecule polycrystalline thin films often suffer from the problems of inhomogeneity and discontinuity. Here, we describe a strategy to solve these problems through deposition of the active layer from a blended solution of crystalline (2-phenyl[1]benzothieno[3,2-b][1]benzothiophene, Ph-BTBT) and liquid crystalline (2-(4-dodecylphenyl) [1]benzothieno[3,2-b]benzothiophene, C12-Ph-BTBT) small molecule semiconductors with the hot spin-coating method. Organic thin film transistors with average hole mobility approaching 1 cm2/V s, much higher than that of single component devices, have been demonstrated, mainly due to the improved uniformity, continuity, crystallinity, and stronger intermolecular π-π stacking in blend thin films. Our results indicate that the crystalline/liquid crystalline semiconductor blend method is an effective way to enhance the performance of organic transistors.

  4. Synthesis and nonlinear optical property of polycrystalline MnTeMoO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Chengguo [Yibin University, Key Laboratory of Computational Physics of Sichuan Province, Yibin (China); Yibin University, School of Physics and Electronic Engineering, Yibin (China)

    2017-04-15

    Polycrystalline MnTeMoO{sub 6} powder has been synthesized by a new approach that MnO{sub 2} is used as the manganese source. The transformation mechanism of manganese ions in the new approach has been discussed. The nonlinear optical property of polycrystalline MnTeMoO{sub 6} has been investigated, and compared with single-crystalline samples. The transformation Mn{sup 4+} → Mn{sup 2+} may be formed directly without stable intermediates, and TeO{sub 2} may serve as catalyst. The SHG response of polycrystalline MnTeMoO{sub 6} powder is worse than that of single-crystalline powder in the same particle size distribution as its pseudo-size. The results indicate that it should pay special attention with the pseudo-size of polycrystalline powder when the potential nonlinear optical materials are screened by powder second harmonic generation measurements. (orig.)

  5. Investigation of the Anisotropic Thermoelectric Properties of Oriented Polycrystalline SnSe

    Directory of Open Access Journals (Sweden)

    Yulong Li

    2015-06-01

    Full Text Available Polycrystalline SnSe was synthesized by a melting-annealing-sintering process. X-ray diffraction reveals the sample possesses pure phase and strong orientation along [h00] direction. The degree of the orientations was estimated and the anisotropic thermoelectric properties are characterized. The polycrystalline sample shows a low electrical conductivity and a positive and large Seebeck coefficient. The low thermal conductivity is also observed in polycrystalline sample, but slightly higher than that of single crystal. The minimum value of thermal conductivity was measured as 0.3 W/m·K at 790 K. With the increase of the orientation factor, both electrical and thermal conductivities decrease, but the thermopowers are unchanged. As a consequence, the zT values remain unchanged in the polycrystalline samples despite the large variation in the degree of orientation.

  6. Solvent-free synthesis of nanosized hierarchical sodalite zeolite with a multi-hollow polycrystalline structure

    KAUST Repository

    Zeng, Shangjing; Wang, Runwei; Li, Ang; Huang, Weiwei; Zhang, Zongtao; Qiu, Shilun

    2016-01-01

    A solvent-free route is developed for preparing nanoscale sodalite zeolite with a multi-hollow structure. Furthermore, the synthesis of nanosized hollow sodalite polycrystalline aggregates with a mesoporous structure and high crystallinity

  7. The adhesion and tribology analysis of polycrystalline diamond coated on Si3N4 substrate

    International Nuclear Information System (INIS)

    Hamzah, E.; Purniawan, A.

    2007-01-01

    Cauliflower and octahedral structure of polycrystalline diamond was deposited on silicon nitride (Si 3 N 4 ) substrate by microwave plasma assisted chemical vapor deposition (MPACVD). In our earlier work, the effects of deposition parameters namely, % Methane (CH 4 ) diluted in hydrogen (H 2 ), microwave power and chamber pressure on surface morphology were studied. In the present work the polycrystalline diamond coating adhesion and tribology behaviour were investigated. Rockwell C hardness tester and pin-on-disk tribometer were used to determine the adhesion and tribology properties on diamond coating, respectively. The morphology of the diamond before and after indentation was observed using field emission scanning electron microscopy (FESEM). Based on the adhesion analysis results, it was found that octahedral morphology has better adhesion than cauliflower structure. It was indicated by few cracks and less peel-off than cauliflower structure of polycrystalline diamond after indentation. Based on tribology analysis, polycrystalline diamond coated on substrate has better tribology properties than uncoated substrate. (author)

  8. Synthesis and nonlinear optical property of polycrystalline MnTeMoO_6

    International Nuclear Information System (INIS)

    Jin, Chengguo

    2017-01-01

    Polycrystalline MnTeMoO_6 powder has been synthesized by a new approach that MnO_2 is used as the manganese source. The transformation mechanism of manganese ions in the new approach has been discussed. The nonlinear optical property of polycrystalline MnTeMoO_6 has been investigated, and compared with single-crystalline samples. The transformation Mn"4"+ → Mn"2"+ may be formed directly without stable intermediates, and TeO_2 may serve as catalyst. The SHG response of polycrystalline MnTeMoO_6 powder is worse than that of single-crystalline powder in the same particle size distribution as its pseudo-size. The results indicate that it should pay special attention with the pseudo-size of polycrystalline powder when the potential nonlinear optical materials are screened by powder second harmonic generation measurements. (orig.)

  9. Waveguide based external cavity semiconductor lasers

    NARCIS (Netherlands)

    Oldenbeuving, Ruud; Klein, E.J.; Offerhaus, Herman L.; Lee, Christopher James; Verhaegen, M.; Boller, Klaus J.

    2012-01-01

    We report on progress of the project waveguide based external cavity semiconductor laser (WECSL) arrays. Here we present the latest results on our efforts to mode lock an array of tunable, external cavity semiconductor lasers.

  10. Influence of phonons on semiconductor quantum emission

    Energy Technology Data Exchange (ETDEWEB)

    Feldtmann, Thomas

    2009-07-06

    A microscopic theory of interacting charge carriers, lattice vibrations, and light modes in semiconductor systems is presented. The theory is applied to study quantum dots and phonon-assisted luminescence in bulk semiconductors and heterostructures. (orig.)

  11. Semiconductor structure and recess formation etch technique

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Bin; Sun, Min; Palacios, Tomas Apostol

    2017-02-14

    A semiconductor structure has a first layer that includes a first semiconductor material and a second layer that includes a second semiconductor material. The first semiconductor material is selectively etchable over the second semiconductor material using a first etching process. The first layer is disposed over the second layer. A recess is disposed at least in the first layer. Also described is a method of forming a semiconductor structure that includes a recess. The method includes etching a region in a first layer using a first etching process. The first layer includes a first semiconductor material. The first etching process stops at a second layer beneath the first layer. The second layer includes a second semiconductor material.

  12. Fundamentals of semiconductors physics and materials properties

    CERN Document Server

    Yu, Peter Y

    2005-01-01

    Provides detailed explanations of the electronic, vibrational, transport, and optical properties of semiconductors. This textbook emphasizes understanding the physical properties of Si and similar tetrahedrally coordinated semiconductors and features an extensive collection of tables of material parameters, figures, and problems.

