Magnon-drag thermopile.

Science.gov (United States)

Costache, Marius V; Bridoux, German; Neumann, Ingmar; Valenzuela, Sergio O

2011-12-18

Thermoelectric effects in spintronics are gathering increasing attention as a means of managing heat in nanoscale structures and of controlling spin information by using heat flow. Thermal magnons (spin-wave quanta) are expected to play a major role; however, little is known about the underlying physical mechanisms involved. The reason is the lack of information about magnon interactions and of reliable methods to obtain it, in particular for electrical conductors because of the intricate influence of electrons. Here, we demonstrate a conceptually new device that enables us to gather information on magnon-electron scattering and magnon-drag effects. The device resembles a thermopile formed by a large number of pairs of ferromagnetic wires placed between a hot and a cold source and connected thermally in parallel and electrically in series. By controlling the relative orientation of the magnetization in pairs of wires, the magnon drag can be studied independently of the electron and phonon-drag thermoelectric effects. Measurements as a function of temperature reveal the effect on magnon drag following a variation of magnon and phonon populations. This information is crucial to understand the physics of electron-magnon interactions, magnon dynamics and thermal spin transport.

Capas de SiGe policristalino hidrogenado y su aplicación en transistores de película delgada

Directory of Open Access Journals (Sweden)

Rodríguez, A.

2004-04-01

Full Text Available The hydrogenation of polycrystalline SiGe layers, obtained by solid phase crystallization, by an electron ciclotron resonance hydrogen plasma and the influence of this hydrogenation process on the electrical characteristics of thin film transistors fabricated using this material as active layer have been studied. The hydrogenation processes were carried out at 150 and 250 ºC for several times, up to 11 hours. Infrared transmission spectra of these samples show only the absorption bands corresponding to Si-H bonds, indicating that hydrogen atoms are bonded mainly to silicon atoms. Ultraviolet reflectance measurements show that the surface damage caused by the plasma exposure increases as the Ge content of the film does. The transistors fabricated using polycrystalline SiGe films as active layer show a degradation phenomenon, consisting of a progressive decrease of the drain current at constant gate and drain bias. The degradation slows down as the hydrogenation time increases at constant temperature.

En este trabajo se ha caracterizado el proceso de hidrogenación en un plasma generado por resonancia ciclotrónica de electrones de capas de SiGe policristalino obtenidas mediante cristalización en fase sólida y el efecto de la hidrogenación en las características eléctricas de transistores de película delgada fabricados usando dicho material. Los procesos de hidrogenación se realizaron a 150 y 250 ºC, con duraciones de hasta 11 horas. Los espectros de transmitancia en infrarrojo muestran solamente las bandas de absorción características de los enlaces Si-H. Estas bandas indican que el hidrógeno se incorpora al material enlazándose principalmente con los átomos de silicio. Las medidas de reflectancia en el ultravioleta indican que se crea daño en la superficie de la muestra y que éste aumenta a medida que lo hace el contenido en Ge. Los transistores de película delgada con capa activa de SiGe policristalino muestran un fen

Experimental and Numerical Investigations in Shallow Cut Grinding by Workpiece Integrated Infrared Thermopile Array

Directory of Open Access Journals (Sweden)

Marcel Reimers

2017-09-01

Full Text Available The purpose of our study is to investigate the heat distribution and the occurring temperatures during grinding. Therefore, we did both experimental and numerical investigations. In the first part, we present the integration of an infrared thermopile array in a steel workpiece. Experiments are done by acquiring data from the thermopile array during grinding of a groove in a workpiece made of steel. In the second part, we present numerical investigations in the grinding process to further understand the thermal characteristic during grinding. Finally, we conclude our work. Increasing the feed speed leads to two things: higher heat flux densities in the workpiece and higher temperature gradients in the material.

Band structure analysis in SiGe nanowires

Energy Technology Data Exchange (ETDEWEB)

Amato, Michele [' Centro S3' , CNR-Istituto Nanoscienze, via Campi 213/A, 41100 Modena (Italy); Dipartimento di Scienze e Metodi dell' Ingegneria, Universita di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia (Italy); Palummo, Maurizia [European Theoretical Spectroscopy Facility (ETSF) (Italy); CNR-INFM-SMC, Dipartimento di Fisica, Universita di Roma, ' Tor Vergata' , via della Ricerca Scientifica 1, 00133 Roma (Italy); Ossicini, Stefano, E-mail: stefano.ossicini@unimore.it [' Centro S3' , CNR-Istituto Nanoscienze, via Campi 213/A, 41100 Modena (Italy) and Dipartimento di Scienze e Metodi dell' Ingegneria, Universita di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia (Italy) and European Theoretical Spectroscopy Facility - ETSF (Italy) and Centro Interdipartimentale ' En and Tech' , Universita di Modena e Reggio Emilia, via Amendola 2 Pad. Morselli, I-42100 Reggio Emilia (Italy)

2012-06-05

One of the main challenges for Silicon-Germanium nanowires (SiGe NWs) electronics is the possibility to modulate and engine their electronic properties in an easy way, in order to obtain a material with the desired electronic features. Diameter and composition constitute two crucial ways for the modification of the band gap and of the band structure of SiGe NWs. Within the framework of density functional theory we present results of ab initio calculations regarding the band structure dependence of SiGe NWs on diameter and composition. We point out the main differences with respect to the case of pure Si and Ge wires and we discuss the particular features of SiGe NWs that are useful for future technological applications.

Band structure analysis in SiGe nanowires

International Nuclear Information System (INIS)

Amato, Michele; Palummo, Maurizia; Ossicini, Stefano

2012-01-01

One of the main challenges for Silicon-Germanium nanowires (SiGe NWs) electronics is the possibility to modulate and engine their electronic properties in an easy way, in order to obtain a material with the desired electronic features. Diameter and composition constitute two crucial ways for the modification of the band gap and of the band structure of SiGe NWs. Within the framework of density functional theory we present results of ab initio calculations regarding the band structure dependence of SiGe NWs on diameter and composition. We point out the main differences with respect to the case of pure Si and Ge wires and we discuss the particular features of SiGe NWs that are useful for future technological applications.

Silicon-germanium (Sige) nanostructures production, properties and applications in electronics

CERN Document Server

Usami, N

2011-01-01

Nanostructured silicon-germanium (SiGe) provides the prospect of novel and enhanced electronic device performance. This book reviews the materials science and technology of SiGe nanostructures, including crystal growth, fabrication of nanostructures, material properties and applications in electronics.$bNanostructured silicon-germanium (SiGe) opens up the prospects of novel and enhanced electronic device performance, especially for semiconductor devices. Silicon-germanium (SiGe) nanostructures reviews the materials science of nanostructures and their properties and applications in different electronic devices. The introductory part one covers the structural properties of SiGe nanostructures, with a further chapter discussing electronic band structures of SiGe alloys. Part two concentrates on the formation of SiGe nanostructures, with chapters on different methods of crystal growth such as molecular beam epitaxy and chemical vapour deposition. This part also includes chapters covering strain engineering and mo...

Phosphorus atomic layer doping in SiGe using reduced pressure chemical vapor deposition

International Nuclear Information System (INIS)

Yamamoto, Yuji; Heinemann, Bernd; Murota, Junichi; Tillack, Bernd

2014-01-01

Phosphorus (P) atomic layer doping in SiGe is investigated at temperatures between 100 °C to 600 °C using a single wafer reduced pressure chemical vapor deposition system. SiGe(100) surface is exposed to PH 3 at different PH 3 partial pressures by interrupting SiGe growth. The impact of the SiGe buffer/cap growth condition (total pressure/SiGe deposition precursors) on P adsorption, incorporation, and segregation are investigated. In the case of SiH 4 -GeH 4 -H 2 gas system, steeper P spikes due to lower segregation are observed by SiGe cap deposition at atmospheric (ATM) pressure compared with reduced pressure (RP). The steepness of P spike of ∼ 5.7 nm/dec is obtained for ATM pressure without reducing deposition temperature. This result may be due to the shift of equilibrium of P adsorption/desorption to desorption direction by higher H 2 pressure. Using Si 2 H 6 -GeH 4 -H 2 gas system for SiGe cap deposition in RP, lowering the SiGe growth temperature is possible, resulting in higher P incorporation and steeper P profile due to reduced desorption and segregation. In the case of Si 2 H 6 -GeH 4 -H 2 gas system, the P dose could be simulated assuming a Langmuir-type kinetics model. Incorporated P shows high electrical activity, indicating P is adsorbed mostly in lattice position. - Highlights: • Phosphorus (P) atomic layer doping in SiGe (100) is investigated using CVD. • P adsorption is suppressed by the hydrogen termination of Ge surface. • By SiGe cap deposition at atmospheric pressure, P segregation was suppressed. • By using Si 2 H 6 -based SiGe cap, P segregation was also suppressed. • The P adsorption process is self-limited and follows Langmuir-type kinetics model

Electrical characterisation of SiGe heterojunction bipolar transistors and Si pseudo-HBTS

Science.gov (United States)

De Barros, O.; Le Tron, B.; Woods, R. C.; Giroult-Matlakowski, G.; Vincent, G.; Brémond, G.

1996-08-01

This paper reports an electrical characterisation of the emitter-base junction of Si pseudo-HBTs and SiGe HBTs fabricated in a CMOS compatible single polysilicon self-aligned process. From the reverse characteristics it appears that the definition of the emitter-base junction by plasma etching induces peripheral defects that increase the base current of the transistors. Deep level transient spectroscopy measurements show a deep level in the case of SiGe base, whose spatial origin is not fully determinate up to now.

Quantitative SIMS analysis of SiGe composition with low energy O2+ beams

International Nuclear Information System (INIS)

Jiang, Z.X.; Kim, K.; Lerma, J.; Corbett, A.; Sieloff, D.; Kottke, M.; Gregory, R.; Schauer, S.

2006-01-01

This work explored quantitative analyses of SiGe films on either Si bulk or SOI wafers with low energy SIMS by assuming a constant ratio between the secondary ion yields of Si + and Ge + inside SiGe films. SiGe samples with Ge contents ranging from 15 to 65% have been analyzed with a 1 keV O 2 + beam at normal incidence. For comparison, the samples were also analyzed with RBS and/or AES. The Ge content as measured with SIMS, based on a single SiGe/Si or SiGe/SOI standard, exhibited good agreement with the corresponding RBS and AES data. It was concluded that SIMS was capable of providing accurate characterization of the SiGe composition with the Ge content up to 65%

Experiments and Modeling of Si-Ge Interdiffusion with Partial Strain Relaxation in Epitaxial SiGe Heterostructures

KAUST Repository

Dong, Y.

2014-07-26

Si-Ge interdiffusion and strain relaxation were studied in a metastable SiGe epitaxial structure. With Ge concentration profiling and ex-situ strain analysis, it was shown that during thermal anneals, both Si-Ge interdiffusion and strain relaxation occurred. Furthermore, the time evolutions of both strain relaxation and interdiffusion were characterized. It showed that during the ramp-up stage of thermal anneals at higher temperatures (800°C and 840°C), the degree of relaxation, R, reached a “plateau”, while interdiffusion was negligible. With the approximation that the R value is constant after the ramp-up stage, a quantitative interdiffusivity model was built to account for both the effect of strain relaxation and the impact of the relaxation induced dislocations, which gave good agreement with the experiment data.

Flow Type Bio-Chemical Calorimeter with Micro Differential Thermopile Sensor.

Science.gov (United States)

Saito, Masataka; Nakabeppu, Osamu

2015-04-01

Bio-chemical calorimeters with a MEMS (Micro-Electro-Mechanical Systems) thermopile sensor have been studied for monitoring detailed processes of the biochemical reactions of a minute sample with a high temporal resolution. The bio-calorimeters are generally divided into a batch-type and a flow-type. We developed a highly sensitive batch-type calorimeter which can detect a 100 nW level thermal reaction. However it shows a long settling time of 2 hours because of the heat capacity of a whole calorimeter. Thus, the flow-type calorimeters in passive and active mode have been studied for measuring the thermal reactions in an early stage after starting an analysis. The flow-type calorimeter consists of the MEMS differential thermopile sensor, a pair of micro channel reactor in a PDMS (polydimethylsiloxane) sheet in a three-fold thermostat chamber. The calorimeter in the passive mode was tested with dilution reactions of ethanol to water and NaCl aqueous solution to water. It was shown that the calorimeter detects exo- and endothermic reaction over 250 nW at solution flow rate of 0.05 ~ 1 µl/min with a settling time of about 4 minutes. In the active mode, a response test was conducted by using heat removal by water flow from the reactor channel. The active calorimetry enhances the response time about three to four times faster.

SiGe Integrated Circuit Developments for SQUID/TES Readout

Science.gov (United States)

Prêle, D.; Voisin, F.; Beillimaz, C.; Chen, S.; Piat, M.; Goldwurm, A.; Laurent, P.

2018-03-01

SiGe integrated circuits dedicated to the readout of superconducting bolometer arrays for astrophysics have been developed since more than 10 years at APC. Whether for Cosmic Microwave Background (CMB) observations with the QUBIC ground-based experiment (Aumont et al. in astro-ph.IM, 2016. arXiv:1609.04372) or for the Hot and Energetic Universe science theme with the X-IFU instrument on-board of the ATHENA space mission (Barret et al. in SPIE 9905, space telescopes & instrumentation 2016: UV to γ Ray, 2016. https://doi.org/10.1117/12.2232432), several kinds of Transition Edge Sensor (TES) (Irwin and Hilton, in ENSS (ed) Cryogenic particle detection, Springer, Berlin, 2005) arrays have been investigated. To readout such superconducting detector arrays, we use time or frequency domain multiplexers (TDM, FDM) (Prêle in JINST 10:C08015, 2016. https://doi.org/10.1088/1748-0221/10/08/C08015) with Superconducting QUantum Interference Devices (SQUID). In addition to the SQUID devices, low-noise biasing and amplification are needed. These last functions can be obtained by using BiCMOS SiGe technology in an Application Specific Integrated Circuit (ASIC). ASIC technology allows integration of highly optimised circuits specifically designed for a unique application. Moreover, we could reach very low-noise and wide band amplification using SiGe bipolar transistor either at room or cryogenic temperatures (Cressler in J Phys IV 04(C6):C6-101, 1994. https://doi.org/10.1051/jp4:1994616). This paper discusses the use of SiGe integrated circuits for SQUID/TES readout and gives an update of the last developments dedicated to the QUBIC telescope and to the X-IFU instrument. Both ASIC called SQmux128 and AwaXe are described showing the interest of such SiGe technology for SQUID multiplexer controls.

The reliability studies of nano-engineered SiGe HBTs using Pelletron accelerator

Science.gov (United States)

Prakash, A. P. Gnana; Praveen, K. C.; Pushpa, N.; Cressler, John D.

2015-05-01

The effects of high energy ions on the electrical characteristics of silicon-germanium heterojunction bipolar transistors (SiGe HBTs) were studied in the total dose of ranging from 600 krad to 100 Mrad (Si). The two generations (50 GHz and 200 GHz) of SiGe HBTs were exposed to 50 MeV lithium, 75 MeV boron and 100 MeV oxygen ions. The electrical characteristics of SiGe HBTs were studied before and after irradiation. The SiGe HBTs were exposed to 60Co gamma radiation in the same total dose. The results are systematically compared in order to understand the interaction of ions and ionizing radiation with SiGe HBTs.

The reliability studies of nano-engineered SiGe HBTs using Pelletron accelerator

Energy Technology Data Exchange (ETDEWEB)

Prakash, A. P. Gnana, E-mail: gnanaprakash@physics.uni-mysore.ac.in; Praveen, K. C. [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore, Karnataka-570006 (India); Pushpa, N. [Department of PG Studies in Physics, JSS College, Ooty Road, Mysore-570025 (India); Cressler, John D. [School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, 30332 (United States)

2015-05-15

The effects of high energy ions on the electrical characteristics of silicon-germanium heterojunction bipolar transistors (SiGe HBTs) were studied in the total dose of ranging from 600 krad to 100 Mrad (Si). The two generations (50 GHz and 200 GHz) of SiGe HBTs were exposed to 50 MeV lithium, 75 MeV boron and 100 MeV oxygen ions. The electrical characteristics of SiGe HBTs were studied before and after irradiation. The SiGe HBTs were exposed to {sup 60}Co gamma radiation in the same total dose. The results are systematically compared in order to understand the interaction of ions and ionizing radiation with SiGe HBTs.

Reduced thermal conductivity due to scattering centers in p-type SiGe alloys

International Nuclear Information System (INIS)

Beaty, J.S.; Rolfe, J.L.; Vandersande, J.; Fleurial. J.P.