  13. Polycrystalline Mn-alloyed indium tin oxide films

    International Nuclear Information System (INIS)

    Scarlat, Camelia; Schmidt, Heidemarie; Xu, Qingyu; Vinnichenko, Mykola; Kolitsch, Andreas; Helm, Manfred; Iacomi, Felicia

    2008-01-01

    Magnetic ITO films are interesting for integrating ITO into magneto-optoelectronic devices. We investigated n-conducting indium tin oxide (ITO) films with different Mn doping concentration which have been grown by chemical vapour deposition using targets with the atomic ratio In:Sn:Mn=122:12:0,114:12:7, and 109:12:13. The average film roughness ranges between 30 and 50 nm and XRD patterns revealed a polycrystalline structure. Magnetotransport measurements revealed negative magnetoresistance for all the samples, but high field positive MR can be clearly observed at 5 K with increasing Mn doping concentration. Spectroscopic ellipsometry (SE) has been used to prove the existence of midgap states in the Mn-alloyed ITO films revealing a transmittance less than 80%. A reasonable model for the ca. 250 nm thick Mn-alloyed ITO films has been developed to extract optical constants from SE data below 3 eV. Depending on the Mn content, a Lorentz oscillator placed between 1 and 2 eV was used to model optical absorption below the band gap

  14. Correlation length estimation in a polycrystalline material model

    International Nuclear Information System (INIS)

    Simonovski, I.; Cizelj, L.

    2005-01-01

    This paper deals with the correlation length estimated from a mesoscopic model of a polycrystalline material. The correlation length can be used in some macroscopic material models as a material parameter that describes the internal length. It can be estimated directly from the strain and stress fields calculated from a finite-element model, which explicitly accounts for the selected mesoscopic features such as the random orientation, shape and size of the grains. A crystal plasticity material model was applied in the finite-element analysis. Different correlation lengths were obtained depending on the used set of crystallographic orientations. We determined that the different sets of crystallographic orientations affect the general level of the correlation length, however, as the external load is increased the behaviour of correlation length is similar in all the analyzed cases. The correlation lengths also changed with the macroscopic load. If the load is below the yield strength the correlation lengths are constant, and are slightly higher than the average grain size. The correlation length can therefore be considered as an indicator of first plastic deformations in the material. Increasing the load above the yield strength creates shear bands that temporarily increase the values of the correlation lengths calculated from the strain fields. With a further load increase the correlation lengths decrease slightly but stay above the average grain size. (author)

  15. Estimating minimum polycrystalline aggregate size for macroscopic material homogeneity

    International Nuclear Information System (INIS)

    Kovac, M.; Simonovski, I.; Cizelj, L.

    2002-01-01

    During severe accidents the pressure boundary of reactor coolant system can be subjected to extreme loadings, which might cause failure. Reliable estimation of the extreme deformations can be crucial to determine the consequences of severe accidents. Important drawback of classical continuum mechanics is idealization of inhomogenous microstructure of materials. Classical continuum mechanics therefore cannot predict accurately the differences between measured responses of specimens, which are different in size but geometrical similar (size effect). A numerical approach, which models elastic-plastic behavior on mesoscopic level, is proposed to estimate minimum size of polycrystalline aggregate above which it can be considered macroscopically homogeneous. The main idea is to divide continuum into a set of sub-continua. Analysis of macroscopic element is divided into modeling the random grain structure (using Voronoi tessellation and random orientation of crystal lattice) and calculation of strain/stress field. Finite element method is used to obtain numerical solutions of strain and stress fields. The analysis is limited to 2D models.(author)

  16. The interpretation of polycrystalline coherent inelastic neutron scattering from aluminium

    Science.gov (United States)

    Roach, Daniel L.; Ross, D. Keith; Gale, Julian D.; Taylor, Jon W.

    2013-01-01

    A new approach to the interpretation and analysis of coherent inelastic neutron scattering from polycrystals (poly-CINS) is presented. This article describes a simulation of the one-phonon coherent inelastic scattering from a lattice model of an arbitrary crystal system. The one-phonon component is characterized by sharp features, determined, for example, by boundaries of the (Q, ω) regions where one-phonon scattering is allowed. These features may be identified with the same features apparent in the measured total coherent inelastic cross section, the other components of which (multiphonon or multiple scattering) show no sharp features. The parameters of the model can then be relaxed to improve the fit between model and experiment. This method is of particular interest where no single crystals are available. To test the approach, the poly-CINS has been measured for polycrystalline aluminium using the MARI spectrometer (ISIS), because both lattice dynamical models and measured dispersion curves are available for this material. The models used include a simple Lennard-Jones model fitted to the elastic constants of this material plus a number of embedded atom method force fields. The agreement obtained suggests that the method demonstrated should be effective in developing models for other materials where single-crystal dispersion curves are not available. PMID:24282332

  17. Monokinetic electron backsttering from amorphous or polycrystalline specimens

    International Nuclear Information System (INIS)

    Ahmed, H.E.D.H.

    1983-06-01

    We have considered the interaction of electrons with thin amorphous specimens: one part of these electrons is transmitted through the substance, the other being backscattered. This last phenomena, which is not perfectly understood, has been studied in the energy range from 0.3 to 3 MeV. First this work deals with the realization of a fully automatic apparatus which has been adapted to the column of the 3 MeV electron microscope of the HVFM laboratory in Toulouse. The variation of the transmission and backscattering coefficients, for amorphous and polycrystalline specimens, is determined. From this coefficient the electron range in this substance can be deduced. In addition the experimental results can be used to understand the image contrast in scanning electron microscopy. A short presentation of the cross-section, introduces the theoretical study of Monte-Carlo calculation. The Monte-Carlo calculation is used to take into account all elementary processus, which take place during electron scattering [fr

  18. Platinum-induced structural collapse in layered oxide polycrystalline films

    International Nuclear Information System (INIS)

    Wang, Jianlin; Liu, Changhui; Huang, Haoliang; Fu, Zhengping; Peng, Ranran; Zhai, Xiaofang; Lu, Yalin

    2015-01-01

    Effect of a platinum bottom electrode on the SrBi 5 Fe 1−x Co x Ti 4 O 18 layered oxide polycrystalline films was systematically studied. The doped cobalt ions react with the platinum to form a secondary phase of PtCoO 2 , which has a typical Delafossite structure with a weak antiferromagnetism and an exceptionally high in-plane electrical conductivity. Formation of PtCoO 2 at the interface partially consumes the cobalt dopant and leads to the structural collapsing from 5 to 4 layers, which was confirmed by X-ray diffraction and high resolution transmission electron microscopy measurements. Considering the weak magnetic contribution from PtCoO 2 , the observed ferromagnetism should be intrinsic of the Aurivillius compounds. Ferroelectric properties were also indicated by the piezoresponse force microscopy. In this work, the platinum induced secondary phase at the interface was observed, which has a strong impact on Aurivillius structural configuration and thus the ferromagnetic and ferroelectric properties

  19. Rare Earth Doped Lanthanum Calcium Borate Polycrystalline Red Phosphors

    Directory of Open Access Journals (Sweden)

    H. H. Xiong

    2014-01-01

    Full Text Available Single-phased Sm3+ doped lanthanum calcium borate (SmxLa2−xCaB10O19, SLCB, x=0.06 polycrystalline red phosphor was prepared by solid-state reaction method. The phosphor has two main excitation peaks located at 398.5 nm and 469.0 nm, which are nicely in accordance with the emitting wavelengths of commercial near-UV and blue light emitting diode chips. Under the excitation of 398.0 nm, the dominant red emission of Sm3+ in SLCB phosphor is centered at 598.0 nm corresponding to the transition of 4G5/2 → 6H7/2. The Eu3+ fluorescence in the red spectral region is applied as a spectroscopic probe to reveal the local site symmetry in the host lattice and, hence, Judd-Ofelt parameters Ωt  (t=2, 4 of Eu3+ in the phosphor matrix are derived to be 3.62×10-20 and 1.97×10-20 cm2, indicating a high asymmetrical and strong covalent environment around rare earth luminescence centers. Herein, the red phosphors are promising good candidates employed in white light emitting diodes (LEDs illumination.

  20. CVD-graphene growth on different polycrystalline transition metals

    Directory of Open Access Journals (Sweden)

    M. P. Lavin-Lopez

    2017-01-01

    Full Text Available The chemical vapor deposition (CVD graphene growth on two polycrystalline transition metals (Ni and Cu was investigated in detail using Raman spectroscopy and optical microscopy as a way to synthesize graphene of the highest quality (i.e. uniform growth of monolayer graphene, which is considered a key issue for electronic devices. Key CVD process parameters (reaction temperature, CH4/H2flow rate ratio, total flow of gases (CH4+H2, reaction time were optimized for both metals in order to obtain the highest graphene uniformity and quality. The conclusions previously reported in literature about the performance of low and high carbon solubility metals in the synthesis of graphene and their associated reaction mechanisms, i.e. surface depositionand precipitation on cooling, respectively, was not corroborated by the results obtained in this work. Under the optimal reaction conditions, a large percentage of monolayer graphene was obtained over the Ni foil since the carbon saturation was not complete, allowing carbon atoms to be stored in the bulk metal, which could diffuse forming high quality monolayer graphene at the surface. However, under the optimal reaction conditions, the formation of a non-uniform mixture of few layers and multilayer graphene on the Cu foil was related to the presence of an excess of active carbon atoms on the Cu surface.

  1. Plastic strain caused by contraction of pores in polycrystalline graphites

    International Nuclear Information System (INIS)

    Ioka, Ikuo; Yoda, Shinichi; Konishi, Takashi.

    1989-01-01

    The effects of porosity on mechanical properties and deformation behavior of four isotropic polycrystalline graphites were studied. The pore size distributions of the graphites were measured using a conventional mercury penetration technique. The average pore radius of ISO-88 graphite was about one-tenth of that of ISEM-1, IG-11 or IG-15 graphites. Young's modulus of the graphites decreased with increasing porosity. The stress-strain curve of each graphite was measured in its lateral and axial directions. Young's modulus of graphite decreased with increasing load. The plastic strain at a given compressive load was calculated from the stress-strain curve and the initial gradient of the unloading curve at the load. The ratio of lateral plastic strain to axial plastic strain for the graphites was less than 0.5, indicating that the volume of the graphites decreased during compressive loading. By assuming that the volume change was caused by contraction of pores, plastic strain associated with contraction of pores was calculated from the axial plastic strain and lateral plastic strain by slips along the basal planes. The plastic strain increased with increasing axial plastic strain and porosity of graphite. (author)

  2. Polycrystalline-Diamond MEMS Biosensors Including Neural Microelectrode-Arrays

    Directory of Open Access Journals (Sweden)

    Donna H. Wang

    2011-08-01

    Full Text Available Diamond is a material of interest due to its unique combination of properties, including its chemical inertness and biocompatibility. Polycrystalline diamond (poly-C has been used in experimental biosensors that utilize electrochemical methods and antigen-antibody binding for the detection of biological molecules. Boron-doped poly-C electrodes have been found to be very advantageous for electrochemical applications due to their large potential window, low background current and noise, and low detection limits (as low as 500 fM. The biocompatibility of poly-C is found to be comparable, or superior to, other materials commonly used for implants, such as titanium and 316 stainless steel. We have developed a diamond-based, neural microelectrode-array (MEA, due to the desirability of poly-C as a biosensor. These diamond probes have been used for in vivo electrical recording and in vitro electrochemical detection. Poly-C electrodes have been used for electrical recording of neural activity. In vitro studies indicate that the diamond probe can detect norepinephrine at a 5 nM level. We propose a combination of diamond micro-machining and surface functionalization for manufacturing diamond pathogen-microsensors.

  3. Correlation between some mechanical and physical properties of polycrystalline graphites

    International Nuclear Information System (INIS)

    Yoda, Shinichi; Fujisaki, Katsuo

    1982-01-01

    Mechanical and physical properties of polycrystalline graphites, tensile strength, compressive strength, flexural strength, Young's modulus, thermal expansion coefficient, electrical resistivity, volume fraction of porosity, and graphitisation were measured for ten brand graphites. Correlation between the mechanical and physical properties of the graphites were studied. Young's modulus and thermal expansion coefficient of the graphites depend on volume fraction of porosity. The Young's modulus of the graphites tended to increase with increasing the thermal expansion coefficient. For an anisotropic graphite, an interesting relationship between the Young's modulus E and the thermal expansion coefficient al pha was found in any specimen orientations; alpha E=constant. The value of alphah E was dependent upon the volume fraction of porosity. It should be noted here that the electrical resistivity increased with decreasing grain size. The flexural and the compressive strength were related with the volume fraction of porosity while the tensile strength was not, The relationships between the tensile, the compressive and the flexural strength can be approximately expressed as linear functions over a wide range of the stresses. (author)

  4. Helium-induced hardening effect in polycrystalline tungsten

    Science.gov (United States)

    Kong, Fanhang; Qu, Miao; Yan, Sha; Zhang, Ailin; Peng, Shixiang; Xue, Jianming; Wang, Yugang

    2017-09-01

    In this paper, helium induced hardening effect of tungsten was investigated. 50 keV He2+ ions at fluences vary from 5 × 1015 cm-2 to 5 × 1017 cm-2 were implanted into polycrystalline tungsten at RT to create helium bubble-rich layers near the surface. The microstructure and mechanical properties of the irradiated specimens were studied by TEM and nano-indentor. Helium bubble rich layers are formed in near surface region, and the layers become thicker with the rise of fluences. Helium bubbles in the area of helium concentration peak are found to grow up, while the bubble density is almost unchanged. Obvious hardening effect is induced by helium implantation in tungsten. Micro hardness increases rapidly with the fluence firstly, and more slowly when the fluence is above 5 × 1016 cm-2. The hardening effect of tungsten can be attributed to helium bubbles, which is found to be in agreement with the Bacon-Orowan stress formula. The growing diameter is the major factor rather than helium bubbles density (voids distance) in the process of helium implantation at fluences below 5 × 1017 cm-2.

  5. Influence of wavelength on transient short-circuit current in polycrystalline silicon solar cells

    International Nuclear Information System (INIS)

    Ba, B.; Kane, M.

    1993-10-01

    The influence of the wavelength of a monochromatic illumination on transient short-circuit current in an n/p polycrystalline silicon part solar cell junction is investigated. A wavelength dependence in the initial part of the current decay is observed in the case of cells with moderate grain boundary effects. This influence is attenuated in polycrystalline cells with strong grain boundary activity. (author). 10 refs, 6 figs

  6. In vitro study of color stability of polycrystalline and monocrystalline ceramic brackets

    OpenAIRE

    de Oliveira, Cibele Braga; Maia, Luiz Guilherme Martins; Santos-Pinto, Ary; Gandini J?nior, Luiz Gonzaga

    2014-01-01

    OBJECTIVE: The aim of this in vitro study was to analyze color stability of monocrystalline and polycrystalline ceramic brackets after immersion in dye solutions. METHODS: Seven ceramic brackets of four commercial brands were tested: Two monocrystalline and two polycrystalline. The brackets were immersed in four dye solutions (coffee, red wine, Coke and black tea) and in artificial saliva for the following times: 24 hours, 7, 14 and 21 days, respectively. Color changes were measured by a...