1992-01-01

This paper reports that a theoretical model has been developed that predicts that the addition of ultra-fine, inert, phonon-scattering centers to SiGe thermoelectric material will reduce its thermal conductivity and improve its figure-of-merit. To investigate this prediction, ultra-fine particulates (20 Angstrom to 200 Angstrom) of boron nitride have been added to boron doped, p-type, 80/20 SiGe. All previous SiGe samples produced from ultra-fine SiGe powder without additions had lower thermal conductivities than standard SiGe, but high temperature (1525 K) heat treatment increased their thermal conductivity back to the value for standard SiGe. Transmission Electron Microscopy has been used to confirm the presence of occluded particulates and X-ray diffraction has been used to determine the composition to be BN

Surface tension and density of Si-Ge melts

Science.gov (United States)

Ricci, Enrica; Amore, Stefano; Giuranno, Donatella; Novakovic, Rada; Tuissi, Ausonio; Sobczak, Natalia; Nowak, Rafal; Korpala, Bartłomiej; Bruzda, Grzegorz

2014-06-01

In this work, the surface tension and density of Si-Ge liquid alloys were determined by the pendant drop method. Over the range of measurements, both properties show a linear temperature dependence and a nonlinear concentration dependence. Indeed, the density decreases with increasing silicon content exhibiting positive deviation from ideality, while the surface tension increases and deviates negatively with respect to the ideal solution model. Taking into account the Si-Ge phase diagram, a simple lens type, the surface tension behavior of the Si-Ge liquid alloys was analyzed in the framework of the Quasi-Chemical Approximation for the Regular Solutions model. The new experimental results were compared with a few data available in the literature, obtained by the containerless method.

Electronic structure of O-doped SiGe calculated by DFT + U method

Science.gov (United States)

Zhao, Zong-Yan; Yang, Wen; Yang, Pei-Zhi

2016-12-01

To more in depth understand the doping effects of oxygen on SiGe alloys, both the micro-structure and properties of O-doped SiGe (including: bulk, (001) surface, and (110) surface) are calculated by DFT + U method in the present work. The calculated results are as follows. (i) The (110) surface is the main exposing surface of SiGe, in which O impurity prefers to occupy the surface vacancy sites. (ii) For O interstitial doping on SiGe (110) surface, the existences of energy states caused by O doping in the band gap not only enhance the infrared light absorption, but also improve the behaviors of photo-generated carriers. (iii) The finding about decreased surface work function of O-doped SiGe (110) surface can confirm previous experimental observations. (iv) In all cases, O doing mainly induces the electronic structures near the band gap to vary, but is not directly involved in these variations. Therefore, these findings in the present work not only can provide further explanation and analysis for the corresponding underlying mechanism for some of the experimental findings reported in the literature, but also conduce to the development of μc-SiGe-based solar cells in the future. Project supported by the Natural Science Foundation of Yunnan Province, China (Grant No. 2015FB123), the 18th Yunnan Province Young Academic and Technical Leaders Reserve Talent Project, China (Grant No. 2015HB015), and the National Natural Science Foundation of China (Grant No. U1037604).

Human location estimation using thermopile array sensor

Science.gov (United States)

Parnin, S.; Rahman, M. M.

2017-11-01

Utilization of Thermopile sensor at an early stage of human detection is challenging as there are many things that produce thermal heat other than human such as electrical appliances and animals. Therefrom, an algorithm for early presence detection has been developed through the study of human body temperature behaviour with respect to the room temperature. The change in non-contact detected temperature of human varied according to body parts. In an indoor room, upper parts of human body change up to 3°C whereas lower part ranging from 0.58°C to 1.71°C. The average changes in temperature of human is used as a conditional set-point value in the program algorithm to detect human presence. The current position of human and its respective angle is gained when human is presence at certain pixels of Thermopile’s sensor array. Human position is estimated successfully as the developed sensory system is tested to the actuator of a stand fan.

SiGe derivatization by spontaneous reduction of aryl diazonium salts

Science.gov (United States)

Girard, A.; Geneste, F.; Coulon, N.; Cardinaud, C.; Mohammed-Brahim, T.

2013-10-01

Germanium semiconductors have interesting properties for FET-based biosensor applications since they possess high surface roughness allowing the immobilization of a high amount of receptors on a small surface area. Since SiGe combined low cost of Si and intrinsic properties of Ge with high mobility carriers, we focused the study on this particularly interesting material. The comparison of the efficiency of a functionalization process involving the spontaneous reduction of diazonium salts is studied on Si(1 0 0), SiGe and Ge semiconductors. XPS analysis of the functionalized surfaces reveals the presence of a covalent grafted layer on all the substrates that was confirmed by AFM. Interestingly, the modified Ge derivatives have still higher surface roughness after derivatization. To support the estimated thickness by XPS, a step measurement of the organic layers is done by AFM or by profilometer technique after a O2 plasma etching of the functionalized layer. This original method is well-adapted to measure the thickness of thin organic films on rough substrates such as germanium. The analyses show a higher chemical grafting on SiGe substrates compared with Si and Ge semiconductors.

Noise Parameter Analysis of SiGe HBTs for Different Sizes in the Breakdown Region

Directory of Open Access Journals (Sweden)

Chie-In Lee

2016-01-01

Full Text Available Noise parameters of silicon germanium (SiGe heterojunction bipolar transistors (HBTs for different sizes are investigated in the breakdown region for the first time. When the emitter length of SiGe HBTs shortens, minimum noise figure at breakdown decreases. In addition, narrower emitter width also decreases noise figure of SiGe HBTs in the avalanche region. Reduction of noise performance for smaller emitter length and width of SiGe HBTs at breakdown resulted from the lower noise spectral density resulting from the breakdown mechanism. Good agreement between experimental and simulated noise performance at breakdown is achieved for different sized SiGe HBTs. The presented analysis can benefit the RF circuits operating in the breakdown region.

Effect of a static magnetic field on silicon transport in liquid phase diffusion growth of SiGe

Energy Technology Data Exchange (ETDEWEB)

Armour, N.; Dost, S. [Crystal Growth Laboratory, University of Victoria, Victoria, BC V8W 3P6 (Canada)

2010-03-15

Liquid phase diffusion experiments have been performed without and with the application of a 0.4 T static magnetic field using a three-zone DC furnace system. SiGe crystals were grown from the germanium side for a period of 72 h. Experiments have led to the growth of single crystal sections varying from 0 to 10 mm thicknesses. Examination of the processed samples (single and polycrystalline sections) has shown that the effect of the applied static magnetic field is significant. It alters the temperature distribution in the system, reduces mass transport in the melt, and leads to a much lower growth rate. The initial curved growth interface was slightly flattened under the effect of magnetic field. There were no growth striations in the single crystal sections of the samples. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

σ and η Phase formation in advanced polycrystalline Ni-base superalloys

Energy Technology Data Exchange (ETDEWEB)

Antonov, Stoichko, E-mail: santonov@hawk.iit.edu [Illinois Institute of Technology, 10 W. 32nd Street, Chicago, IL 60616 (United States); Huo, Jiajie; Feng, Qiang [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Isheim, Dieter; Seidman, David N. [Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208 (United States); Northwestern University Center for Atom Probe Tomography (NUCAPT), 2220 Campus Drive, Evanston, IL 60208 (United States); Helmink, Randolph C.; Sun, Eugene [Rolls-Royce Corporation, 450 S. Meridian Street, Indianapolis, IN 46225 (United States); Tin, Sammy [Illinois Institute of Technology, 10 W. 32nd Street, Chicago, IL 60616 (United States)

2017-02-27

In polycrystalline Ni-base superalloys, grain boundary precipitation of secondary phases can be significant due to the effects they pose on the mechanical properties. As new alloying concepts for polycrystalline Ni-base superalloys are being developed to extend their temperature capability, the effect of increasing levels of Nb alloying additions on long term phase stability and the formation of topologically close packed (TCP) phases needs to be studied. Elevated levels of Nb can result in increased matrix supersaturation and promote the precipitation of secondary phases. Long term thermal exposures on two experimental powder processed Ni-base superalloys containing various levels of Nb were completed to assess the stability and precipitation of TCP phases. It was found that additions of Nb promoted the precipitation of η-Ni{sub 6}AlNb along the grain boundaries in powder processed, polycrystalline Ni-base superalloys, while reduced Nb levels favored the precipitation of blocky Cr and Mo – rich σ phase precipitates along the grain boundary. Evaluation of the thermodynamic stability of these two phases in both alloys using Thermo-calc showed that while σ phase predictions are fairly accurate, predictions of the η phase are limited.

Stable and low contact resistance electrical contacts for high temperature SiGe thermoelectric generators

KAUST Repository

Zhang, Bo

2018-04-14

The thermal stability and contact resistance of TaAlN thin films as electrical contacts to SiGe thermoelectric elements are reported. We demonstrate that a sharp interface is maintained after the device annealed at 800°C for over 100h, indicating that no interdiffusion takes place between TaAlN and SiGe. A specific contact resistivity of (2.1±1.3)×10−6Ω-cm2 for p-type SiGe and (2.8±1.6)×10−5 Ω-cm2 for n-type SiGe is demonstrated after the high temperature annealing. These results show that TaAlN is a promising contact material for high temperature thermoelectrics such as SiGe.

Study of low dimensional SiGe island on Si for potential visible Metal-Semiconductor-Metal photodetector

Science.gov (United States)

Rahim, Alhan Farhanah Abd; Zainal Badri, Nur'Amirah; Radzali, Rosfariza; Mahmood, Ainorkhilah

2017-11-01

In this paper, an investigation of design and simulation of silicon germanium (SiGe) islands on silicon (Si) was presented for potential visible metal semiconductor metal (MSM) photodetector. The characterization of the performances in term of the structural, optical and electrical properties of the structures was analyzed from the simulation results. The project involves simulation using SILVACO Technology Computer Aided Design (TCAD) tools. The different structures of the silicon germanium (SiGe) island on silicon substrate were created, which were large SiGe, small SiGe, combination SiGe and bulk Ge. All the structures were tested for potential Metal Semiconductor Metal (MSM) photodetector. The extracted data such as current versus voltage characteristic, current gain and spectral response were obtained using ATLAS SILVACO tools. The performance of SiGe island structures and bulk Ge on Si substrate as (MSM) photodetector was evaluated by photo and dark current-voltage (I-V) characteristics. It was found that SiGe islands exhibited higher energy band gap compared to bulk Ge. The SiGe islands current-voltage characteristics showed improved current gain compared to bulk Ge. Specifically the enhancement of the islands gain was contributed by the enhanced photo currents and lower dark currents. The spectral responses of the SiGe islands showed peak response at 590 nm (yellow) which is at the visible wavelength. This shows the feasibility of the SiGe islands to be utilized for visible photodetections.

Study of low dimensional SiGe island on Si for potential visible Metal-Semiconductor-Metal photodetector

Directory of Open Access Journals (Sweden)

Abd Rahim Alhan Farhanah

2017-01-01

Full Text Available In this paper, an investigation of design and simulation of silicon germanium (SiGe islands on silicon (Si was presented for potential visible metal semiconductor metal (MSM photodetector. The characterization of the performances in term of the structural, optical and electrical properties of the structures was analyzed from the simulation results. The project involves simulation using SILVACO Technology Computer Aided Design (TCAD tools. The different structures of the silicon germanium (SiGe island on silicon substrate were created, which were large SiGe, small SiGe, combination SiGe and bulk Ge. All the structures were tested for potential Metal Semiconductor Metal (MSM photodetector. The extracted data such as current versus voltage characteristic, current gain and spectral response were obtained using ATLAS SILVACO tools. The performance of SiGe island structures and bulk Ge on Si substrate as (MSM photodetector was evaluated by photo and dark current-voltage (I-V characteristics. It was found that SiGe islands exhibited higher energy band gap compared to bulk Ge. The SiGe islands current-voltage characteristics showed improved current gain compared to bulk Ge. Specifically the enhancement of the islands gain was contributed by the enhanced photo currents and lower dark currents. The spectral responses of the SiGe islands showed peak response at 590 nm (yellow which is at the visible wavelength. This shows the feasibility of the SiGe islands to be utilized for visible photodetections.

Enhanced Emission of Quantum System in Si-Ge Nanolayer Structure.

Science.gov (United States)

Huang, Zhong-Mei; Huang, Wei-Qi; Dong, Tai-Ge; Wang, Gang; Wu, Xue-Ke

2016-12-01

It is very interesting that the enhanced peaks near 1150 and 1550 nm are observed in the photoluminescence (PL) spectra in the quantum system of Si-Ge nanolayer structure, which have the emission characteristics of a three-level system with quantum dots (QDs) pumping and emission of quasi-direct-gap band, in our experiment. In the preparing process of Si-Ge nanolayer structure by using a pulsed laser deposition method, it is discovered that the nanocrystals of Si and Ge grow in the (100) and (111) directions after annealing or electron beam irradiation. The enhanced PL peaks with multi-longitudinal-mode are measured at room temperature in the super-lattice of Si-Ge nanolayer quantum system on SOI.

Heavy Ion Current Transients in SiGe HBTs

Science.gov (United States)

Pellish, Jonathan A.; Reed, Robert A.; Vizkelethy, Gyorgy; McMorrow, Dale; Ferlet-Cavrois, Veronique; Baggio, Jacques; Paillet, Philipe; Duhanel, Olivier; Phillips, Stanley D.; Sutton, Akil K.;

Secondary growth mechanism of SiGe islands deposited on a mixed-phase microcrystalline Si by ion beam co-sputtering.

Science.gov (United States)

Ke, S Y; Yang, J; Qiu, F; Wang, Z Q; Wang, C; Yang, Y

2015-11-06

We discuss the SiGe island co-sputtering deposition on a microcrystalline silicon (μc-Si) buffer layer and the secondary island growth based on this pre-SiGe island layer. The growth phenomenon of SiGe islands on crystalline silicon (c-Si) is also investigated for comparison. The pre-SiGe layer grown on μc-Si exhibits a mixed-phase structure, including SiGe islands and amorphous SiGe (a-SiGe) alloy, while the layer deposited on c-Si shows a single-phase island structure. The preferential growth and Ostwald ripening growth are shown to be the secondary growth mechanism of SiGe islands on μc-Si and c-Si, respectively. This difference may result from the effect of amorphous phase Si (AP-Si) in μc-Si on the island growth. In addition, the Si-Ge intermixing behavior of the secondary-grown islands on μc-Si is interpreted by constructing the model of lateral atomic migration, while this behavior on c-Si is ascribed to traditional uphill atomic diffusion. It is found that the aspect ratios of the preferential-grown super islands are higher than those of the Ostwald-ripening ones. The lower lateral growth rate of super islands due to the lower surface energy of AP-Si on the μc-Si buffer layer for the non-wetting of Ge at 700 °C and the stronger Si-Ge intermixing effect at 730 °C may be responsible for this aspect ratio difference.

Silicon transport under rotating and combined magnetic fields in liquid phase diffusion growth of SiGe

Energy Technology Data Exchange (ETDEWEB)

Armour, N.; Dost, S. [Crystal Growth Laboratory, University of Victoria, Victoria, BC, V8W 3P6 (Canada)

2010-04-15

The effect of applied rotating and combined (rotating and static) magnetic fields on silicon transport during the liquid phase diffusion growth of SiGe was experimentally studied. 72-hour growth periods produced some single crystal sections. Single and polycrystalline sections of the processed samples were examined for silicon composition. Results show that the application of a rotating magnetic field enhances silicon transport in the melt. It also has a slight positive effect on flattening the initial growth interface. For comparison, growth experiments were also conducted under combined (rotating and static) magnetic fields. The processed samples revealed that the addition of static field altered the thermal characteristics of the system significantly and led to a complete melt back of the germanium seed. Silicon transport in the melt was also enhanced under combined fields compared with experiments with no magnetic field. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Stable and low contact resistance electrical contacts for high temperature SiGe thermoelectric generators

KAUST Repository

Zhang, Bo; Zheng, Tao; Wang, Qingxiao; Guo, Zaibing; Kim, Moon J.; Alshareef, Husam N.; Gnade, Bruce E.

2018-01-01

that no interdiffusion takes place between TaAlN and SiGe. A specific contact resistivity of (2.1±1.3)×10−6Ω-cm2 for p-type SiGe and (2.8±1.6)×10−5 Ω-cm2 for n-type SiGe is demonstrated after the high temperature annealing. These results show that TaAlN is a promising

Substrate Effects in Wideband SiGe HBT Mixer Circuits

DEFF Research Database (Denmark)

Johansen, Tom Keinicke; Vidkjær, Jens; Krozer, Viktor

2005-01-01

are also applied to predict short distance substrate coupling effects. Simulation results using extracted equivalent circuit models and substrate coupling networks are compared with experimental results obtained on a wideband mixer circuit implemented in a 0.35 μm, 60 GHz ft SiGe HBT BiCMOS process.......In this paper, the influence from substrate effects on the performance of wideband SiGe HBT mixer circuits is investigated. Equivalent circuit models including substrate networks are extracted from on-wafer test structures and compared with electromagnetic simulations. Electromagnetic simulations...

Strain-induced formation of fourfold symmetric SiGe quantum dot molecules.

Science.gov (United States)

Zinovyev, V A; Dvurechenskii, A V; Kuchinskaya, P A; Armbrister, V A

2013-12-27

The strain field distribution at the surface of a multilayer structure with disklike SiGe nanomounds formed by heteroepitaxy is exploited to arrange the symmetric quantum dot molecules typically consisting of four elongated quantum dots ordered along the [010] and [100] directions. The morphological transition from fourfold quantum dot molecules to continuous fortresslike quantum rings with an increasing amount of deposited Ge is revealed. We examine key mechanisms underlying the formation of lateral quantum dot molecules by using scanning tunneling microscopy and numerical calculations of the strain energy distribution on the top of disklike SiGe nanomounds. Experimental data are well described by a simple thermodynamic model based on the accurate evaluation of the strain dependent part of the surface chemical potential. The spatial arrangement of quantum dots inside molecules is attributed to the effect of elastic property anisotropy.