  7. Nanopores creation in boron and nitrogen doped polycrystalline graphene: A molecular dynamics study

    Science.gov (United States)

    Izadifar, Mohammadreza; Abadi, Rouzbeh; Nezhad Shirazi, Ali Hossein; Alajlan, Naif; Rabczuk, Timon

    2018-05-01

    In the present paper, molecular dynamic simulations have been conducted to investigate the nanopores creation on 10% of boron and nitrogen doped polycrystalline graphene by silicon and diamond nanoclusters. Two types of nanoclusters based on silicon and diamond are used to investigate their effect for the fabrication of nanopores. Therefore, three different diameter sizes of the clusters with five kinetic energies of 10, 50, 100, 300 and 500 eV/atom at four different locations in boron or nitrogen doped polycrystalline graphene nanosheets have been perused. We also study the effect of 3% and 6% of boron doped polycrystalline graphene with the best outcome from 10% of doping. Our results reveal that the diamond cluster with diameter of 2 and 2.5 nm fabricates the largest nanopore areas on boron and nitrogen doped polycrystalline graphene, respectively. Furthermore, the kinetic energies of 10 and 50 eV/atom can not fabricate nanopores in some cases for silicon and diamond clusters on boron doped polycrystalline graphene nanosheets. On the other hand, silicon and diamond clusters fabricate nanopores for all locations and all tested energies on nitrogen doped polycrystalline graphene. The area sizes of nanopores fabricated by silicon and diamond clusters with diameter of 2 and 2.5 nm are close to the actual area size of the related clusters for the kinetic energy of 300 eV/atom in all locations on boron doped polycrystalline graphene. The maximum area and the average maximum area of nanopores are fabricated by the kinetic energy of 500 eV/atom inside the grain boundary at the center of the nanosheet and in the corner of nanosheet with diameters of 2 and 3 nm for silicon and diamond clusters on boron and nitrogen doped polycrystalline graphene.

  8. Structural, optical, and magnetic properties of polycrystalline Co-doped TiO{sub 2} synthesized by solid-state method

    Energy Technology Data Exchange (ETDEWEB)

    Bouaine, Abdelhamid, E-mail: abdelhamidfethi@yahoo.fr [Laboratoire d' Etude des Materiaux (LEM), Departement de Physique, Faculte des Sciences Exactes et des Sciences de la Nature et de la vie, Universite de Jijel, cite Oued-Aissa, B.P 98, Jijel 18000 (Algeria); Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), UMR 7504 CNRS - UdS, 23 rue du Loess, B.P. 43, 67034 Strasbourg Cedex 2 (France); Schmerber, G.; Ihiawakrim, D.; Derory, A. [Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS), UMR 7504 CNRS - UdS, 23 rue du Loess, B.P. 43, 67034 Strasbourg Cedex 2 (France)

    2012-11-01

    Highlights: Black-Right-Pointing-Pointer Influence of Co doping on the TiO{sub 2} tetragonal structure. Black-Right-Pointing-Pointer Decrease of the energy band gap after doping with Co atoms. Black-Right-Pointing-Pointer Appearance of ferromagnetism in Co-doped TiO{sub 2} diluted magnetic semiconductors. - Abstract: We have used a solid-state method to synthesize polycrystalline Co-doped TiO{sub 2} diluted magnetic semiconductors (DMSs) with Co concentrations of 0, and 0.5 at.%. X-ray diffraction patterns reveal that Co doped TiO{sub 2} crystallizes in the rutile tetragonal structure with no additional peaks. Transmission electron microscopy (TEM) did not indicate the presence of magnetic parasitic phases and confirmed that Co ions are uniformly distributed inside the samples. Optical absorbance measurements showed an energy band gap which decreases after doping with the Co atoms into the TiO{sub 2} matrix. Magnetization measurements revealed a paramagnetic behavior for the as-prepared Co-doped TiO{sub 2} and a ferromagnetic behavior for the same samples after annealed under a mixture of H{sub 2}/N{sub 2} atmosphere.

  9. Nuclear radiation detection by a variband semiconductor

    International Nuclear Information System (INIS)

    Volkov, A.S.

    1981-01-01

    Possibilities of using a variband semiconductor for detecting nuclear radiations are considered. It is shown that the variaband quasielectric field effectively collects charges induced by a nuclear particle only at a small mean free path in the semiconductor (up to 100 μm), the luminescence spectrum of the variband semiconductor when a nuclear particle gets into it, in principle, permits to determine both the energy and mean free path in the semiconductor (even at large mean free paths) [ru

  10. Ultrafast THz Saturable Absorption in Doped Semiconductors

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Hoffmann, Matthias C.

    2011-01-01

    We demonstrate ultrafast THz saturable absorption in n-doped semiconductors by nonlinear THz time-domain spectroscopy. This effect is caused by the semiconductor conductivity modulation due to electron heating and satellite-valley scattering in strong THz fields.......We demonstrate ultrafast THz saturable absorption in n-doped semiconductors by nonlinear THz time-domain spectroscopy. This effect is caused by the semiconductor conductivity modulation due to electron heating and satellite-valley scattering in strong THz fields....

  11. Laser semiconductor diode integrated with frequency doubler

    International Nuclear Information System (INIS)

    Tighineanu, I.; Dorogan, V.; Suruceanu, G.

    2003-01-01

    The invention relates to the technology of optoelectronic semiconductor devices and may be used in the production of laser semiconductor diodes integrated with optical nonlinear elements. The laser semiconductor diode integrated with frequency doubler includes a semiconductor substrate, a laser structure with waveguide. metal contacts in the waveguide of the laser structure it is formed a nanostructured field so that the nanostructure provides for the fulfillment of the phase synchronism conditions

  12. Diode having trenches in a semiconductor region

    Energy Technology Data Exchange (ETDEWEB)

    Palacios, Tomas Apostol; Lu, Bin; Matioli, Elison de Nazareth

    2016-03-22

    An electrode structure is described in which conductive regions are recessed into a semiconductor region. Trenches may be formed in a semiconductor region, such that conductive regions can be formed in the trenches. The electrode structure may be used in semiconductor devices such as field effect transistors or diodes. Nitride-based power semiconductor devices are described including such an electrode structure, which can reduce leakage current and otherwise improve performance.

  13. The electronic properties of semiconductor quantum dots

    International Nuclear Information System (INIS)

    Barker, J.A.

    2000-10-01

    This work is an investigation into the electronic behaviour of semiconductor quantum dots, particularly self-assembled quantum dot arrays. Processor-efficient models are developed to describe the electronic structure of dots, deriving analytic formulae for the strain tensor, piezoelectric distribution and diffusion- induced evolution of the confinement potential, for dots of arbitrary initial shape and composition profile. These models are then applied to experimental data. Transitions due to individual quantum dots have a narrow linewidth as a result of their discrete density of states. By contrast, quantum dot arrays exhibit inhomogeneous broadening which is generally attributed to size variations between the individual dots in the ensemble. Interpreting the results of double resonance spectroscopy, it is seen that variation in the indium composition of the nominally InAs dots is also present. This result also explains the otherwise confusing relationship between the spread in the ground-state and excited-state transition energies. Careful analysis shows that, in addition to the variations in size and composition, some other as yet unidentified broadening mechanism must also be present. The influence of rapid thermal annealing on dot electronic structure is also considered, finding that the experimentally observed blue-shift and narrowing of the photoluminescence linewidth may both be explained in terms of normal In/Ga interdiffusion. InAs/GaAs self-assembled quantum dots are commonly assumed to have a pyramidal geometry, so that we would expect the energy separation of the ground-state electron and hole levels in the dot to be largest at a positive applied field. This should also be the case for any dot of uniform composition whose shape tapers inwards from base to top, counter to the results of experimental Stark-shift spectroscopy which show a peak transition energy at a negative applied field. It is demonstrated that this inversion of the ground state

  14. Three-dimensional minority carrier lifetime mapping of thin film semiconductors for solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Hardin, Brian [PLANT PV, Inc., Belmont, CA (United States); Peters, Craig [PLANT PV, Inc., Belmont, CA (United States); Barnard, Edward [PLANT PV, Inc., Belmont, CA (United States)

    2015-09-30

    This project addresses the difficulty of accurately measuring charge carrier dynamics in novel semiconductor materials for thin film photovoltaic cells. We have developed a two- photon lifetime tomography technique to separate bulk minority carrier lifetime from surface recombination effects and effects of recombination at sub-surface defects. This technique also enables us to characterize how local defects such as grain boundaries– buried below the surface of a sample–affect carrier lifetimes in the active layer, dynamics that have been previously inaccessible. We have applied this newly developed technique to illuminate how CdCl2 treatment improves CdTe PV efficiency. From striking 3D lifetime tomography maps, a clear, sub- surface understanding emerges of the photophysical changes that occur in CdTe active medium following exposure to CdCl2, a standard step in the fabrication of high-efficiency CdTe-based solar cells. This work demonstrates a well-defined method to quantify grain-boundary, interface, and bulk recombination in CdTe and other optically-active polycrystalline semiconductor materials; information that can provide critical information to the development of next- generation photovoltaics and many other semiconductor technologies.