Characterization of nanometer-thick polycrystalline silicon with phonon-boundary scattering enhanced thermoelectric properties and its application in infrared sensors.

Science.gov (United States)

Zhou, Huchuan; Kropelnicki, Piotr; Lee, Chengkuo

2015-01-14

Although significantly reducing the thermal conductivity of silicon nanowires has been reported, it remains a challenge to integrate silicon nanowires with structure materials and electrodes in the complementary metal-oxide-semiconductor (CMOS) process. In this paper, we investigated the thermal conductivity of nanometer-thick polycrystalline silicon (poly-Si) theoretically and experimentally. By leveraging the phonon-boundary scattering, the thermal conductivity of 52 nm thick poly-Si was measured as low as around 12 W mK(-1) which is only about 10% of the value of bulk single crystalline silicon. The ZT of n-doped and p-doped 52 nm thick poly-Si was measured as 0.067 and 0.024, respectively, while most previously reported data had values of about 0.02 and 0.01 for a poly-Si layer with a thickness of 0.5 μm and above. Thermopile infrared sensors comprising 128 pairs of thermocouples made of either n-doped or p-doped nanometer-thick poly-Si strips in a series connected by an aluminium (Al) metal interconnect layer are fabricated using microelectromechanical system (MEMS) technology. The measured vacuum specific detectivity (D*) of the n-doped and p-doped thermopile infrared (IR) sensors are 3.00 × 10(8) and 1.83 × 10(8) cm Hz(1/2) W(-1) for sensors of 52 nm thick poly-Si, and 5.75 × 10(7) and 3.95 × 10(7) cm Hz(1/2) W(-1) for sensors of 300 nm thick poly-Si, respectively. The outstanding thermoelectric properties indicate our approach is promising for diverse applications using ultrathin poly-Si technology.

Extended x-ray absorption fine structure studies of amorphous and crystalline Si-Ge alloys with synchrotron radiation

International Nuclear Information System (INIS)

Kajiyama, Hiroshi

1988-01-01

Extended X-ray absorption fine structure (EXAFS) is a powerful probe to study the local structure around the atom of a specific element. In conventional EXAFS analysis, it has been known that reliable structures are obtained with the different values of absorption edge energy for different neighboring atoms. It is shown in this study that the Ge-K edge EXAFS resulting from the Ge-Ge and Ge-Si bonds in hydrogenated amorphous Si-Ge alloys was able to be excellently explained by a unique absorption edge energy value, provided that a newly developed formula based on the spherical wave function of photoelectrons is used. The microscopic structures of hydrogenated amorphous Si-Ge alloys and crystalline Si-Ge alloys have been determined using the EXAFS method. The lengths of Ge-Ge and Ge-Si bonds were constant throughout their entire composition range, and it was found that the length of Ge-Si bond was close to the average value of the bond lengths of both Ge and Si crystals. In crystalline Si-Ge alloys, it has been shown that the bonds relaxed completely, while the lattice constant varied monotonously with the composition. (Kako, I.)

Metastability and relaxation in tensile SiGe on Ge(001) virtual substrates

International Nuclear Information System (INIS)

Frigerio, Jacopo; Lodari, Mario; Chrastina, Daniel; Mondiali, Valeria; Isella, Giovanni; Bollani, Monica

2014-01-01

We systematically study the heteroepitaxy of SiGe alloys on Ge virtual substrates in order to understand strain relaxation processes and maximize the tensile strain in the SiGe layer. The degree of relaxation is measured by high-resolution x-ray diffraction, and surface morphology is characterized by atomic force microscopy. The results are analyzed in terms of a numerical model, which considers dislocation nucleation, multiplication, thermally activated glide, and strain-dependent blocking. Relaxation is found to be sensitive to growth rate and substrate temperature as well as epilayer misfit and thickness, and growth parameters are found which allow a SiGe film with over 4 GPa of tensile stress to be obtained.

Efficient tunable luminescence of SiGe alloy sheet polymers

International Nuclear Information System (INIS)

Vogg, G.; Meyer, A. J.-P.; Miesner, C.; Brandt, M. S.; Stutzmann, M.

2001-01-01

Crystalline SiGe alloy sheet polymers were topotactically prepared from epitaxially grown calcium germanosilicide Ca(Si 1-x Ge x ) 2 precursor films in the whole composition range. These polygermanosilynes are found to be a well-defined mixture of the known siloxene and polygermyne sheet polymers with the OH groups exclusively bonded to silicon. The optical properties determined by photoluminescence and optical reflection measurements identify the mixed SiGe sheet polymers as direct semiconductors with efficient luminescence tunable in the energy range between 2.4 and 1.3 eV. [copyright] 2001 American Institute of Physics

SiGe epitaxial memory for neuromorphic computing with reproducible high performance based on engineered dislocations

Science.gov (United States)

Choi, Shinhyun; Tan, Scott H.; Li, Zefan; Kim, Yunjo; Choi, Chanyeol; Chen, Pai-Yu; Yeon, Hanwool; Yu, Shimeng; Kim, Jeehwan

2018-01-01

Although several types of architecture combining memory cells and transistors have been used to demonstrate artificial synaptic arrays, they usually present limited scalability and high power consumption. Transistor-free analog switching devices may overcome these limitations, yet the typical switching process they rely on—formation of filaments in an amorphous medium—is not easily controlled and hence hampers the spatial and temporal reproducibility of the performance. Here, we demonstrate analog resistive switching devices that possess desired characteristics for neuromorphic computing networks with minimal performance variations using a single-crystalline SiGe layer epitaxially grown on Si as a switching medium. Such epitaxial random access memories utilize threading dislocations in SiGe to confine metal filaments in a defined, one-dimensional channel. This confinement results in drastically enhanced switching uniformity and long retention/high endurance with a high analog on/off ratio. Simulations using the MNIST handwritten recognition data set prove that epitaxial random access memories can operate with an online learning accuracy of 95.1%.

Towards rhombohedral SiGe epitaxy on 150mm c-plane sapphire substrates

Science.gov (United States)

Duzik, Adam J.; Park, Yeonjoon; Choi, Sang H.

2015-04-01

Previous work demonstrated for the first time the ability to epitaxially grow uniform single crystal diamond cubic SiGe (111) films on trigonal sapphire (0001) substrates. While SiGe (111) forms two possible crystallographic twins on sapphire (0001), films consisting primarily of one twin were produced on up to 99.95% of the total wafer area. This permits new bandgap engineering possibilities and improved group IV based devices that can exploit the higher carrier mobility in Ge compared to Si. Models are proposed on the epitaxy of such dissimilar crystal structures based on the energetic favorability of crystallographic twins and surface reconstructions. This new method permits Ge (111) on sapphire (0001) epitaxy, rendering Ge an economically feasible replacement for Si in some applications, including higher efficiency Si/Ge/Si quantum well solar cells. Epitaxial SiGe films on sapphire showed a 280% increase in electron mobility and a 500% increase in hole mobility over single crystal Si. Moreover, Ge possesses a wider bandgap for solar spectrum conversion than Si, while the transparent sapphire substrate permits an inverted device structure, increasing the total efficiency to an estimated 30-40%, much higher than traditional Si solar cells. Hall Effect mobility measurements of the Ge layer in the Si/Ge/Si quantum well structure were performed to demonstrate the advantage in carrier mobility over a pure Si solar cell. Another application comes in the use of microelectromechanical devices technology, where high-resistivity Si is currently used as a substrate. Sapphire is a more resistive substrate and offers better performance via lower parasitic capacitance and higher film carrier mobility over the current Si-based technology.

Effect of Grain Boundaries on the Performance of Thin-Film-Based Polycrystalline Silicon Solar Cells: A Numerical Modeling

Science.gov (United States)

Chhetri, Nikita; Chatterjee, Somenath

2018-01-01

Solar cells/photovoltaic, a renewable energy source, is appraised to be the most effective alternative to the conventional electrical energy generator. A cost-effective alternative of crystalline wafer-based solar cell is thin-film polycrystalline-based solar cell. This paper reports the numerical analysis of dependency of the solar cell parameters (i.e., efficiency, fill factor, open-circuit voltage and short-circuit current density) on grain size for thin-film-based polycrystalline silicon (Si) solar cells. A minority carrier lifetime model is proposed to do a correlation between the grains, grain boundaries and lifetime for thin-film-based polycrystalline Si solar cells in MATLAB environment. As observed, the increment in the grain size diameter results in increase in minority carrier lifetime in polycrystalline Si thin film. A non-equivalent series resistance double-diode model is used to find the dark as well as light (AM1.5) current-voltage (I-V) characteristics for thin-film-based polycrystalline Si solar cells. To optimize the effectiveness of the proposed model, a successive approximation method is used and the corresponding fitting parameters are obtained. The model is validated with the experimentally obtained results reported elsewhere. The experimentally reported solar cell parameters can be found using the proposed model described here.

SiGe layer thickness effect on the structural and optical properties of well-organized SiGe/SiO2 multilayers

Science.gov (United States)

Vieira, E. M. F.; Toudert, J.; Rolo, A. G.; Parisini, A.; Leitão, J. P.; Correia, M. R.; Franco, N.; Alves, E.; Chahboun, A.; Martín-Sánchez, J.; Serna, R.; Gomes, M. J. M.

2017-08-01

In this work, we report on the production of regular (SiGe/SiO2)20 multilayer structures by conventional RF-magnetron sputtering, at 350 °C. Transmission electron microscopy, scanning transmission electron microscopy, raman spectroscopy, and x-ray reflectometry measurements revealed that annealing at a temperature of 1000 °C leads to the formation of SiGe nanocrystals between SiO2 thin layers with good multilayer stability. Reducing the nominal SiGe layer thickness (t SiGe) from 3.5-2 nm results in a transition from continuous SiGe crystalline layer (t SiGe ˜ 3.5 nm) to layers consisting of isolated nanocrystals (t SiGe ˜ 2 nm). Namely, in the latter case, the presence of SiGe nanocrystals ˜3-8 nm in size, is observed. Spectroscopic ellipsometry was applied to determine the evolution of the onset in the effective optical absorption, as well as the dielectric function, in SiGe multilayers as a function of the SiGe thickness. A clear blue-shift in the optical absorption is observed for t SiGe ˜ 2 nm multilayer, as a consequence of the presence of isolated nanocrystals. Furthermore, the observed near infrared values of n = 2.8 and k = 1.5 are lower than those of bulk SiGe compounds, suggesting the presence of electronic confinement effects in the nanocrystals. The low temperature (70 K) photoluminescence measurements performed on annealed SiGe/SiO2 nanostructures show an emission band located between 0.7-0.9 eV associated with the development of interface states between the formed nanocrystals and surrounding amorphous matrix.

Interface bond relaxation on the thermal conductivity of Si/Ge core-shell nanowires

Energy Technology Data Exchange (ETDEWEB)

Chen, Weifeng; He, Yan; Ouyang, Gang, E-mail: gangouy@hunnu.edu.cn [Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, Synergetic Innovation Center for Quantum Effects and Applications(SICQEA), Hunan Normal University, Changsha 410081 (China); Sun, Changqing [School of Electrical & Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

2016-01-15

The thermal conductivity of Si/Ge core-shell nanowires (CSNWs) is investigated on the basis of atomic-bond-relaxation consideration and continuum mechanics. An analytical model is developed to clarify the interface bond relaxation of Si/Ge CSNWs. It is found that the thermal conductivity of Si core can be modulated through covering with Ge epitaxial layers. The change of thermal conductivity in Si/Ge CSNWs should be attributed to the surface relaxation and interface mismatch between inner Si nanowire and outer Ge epitaxial layer. Our results are in well agreement with the experimental measurements and simulations, suggesting that the presented method provides a fundamental insight of the thermal conductivity of CSNWs from the atomistic origin.

Characterisation of diode-connected SiGe BiCMOS HBTs for space applications

Science.gov (United States)

Venter, Johan; Sinha, Saurabh; Lambrechts, Wynand

2016-02-01

Silicon-germanium (SiGe) bipolar complementary metal-oxide semiconductor (BiCMOS) transistors have vertical doping profiles reaching deeper into the substrate when compared to lateral CMOS transistors. Apart from benefiting from high-speed, high current gain and low-output resistance due to its vertical profile, BiCMOS technology is increasingly becoming a preferred technology for researchers to realise next-generation space-based optoelectronic applications. BiCMOS transistors have inherent radiation hardening, to an extent predictable cryogenic performance and monolithic integration potential. SiGe BiCMOS transistors and p-n junction diodes have been researched and used as a primary active component for over the last two decades. However, further research can be conducted with diode-connected heterojunction bipolar transistors (HBTs) operating at cryogenic temperatures. This work investigates these characteristics and models devices by adapting standard fabrication technology components. This work focuses on measurements of the current-voltage relationship (I-V curves) and capacitance-voltage relationships (C-V curves) of diode-connected HBTs. One configuration is proposed and measured, which is emitterbase shorted. The I-V curves are measured for various temperature points ranging from room temperature (300 K) to the temperature of liquid nitrogen (77 K). The measured datasets are used to extract a model of the formed diode operating at cryogenic temperatures and used as a standard library component in computer aided software designs. The advantage of having broad-range temperature models of SiGe transistors becomes apparent when considering implementation of application-specific integrated circuits and silicon-based infrared radiation photodetectors on a single wafer, thus shortening interconnects and lowering parasitic interference, decreasing the overall die size and improving on overall cost-effectiveness. Primary applications include space-based geothermal

A Radiation Hardened by Design CMOS ASIC for Thermopile Readouts

Science.gov (United States)

Quilligan, G.; Aslam, S.; DuMonthier, J.

2012-01-01

A radiation hardened by design (RHBD) mixed-signal application specific integrated circuit (ASIC) has been designed for a thermopile readout for operation in the harsh Jovian orbital environment. The multi-channel digitizer (MCD) ASIC includes 18 low noise amplifier channels which have tunable gain/filtering coefficients, a 16-bit sigma-delta analog-digital converter (SDADC) and an on-chip controller. The 18 channels, SDADC and controller were designed to operate with immunity to single event latchup (SEL) and to at least 10 Mrad total ionizing dose (TID). The ASIC also contains a radiation tolerant 16-bit 20 MHz Nyquist ADC for general purpose instrumentation digitizer needs. The ASIC is currently undergoing fabrication in a commercial 180 nm CMOS process. Although this ASIC was designed specifically for the harsh radiation environment of the NASA led JEO mission it is suitable for integration into instrumentation payloads 011 the ESA JUICE mission where the radiation hardness requirements are slightly less stringent.

SiGe BiCMOS manufacturing platform for mmWave applications

Science.gov (United States)

Kar-Roy, Arjun; Howard, David; Preisler, Edward; Racanelli, Marco; Chaudhry, Samir; Blaschke, Volker

2010-10-01

TowerJazz offers high volume manufacturable commercial SiGe BiCMOS technology platforms to address the mmWave market. In this paper, first, the SiGe BiCMOS process technology platforms such as SBC18 and SBC13 are described. These manufacturing platforms integrate 200 GHz fT/fMAX SiGe NPN with deep trench isolation into 0.18μm and 0.13μm node CMOS processes along with high density 5.6fF/μm2 stacked MIM capacitors, high value polysilicon resistors, high-Q metal resistors, lateral PNP transistors, and triple well isolation using deep n-well for mixed-signal integration, and, multiple varactors and compact high-Q inductors for RF needs. Second, design enablement tools that maximize performance and lowers costs and time to market such as scalable PSP and HICUM models, statistical and Xsigma models, reliability modeling tools, process control model tools, inductor toolbox and transmission line models are described. Finally, demonstrations in silicon for mmWave applications in the areas of optical networking, mobile broadband, phased array radar, collision avoidance radar and W-band imaging are listed.

sigE facilitates the adaptation of Bordetella bronchiseptica to stress conditions and lethal infection in immunocompromised mice

Directory of Open Access Journals (Sweden)

Barchinger Sarah E

2012-08-01

Full Text Available Abstract Background The cell envelope of a bacterial pathogen can be damaged by harsh conditions in the environment outside a host and by immune factors during infection. Cell envelope stress responses preserve the integrity of this essential compartment and are often required for virulence. Bordetella species are important respiratory pathogens that possess a large number of putative transcription factors. However, no cell envelope stress responses have been described in these species. Among the putative Bordetella transcription factors are a number of genes belonging to the extracytoplasmic function (ECF group of alternative sigma factors, some of which are known to mediate cell envelope stress responses in other bacteria. Here we investigate the role of one such gene, sigE, in stress survival and pathogenesis of Bordetella bronchiseptica. Results We demonstrate that sigE encodes a functional sigma factor that mediates a cell envelope stress response. Mutants of B. bronchiseptica strain RB50 lacking sigE are more sensitive to high temperature, ethanol, and perturbation of the envelope by SDS-EDTA and certain β-lactam antibiotics. Using a series of immunocompromised mice deficient in different components of the innate and adaptive immune responses, we show that SigE plays an important role in evading the innate immune response during lethal infections of mice lacking B cells and T cells. SigE is not required, however, for colonization of the respiratory tract of immunocompetent mice. The sigE mutant is more efficiently phagocytosed and killed by peripheral blood polymorphonuclear leukocytes (PMNs than RB50, and exhibits decreased cytotoxicity toward macrophages. These altered interactions with phagocytes could contribute to the defects observed during lethal infection. Conclusions Much of the work on transcriptional regulation during infection in B. bronchiseptica has focused on the BvgAS two-component system. This study reveals that the SigE

Improved high-frequency equivalent circuit model based on distributed effects for SiGe HBTs with CBE layout

International Nuclear Information System (INIS)

Sun Ya-Bin; Li Xiao-Jin; Zhang Jin-Zhong; Shi Yan-Ling

2017-01-01

In this paper, we present an improved high-frequency equivalent circuit for SiGe heterojunction bipolar transistors (HBTs) with a CBE layout, where we consider the distributed effects along the base region. The actual device structure is divided into three parts: a link base region under a spacer oxide, an intrinsic transistor region under the emitter window, and an extrinsic base region. Each region is considered as a two-port network, and is composed of a distributed resistance and capacitance. We solve the admittance parameters by solving the transmission-line equation. Then, we obtain the small-signal equivalent circuit depending on the reasonable approximations. Unlike previous compact models, in our proposed model, we introduce an additional internal base node, and the intrinsic base resistance is shifted into this internal base node, which can theoretically explain the anomalous change in the intrinsic bias-dependent collector resistance in the conventional compact model. (paper)

SiGe HBT linear-in-dB high dynamic range RF envelope detectors and wideband high linearity amplifiers

OpenAIRE

Pan, Hsuan-yu

2010-01-01

This research work aims on exploiting SiGe HBT technologies in high dynamic range wideband RF linear-in- dB envelope detectors and linear amplifiers. First, an improved all-npn broadband highly linear SiGe HBT differential amplifier is presented based on a variation of Caprio's Quad. A broadband linear amplifier with 46dBm OIP₃ at 20MHz, 34dBm OIP₃ at 1GHz, 6dB noise figure and 10.3dBm P₁dB is demonstrated. Second, an improved exact dynamic model of a fast-settling linear-in-dB Automatic Gain...

SiGe HBTs Optimization for Wireless Power Amplifier Applications

Directory of Open Access Journals (Sweden)

Pierre-Marie Mans

2010-01-01

Full Text Available This paper deals with SiGe HBTs optimization for power amplifier applications dedicated to wireless communications. In this work, we investigate the fT-BVCEO tradeoff by various collector optimization schemes such as epilayer thickness and dopant concentration, and SIC and CAP characteristics. Furthermore, a new trapezoidal base Germanium (Ge profile is proposed. Thanks to this profile, precise control of Ge content at the metallurgical emitter-base junction is obtained. Gain stability is obtained for a wide range of temperatures through tuning the emitter-base junction Ge percent. Finally, a comprehensive investigation of Ge introduction into the collector (backside Ge profile is conducted in order to improve the fT values at high injection levels.

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)

Application of a Pelletron accelerator to study total dose radiation effects on 50 GHz SiGe HBTs

Energy Technology Data Exchange (ETDEWEB)

Praveen, K.C.; Pushpa, N.; Naik, P.S. [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570 006 (India); Cressler, John D. [School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA (United States); Tripathi, Ambuj [Inter University Accelerator Centre (IUAC), New Delhi 110 067 (India); Gnana Prakash, A.P., E-mail: gnanaprakash@physics.uni-mysore.ac.in [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570 006 (India)

2012-02-15

Highlights: Black-Right-Pointing-Pointer Total dose effects of 50 MeV Li3+ ion on 50 GHz SiGe HBTs is investigated. Black-Right-Pointing-Pointer Ion irradiated results were compared with Co-60 gamma results. Black-Right-Pointing-Pointer 50 MeV Li ions create more damage in E-B spacer oxide when compared to Co-60 gamma radiation. Black-Right-Pointing-Pointer Co-60 gamma radiation create more damage in STI oxide when compared to 50 MeV Li ions. Black-Right-Pointing-Pointer Worst case total dose radiation effects can be studied using Pelletron accelerator facilities. - Abstract: We have investigated the effects of 50 MeV lithium ion irradiation on the DC electrical characteristics of first-generation silicon-germanium heterojunction bipolar transistors (50 GHz SiGe HBTs) in the dose range of 600 krad to 100 Mrad. The results of 50 MeV Li{sup 3+} ion irradiation on the SiGe HBTs are compared with 63 MeV proton and Co-60 gamma irradiation results in the same dose range in order to understand the damage induced by different LET species. The radiation response of emitter-base (EB) spacer oxide and shallow trench isolation (STI) oxide to different irradiation types are discussed in this paper. We have also focused on the efficacy in the application of a Pelletron accelerator to study total dose irradiation studies in SiGe HBTs.

Delayed plastic relaxation limit in SiGe islands grown by Ge diffusion from a local source

Energy Technology Data Exchange (ETDEWEB)

Vanacore, G. M.; Zani, M.; Tagliaferri, A., E-mail: alberto.tagliaferri@polimi.it [CNISM-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 Milano (Italy); Nicotra, G. [IMM-CNR, Stradale Primosole 50, I-95121 Catania (Italy); Bollani, M. [CNR-IFN, LNESS, Via Anzani 42, I-22100 Como (Italy); Bonera, E.; Montalenti, F.; Picco, A.; Boioli, F. [Dipartimento di Scienza dei Materiali and L-NESS, Università Milano-Bicocca, via Cozzi 53, I-20125 Milano (Italy); Capellini, G. [Department of Sciences at the Università Roma Tre, Via Vasca Navale 79, 00146 Roma (Italy); Isella, G. [CNISM, LNESS, Dipartimento di Fisica, Politecnico di Milano (Polo di Como), Via Anzani 42, I-22100 Como (Italy); Osmond, J. [ICFO–The Institute of Photonic Sciences, Av. Carl Friedrich Gauss, 3, E-08860 Castelldefels (Barcelona) (Spain)

2015-03-14

The hetero-epitaxial strain relaxation in nano-scale systems plays a fundamental role in shaping their properties. Here, the elastic and plastic relaxation of self-assembled SiGe islands grown by surface-thermal-diffusion from a local Ge solid source on Si(100) are studied by atomic force and transmission electron microscopies, enabling the simultaneous investigation of the strain relaxation in different dynamical regimes. Islands grown by this technique remain dislocation-free and preserve a structural coherence with the substrate for a base width as large as 350 nm. The results indicate that a delay of the plastic relaxation is promoted by an enhanced Si-Ge intermixing, induced by the surface-thermal-diffusion, which takes place already in the SiGe overlayer before the formation of a critical nucleus. The local entropy of mixing dominates, leading the system toward a thermodynamic equilibrium, where non-dislocated, shallow islands with a low residual stress are energetically stable. These findings elucidate the role of the interface dynamics in modulating the lattice distortion at the nano-scale, and highlight the potential use of our growth strategy to create composition and strain-controlled nano-structures for new-generation devices.

Magnetic behavior of Si-Ge bond in SixGe4-x nano-clusters

Science.gov (United States)

Nahali, Masoud; Mehri, Ali

2018-06-01

The structure of SixGe4-x nano-clusters were optimized by MPW1B95 level of theory using MG3S and SDB-aug-cc-PVTZ basis set. The agreement of the calculated ionization and dissociation energies with experimental values validates the reported structures of nano-clusters and justifies the use of hybrid meta density functional method. Since the Si-Si bond is stronger than Si-Ge and Ge-Ge bonds, the Si-Si, Si-Ge, and Ge-Ge diagonal bonds determine the precedence of the stability in these nano-clusters. The hybrid meta density functional calculations were carried out to investigate the adsorption of CO on all possible SixGe4-x nano-clusters. It was found that the silicon atom generally makes a stronger bond with CO than germanium and thereby preferentially affects the shape of structures having higher multiplicity. In Si-Ge structures with higher spin more than 95% of spins accumulate on positions with less bonds to other atoms of the cluster. Through CO adsorption on these clusters bridge structures are made that behave as spin bridge which conduct the spin from the nano-cluster surface to the adsorbate atoms. A better understanding of bridged structures was achieved upon introducing the 'spin bridge' concept. Based on exhaustive spin density analysis, it was found that the reason for the extra negative charge on oxygen in the bridged structures is the relocation of spin from the surface through the bridge.

Heteroepitaxial Growth of Vacuum-Evaporated Si-Ge Films on Nano structured Silicon Substrates

International Nuclear Information System (INIS)

Ayu Wazira Azhari; Ayu Wazira Azhari; Kamaruzzaman Sopian; Saleem Hussain Zaidi

2015-01-01

In this study, a low-cost vacuum-evaporated technique is used in the heteroepitaxial growth of Si-Ge films. Three different surface variations are employed: for example polished Si, Si micro pyramids and Si nano pillars profiles. A simple metal-assisted chemical etching method is used to fabricate the Si nano pillars, with Ag acting as a catalyst. Following deposition, substrates are subjected to post-deposition thermal annealing at 1000 degree Celsius to improve the crystallinity of the Ge layer. Optical and morphological studies of surface area are conducted using field emission scanning electron microscopy (FE-SEM), Energy Dispersive X-ray (EDX), Raman spectroscopy and infrared spectroscopy. From the infrared spectroscopy analysis, the energy bandgap for Si-Ge films is estimated to be around 0.94 eV. This high-quality Si-Ge film is most favourable for optics, optoelectronics and high-efficiency solar cell applications. (author)

Templated self-assembly of SiGe quantum dots

Energy Technology Data Exchange (ETDEWEB)

Dais, Christian

2009-08-19

This PhD thesis reports on the fabrication and characterization of exact aligned SiGe quantum dot structures. In general, SiGe quantum dots which nucleate via the Stranski-Krastanov growth mode exhibit broad size dispersion and nucleate randomly on the surface. However, to tap the full potential of SiGe quantum dots it is necessary to control the positioning and size of the dots on a nanometer length, e.g. for electronically addressing of individual dots. This can be realized by so-called templated self-assembly, which combines top-down lithography with bottom-up selfassembly. In this process the lithographically defined pits serve as pre-defined nucleation points for the epitaxially grown quantum dots. In this thesis, extreme ultraviolet interference lithography at a wavelength of e=13.4 nm is employed for prepatterning of the Si substrates. This technique allows the precise and fast fabrication of high-resolution templates with a high degree of reproducibility. The subsequent epitaxial deposition is either performed by molecular beam epitaxy or low-pressure chemical vapour deposition. It is shown that the dot nucleation on pre-patterned substrates depends strongly on the lithography parameters, e.g. size and periodicity of the pits, as well as on the epitaxy parameters, e.g. growth temperature or material coverage. The interrelations are carefully analyzed by means of scanning force microscopy, transmission electron microscopy and X-ray diffraction measurements. Provided that correct template and overgrowth parameters are chosen, perfectly aligned and uniform SiGe quantum dot arrays of different period, size as well as symmetry are created. In particular, the quantum dot arrays with the so far smallest period (35 nm) and smallest size dispersion are fabricated in this thesis. Furthermore, the strain fields of the underlying quantum dots allow the fabrication of vertically aligned quantum dot stacks. Combining lateral and vertical dot alignment results in three

Fabrication of SGOI material by oxidation of an epitaxial SiGe layer on an SOI wafer with H ions implantation

International Nuclear Information System (INIS)

Cheng Xinli; Chen Zhijun; Wang Yongjin; Jin Bo; Zhang Feng; Zou Shichang

2005-01-01

SGOI materials were fabricated by thermal dry oxidation of epitaxial H-ion implanted SiGe layers on SOI wafers. The hydrogen implantation was found to delay the oxidation rate of SiGe layer and to decrease the loss of Ge atoms during oxidation. Further, the H implantation did not degrade the crystallinity of SiGe layer during fabrication of the SGOI

SigE Is a Chaperone for the Salmonella enterica Serovar Typhimurium Invasion Protein SigD

OpenAIRE

Darwin, K. Heran; Robinson, Lloyd S.; Miller, Virginia L.

2001-01-01

SigD is translocated into eucaryotic cells by a type III secretion system. In this work, evidence that the putative chaperone SigE directly interacts with SigD is presented. A bacterial two-hybrid system demonstrated that SigE can interact with itself and SigD. In addition, SigD was specifically copurified with SigE-His6 on a nickel column.

Thermal transport in nanocrystalline Si and SiGe by ab initio based Monte Carlo simulation.

Science.gov (United States)

Yang, Lina; Minnich, Austin J

2017-03-14

Nanocrystalline thermoelectric materials based on Si have long been of interest because Si is earth-abundant, inexpensive, and non-toxic. However, a poor understanding of phonon grain boundary scattering and its effect on thermal conductivity has impeded efforts to improve the thermoelectric figure of merit. Here, we report an ab-initio based computational study of thermal transport in nanocrystalline Si-based materials using a variance-reduced Monte Carlo method with the full phonon dispersion and intrinsic lifetimes from first-principles as input. By fitting the transmission profile of grain boundaries, we obtain excellent agreement with experimental thermal conductivity of nanocrystalline Si [Wang et al. Nano Letters 11, 2206 (2011)]. Based on these calculations, we examine phonon transport in nanocrystalline SiGe alloys with ab-initio electron-phonon scattering rates. Our calculations show that low energy phonons still transport substantial amounts of heat in these materials, despite scattering by electron-phonon interactions, due to the high transmission of phonons at grain boundaries, and thus improvements in ZT are still possible by disrupting these modes. This work demonstrates the important insights into phonon transport that can be obtained using ab-initio based Monte Carlo simulations in complex nanostructured materials.

Heavy Ion Microbeam and Broadbeam Transients in SiGe HBTs

Science.gov (United States)

Pellish, Jonathan A.; Reed, Robert A.; McMorrow, Dale; Vizkelethy, Gyorgy; Dodd, Paul E.; Ferlet-Cavrois, Veronique; Baggio, Jacques; Paillet, Philippe; Duhamel, Olivier; Phillips, Stanley D.;

De-embedding and Modelling of pnp SiGe HBTs

DEFF Research Database (Denmark)

Hadziabdic, Dzenan; Jiang, Chenhui; Johansen, Tom Keinicke

2007-01-01

In this work we present a direct parameter extraction procedure for SiGe pnp heterojunction bipolar transistor (HBT) large-signal and small-signal models. Test structure parasitics are removed from the measured small-signal parameters using an open-short de-embedding technique, improved to accoun...

Critical Role of a Single Position in the −35 Element for Promoter Recognition by Mycobacterium tuberculosis SigE and SigH▿

OpenAIRE

Song, Taeksun; Song, Seung-Eun; Raman, Sahadevan; Anaya, Mauricio; Husson, Robert N.

2008-01-01

Mycobacterial SigE and SigH both initiate transcription from the sigB promoter, suggesting that they recognize similar sequences. Through mutational and primer extension analyses, we determined that SigE and SigH recognize nearly identical promoters, with differences at the 3′ end of the −35 element distinguishing between SigE- and SigH-dependent promoters.

Ge nanobelts with high compressive strain fabricated by secondary oxidation of self-assembly SiGe rings

DEFF Research Database (Denmark)

Lu, Weifang; Li, Cheng; Lin, Guangyang

2015-01-01

Curled Ge nanobelts were fabricated by secondary oxidation of self-assembly SiGe rings, which were exfoliated from the SiGe stripes on the insulator. The Ge-rich SiGe stripes on insulator were formed by hololithography and modified Ge condensation processes of Si0.82Ge0.18 on SOI substrate. Ge...... nanobelts under a residual compressive strain of 2% were achieved, and the strain should be higher before partly releasing through bulge islands and breakage of the curled Ge nanobelts during the secondary oxidation process. The primary factor leading to compressive strain is thermal shrinkage of Ge...... nanobelts, which extrudes to Ge nanobelts in radial and tangent directions during the cooling process. This technique is promising for application in high-mobility Ge nano-scale transistors...

Nitride passivation of the interface between high-k dielectrics and SiGe

Energy Technology Data Exchange (ETDEWEB)

Sardashti, Kasra [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358 (United States); Materials Science and Engineering Program, University of California, San Diego, La Jolla, California 92093-0411 (United States); Hu, Kai-Ting [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358 (United States); Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093-0411 (United States); Tang, Kechao; McIntyre, Paul [Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States); Madisetti, Shailesh; Oktyabrsky, Serge [Colleges of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, New York 12222 (United States); Siddiqui, Shariq; Sahu, Bhagawan [TD Research, GLOBALFOUNDRIES US, Inc., Albany, New York 12203 (United States); Yoshida, Naomi; Kachian, Jessica; Dong, Lin [Applied Materials, Inc., Santa Clara, California 95054 (United States); Fruhberger, Bernd [California Institute for Telecommunications and Information Technology, University of California San Diego, La Jolla, California 92093-0436 (United States); Kummel, Andrew C., E-mail: akummel@ucsd.edu [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0358 (United States)

2016-01-04

In-situ direct ammonia (NH{sub 3}) plasma nitridation has been used to passivate the Al{sub 2}O{sub 3}/SiGe interfaces with Si nitride and oxynitride. X-ray photoelectron spectroscopy of the buried Al{sub 2}O{sub 3}/SiGe interface shows that NH{sub 3} plasma pre-treatment should be performed at high temperatures (300 °C) to fully prevent Ge nitride and oxynitride formation at the interface and Ge out-diffusion into the oxide. C-V and I-V spectroscopy results show a lower density of interface traps and smaller gate leakage for samples with plasma nitridation at 300 °C.