  15. Automation and Integration in Semiconductor Manufacturing

    OpenAIRE

    Liao, Da-Yin

    2010-01-01

    Semiconductor automation originates from the prevention and avoidance of frauds in daily fab operations. As semiconductor technology and business continuously advance and grow, manufacturing systems must aggressively evolve to meet the changing technical and business requirements in this industry. Semiconductor manufacturing has been suffering pains from islands of automation. The problems associated with these systems are limited

  16. Coherent photoluminescence excitation spectroscopy of semicrystalline polymeric semiconductors

    Science.gov (United States)

    Silva, Carlos; Grégoire, Pascal; Thouin, Félix

    In polymeric semiconductors, the competition between through-bond (intrachain) and through-space (interchain) electronic coupling determines two-dimensional spatial coherence of excitons. The balance of intra- and interchain excitonic coupling depends very sensitively on solid-state microstructure of the polymer film (polycrystalline, semicrystalline with amorphous domains, etc.). Regioregular poly(3-hexylthiophene) has emerged as a model material because its photoluminescence (PL) spectral lineshape reveals intricate information on the magnitude of excitonic coupling, the extent of energetic disorder, and on the extent to which the disordered energy landscape is correlated. I discuss implementation of coherent two-dimensional electronic spectroscopy. We identify cross peaks between 0-0 and 0-1 excitation peaks, and we measure their time evolution, which we interpret within the context of a hybrid HJ aggregate model. By measurement of the homogeneous linewidth in diverse polymer microstructures, we address the nature of optical transitions within such hynbrid aggregate model. These depend strongly on sample processing, and I discuss the relationship between microstructure, steady-state absorption and PL spectral lineshape, and 2D coherent PL excitation spectral lineshapes.

  17. III–V semiconductors

    CERN Document Server

    Freyhardt, H C

    1980-01-01

    Springer-Verlag, Berlin Heidelberg, in conjunction with Springer-Verlag New York, is pleased to announce a new series: CRYSTALS Growth, Properties, and Applications The series presents critical reviews of recent developments in the field of crystal growth, properties, and applications. A substantial portion of the new series will be devoted to the theory, mechanisms, and techniques of crystal growth. Occasionally, clear, concise, complete, and tested instructions for growing crystals will be published, particularly in the case of methods and procedures that promise to have general applicability. Responding to the ever-increasing need for crystal substances in research and industry, appropriate space will be devoted to methods of crystal characterization and analysis in the broadest sense, even though reproducible results may be expected only when structures, microstructures, and composition are really known. Relations among procedures, properties, and the morphology of crystals will also be treated with refer...

  18. Semiconductor nanostructures for infrared applications

    NARCIS (Netherlands)

    Zurauskiene, N.; Asmontas, S.; Dargys, A.; Kundrotas, J.; Janssen, G.; Goovaerts, E.; Marcinkevicius, S.; Koenraad, P.M.; Wolter, J.H.; Leon, R.

    2004-01-01

    We present the results of time-resolved photoluminescence (TRPL) and optically detected microwave resonance (ODMR) spectroscopy investigations of semiconductor quantum dots and quantum wells. The ODMR spectra of InAs/GaAs QDs were detected via modulation of the total intensity of the QDs emission

  19. A Brief History of ... Semiconductors

    Science.gov (United States)

    Jenkins, Tudor

    2005-01-01

    The development of studies in semiconductor materials is traced from its beginnings with Michael Faraday in 1833 to the production of the first silicon transistor in 1954, which heralded the age of silicon electronics and microelectronics. Prior to the advent of band theory, work was patchy and driven by needs of technology. However, the arrival…

  20. Semiconductor radiation detectors: device physics

    National Research Council Canada - National Science Library

    Lutz, Gerhard

    1999-01-01

    ..., including nuclear physics, elementary particle physics, optical and x-ray astronomy, medicine, and materials testing - and the number of applications is growing continually. Closely related, and initiated by the application of semiconductors, is the development of low-noise low-power integrated electronics for signal readout. The success of semicond...

  1. Towards filament free semiconductor lasers

    DEFF Research Database (Denmark)

    McInerney, John; O'Brien, Peter; Skovgaard, Peter M. W.

    2000-01-01

    We outline physical models and simulations for suppression of self-focusing and filamentation in large aperture semiconductor lasers. The principal technical objective is to generate multi-watt CW or quasi-CW outputs with nearly diffraction limited beams, suitable for long distance free space...... propagation structures in lasers and amplifiers which suppress lateral reflections....

  2. Ultrafast Spectroscopy of Semiconductor Devices

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, Wolfgang; Hvam, Jørn Marcher

    1999-01-01

    In this work we present an experimental technique for investigating ultrafast carrier dynamics in semiconductor optical amplifiers at room temperature. These dynamics, influenced by carrier heating, spectral hole-burning and two-photon absorption, are very important for device applications in inf...

  3. Radiation damage in semiconductor detectors

    International Nuclear Information System (INIS)

    Kraner, H.W.

    1981-12-01

    A survey is presented of the important damage-producing interactions in semiconductor detectors and estimates of defect numbers are made for MeV protons, neutrons and electrons. Damage effects of fast neutrons in germanium gamma ray spectrometers are given in some detail. General effects in silicon detectors are discussed and damage constants and their relationship to leakage current is introduced

  4. Transient photoconductivity in amorphous semiconductors

    International Nuclear Information System (INIS)

    Mpawenayo, P.

    1997-07-01

    Localized states in amorphous semiconductors are divided in disorder induced shallow trap levels and dangling bonds deep states. Dangling bonds are assumed here to be either neutral or charged and their energy distribution is a single gaussian. Here, it is shown analytically that transient photocurrent in amorphous semiconductors is fully controlled by charge carriers transitions between localized states for one part and tunneling hopping carriers on the other. Localized dangling bonds deep states act as non radiative recombination centres, while hopping tunnelling is assisted by the Coulomb interaction between defects sites. The half-width of defects distribution is the disorder parameter that determines the carrier hopping time between defects sites. The macroscopic time that explains the long decay response times observed will all types of amorphous semiconductors is duly thought to be temperature dependent. Basic equations developed by Longeaud and Kleider are solved for the general case of a semiconductor after photo-generation. It turns out that the transient photoconductivity decay has two components; one with short response times from carriers trap-release transitions between shallow levels and extended states and a hopping component made of inter-dependent exponentials whose time constants span in larger ranges depending on disorder. The photoconductivity hopping component appears as an additional term to be added to photocurrents derived from existing models. The results of the present study explain and complete the power law decay derived in the multiple trapping models developed 20 years ago only in the approximation of the short response time regime. The long response time regime is described by the hopping macroscopic time. The present model is verified for all samples of amorphous semiconductors known so far. Finally, it is proposed to improved the modulated photoconductivity calculation techniques by including the long-lasting hopping dark documents