Significant reduction of thermal conductivity in Si/Ge core-shell nanowires.

Science.gov (United States)

Hu, Ming; Giapis, Konstantinos P; Goicochea, Javier V; Zhang, Xiaoliang; Poulikakos, Dimos

2011-02-09

We report on the effect of germanium (Ge) coatings on the thermal transport properties of silicon (Si) nanowires using nonequilibrium molecular dynamics simulations. Our results show that a simple deposition of a Ge shell of only 1 to 2 unit cells in thickness on a single crystalline Si nanowire can lead to a dramatic 75% decrease in thermal conductivity at room temperature compared to an uncoated Si nanowire. By analyzing the vibrational density states of phonons and the participation ratio of each specific mode, we demonstrate that the reduction in the thermal conductivity of Si/Ge core-shell nanowire stems from the depression and localization of long-wavelength phonon modes at the Si/Ge interface and of high frequency nonpropagating diffusive modes.

Effect of Synthesis Procedure on Thermoelectric Property of SiGe Alloy

Science.gov (United States)

Li, Jing; Han, Jun; Jiang, Tao; Luo, Lili; Xiang, Yongchun

2018-05-01

SiGe thermoelectric material has been synthesized by ball milling combined with hot pressing (HP) or spark plasma sintering (SPS). Effects of ball milling time, powder to ball weight ratio and sintering method on microstructure and thermoelectric properties of SiGe are studied. The results show that longer ball milling time leads to decreased density and worse electrical properties. In the sintering process, SPS results in much larger density and better electrical properties than HP. The Si0.795Ge0.2B0.005 sample prepared by 2 h ball milling combined with SPS obtains a maximum power factor of 3.0 mW m-1 K-2 at 860 K and ZT of 0.95 at 1000 K.

Diffusion of $^{56}$Co in GaAs and SiGe alloys

CERN Multimedia

Koskelo, O K

2007-01-01

Following our previous diffusion studies performed with the modified radiotracer technique, we propose to determine the diffusion of cobalt in GaAs and SiGe alloys under intrinsic conditions. In the literature only three previous studies for Co diffusion in GaAs may be found and the results differ by over four orders of magnitude from each other. For Co diffusion in SiGe alloys no previous data is available in the literature. For Co diffusion in Ge one study may be found but the results have been obtained with material having increased dislocation density. For dislocation-free material no previous measurements are available. For such experiments we ask for two runs of 3 shifts (total of 6 shifts) with $^{56}$Co$^{+}$ ion beam.

Ordered Arrays of SiGe Islands from Low-Energy PECVD

Directory of Open Access Journals (Sweden)

Chrastina D

2010-01-01

Full Text Available Abstract SiGe islands have been proposed for applications in the fields of microelectronics, optoelectronics and thermoelectrics. Although most of the works in literature are based on MBE, one of the possible advantages of low-energy plasma-enhanced chemical vapor deposition (LEPECVD is a wider range of deposition rates, which in turn results in the possibility of growing islands with a high Ge concentration. We will show that LEPECVD can be effectively used for the controlled growth of ordered arrays of SiGe islands. In order to control the nucleation of the islands, patterned Si (001 substrates were obtained by e-beam lithography (EBL and dry etching. We realized periodic circular pits with diameters ranging from 80 to 300 nm and depths from 65 to 75 nm. Subsequently, thin films (0.8–3.2 nm of pure Ge were deposited by LEPECVD, resulting in regular and uniform arrays of Ge-rich islands. LEPECVD allowed the use of a wide range of growth rates (0.01–0.1 nm s−1 and substrates temperatures (600–750°C, so that the Ge content of the islands could be varied. Island morphology was characterized by AFM, while μ-Raman was used to analyze the Ge content inside the islands and the composition differences between islands on patterned and unpatterned areas of the substrate.

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.

Transformation of point defects under annealing of neutron-irradiated Si and Si:Ge

International Nuclear Information System (INIS)

Pomozov, Yu.V.; Khirunenko, L.I.; Shakhovtsev, V.I.; Yashnik, V.I.

1990-01-01

Transformation of point radiation defects under isochronous annealing of neurton-irradaited Si and Si:Ge is studied. It is determined, that occurence of several new centers which produce A-centre range absorption bands is observed at annealing within 423-493 K temperature range. It is shown that vacancy and oxygen are included in the centers composition. It is found that VO centre transformation into VO 2 at annealing occurs via intermediate stage in contrast to that occuring in electron-irradiated crystals via VO direct diffusion to interstitial oxygen. Transformation of centers under Si ansd Si:Ge annealing occurs similarly

Porous silicon-based passivation and gettering in polycrystalline silicon solar cells

International Nuclear Information System (INIS)

Dimassi, W.; Bouaiecha, M.; Saadoun, M.; Bessaies, B.; Ezzaouia, H.; Bennaceur, R.

2002-01-01

In this work, we report on the effect of introducing a superficial porous silicon (PS) layer on the electrical characteristics of polycrystalline silicon solar cells. The PS layer was formed using a vapour etching (VE)-based method. In addition to its known anti-reflecting action, the forming hydrogen-rich PS layer acts as a passivating agent for the surface of the cell. As a result we found an improvement of the I-V characteristics in dark conditions and AM1 illumination. We show that when the formation of a superficial PS layer is followed by a heat treatment, gettering of impurities from the polycrystalline silicon material is possible. After the removal of the PS layer and the formation of the photovoltaic (PV) structure, we observed an increase of the light-beam-induced-current (LBIC) for treatment temperatures not exceeding 900 deg. C. An improvement of the bulk minority carrier diffusion length and the grain boundary (GB) recombination velocity were observed as the temperature rises, although a global decrease of the LBIC current was observed for temperatures greater than 900 deg. C

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

Measurement of low-frequency base and collector current noise and coherence in SiGe heterojunction bipolar transistors using transimpedance amplifiers

NARCIS (Netherlands)

Bruce, S.P.O.; Vandamme, L.K.J.; Rydberg, A.

1999-01-01

Transimpedance amplifiers have been used for direct study of current noise in silicon germanium (SiGe) heterojunction bipolar transistors (HBT's) at different biasing conditions. This has facilitated a wider range of resistances in the measurement circuit around the transistor than is possible when

270GHz SiGe BiCMOS manufacturing process platform for mmWave applications

Science.gov (United States)

Kar-Roy, Arjun; Preisler, Edward J.; Talor, George; Yan, Zhixin; Booth, Roger; Zheng, Jie; Chaudhry, Samir; Howard, David; Racanelli, Marco

2011-11-01

TowerJazz has been offering the high volume commercial SiGe BiCMOS process technology platform, SBC18, for more than a decade. In this paper, we describe the TowerJazz SBC18H3 SiGe BiCMOS process which integrates a production ready 240GHz FT / 270 GHz FMAX SiGe HBT on a 1.8V/3.3V dual gate oxide CMOS process in the SBC18 technology platform. The high-speed NPNs in SBC18H3 process have demonstrated NFMIN of ~2dB at 40GHz, a BVceo of 1.6V and a dc current gain of 1200. This state-of-the-art process also comes with P-I-N diodes with high isolation and low insertion losses, Schottky diodes capable of exceeding cut-off frequencies of 1THz, high density stacked MIM capacitors, MOS and high performance junction varactors characterized up to 50GHz, thick upper metal layers for inductors, and various resistors such as low value and high value unsilicided poly resistors, metal and nwell resistors. Applications of the SBC18H3 platform for millimeter-wave products for automotive radars, phased array radars and Wband imaging are presented.

Sensitivity of the crystal quality of SiGe layers grown at low temperatures by trisilane and germane

Energy Technology Data Exchange (ETDEWEB)

Abedin, A., E-mail: aabedin@kth.se; Moeen, M.; Cappetta, C.; Östling, M.; Radamson, H.H., E-mail: rad@kth.se

2016-08-31

This work investigates the crystal quality of SiGe layers grown at low temperatures using trisilane, and germane precursors. The crystal quality sensitivity was monitored for hydrogen chloride and/or minor oxygen amount during SiGe epitaxy or at the interface of SiGe/Si layers. The quality of the epi-layers was examined by quantifying noise parameter, K{sub 1/f} obtained from the power spectral density vs. 1/f curves. The results indicate that while it is difficult to detect small defect densities in SiGe layers by physical material characterization, the noise measurement could reveal the effects of oxygen contamination as low as 0.16 mPa inside and in the interface of the layers. - Highlights: • SiGe layers were grown using trisilane and germane. • Effect of HCl flow on Ge content and growth rate was investigated. • O{sub 2} partial pressures up to 4.3 mPa did not affect x-ray diffraction pattern. • O{sub 2} partial pressures as low as 0.16 mPa increased the noise level. • HCl increased metal contaminations of the layers and the noise level consequently.

The Relationship between Nanocluster Precipitation and Thermal Conductivity in Si/Ge Amorphous Multilayer Films: Effects of Cu Addition

Directory of Open Access Journals (Sweden)

Ahmad Ehsan Mohd Tamidi

2016-01-01

Full Text Available We have used a molecular dynamics technique to simulate the relationship between nanocluster precipitation and thermal conductivity in Si/Ge amorphous multilayer films, with and without Cu addition. In the study, the Green-Kubo equation was used to calculate thermal conductivity in these materials. Five specimens were prepared: Si/Ge layers, Si/(Ge + Cu layers, (Si + Cu/(Ge + Cu layers, Si/Cu/Ge/Cu layers, and Si/Cu/Ge layers. The number of precipitated nanoclusters in these specimens, which is defined as the number of four-coordinate atoms, was counted along the lateral direction of the specimens. The observed results of precipitate formation were considered in relation to the thermal conductivity results. Enhancement of precipitation of nanoclusters by Cu addition, that is, densification of four-coordinate atoms, can prevent the increment of thermal conductivity. Cu dopant increases the thermal conductivity of these materials. Combining these two points, we concluded that Si/Cu/Ge is the best structure to improve the conversion efficiency of the Si/Ge amorphous multilayer films.

Ultra-broadband Nonlinear Microwave Monolithic Integrated Circuits in SiGe, GaAs and InP

DEFF Research Database (Denmark)

Krozer, Viktor; Johansen, Tom Keinicke; Djurhuus, Torsten

2006-01-01

.5 GHz and ≫ 10 GHz for SiGe BiCMOS and GaAs MMIC, respectively. Analysis of the frequency behaviour of frequency converting devices is presented for improved mixer design. Millimeter-wave front-end components for advanced microwave imaging and communications purposes have also been demonstrated......Analog MMIC circuits with ultra-wideband operation are discussed in view of their frequency limitation and different circuit topologies. Results for designed and fabricated frequency converters in SiGe, GaAs, and InP technologies are presented in the paper. RF type circuit topologies exhibit a flat...... conversion gain with a 3 dB bandwidth of 10 GHz for SiGe and in excess of 20 GHz for GaAs processes. The concurrent LO-IF isolation is better than -25 dB, without including the improvement due to the combiner circuit. The converter circuits exhibit similar instantaneous bandwidth at IF and RF ports of ≫ 7...

Interfacial Phonon Transport Through Si/Ge Multilayer Film Using Monte Carlo Scheme With Spectral Transmissivity

Directory of Open Access Journals (Sweden)

Xin Ran

2018-05-01

Full Text Available The knowledge of interfacial phonon transport accounting for detailed phonon spectral properties is desired because of its importance for design of nanoscale energy systems. In this work, we investigate the interfacial phonon transport through Si/Ge multilayer films using an efficient Monte Carlo scheme with spectral transmissivity, which is validated for cross-plane phonon transport through both Si/Ge single-layer and Si/Ge bi-layer thin films by comparing with the discrete-ordinates solution. Different thermal boundary conductances between even the same material pair are declared at different interfaces within the multilayer system. Furthermore, the thermal boundary conductances at different interfaces show different trends with varying total system size, with the variation slope, very different as well. The results are much different from those in the bi-layer thin film or periodic superlattice. These unusual behaviors can be attributed to the combined interfacial local non-equilibrium effect and constraint effect from other interfaces.

Unlocking the Origin of Superior Performance of a Si-Ge Core-Shell Nanowire Quantum Dot Field Effect Transistor.

Science.gov (United States)

Dhungana, Kamal B; Jaishi, Meghnath; Pati, Ranjit

2016-07-13

The sustained advancement in semiconducting core-shell nanowire technology has unlocked a tantalizing route for making next generation field effect transistor (FET). Understanding how to control carrier mobility of these nanowire channels by applying a gate field is the key to developing a high performance FET. Herein, we have identified the switching mechanism responsible for the superior performance of a Si-Ge core-shell nanowire quantum dot FET over its homogeneous Si counterpart. A quantum transport approach is used to investigate the gate-field modulated switching behavior in electronic current for ultranarrow Si and Si-Ge core-shell nanowire quantum dot FETs. Our calculations reveal that for the ON state, the gate-field induced transverse localization of the wave function restricts the carrier transport to the outer (shell) layer with the pz orbitals providing the pathway for tunneling of electrons in the channels. The higher ON state current in the Si-Ge core-shell nanowire FET is attributed to the pz orbitals that are distributed over the entire channel; in the case of Si nanowire, the participating pz orbital is restricted to a few Si atoms in the channel resulting in a smaller tunneling current. Within the gate bias range considered here, the transconductance is found to be substantially higher in the case of a Si-Ge core-shell nanowire FET than in a Si nanowire FET, which suggests a much higher mobility in the Si-Ge nanowire device.

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.

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

Low thermal budget surface preparation of Si and SiGe

International Nuclear Information System (INIS)

Abbadie, A.; Hartmann, J.M.; Holliger, P.; Semeria, M.N.; Besson, P.; Gentile, P.

2004-01-01

Using a two-step cleaning, we have investigated the low thermal budget surface preparation of Si and Si 1-x Ge x (x=0.2-0.33). It consists of an ex situ 'HF-last' wet-cleaning and an in situ low thermal budget H 2 bake in a reduced pressure-chemical vapor deposition reactor. Using secondary ion mass spectrometry, we have evaluated the effects of different H 2 bake temperatures (in between 750 and 850 deg. C for 2 min) on the removal efficiency of C, O and F atoms still present on the surface of Si and SiGe virtual substrates after the 'HF-last' wet-cleaning. We have then examined the impact of the (wet-cleaning+H 2 bake) combination on the surface cross-hatch of SiGe as-grown virtual substrates, focusing on the analysis, notably by atomic force microscopy, of the surface topography before and after the miscellaneous thermal treatments. In situ hydrogen baking steps in between 775 and 850 deg. C do not modify the surface morphology and roughness. An easy and rapid optical characterization method, i.e. the optical interferometry, is presented as well to monitor in line the morphological changes induced by such processing steps as chemical mechanical polishing, wet-cleaning, H 2 bake, etc. Despite the lower resolution of the optical profilometer, the surface roughness values coming from it have been correctly correlated with those obtained from AFM. An optimized 'HF-last' wet-cleaning using a diluted chemistry in conjunction with a H 2 bake at 800 deg. C for 2 min (775 deg. C, 2') is a good compromise for SiGe (Si) surface preparation

The effect of fluorine in low thermal budget polysilicon emitters for SiGe heterojunction bipolar transistors

International Nuclear Information System (INIS)

Schiz, F.J.W.

1999-03-01

This thesis investigates the behaviour of fluorine in two types of polysilicon emitter. In the first type the emitter is deposited at 610 deg. C as polycrystalline silicon (p-Si). In the second type the emitter is deposited at 560 deg. C as amorphous silicon (α-Si). The amorphous silicon 1 then regrows to polysilicon during subsequent high temperature anneals. Remarkably different behaviour of fluorine is seen in as-deposited α-Si and as-deposited p-Si emitter bipolar transistors. In the most extreme case, fluorine-implanted as-deposited p-Si devices show a base current increase by a factor of 1.5 and equivalent α-Si devices a base current decrease by a factor of 10.0 compared to unimplanted devices. Cross-section TEM observations are made to study the structure of the polysilicon/silicon interface and SIMS measurements to study the distribution of the fluorine in the polysilicon. The TEM results correlate well with the electrical results and show that fluorine accelerates interfacial oxide breakup. Furthermore, they show that for a given thermal budget, more interfacial oxide breakup and thus more epitaxial regrowth is obtained for transistors with p-Si polysilicon emitters. This results in a lower emitter resistance, for example as low as 12Ωμm 2 for as-deposited p-Si devices. The base current suppression for as-deposited α-Si devices is explained by fluorine passivation of trapping states at the interface. Analysis of the fluorine SIMS profiles suggests that they do not resemble normal diffusion profiles, but are due to fluorine trapped at defects. It is shown that a reciprocal relationship exists between the fluorine dose in the bulk polysilicon layer and the fluorine dose at the interface. In as-deposited α-Si devices, there is more fluorine trapped at defects in the bulk polysilicon layer, so less is available to diffuse to the interface. As a result there is less interfacial oxide breakup and more passivation in the as-deposited α-Si devices. These

Growth of light-emitting SiGe heterostructures on strained silicon-on-insulator substrates with a thin oxide layer

Energy Technology Data Exchange (ETDEWEB)

Baidakova, N. A., E-mail: banatale@ipmras.ru [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Bobrov, A. I. [University of Nizhny Novgorod (Russian Federation); Drozdov, M. N.; Novikov, A. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Pavlov, D. A. [University of Nizhny Novgorod (Russian Federation); Shaleev, M. V.; Yunin, P. A.; Yurasov, D. V.; Krasilnik, Z. F. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)

2015-08-15

The possibility of using substrates based on “strained silicon on insulator” structures with a thin (25 nm) buried oxide layer for the growth of light-emitting SiGe structures is studied. It is shown that, in contrast to “strained silicon on insulator” substrates with a thick (hundreds of nanometers) oxide layer, the temperature stability of substrates with a thin oxide is much lower. Methods for the chemical and thermal cleaning of the surface of such substrates, which make it possible to both retain the elastic stresses in the thin Si layer on the oxide and provide cleaning of the surface from contaminating impurities, are perfecte. It is demonstrated that it is possible to use the method of molecular-beam epitaxy to grow light-emitting SiGe structures of high crystalline quality on such substrates.

The influence of a Si cap on self-organized SiGe islands and the underlying wetting layer

International Nuclear Information System (INIS)

Brehm, M.; Grydlik, M.; Groiss, H.; Hackl, F.; Schaeffler, F.; Fromherz, T.; Bauer, G.

2011-01-01

For the prototypical SiGe/Si(001) Stranski-Krastanow (SK) growth system, the influence of intermixing caused by the deposition of a Si cap layer at temperatures T cap between 300 deg. C and 700 deg. C is studied both for the SiGe wetting layer (WL) and the SiGe islands. Systematic growth experiments were carried out with an ultrahigh resolution of down to 0.005 monolayers (ML) of deposited Ge. The properties of the samples were investigated via photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy. We studied in detail the influence of T cap in the three main coverage regions of SiGe SK growth, which are (i) the WL build-up regime, (ii) the island nucleation regime, where most of the Ge is supplied via material transfer from the WL, and (iii) the saturation regime, where the WL thickness remains initially stable. At T cap = 300 deg. C, we found that both the WL and the island are essentially preserved in composition and shape, whereas at 500 deg. C the WL becomes heavily alloyed during capping, and at 700 deg. C the islands also become alloyed. At T cap = 500 deg. C we found enhanced WL intermixing in the presence of dome-shaped islands, whereas at T cap 700 deg. C the WL properties become dominated by the dissolution of pyramid-shaped islands upon capping. At Ge coverages above ≅6 ML, we found an unexpected thickening of the WL, almost independently of T cap . This finding suggests that the density and the volume of the dome-shaped islands have an upper limit, beyond which excess Ge from the external source again becomes incorporated into the WL. Finally, we compared PL spectra with AFM-based evaluations of the integral island volumes in order to determine in a straightforward manner the average composition of the SiGe islands.

The effects of hot carrier and swift heavy ion irradiation on electrical characteristics of advanced 200 GHz SiGe HBTs

Energy Technology Data Exchange (ETDEWEB)

Vinayakprasanna, N. H.; Praveen, K. C.; Prakash, A. P. Gnana, E-mail: gnanaprakash@physics.uni-mysore.ac.in [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore-570006 (India); Cressler, J. D. [School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta-30332, GA (United States)

2016-05-23

The 200 GHz SiGe HBTs were irradiated with 80 MeV Carbon ions up to a total dose of 100 Mrad to understand the degradation in electrical characteristics. The degradation in the electrical characteristics of SiGe HBTs was also studied by mixed mode electrical stress up to 10,000 s. The electrical characteristics were measured before and after every total dose and after fixed stress time. The normalized peak h{sub FE} of the stressed and irradiated SiGe HBTs are compared to estimate the equivalent stress time for a particular total dose. These correlations are drawn for the first time and the results will establish a systematic relation between stress time and total dose.

The effects of hot carrier and swift heavy ion irradiation on electrical characteristics of advanced 200 GHz SiGe HBTs

International Nuclear Information System (INIS)

Vinayakprasanna, N. H.; Praveen, K. C.; Prakash, A. P. Gnana; Cressler, J. D.

2016-01-01

The 200 GHz SiGe HBTs were irradiated with 80 MeV Carbon ions up to a total dose of 100 Mrad to understand the degradation in electrical characteristics. The degradation in the electrical characteristics of SiGe HBTs was also studied by mixed mode electrical stress up to 10,000 s. The electrical characteristics were measured before and after every total dose and after fixed stress time. The normalized peak h_F_E of the stressed and irradiated SiGe HBTs are compared to estimate the equivalent stress time for a particular total dose. These correlations are drawn for the first time and the results will establish a systematic relation between stress time and total dose.

Performance enhancement in p-channel charge-trapping flash memory devices with Si/Ge super-lattice channel and band-to-band tunneling induced hot-electron injection

International Nuclear Information System (INIS)

Liu, Li-Jung; Chang-Liao, Kuei-Shu; Jian, Yi-Chuen; Wang, Tien-Ko; Tsai, Ming-Jinn

2013-01-01

P-channel charge-trapping flash memory devices with Si, SiGe, and Si/Ge super-lattice channel are investigated in this work. A Si/Ge super-lattice structure with extremely low roughness and good crystal structure is obtained by precisely controlling the epitaxy thickness of Ge layer. Both programming and erasing (P/E) speeds are significantly improved by employing this Si/Ge super-lattice channel. Moreover, satisfactory retention and excellent endurance characteristics up to 10 6 P/E cycles with 3.8 V memory window show that the degradation on reliability properties is negligible when super-lattice channel is introduced. - Highlights: ► A super-lattice structure is proposed to introduce more Ge content into channel. ► Super-lattice structure possesses low roughness and good crystal structure. ► P-channel flash devices with Si, SiGe, and super-lattice channel are investigated. ► Programming/erasing speeds are significantly improved. ► Reliability properties can be kept for device with super-lattice channel

Boron diffusion in strained and strain-relaxed SiGe

International Nuclear Information System (INIS)

Wang, C.C.; Sheu, Y.M.; Liu, Sally; Duffy, R.; Heringa, A.; Cowern, N.E.B.; Griffin, P.B.

2005-01-01

SiGe has been utilized for aggressive CMOS technologies development recently and there are many references [M. Shima, T. Ueno, T. Kumise, H. Shido, Y. Sakuma, S. Nakamura, Symposium on VLSI Technology Technical Digest, 2002, pp. 94-95; T. Ghani, M. Armstrong, C. Auth, M. Bost, P. Charvat, G. Glass, T. Hoffmann, K. Johnson, C. Kenyon, J. Klaus, B. McIntyre, K. Mistry, A. Murthy, J. Sandford, M. Silberstein, S. Sivakumar, P. Smith, K. Zawadzki, S. Thompson, M. Bohr, International Electron Devices Meeting Technical Digest, December 2003, pp. 978-980; P. Bai, C. Auth, S. Balakrishnan, M. Bost, R. Brain, V. Chikarmane, R. Heussner, M. Hussein, J. Hwang, D. Ingerly, R. James, J. Jeong, C. Kenyon, E. Lee, S. Lee, N. Lindert, M. Liu, Z. Ma, T. Marieb, A. Murthy, R. Nagisetty, S. Natarajan, J. Neirynck, A. Ott, C. Parker, J. Sebastian, R. Shaheed, S. Sivakumar, J. Steigerwald, S. Tyagi, C. Weber, B. Woolery, A. Yeoh, K. Zhang, M. Bohr, International Electron Devices Meeting Technical Digest, December 2004, pp. 657-660] presenting the advantages brought by it. A better understanding regarding the boron diffusion behavior within and in the vicinity of SiGe is necessary to optimize the extension and the source/drain in pMOSFET. In order to achieve the goal, both effects from mechanical strain and Ge doping on boron diffusion have been investigated. However, only a few publications discuss the impacts of both. Furthermore, most researches investigate these two effects under the conditions of low boron concentration [P. Kuo, J.L. Hoyt, J.F. Gibbons, J.E. Turner, D. Lefforge, Appl. Phys. Lett. 66 (January (5)) (1995) 580-582; N.R. Zangenberg, J. Fage-Pedersen, J. Lundsgaard Hansen, A. Nylandsted Larsen, J. Appl. Phys. 94 (September (6)) (2003) 3883-3890] and high thermal budget anneal [P. Kuo, J.L. Hoyt, J.F. Gibbons, J.E. Turner, D. Lefforge, Appl. Phys. Lett. 66 (January (5)) (1995) 580-582; N.R. Zangenberg, J. Fage-Pedersen, J. Lundsgaard Hansen, A. Nylandsted Larsen, J. Appl

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.

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

Stress-directed compositional patterning of SiGe substrates for lateral quantum barrier manipulation

International Nuclear Information System (INIS)

Ghosh, Swapnadip; Kaiser, Daniel; Sinno, Talid; Bonilla, Jose; Han, Sang M.

2015-01-01

While vertical stacking of quantum well and dot structures is well established in heteroepitaxial semiconductor materials, manipulation of quantum barriers in the lateral directions poses a significant engineering challenge. Here, we demonstrate lateral quantum barrier manipulation in a crystalline SiGe alloy using structured mechanical fields to drive compositional redistribution. To apply stress, we make use of a nano-indenter array that is pressed against a Si 0.8 Ge 0.2 wafer in a custom-made mechanical press. The entire assembly is then annealed at high temperatures, during which the larger Ge atoms are selectively driven away from areas of compressive stress. Compositional analysis of the SiGe substrates reveals that this approach leads to a transfer of the indenter array pattern to the near-surface elemental composition, resulting in near 100% Si regions underneath each indenter that are separated from each other by the surrounding Si 0.8 Ge 0.2 bulk. The “stress transfer” process is studied in detail using multiscale computer simulations that demonstrate its robustness across a wide range of applied stresses and annealing temperatures. While the “Si nanodot” structures formed here are not intrinsically useful as quantum structures, it is anticipated that the stress transfer process may be modified by judicious control of the SiGe film thickness and indenter array pattern to form more technologically useful structures

Structural, Dynamic, and Vibrational Properties during Heat Transfer in Si/Ge Superlattices: A Car-Parrinello Molecular Dynamics Study

OpenAIRE

Ji, Pengfei; Zhang, Yuwen; Yang, Mo

2016-01-01

The structural, dynamic, and vibrational properties during the heat transfer process in Si/Ge superlattices, are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) ar...

Technology computer aided design for Si, SiGe and GaAs integrated circuits

CERN Document Server

Armstrong, GA

2007-01-01

The first book to deal with a broad spectrum of process and device design, and modelling issues related to semiconductor devices, bridging the gap between device modelling and process design using TCAD. Examples for types of Si-, SiGe-, GaAs- and InP-based heterostructure MOS and bipolar transistors are compared with experimental data from state-of-the-art devices. With various aspects of silicon heterostructures, this book presents a comprehensive perspective of emerging fields and covers topics ranging from materials to fabrication, devices, modelling and applications. Aimed at research-and-

Raman and photoluminescence spectroscopy of SiGe layer evolution on Si(100) induced by dewetting

Science.gov (United States)

Shklyaev, A. A.; Volodin, V. A.; Stoffel, M.; Rinnert, H.; Vergnat, M.

2018-01-01

High temperature annealing of thick (40-100 nm) Ge layers deposited on Si(100) at ˜400 °C leads to the formation of continuous films prior to their transformation into porous-like films due to dewetting. The evolution of Si-Ge composition, lattice strain, and surface morphology caused by dewetting is analyzed using scanning electron microscopy, Raman, and photoluminescence (PL) spectroscopies. The Raman data reveal that the transformation from the continuous to porous film proceeds through strong Si-Ge interdiffusion, reducing the Ge content from 60% to about 20%, and changing the stress from compressive to tensile. We expect that Ge atoms migrate into the Si substrate occupying interstitial sites and providing thereby the compensation of the lattice mismatch. Annealing generates only one type of radiative recombination centers in SiGe resulting in a PL peak located at about 0.7 and 0.8 eV for continuous and porous film areas, respectively. Since annealing leads to the propagation of threading dislocations through the SiGe/Si interface, we can tentatively associate the observed PL peak to the well-known dislocation-related D1 band.

A Physics-Based Engineering Methodology for Calculating Soft Error Rates of Bulk CMOS and SiGe Heterojunction Bipolar Transistor Integrated Circuits

Science.gov (United States)

Fulkerson, David E.

2010-02-01

This paper describes a new methodology for characterizing the electrical behavior and soft error rate (SER) of CMOS and SiGe HBT integrated circuits that are struck by ions. A typical engineering design problem is to calculate the SER of a critical path that commonly includes several circuits such as an input buffer, several logic gates, logic storage, clock tree circuitry, and an output buffer. Using multiple 3D TCAD simulations to solve this problem is too costly and time-consuming for general engineering use. The new and simple methodology handles the problem with ease by simple SPICE simulations. The methodology accurately predicts the measured threshold linear energy transfer (LET) of a bulk CMOS SRAM. It solves for circuit currents and voltage spikes that are close to those predicted by expensive 3D TCAD simulations. It accurately predicts the measured event cross-section vs. LET curve of an experimental SiGe HBT flip-flop. The experimental cross section vs. frequency behavior and other subtle effects are also accurately predicted.

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.

Sulfur passivation for the formation of Si-terminated Al{sub 2}O{sub 3/}SiGe(0 0 1) interfaces

Energy Technology Data Exchange (ETDEWEB)

Sardashti, Kasra [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States); Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA (United States); Hu, Kai-Ting [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States); Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA (United States); Tang, Kechao [Department of Materials Science and Engineering, Stanford University, CA (United States); Park, Sangwook; Kim, Hyonwoong [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States); Materials Science and Engineering Program, University of California, San Diego, La Jolla, CA (United States); Madisetti, Shailesh [Department of Nanoscale Science and Engineering, University at Albany—State University of New York, Albany, NY (United States); McIntyre, Paul [Department of Materials Science and Engineering, Stanford University, CA (United States); Oktyabrsky, Serge [Department of Nanoscale Science and Engineering, University at Albany—State University of New York, Albany, NY (United States); Siddiqui, Shariq; Sahu, Bhagawan [TD Research, GLOBALFOUNDRIES USA, Inc., Albany, NY (United States); Yoshida, Noami; Kachian, Jessica [Applied Materials, Inc., Santa Clara, CA (United States); Kummel, Andrew, E-mail: akummel@ucsd.edu [Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA (United States)

2016-03-15

Graphical abstract: - Highlights: • Effect of wet sulfur passivation on the electrical properties of Al{sub 2}O{sub 3}/SiGe(0 0 1) interfaces has been determined. • EOT of 2.1 nm has been achieved for ALD Al{sub 2}O{sub 3} deposited directly on SiGe(0 0 1) surfaces. • Sulfur passivation has been found to passivate the Al{sub 2}O{sub 3} interface with Si−O−Al bonds. • Sulfur passivation is found to significantly reduce the GeO{sub x} or Ge−O−Al content at the Al{sub 2}O{sub 3}/SiGe interface therefore improving the reliability. • Sulfur passivation extends the surface stability prior to oxide ALD to up to an hour with no dramatic change in D{sub it}, C{sub ox} or V{sub FB} of the resulting devices. - Abstract: Sulfur passivation is used to electrically and chemically passivate the silicon–germanium (SiGe) surfaces before and during the atomic layer deposition (ALD) of aluminum oxide (Al{sub 2}O{sub 3}). The electrical properties of the interfaces were examined by variable frequency capacitance–voltage (C–V) spectroscopy. Interface compositions were determined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The sulfur adsorbs to a large fraction of surface sites on the SiGe(0 0 1) surface, protecting the surface from deleterious surface reactions during processing. Sulfur passivation (a) improved the air stability of the cleaned surfaces prior to ALD, (b) increased the stability of the surface during high-temperature deposition, and (c) increased the Al{sub 2}O{sub 3} ALD nucleation density on SiGe, thereby lowering the leakage current. S passivation suppressed formation of Ge−O bonds at the interface, leaving the majority of the Al{sub 2}O{sub 3}–SiGe interface terminated with direct Si−O−Al bonding.

Thermal conductivity engineering of bulk and one-dimensional Si-Ge nanoarchitectures.