  5. Highly stable copper oxide composite as an effective photocathode for water splitting via a facile electrochemical synthesis strategy

    KAUST Repository

    Zhang, Zhonghai; Wang, Peng

    2012-01-01

    focused on n-type metal oxide semiconductors as photoanodes, whereas studies of p-type metal oxide semiconductors as photocathodes where hydrogen is generated are scarce. In this paper, highly efficient and stable copper oxide composite photocathode

  6. Characterization and application of halloysite nanotubes in semiconductor

    International Nuclear Information System (INIS)

    Basilia, Blessie; Sudario, Franck; Clemente, Richard; Millare, Jeremiah; Abad, Jojo

    2013-01-01

    The demand for low cost and reliable conductive die attach paste continues to increase because of the recent development in the semiconductor and electronics industry. Hybrid products with vertically and horizontally integrated components attach material with good electrical conductivity and excellent reliability. This has driven interest in polymers filled with silver particles that can deliver good performance and reliability at reduced cost. The challenge lies with the metal and polymer composition of the available die attach epoxies in the market with low Tg (glass transition temperature) and high CTE (coefficient of thermal expansion) compared to other components. Adding Halloysite Nanotube (HNT) to make a silver-filled epoxy (SFE) nanocomposite by in-situ intercalation method, the desired electrical conductivity of the epoxy matrix can be achieved without compromising its adhesion strength which is suitable for semiconductor die attach application. A custom design of experiment was used to study the effects of HNT mixed at varying composition into the silver filled epoxy matrix. Test results based on ASTM, JEDEC and military standards indicated that the desirable electrical conductivity and shear strength applicable to semiconductor die attach application can be achieved at 3% to 6% HNT composition. There was a substantial increase in Tg from 219°C t 228°C and reduction in CTE from 117 to 76 ppm/°C. Exfoliated structures of embedded HNT in the cured polymer matrix were observed in the SEM (Scanning Electron Microscopy) micrographs. Considering the electrical conductivity, adhesion strength, Tg and CTE, the HNT content of 3 to 6% is a good range to produce this material to attain good functionality and reliability. Combining HNT to make a silver filled epoxy-clay nanocomposite is highly feasible for semiconductor and electronics application. (author)

  7. Characterization of nanostructured photosensitive (NiS)x(CdS)(1-x) composite thin films grown by successive ionic layer adsorption and reaction (SILAR) route

    International Nuclear Information System (INIS)

    Ubale, A.U.; Bargal, A.N.

    2011-01-01

    Highlights: → Thin films of (NiS) x (CdS) (1-x) with variable composition (x = 1 to 0) were deposited onto glass substrates by the successive ionic layer adsorption and reaction (SILAR) method. → The structural, surface morphological and electrical characterizations of the as deposited and annealed films were studied. → The bandgap and activation energy of annealed (NiS) x (CdS) (1-x) film decrease with improvement in photosensitive nature. -- Abstract: Recently ternary semiconductor nanostructured composite materials have attracted the interest of researchers because of their photovoltaic applications. Thin films of (NiS) x (CdS) (1-x) with variable composition (x = 1-0) had been deposited onto glass substrates by the successive ionic layer adsorption and reaction (SILAR) method. As grown and annealed films were characterised by X-ray diffraction, scanning electron microscopy and EDAX to investigate structural and morphological properties. The (NiS) x (CdS) (1-x) films were polycrystalline in nature having mixed phase of rhombohedral and hexagonal crystal structure due to NiS and CdS respectively. The optical and electrical properties of (NiS) x (CdS) (1-x) thin films were studied to determine compsition dependent bandgap, activation energy and photconductivity. The bandgap and activation energy of annealed (NiS) x (CdS) (1-x) film decrease with improvement in photosensitive nature.

  8. Characterization of nanostructured photosensitive (NiS){sub x}(CdS){sub (1-x)} composite thin films grown by successive ionic layer adsorption and reaction (SILAR) route

    Energy Technology Data Exchange (ETDEWEB)

    Ubale, A.U., E-mail: ashokuu@yahoo.com [Nanostructured Thin Film Materials Laboratory, Department of Physics, Govt. Vidarbha Institute of Science and Humanities, Amravati 444604, Maharashtra (India); Bargal, A.N. [Nanostructured Thin Film Materials Laboratory, Department of Physics, Govt. Vidarbha Institute of Science and Humanities, Amravati 444604, Maharashtra (India)

    2011-07-15

    Highlights: {yields} Thin films of (NiS){sub x}(CdS){sub (1-x)} with variable composition (x = 1 to 0) were deposited onto glass substrates by the successive ionic layer adsorption and reaction (SILAR) method. {yields} The structural, surface morphological and electrical characterizations of the as deposited and annealed films were studied. {yields} The bandgap and activation energy of annealed (NiS){sub x}(CdS){sub (1-x)} film decrease with improvement in photosensitive nature. -- Abstract: Recently ternary semiconductor nanostructured composite materials have attracted the interest of researchers because of their photovoltaic applications. Thin films of (NiS){sub x}(CdS){sub (1-x)} with variable composition (x = 1-0) had been deposited onto glass substrates by the successive ionic layer adsorption and reaction (SILAR) method. As grown and annealed films were characterised by X-ray diffraction, scanning electron microscopy and EDAX to investigate structural and morphological properties. The (NiS){sub x}(CdS){sub (1-x)} films were polycrystalline in nature having mixed phase of rhombohedral and hexagonal crystal structure due to NiS and CdS respectively. The optical and electrical properties of (NiS){sub x}(CdS){sub (1-x)} thin films were studied to determine compsition dependent bandgap, activation energy and photconductivity. The bandgap and activation energy of annealed (NiS){sub x}(CdS){sub (1-x)} film decrease with improvement in photosensitive nature.

  9. Fermi level dependent native defect formation: Consequences for metal-semiconductor and semiconductor-semiconductor interfaces

    International Nuclear Information System (INIS)

    Walukiewicz, W.

    1988-02-01

    The amphoteric native defect model of the Schottky barrier formation is used to analyze the Fermi level pinning at metal/semiconductor interfaces for submonolayer metal coverages. It is assumed that the energy required for defect generation is released in the process of surface back-relaxation. Model calculations for metal/GaAs interfaces show a weak dependence of the Fermi level pinning on the thickness of metal deposited at room temperature. This weak dependence indicates a strong dependence of the defect formation energy on the Fermi level, a unique feature of amphoteric native defects. This result is in very good agreement with experimental data. It is shown that a very distinct asymmetry in the Fermi level pinning on p- and n-type GaAs observed at liquid nitrogen temperatures can be understood in terms of much different recombination rates for amphoteric native defects in those two types of materials. Also, it is demonstrated that the Fermi level stabilization energy, a central concept of the amphoteric defect system, plays a fundamental role in other phenomena in semiconductors such as semiconductor/semiconductor heterointerface intermixing and saturation of free carrier concentration. 33 refs., 6 figs

  10. Structural evolution and mechanisms of fatigue in polycrystalline brass

    International Nuclear Information System (INIS)

    Vejloe Carstensen, J.