Science.gov (United States)

Kandemir, Ali; Ozden, Ayberk; Cagin, Tahir; Sevik, Cem

2017-01-01

Various theoretical and experimental methods are utilized to investigate the thermal conductivity of nanostructured materials; this is a critical parameter to increase performance of thermoelectric devices. Among these methods, equilibrium molecular dynamics (EMD) is an accurate technique to predict lattice thermal conductivity. In this study, by means of systematic EMD simulations, thermal conductivity of bulk Si-Ge structures (pristine, alloy and superlattice) and their nanostructured one dimensional forms with square and circular cross-section geometries (asymmetric and symmetric) are calculated for different crystallographic directions. A comprehensive temperature analysis is evaluated for selected structures as well. The results show that one-dimensional structures are superior candidates in terms of their low lattice thermal conductivity and thermal conductivity tunability by nanostructuring, such as by diameter modulation, interface roughness, periodicity and number of interfaces. We find that thermal conductivity decreases with smaller diameters or cross section areas. Furthermore, interface roughness decreases thermal conductivity with a profound impact. Moreover, we predicted that there is a specific periodicity that gives minimum thermal conductivity in symmetric superlattice structures. The decreasing thermal conductivity is due to the reducing phonon movement in the system due to the effect of the number of interfaces that determine regimes of ballistic and wave transport phenomena. In some nanostructures, such as nanowire superlattices, thermal conductivity of the Si/Ge system can be reduced to nearly twice that of an amorphous silicon thermal conductivity. Additionally, it is found that one crystal orientation, [Formula: see text]100[Formula: see text], is better than the [Formula: see text]111[Formula: see text] crystal orientation in one-dimensional and bulk SiGe systems. Our results clearly point out the importance of lattice thermal conductivity

Total dose hardness of a commercial SiGe BiCMOS technology

International Nuclear Information System (INIS)

Van Vonno, N.; Lucas, R.; Thornberry, D.

1999-01-01

Over the past decade SiGe HBT technology has progress from the laboratory to actual commercial applications. When integrated into a BiMOS process, this technology has applications in low-cost space systems. In this paper, we report results of total dose testing of a SiGe/CMOS process accessible through a commercial foundry. (authors)

Influencing factors on the size uniformity of self-assembled SiGe quantum rings grown by molecular beam epitaxy.

Science.gov (United States)

Cui, J; Lv, Y; Yang, X J; Fan, Y L; Zhong, Z; Jiang, Z M

2011-03-25

The size uniformity of self-assembled SiGe quantum rings, which are formed by capping SiGe quantum dots with a thin Si layer, is found to be greatly influenced by the growth temperature and the areal density of SiGe quantum dots. Higher growth temperature benefits the size uniformity of quantum dots, but results in low Ge concentration as well as asymmetric Ge distribution in the dots, which induces the subsequently formed quantum rings to be asymmetric in shape or even broken somewhere in the ridge of rings. Low growth temperature degrades the size uniformity of quantum dots, and thus that of quantum rings. A high areal density results in the expansion and coalescence of neighboring quantum dots to form a chain, rather than quantum rings. Uniform quantum rings with a size dispersion of 4.6% and an areal density of 7.8×10(8) cm(-2) are obtained at the optimized growth temperature of 640°C.

Integrated X-band FMCW front-end in SiGe BiCMOS

NARCIS (Netherlands)

Suijker, Erwin; de Boer, Lex; Visser, Guido; van Dijk, Raymond; Poschmann, Michael; van Vliet, Frank Edward

2010-01-01

An integrated X-band FMCW front-end is reported. The front-end unites the core functionality of an FMCW transmitter and receiver in a 0.25 μm SiGe BiCMOS process. The chip integrates a PLL for the carrier generation, and single-side band and image-reject mixers for up- and down-conversion of the

Self-Passivation by Fluorine Plasma Treatment and Low-Temperature Annealing in SiGe Nano wires for Biochemical Sensors

International Nuclear Information System (INIS)

Chang, K.; Chen, C.; Kuo, P.; Chen, Y.; Chang, T.; Lai, C.; Whang, A. J.; Lai, Y.; Chen, H.; Hsieh, I.

2014-01-01

Nano wires are widely used as highly sensitive sensors for electrical detection of biological and chemical species. Modifying the band structure of strained-Si metal-oxide-semiconductor field-effect transistors by applying the in-plane tensile strain reportedly improves electron and hole mobility. The oxidation-induced Ge condensation increases the Ge fraction in a SiGe-on-insulator (SGOI) and substantially increases hole mobility. However, oxidation increases the number of surface states, resulting in hole mobility degradation. In this work, 3-aminopropyltrimethoxysilane (APTMS) was used as a biochemical reagent. The hydroxyl molecule on the oxide surface was replaced by the methoxy groups of the APTMS molecule. We proposed a surface plasma treatment to improve the electrical properties of SiGe nano wires. Fluorine plasma treatment can result in enhanced rates of thermal oxidation and speed up the formation of a self-passivation oxide layer. Like a capping oxide layer, the self-passivation oxide layer reduces the rate of follow-up oxidation. Pre oxidation treatment also improved the sensitivity of SiGe nano wires because the Si-F binding was held at a more stable interface state compared to bare nano wire on the SiGe surface. Additionally, the sensitivity can be further improved by either the N 2 plasma posttreatment or the low-temperature post annealing due to the suppression of out diffusion of Ge and F atoms from the SiGe nano wire surface.

Silicon germanium mask for deep silicon etching

KAUST Repository

Serry, Mohamed

2014-07-29

Polycrystalline silicon germanium (SiGe) can offer excellent etch selectivity to silicon during cryogenic deep reactive ion etching in an SF.sub.6/O.sub.2 plasma. Etch selectivity of over 800:1 (Si:SiGe) may be achieved at etch temperatures from -80 degrees Celsius to -140 degrees Celsius. High aspect ratio structures with high resolution may be patterned into Si substrates using SiGe as a hard mask layer for construction of microelectromechanical systems (MEMS) devices and semiconductor devices.

Silicon germanium mask for deep silicon etching

KAUST Repository

Serry, Mohamed; Rubin, Andrew; Refaat, Mohamed; Sedky, Sherif; Abdo, Mohammad

2014-01-01

Polycrystalline silicon germanium (SiGe) can offer excellent etch selectivity to silicon during cryogenic deep reactive ion etching in an SF.sub.6/O.sub.2 plasma. Etch selectivity of over 800:1 (Si:SiGe) may be achieved at etch temperatures from -80 degrees Celsius to -140 degrees Celsius. High aspect ratio structures with high resolution may be patterned into Si substrates using SiGe as a hard mask layer for construction of microelectromechanical systems (MEMS) devices and semiconductor devices.

A note on the Sumerian expression SI-ge4-de3/dam

Directory of Open Access Journals (Sweden)

Widell, Magnus

2002-12-01

Full Text Available The expression SI-ge4-dam/de3 appears in some of the loan documents of the Ur III period where it was used to establish the interest rate or the loan fee. In addition, it is sometimes preceded by ki-ba 'in its/this place/ground' or, in some cases, ma2 -a 'in the boat'. The regular verb SI.g was closely related, perhaps even synonymous with, the reduplication verb ḡar/ḡa2-ḡa2 'to put' or 'to place'. While it may be concluded that SI-ge4-dam/de3 had nothing to do with the verb si 'to fill' or gi4 'to return', the correct analysis of the expression remains somewhat uncertain. The article proposes that the SI should be read se and understood as a phonetic writing for the regular verb se3.g 'to put', 'to place'. The combination of the verb with the ki-ba may suggest that a more parochial form of keeping products existed side by side with the large centralized granaries and storehouses of the city.La expresión SI-ge4-dam/de3 aparece en algunos contratos de préstamo del período de Ur III, donde se empleaba para determinar el interés de dicho préstamo. Por otra parte, este término se hallaba a veces precedido de ki-ba 'en su/este lugar/suelo', y en algunos casos por ma2 -a 'en la barca'. El verbo regular SI.g está muy relacionado (quizás es incluso sinónimo con el verbo de la clase de la reduplicación ḡar/ḡa2-ḡa2 'poner' o 'colocar'. Mientras que puede concluirse que SI-ge4-dam/de3 no tiene nada que ver con el verbo si 'llenar', ni con gi4 'regresar, devolver', el análisis correcto de la expresión sigue siendo, de algún modo, incierto. En el artículo se propone que SI puede leerse como se , entendiéndolo como una escritura fonética del verbo regular se3.g 'poner', 'colocar'. La combinación del verbo con ki-ba podría indicar que, junto a los grandes graneros y almacenes centrales de la ciudad, había un modo distinto y más modesto de conservar los productos.

Alternative Sigma Factors SigF, SigE, and SigG Are Essential for Sporulation in Clostridium botulinum ATCC 3502

OpenAIRE

Kirk, David G.; Zhang, Zhen; Korkeala, Hannu; Lindström, Miia

2014-01-01

Clostridium botulinum produces heat-resistant endospores that may germinate and outgrow into neurotoxic cultures in foods. Sporulation is regulated by the transcription factor Spo0A and the alternative sigma factors SigF, SigE, SigG, and SigK in most spore formers studied to date. We constructed mutants of sigF, sigE, and sigG in C. botulinum ATCC 3502 and used quantitative reverse transcriptase PCR and electron microscopy to assess their expression of the sporulation pathway on transcription...

Nanogrids and Beehive-Like Nanostructures Formed by Plasma Etching the Self-Organized SiGe Islands

Science.gov (United States)

Chang, Yuan-Ming; Jian, Sheng-Rui; Juang, Jenh-Yih

2010-09-01

A lithography-free method for fabricating the nanogrids and quasi-beehive nanostructures on Si substrates is developed. It combines sequential treatments of thermal annealing with reactive ion etching (RIE) on SiGe thin films grown on (100)-Si substrates. The SiGe thin films deposited by ultrahigh vacuum chemical vapor deposition form self-assembled nanoislands via the strain-induced surface roughening (Asaro-Tiller-Grinfeld instability) during thermal annealing, which, in turn, serve as patterned sacrifice regions for subsequent RIE process carried out for fabricating nanogrids and beehive-like nanostructures on Si substrates. The scanning electron microscopy and atomic force microscopy observations confirmed that the resultant pattern of the obtained structures can be manipulated by tuning the treatment conditions, suggesting an interesting alternative route of producing self-organized nanostructures.

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.

A new computer-aided simulation model for polycrystalline silicon film resistors

Science.gov (United States)

Ching-Yuan Wu; Weng-Dah Ken

1983-07-01

A general transport theory for the I-V characteristics of a polycrystalline film resistor has been derived by including the effects of carrier degeneracy, majority-carrier thermionic-diffusion across the space charge regions produced by carrier trapping in the grain boundaries, and quantum mechanical tunneling through the grain boundaries. Based on the derived transport theory, a new conduction model for the electrical resistivity of polycrystalline film resitors has been developed by incorporating the effects of carrier trapping and dopant segregation in the grain boundaries. Moreover, an empirical formula for the coefficient of the dopant-segregation effects has been proposed, which enables us to predict the dependence of the electrical resistivity of phosphorus-and arsenic-doped polycrystalline silicon films on thermal annealing temperature. Phosphorus-doped polycrystalline silicon resistors have been fabricated by using ion-implantation with doses ranged from 1.6 × 10 11 to 5 × 10 15/cm 2. The dependence of the electrical resistivity on doping concentration and temperature have been measured and shown to be in good agreement with the results of computer simulations. In addition, computer simulations for boron-and arsenic-doped polycrystalline silicon resistors have also been performed and shown to be consistent with the experimental results published by previous authors.

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...

Oxidation kinetics of Si and SiGe by dry rapid thermal oxidation, in-situ steam generation oxidation and dry furnace oxidation

Science.gov (United States)

Rozé, Fabien; Gourhant, Olivier; Blanquet, Elisabeth; Bertin, François; Juhel, Marc; Abbate, Francesco; Pribat, Clément; Duru, Romain

2017-06-01

The fabrication of ultrathin compressively strained SiGe-On-Insulator layers by the condensation technique is likely a key milestone towards low-power and high performances FD-SOI logic devices. However, the SiGe condensation technique still requires challenges to be solved for an optimized use in an industrial environment. SiGe oxidation kinetics, upon which the condensation technique is founded, has still not reached a consensus in spite of various studies which gave insights into the matter. This paper aims to bridge the gaps between these studies by covering various oxidation processes relevant to today's technological needs with a new and quantitative analysis methodology. We thus address oxidation kinetics of SiGe with three Ge concentrations (0%, 10%, and 30%) by means of dry rapid thermal oxidation, in-situ steam generation oxidation, and dry furnace oxidation. Oxide thicknesses in the 50 Å to 150 Å range grown with oxidation temperatures between 850 and 1100 °C were targeted. The present work shows first that for all investigated processes, oxidation follows a parabolic regime even for thin oxides, which indicates a diffusion-limited oxidation regime. We also observe that, for all investigated processes, the SiGe oxidation rate is systematically higher than that of Si. The amplitude of the variation of oxidation kinetics of SiGe with respect to Si is found to be strongly dependent on the process type. Second, a new quantitative analysis methodology of oxidation kinetics is introduced. This methodology allows us to highlight the dependence of oxidation kinetics on the Ge concentration at the oxidation interface, which is modulated by the pile-up mechanism. Our results show that the oxidation rate increases with the Ge concentration at the oxidation interface.

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.

Investigating ESD sensitivity in electrostatic SiGe MEMS

International Nuclear Information System (INIS)

Sangameswaran, Sandeep; De Coster, Jeroen; Linten, Dimitri; Scholz, Mirko; Thijs, Steven; Groeseneken, Guido; De Wolf, Ingrid

2010-01-01

The sensitivity of electrostatically actuated SiGe microelectromechanical systems to electrostatic discharge events has been investigated in this paper. Torsional micromirrors and RF microelectromechanical systems (MEMS) actuators have been used as two case studies to perform this study. On-wafer electrostatic discharge (ESD) measurement methods, such as the human body model (HBM) and machine model (MM), are discussed. The impact of HBM ESD zap tests on the functionality and behavior of MEMS is explained and the ESD failure levels of MEMS have been verified by failure analysis. It is demonstrated that electrostatic MEMS devices have a high sensitivity to ESD and that it is essential to protect them.

A Passive X-Band Double Balanced Mixer Utilizing Diode Connected SiGe HBTs

DEFF Research Database (Denmark)

Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke; Tamborg, Kjeld

2013-01-01

In this paper, a passive double balanced mixer in SiGe HBT technology is presented. Due to lack of suitable passive mixing elements in the technology, the mixing elements are formed by diode connected HBTs. The mixer is optimized for use in doppler radars and is highly linear with 1 dB compressio...

Visible and infrared emission from Si/Ge nanowires synthesized by metal-assisted wet etching.

Science.gov (United States)

Irrera, Alessia; Artoni, Pietro; Fioravanti, Valeria; Franzò, Giorgia; Fazio, Barbara; Musumeci, Paolo; Boninelli, Simona; Impellizzeri, Giuliana; Terrasi, Antonio; Priolo, Francesco; Iacona, Fabio

2014-02-12

Multi-quantum well Si/Ge nanowires (NWs) were realized by combining molecular beam epitaxy deposition and metal-assisted wet etching, which is a low-cost technique for the synthesis of extremely dense (about 1011 cm-2) arrays of NWs with a high and controllable aspect ratio. In particular, we prepared ultrathin Si/Ge NWs having a mean diameter of about 8 nm and lengths spanning from 1.0 to 2.7 μm. NW diameter is compatible with the occurrence of quantum confinement effects and, accordingly, we observed light emission assignable to the presence of Si and Ge nanostructures. We performed a detailed study of the photoluminescence properties of the NWs, with particular attention to the excitation and de-excitation properties as a function of the temperature and of the excitation photon flux, evaluating the excitation cross section and investigating the presence of non-radiative phenomena. PACS: 61.46.Km; 78.55.-m; 78.67.Lt.

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.

Si/SiGe heterointerfaces in one-, two-, and three-dimensional nanostructures: their impact on SiGe light emission

Science.gov (United States)

Lockwood, David; Wu, Xiaohua; Baribeau, Jean-Marc; Mala, Selina; Wang, Xialou; Tsybeskov, Leonid

2016-03-01

Fast optical interconnects together with an associated light emitter that are both compatible with conventional Si-based complementary metal-oxide- semiconductor (CMOS) integrated circuit technology is an unavoidable requirement for the next-generation microprocessors and computers. Self-assembled Si/Si1-xGex nanostructures, which can emit light at wavelengths within the important optical communication wavelength range of 1.3 - 1.55 μm, are already compatible with standard CMOS practices. However, the expected long carrier radiative lifetimes observed to date in Si and Si/Si1-xGex nanostructures have prevented the attainment of efficient light-emitting devices including the desired lasers. Thus, the engineering of Si/Si1-xGex heterostructures having a controlled composition and sharp interfaces is crucial for producing the requisite fast and efficient photoluminescence (PL) at energies in the range 0.8-0.9 eV. In this paper we assess how the nature of the interfaces between SiGe nanostructures and Si in heterostructures strongly affects carrier mobility and recombination for physical confinement in three dimensions (corresponding to the case of quantum dots), two dimensions (corresponding to quantum wires), and one dimension (corresponding to quantum wells). The interface sharpness is influenced by many factors such as growth conditions, strain, and thermal processing, which in practice can make it difficult to attain the ideal structures required. This is certainly the case for nanostructure confinement in one dimension. However, we demonstrate that axial Si/Ge nanowire (NW) heterojunctions (HJs) with a Si/Ge NW diameter in the range 50 - 120 nm produce a clear PL signal associated with band-to-band electron-hole recombination at the NW HJ that is attributed to a specific interfacial SiGe alloy composition. For three-dimensional confinement, the experiments outlined here show that two quite different Si1-xGex nanostructures incorporated into a Si0.6Ge0.4 wavy

Anomalous dose rate effects in gamma irradiated SiGe heterojunction bipolar transistors

International Nuclear Information System (INIS)

Banerjee, G.; Niu, G.; Cressler, J.D.; Clark, S.D.; Palmer, M.J.; Ahlgren, D.C.