    1998-03-01

    The plastic strain controlled fatigue behaviour of polycrystalline Cu-15%Zn and Cu-30%Zn has been investigated with the aim of studying the effect of slip mode modification by the addition of zinc to copper. It has been clearly demonstrated, that true cyclic saturation does not occur in the plastic strain controlled fatigue of brass. This complicates the contstruction of a cyclic stress-strain (CSS) curve and thus the comparison with copper. A method to overcome this complication has been suggested. Surface observations on fatigued brass specimens show that individual grains tend to deform by Sachs type single slip. This behaviour has been described by the self-consistent Sachs-Eshelby model, which provides estimates of the CSS curve for brass polycrystals. Successive stages of primary hardening, softening and secondary hardening has been observed in the plastic strain controlled fatigue of brass. It has been found that the primary hardening is attributed to an increase of intergranular stresses whereas the secondary hardening apparently is attributed to an increase of friction stresses. Investigations of the structural evolution show that the softening behaviour can be explained by the presence of short-range order (SRO). SRO promote the formation of extended dipole arrays which hardens the material. The formation of intense shear bands destroy the dipole arrays, which explains the cyclic softening. The present results reveal that Cu-30%Zn in a pure planar slip alloy, while Cu-15%Zn displays both planar and wavy slip. The mechanical and structural behaviour observed in brass resembles recent observations in 316L austenitic stainless steels, and the present results reveal that Cu-30%Zn and 316L have approximately the same fatigue life curve. This emphasizes brass as being a convenient model system for the industrially important austenitic steels. (au)

  11. Micromechanical simulation of Uranium dioxide polycrystalline aggregate behaviour under irradiation

    International Nuclear Information System (INIS)

    Pacull, J.

    2011-02-01

    In pressurized water nuclear power reactor (PWR), the fuel rod is made of dioxide of uranium (UO 2 ) pellet stacked in a metallic cladding. A multi scale and multi-physic approaches are needed for the simulation of fuel behavior under irradiation. The main phenomena to take into account are thermomechanical behavior of the fuel rod and chemical-physic behavior of the fission products. These last years one of the scientific issue to improve the simulation is to take into account the multi-physic coupling problem at the microscopic scale. The objective of this ph-D study is to contribute to this multi-scale approach. The present work concerns the micro-mechanical behavior of a polycrystalline aggregate of UO 2 . Mean field and full field approaches are considered. For the former and the later a self consistent homogenization technique and a periodic Finite Element model base on the 3D Voronoi pattern are respectively used. Fuel visco-plasticity is introduced in the model at the scale of a single grain by taking into account specific dislocation slip systems of UO 2 . A cohesive zone model has also been developed and implemented to simulate grain boundary sliding and intergranular crack opening. The effective homogenous behaviour of a Representative Volume Element (RVE) is fitted with experimental data coming from mechanical tests on a single pellet. Local behavior is also analyzed in order to evaluate the model capacity to assess micro-mechanical state. In particular, intra and inter granular stress gradient are discussed. A first validation of the local behavior assessment is proposed through the simulation of intergranular crack opening measured in a compressive creep test of a single fuel pellet. Concerning the impact of the microstructure on the fuel behavior under irradiation, a RVE simulation with a representative transient loading of a fuel rod during a power ramp test is achieved. The impact of local stress and strain heterogeneities on the multi

  12. The Relationship Between Debris and Grain Growth in Polycrystalline Ice

    Science.gov (United States)

    Rivera, A.; McCarthy, C.

    2017-12-01

    An understanding of the mechanisms of ice flow, as well as the factors that affect it, must be improved in order to make more accurate predictions of glacial melting rates, and hence, sea level rise. Both field and laboratory studies have made an association between smaller grain sizes of ice and more rapid deformation. Therefore, it is essential to understand the different factors that affect grain size. Observations from ice cores have shown a correlation between debris content in layers of ice with smaller grain sizes, whereas layers with very little debris have larger grain sizes. Static grain growth rates for both pure ice and ice containing bubbles are well constrained, but the effect of small rock/dust particles has received less attention. We tested the relationship between debris and grain growth in polycrystalline ice with controlled annealing at -5°C and microstructural characterization. Three samples, two containing fine rock powder and one without, were fabricated, annealed, and imaged over time. The samples containing powder had different initial grain sizes due to solidification temperature during fabrication. Microstructural analysis was done on all samples after initial fabrication and at various times during the anneal using a light microscope housed in a cold room. Microstructural images were analyzed by the linear-intercept method. When comparing average grain size over time between pure ice and ice with debris, it was found that the rate of growth for the pure ice was larger than the rate of growth for the ice with debris at both initial grain sizes. These results confirm the observations seen in nature, and suggest that small grain size is indeed influenced by debris content. By understanding this, scientists could gain a more in-depth understanding of internal ice deformation and the mechanisms of ice flow. This, in turn, helps improve the accuracy of glacial melting predictions, and sea level rise in the future.

  13. The thermoviscoplastic response of polycrystalline tungsten in compression

    International Nuclear Information System (INIS)

    Lennon, A.M.; Ramesh, K.T.

    2000-01-01

    The thermomechanical response of commercially pure polycrystalline tungsten was investigated over a wide range of strain rates and temperatures. The material was examined in two forms: one an equiaxed recrystallized microstructure and the other a heavily deformed extruded microstructure that was loaded in compression along the extrusion axis. Low strain rate (10 -3 -10 0 s -1 ) compression experiments were conducted on an MTS servo-hydraulic load frame equipped with an infra-red furnace capable of sustaining specimen temperatures in excess of 600 C. High strain rate (10 3 -10 4 s -1 ) experiments were performed on a compression Kolsky bar equipped with an infra-red heating system capable of developing specimen temperatures as high as 800 C. Pressure-shear plate impact experiments were used to obtain shear stress versus shear strain curves at very high rates (∝10 4 -10 5 s -1 ). The recrystallized material was able to sustain very substantial plastic deformations in compression (at room temperature), with a flow stress that appears to be rate-dependent. Intergranular microcracks were developed during the compressive deformations. Under quasi-static loadings a few relatively large axial splitting cracks were formed, while under dynamic loadings a very large number of small, uniformly distributed microcracks (that did not link up to form macrocracks) were developed. The rate of nucleation of microcracks increased dramatically with strain rate. The extruded tungsten is also able to sustain large plastic deformations in compression, with a flow stress that increases with the rate of deformation. The strain hardening of the extruded material is lower than that of the recrystallized material, and is relatively insensitive to the strain rate. (orig.)

  14. Structural evolution and mechanisms of fatigue in polycrystalline brass

    Energy Technology Data Exchange (ETDEWEB)

    Vejloe Carstensen, J

    1998-03-01

    The plastic strain controlled fatigue behaviour of polycrystalline Cu-15%Zn and Cu-30%Zn has been investigated with the aim of studying the effect of slip mode modification by the addition of zinc to copper. It has been clearly demonstrated, that true cyclic saturation does not occur in the plastic strain controlled fatigue of brass. This complicates the contstruction of a cyclic stress-strain (CSS) curve and thus the comparison with copper. A method to overcome this complication has been suggested. Surface observations on fatigued brass specimens show that individual grains tend to deform by Sachs type single slip. This behaviour has been described by the self-consistent Sachs-Eshelby model, which provides estimates of the CSS curve for brass polycrystals. Successive stages of primary hardening, softening and secondary hardening has been observed in the plastic strain controlled fatigue of brass. It has been found that the primary hardening is attributed to an increase of intergranular stresses whereas the secondary hardening apparently is attributed to an increase of friction stresses. Investigations of the structural evolution show that the softening behaviour can be explained by the presence of short-range order (SRO). SRO promote the formation of extended dipole arrays which hardens the material. The formation of intense shear bands destroy the dipole arrays, which explains the cyclic softening. The present results reveal that Cu-30%Zn in a pure planar slip alloy, while Cu-15%Zn displays both planar and wavy slip. The mechanical and structural behaviour observed in brass resembles recent observations in 316L austenitic stainless steels, and the present results reveal that Cu-30%Zn and 316L have approximately the same fatigue life curve. This emphasizes brass as being a convenient model system for the industrially important austenitic steels. (au) 9 tabs., 94 ills., 177 refs.; The thesis is also available as DCAMM-R-S80 and as an electronic document on http://www.risoe.dk/rispubl

  15. Semiconductor detectors in nuclear and particle physics

    International Nuclear Information System (INIS)

    Rehak, P.; Gatti, E.

    1992-01-01

    Semiconductor detectors for elementary particle physics and nuclear physics in the energy range above 1 GeV are briefly reviewed. In these two fields semiconductor detectors are used mainly for the precise position sensing. In a typical experiment, the position of a fast charged particle crossing a relatively thin semiconductor detector is measured. The position resolution achievable by semiconductor detectors is compared with the resolution achievable by gas filled position sensing detectors. Semiconductor detectors are divided into two groups: Classical semiconductor diode detectors and semiconductor memory detectors. Principles of the signal formation and the signal read-out for both groups of detectors are described. New developments of silicon detectors of both groups are reported

  16. Semiconductor detectors in nuclear and particle physics

    International Nuclear Information System (INIS)

    Rehak, P.; Gatti, E.

    1995-01-01

    Semiconductor detectors for elementary particle physics and nuclear physics in the energy range above 1 GeV are briefly reviewed. In these two fields semiconductor detectors are used mainly for the precise position sensing. In a typical experiment, the position of a fast charged particle crossing a relatively thin semiconductor detector is measured. The position resolution achievable by semiconductor detectors is compared with the resolution achievable by gas filled position sensing detectors. Semiconductor detectors are divided into two groups; (i) classical semiconductor diode detectors and (ii) semiconductor memory detectors. Principles of the signal formation and the signal read-out for both groups of detectors are described. New developments of silicon detectors of both groups are reported. copyright 1995 American Institute of Physics

  17. Atomic-Resolution Spectrum Imaging of Semiconductor Nanowires.

    Science.gov (United States)

    Zamani, Reza R; Hage, Fredrik S; Lehmann, Sebastian; Ramasse, Quentin M; Dick, Kimberly A

    2018-03-14

    Over the past decade, III-V heterostructure nanowires have attracted a surge of attention for their application in novel semiconductor devices such as tunneling field-effect transistors (TFETs). The functionality of such devices critically depends on the specific atomic arrangement at the semiconductor heterointerfaces. However, most of the currently available characterization techniques lack sufficient spatial resolution to provide local information on the atomic structure and composition of these interfaces. Atomic-resolution spectrum imaging by means of electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM) is a powerful technique with the potential to resolve structure and chemical composition with sub-angstrom spatial resolution and to provide localized information about the physical properties of the material at the atomic scale. Here, we demonstrate the use of atomic-resolution EELS to understand the interface atomic arrangement in three-dimensional heterostructures in semiconductor nanowires. We observed that the radial interfaces of GaSb-InAs heterostructure nanowires are atomically abrupt, while the axial interface in contrast consists of an interfacial region where intermixing of the two compounds occurs over an extended spatial region. The local atomic configuration affects the band alignment at the interface and, hence, the charge transport properties of devices such as GaSb-InAs nanowire TFETs. STEM-EELS thus represents a very promising technique for understanding nanowire physical properties, such as differing electrical behavior across the radial and axial heterointerfaces of GaSb-InAs nanowires for TFET applications.

  18. Structural, optical and vibrational studies of Na{sup +} doped Cd{sub 0.8}Zn{sub 0.2}S semiconductor compounds

    Energy Technology Data Exchange (ETDEWEB)

    Yellaiah, G., E-mail: johngolluri@yahoo.com; Hadasa, K.; Nagabhushanam, M., E-mail: mamidala_nb@yahoo.com

    2013-12-25

    Graphical abstract: FTIR spectra of Cd{sub 0.8}Zn{sub 0.2}S: N{sub x} (x = 0.2 mol%). Highlights: •The energy band gaps of Cd{sub 0.8}Zn{sub 02}S: Nasamples were estimated. •Density and porosity percentages were calculated. •From the FTIR study CdS and ZnS stretching bonds were detected. -- Abstract: Cd{sub 0.8}Zn{sub 0.2}S semiconductor powders doped with different amounts of sodium have been synthesized by controlled co-precipitation technique. X-ray diffraction (XRD), Scanning electron microscope (SEM), Optical absorption and Fourier transform infrared spectroscope (FTIR) studies have been done on all these samples. XRD studies have revealed that the samples are polycrystalline with an average crystallite size ranging from 29 to 55 nm and they crystallize in the hexagonal form with wurtzite structure. The optical measurements revealed that the samples possess direct band gap and the band gap increases with an increase in the dopant concentration. The vibrational modes of Cd–S and Zn–S were obtained from FTIR studies and found to be at 812–618 cm{sup −1} respectively. Experimental and theoretical (XRD) densities were calculated and analyzed. Density from XRD and porosity in percentage varied from 92% to 94% and 5% to 8% respectively. The elemental analysis of the compounds was done by energy dispersive spectroscopy (EDS) and found that the cadmium, zinc, sulphur and sodium elements were present in the compound as per the composition taken. From the theoretical estimations it is understood that the dopant (Na) occupies the interstitial of CdZnS.

  19. Chalcopyrite semiconductors for quantum well solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Afshar, Maziar; Sadewasser, Sascha; Albert, Juergen; Lehmann, Sebastian; Abou-Ras, Daniel; Lux-Steiner, Martha C. [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Berlin (Germany); Marron, David Fuertes [Instituto de Energia Solar - ETSIT, Universidad Politecnica de Madrid, Ciudad Universitaria s.n., 28040 Madrid (Spain); Rockett, Angus A. [Department of Materials Science and Engineering, University of Illinois, 1304 W. Green Street, Urbana, IL 61801 (United States); Raesaenen, Esa [Nanoscience Center, Department of Physics University of Jyvaeskylae, FI-40014 Jyvaeskylae (Finland)

    2011-11-15

    The possibilities of using highly absorbing chalcopyrite semiconductors of the type Cu(In,Ga)Se{sub 2} in a quantum well solar cell structure are explored. Thin alternating layers of 50 nm CuInSe{sub 2} and CuGaSe{sub 2} were grown epitaxially on a GaAs(100) substrate. The optical properties of a resulting structure of three layers indicate charge carrier confinement in the low band gap CuInSe{sub 2} layer. By compositional analysis interdiffusion of In and Ga at the interfaces was found. The compositional profile was converted into a conduction-band diagram, for which the quantization of energy levels was numerically confirmed using the effective-mass approximation. The results provide a promising basis for the future development of chalcopyrite-type quantum well structures and their application, i.e. in quantum well solar cells. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Experimental and ab initio study of Ta-doped ZnO semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Munoz, E. L., E-mail: munoz@fisica.unlp.edu.ar; Richard, D., E-mail: richard@fisica.unlp.edu.ar [UNLP, Departamento de Fisica and Instituto de Fisica La Plata (IFLP, CCT La Plata, CONICET), Fac. de Ciencias Exactas (Argentina); Eversheim, P. D. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen-und Kernphysik (H-ISKP) (Germany); Renteria, M., E-mail: renteria@fisica.unlp.edu.ar [UNLP, Departamento de Fisica and Instituto de Fisica La Plata (IFLP, CCT La Plata, CONICET), Fac. de Ciencias Exactas (Argentina)

    2010-04-15

    In this work, we present {gamma}-{gamma} Perturbed-Angular-Correlation results in polycrystalline ZnO semiconductor implanted with {sup 181}Hf({yields}{sup 181}Ta) probes. Calculations in Ta-doped ZnO were carried out using the Full-Potential Augmented Plane Wave plus local orbital method in a supercell and varying self-consistently the charge state of the impurity. Ta is a triple donor impurity with respect to Zn{sup 2 + } in ZnO and thus it can loose 1, 2 or 3 donor electrons under certain circumstances. As expected, the comparison between the experimental Electric-Field-Gradient tensor results and our ab initio predictions shows that the Ta impurity is in an ionized charge state at room temperature.