1999-01-01

Low dose rate (LDR) cobalt-60 (0.1 rad(Si)/s) gamma irradiated Silicon Germanium (SiGe) Heterojunction Bipolar Transistors (HBTs) were studied. Comparisons were made with devices irradiated with 300 rad(Si)/s gamma radiation to verify if LDR radiation is a serious radiation hardness assurance (RHA) issue. Almost no LDR degradation was observed in this technology up to 50 krad(Si). The assumption of the presence of two competing mechanisms is justified by experimental results. At low total dose (le20 krad), an anomalous base current decrease was observed which is attributed to self-annealing of deep-level traps to shallower levels. An increase in base current at larger total doses is attributed to radiation induced generation-recombination (G/R) center generation. Experiments on gate-assisted lateral PNP transistors and 2D numerical simulations using MEDICI were used to confirm these assertions

Heavy Ion Microbeam- and Broadbeam-Induced Transients in SiGe HBTs

Science.gov (United States)

Pellish, Jonathan A.; Reed, Robert A.; McMorrow, Dale; Vizkelethy, Gyorgy; Ferlet-Cavrois, Veronique; Baggio, Jacques; Duhamel, Olivier; Moen, Kurt A.; Phillips, Stanley D.; Diestelhorst, Ryan M.;

Step-driven surface segregation and ordering during Si-Ge MBE growth

International Nuclear Information System (INIS)

Jesson, D.E.; Pennycook, S.J.; Baribeau, J.M.; Houghton, D.C.

1992-06-01

An important role of type S B step edges in determining the as-grown microstructure of Si-Ge superlattices and alloys is implicated from direct Z-contrast images of as-grown structures. A variety of different ordered phase variants can arise at each Si on Ge interface as a result of vertical segregation during superlattice growth. A new monoclinic-ordered structure is predicted to arise as a result of lateral segregation during alloy growth

Thermal stability improvement of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations using non-uniform finger spacing

International Nuclear Information System (INIS)

Chen Liang; Zhang Wan-Rong; Jin Dong-Yue; Shen Pei; Xie Hong-Yun; Ding Chun-Bao; Xiao Ying; Sun Bo-Tao; Wang Ren-Qing

2011-01-01

A method of non-uniform finger spacing is proposed to enhance thermal stability of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations. Temperature distribution on the emitter fingers of a multi-finger SiGe heterojunction bipolar transistor is studied using a numerical electro-thermal model. The results show that the SiGe heterojunction bipolar transistor with non-uniform finger spacing has a small temperature difference between fingers compared with a traditional uniform finger spacing heterojunction bipolar transistor at the same power dissipation. What is most important is that the ability to improve temperature non-uniformity is not weakened as power dissipation increases. So the method of non-uniform finger spacing is very effective in enhancing the thermal stability and the power handing capability of power device. Experimental results verify our conclusions. (interdisciplinary physics and related areas of science and technology)

Observation of spin-selective tunneling in SiGe nanocrystals.

Science.gov (United States)

Katsaros, G; Golovach, V N; Spathis, P; Ares, N; Stoffel, M; Fournel, F; Schmidt, O G; Glazman, L I; De Franceschi, S

2011-12-09

Spin-selective tunneling of holes in SiGe nanocrystals contacted by normal-metal leads is reported. The spin selectivity arises from an interplay of the orbital effect of the magnetic field with the strong spin-orbit interaction present in the valence band of the semiconductor. We demonstrate both experimentally and theoretically that spin-selective tunneling in semiconductor nanostructures can be achieved without the use of ferromagnetic contacts. The reported effect, which relies on mixing the light and heavy holes, should be observable in a broad class of quantum-dot systems formed in semiconductors with a degenerate valence band.

Si, Ge and SiGe wires for sensor application

International Nuclear Information System (INIS)

Druzhinin, A.A.; Khoverko, Yu.M.; Ostrovskii, I.P.; Nichkalo, S.I.; Nikolaeva, A.A.; Konopko, L.A.; Stich, I.

2011-01-01

Resistance and magnetoresistance of Si, Ge and Si-Ge micro- and nanowires were studied in temperature range 4,2-300 K at magnetic fields up to 14 T. The wires diameters range from 200 nm to 20 μm. Ga-In gates were created to wires and ohmic I-U characteristics were observed in all temperature range. It was found high elastic strain for Ge nanowires (of about 0,7%) as well as high magnitude of magnetoresistance (of about 250% at 14 T), which was used to design multifunctional sensor of simultaneous measurements of strain and magnetic field intensity. (authors)

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)

The role of SiGe buffer in growth and relaxation of Ge on free-standing Si(001) nano-pillars.

Science.gov (United States)

Zaumseil, P; Kozlowski, G; Schubert, M A; Yamamoto, Y; Bauer, J; Schülli, T U; Tillack, B; Schroeder, T

2012-09-07

We study the growth and relaxation processes of Ge nano-clusters selectively grown by chemical vapor deposition on free-standing 90 nm wide Si(001) nano-pillars with a thin Si(0.23)Ge(0.77) buffer layer. We found that the dome-shaped SiGe layer with a height of about 28 nm as well as the Ge dot deposited on top of it partially relaxes, mainly by elastic lattice bending. The Si nano-pillar shows a clear compliance behavior-an elastic response of the substrate on the growing film-with the tensile strained top part of the pillar. Additional annealing at 800 °C leads to the generation of misfit dislocation and reduces the compliance effect significantly. This example demonstrates that despite the compressive strain generated due to the surrounding SiO(2) growth mask it is possible to realize an overall tensile strain in the Si nano-pillar and following a compliant substrate effect by using a SiGe buffer layer. We further show that the SiGe buffer is able to improve the structural quality of the Ge nano-dot.

An X-band Schottky diode mixer in SiGe technology with tunable Marchand balun

DEFF Research Database (Denmark)

Michaelsen, Rasmus Schandorph; Johansen, Tom Keinicke; Tamborg, Kjeld M.

2017-01-01

In this paper, we propose a double balanced mixer with a tunable Marchand balun. The circuit is designed in a SiGe BiCMOS process using Schottky diodes. The tunability of the Marchand balun is used to enhance critical parameters for double balanced mixers. The local oscillator-IF isolation can...

Two-scale characterization of deformation-induced anisotropy of polycrystalline metals

International Nuclear Information System (INIS)

Watanabe, Ikumu; Terada, Kenjiro

2004-01-01

The anisotropic macro-scale mechanical behavior of polycrystalline metals is characterized by incorporating the micro-scale constitutive model of single crystal plasticity into the two-scale modeling based on the mathematical homogenization theory. The two-scale simulations are conducted to analyze the macro-scale anisotropy induced by micro-scale plastic deformation of the polycrystalline aggregate. In the simulations, the micro-scale representative volume element (RVE) of a polycrystalline aggregate is uniformly loaded in one direction, unloaded to macroscopically zero stress in a certain stage of deformation and then re-loaded in the different directions. The last re-loading calculations provide different macro-scale responses of the RVE, which can be the appearance of material anisotropy. We then try to examine the effects of the intergranular and intragranular behaviors on the anisotropy by means of various illustrations of plastic deformation process in stead of the use of pole figures for the change of crystallographic orientations

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.

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.

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

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.

Evaluation of COTS SiGe, SOI, and Mixed Signal Electronic Parts for Extreme Temperature Use in NASA Missions

Science.gov (United States)

Patterson, Richard L.; Hammoud, Ahmad

2010-01-01

The NASA Electronic Parts and Packaging (NEPP) Program sponsors a task at the NASA Glenn Research Center titled "Reliability of SiGe, SOI, and Advanced Mixed Signal Devices for Cryogenic Space Missions." In this task COTS parts and flight-like are evaluated by determining their performance under extreme temperatures and thermal cycling. The results from the evaluations are published on the NEPP website and at professional conferences in order to disseminate information to mission planners and system designers. This presentation discusses the task and the 2010 highlights and technical results. Topics include extreme temperature operation of SiGe and SOI devices, all-silicon oscillators, a floating gate voltage reference, a MEMS oscillator, extreme temperature resistors and capacitors, and a high temperature silicon operational amplifier.

Capacitor-less memory cell fabricated on nano-scale strained Si on a relaxed SiGe layer-on-insulator

International Nuclear Information System (INIS)

Kim, Tae-Hyun; Park, Jea-Gun

2013-01-01

We investigated the combined effect of the strained Si channel and hole confinement on the memory margin enhancement for a capacitor-less memory cell fabricated on nano-scale strained Si on a relaxed SiGe layer-on-insulator (ε-Si SGOI). The memory margin for the ε-Si SGOI capacitor-less memory cell was higher than that of the memory cell fabricated on an unstrained Si-on-insulator (SOI) and increased with increasing Ge concentration of the relaxed SiGe layer; i.e. the memory margin for the ε-Si SGOI capacitor-less memory cell (138.6 µA) at a 32 at% Ge concentration was 3.3 times higher than the SOI capacitor-less memory cell (43 µA). (paper)

Thermopiles - a new thermal desorption technology for recycling highly organic contaminated soils down to natural levels

International Nuclear Information System (INIS)

Haemers, J.; Cardot, J.; Falcinelli, U.; Zwaan, H.

2005-01-01

The Thermopile R technology, developed by Deep Green, provides an implementation system allowing to treat hydrocarbon and PAH contaminated materials down to natural levels or down to levels where they are treatable with a traditional thermal desorption unit, in a controlled batch system. The materials are indirectly heated while a substantial part of the energy is reused to heat the pile of soil. The system differs from most of the indirect thermal desorption systems by its very high energetic efficiency as well as its ability to be set -up remotely. The system does not face preferential path problems, since the heating medium is only conduction, which is very indifferent with regard to soil type (clay, sand, silt, etc.). That property is critical to an in-depth clean-up with a batch system. Other systems, based on heat, are mostly sending heat vectors (gases, hot air, steam, etc.) through the soil, which implies preferential paths, which are the main cause for not completely cleaning the soil with most batch technologies (down to natural levels). The soil to treat is placed in a pile or in a modular container in which perforated steel pipes are installed along a hexagonal pattern. During treatment those pipes are heated by hot gases (about 600 deg. C) coming from the afterburner. Consequently the soil reaches the contaminant's desorption temperature. The desorbed pollutants are then drawn by convection and diffusion into the heating pipes via the perforations. Once in the pipes the desorbed gases are mixed with the heating gases. They are sucked by the ID fan and sent to the afterburner. The hydrocarbons in gaseous phase are then oxidized in the afterburner. In this manner, they provide a part of the energy needed to heat the soil itself. The pilot unit is also equipped with a purge that allows the evacuation of a part of the gases circulating in the system; Different additional gas treatments can be applied as required by the type of contaminants and the

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.

Statistic derivation of Taylor factors for polycrystalline metals with application to pure magnesium

International Nuclear Information System (INIS)

Shen, J.H.; Li, Y.L.; Wei, Q.

2013-01-01

We have investigated the Taylor factors of textured as well as texture-free polycrystalline aggregates. We begin with examining the Schmid factors of single crystals. A statistical model is then introduced to describe the distribution of grain orientations as well as the Schmid factor of individual grains of the polycrystalline system. The grains are classified into “soft” and “hard” ones. Based on this, a model is proposed for the derivation of the Taylor factors of textured as well as texture-free polycrystalline metals, and as a case study it is applied to polycrystalline magnesium. The model predictions are in very good agreement with the available experimental results. No free parameters have been involved in the development of this model, and the physical processes are clearly defined. Based on the fundamental assumption that grains can be classified into “soft” and “hard” in metals, this model should also be applicable to other hexagonal close packed metals such as α-titanium, beryllium and zirconium, as well as metals of other lattice structures such as face-centered cubic and body-centered cubic. It will also be interesting to see if this model can be incorporated into existing crystal plasticity models for the prediction of texture evolution under mechanical loading

A self-ordered, body-centered tetragonal superlattice of SiGe nanodot growth by reduced pressure CVD

Science.gov (United States)

Yamamoto, Yuji; Zaumseil, Peter; Capellini, Giovanni; Schubert, Markus Andreas; Hesse, Anne; Albani, Marco; Bergamaschini, Roberto; Montalenti, Francesco; Schroeder, Thomas; Tillack, Bernd

2017-12-01

Self-ordered three-dimensional body-centered tetragonal (BCT) SiGe nanodot structures are fabricated by depositing SiGe/Si superlattice layer stacks using reduced pressure chemical vapor deposition. For high enough Ge content in the island (>30%) and deposition temperature of the Si spacer layers (T > 700 °C), we observe the formation of an ordered array with islands arranged in staggered position in adjacent layers. The in plane periodicity of the islands can be selected by a suitable choice of the annealing temperature before the Si spacer layer growth and of the SiGe dot volume, while only a weak influence of the Ge concentration is observed. Phase-field simulations are used to clarify the driving force determining the observed BCT ordering, shedding light on the competition between heteroepitaxial strain and surface-energy minimization in the presence of a non-negligible surface roughness.

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.

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

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.

Characterization of Polycrystalline Materials Using Synchrotron X-ray Imaging and Diffraction Techniques

DEFF Research Database (Denmark)

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

2010-01-01

The combination of synchrotron radiation x-ray imaging and diffraction techniques offers new possibilities for in-situ observation of deformation and damage mechanisms in the bulk of polycrystalline materials. Minute changes in electron density (i.e., cracks, porosities) can be detected using...... propagation based phase contrast imaging, a 3-D imaging mode exploiting the coherence properties of third generation synchrotron beams. Furthermore, for some classes of polycrystalline materials, one may use a 3-D variant of x-ray diffraction imaging, termed x-ray diffraction contrast tomography. X-ray...

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.

Influence of the crystallization process on the luminescence of multilayers of SiGe nanocrystals embedded in SiO2

International Nuclear Information System (INIS)

Avella, M.; Prieto, A.C.; Jimenez, J.; Rodriguez, A.; Sangrador, J.; Rodriguez, T.; Ortiz, M.I.; Ballesteros, C.

2008-01-01

Multilayers of SiGe nanocrystals embedded in an oxide matrix have been fabricated by low-pressure chemical vapor deposition of SiGe and SiO 2 onto Si wafers (in a single run at 390 deg. C and 50 mTorr, using GeH 4 , Si 2 H 6 and O 2 ) followed by a rapid thermal annealing treatment to crystallize the SiGe nanoparticles. The main emission band is located at 400 nm in both cathodoluminescence and photoluminescence experiments at 80 K and also at room temperature. The annealing conditions (temperatures ranging from 700 to 1000 deg. C and for times of 30 and 60 s) have been investigated in samples with different diameter of the nanoparticles (from ∼3 to ≥5 nm) and oxide interlayer thickness (15 and 35 nm) in order to establish a correlation between the crystallization of the nanoparticles, the degradation of their composition by Ge diffusion and the intensity of the luminescence emission band. Structures with small nanoparticles (3-4.5 nm) separated by thick oxide barriers (∼35 nm) annealed at 900 deg. C for 60 s yield the maximum intensity of the luminescence. An additional treatment at 450 deg. C in forming gas for dangling-bond passivation increases the intensity of the luminescence band by 25-30%

Measurement of grain size of polycrystalline materials with confocal energy dispersive micro-X-ray diffraction technology based on polycapillary X-ray optics

Energy Technology Data Exchange (ETDEWEB)

Sun, Weiyuan; Liu, Zhiguo [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Sun, Tianxi, E-mail: stx@bnu.edu.cn [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Peng, Song [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Ma, Yongzhong [Center for Disease Control and Prevention of Beijing, Beijing 100013 (China); Li, Fangzuo; Sun, Xuepeng; Ding, Xunliang [The Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, Beijing Normal University, Beijing 100875 (China); College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China)

2014-11-11

The confocal energy dispersive micro-X-ray diffraction (EDMXRD) based on polycapillary X-ray optics was used to determine the grain size of polycrystalline materials. The grain size of a metallographic specimen of nickel base alloy was measured by using the confocal EDMXRD. The experimental results demonstrated that the confocal EDMXRD had potential applications in measuring large grain size.

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)

Influence of airborne pollen counts and length of pollen season of selected allergenic plants on the concentration of sIgE antibodies on the population of Bratislava, Slovakia

Directory of Open Access Journals (Sweden)

Jana Ščevková

2015-09-01

Full Text Available Introduction and objective. The association between airborne pollen counts or duration of pollen season and allergy symptoms is not always distinguished. The purpose of this study was to examine the correlation between pollen exposure (annual total pollen quantity and main pollen season length of selected allergenic plants in the atmosphere of Bratislava, and concentration of allergen-specific immunoglobulin E (sIgE in serum of patients with seasonal allergy during 2002–2003. Materials and methods. The concentration of pollen was monitored by a Burkard volumetric pollen trap. At the same time, 198 pollen allergic patients were testing to determine the values of sIgE antibodies against selected pollen allergens; a panel of 8 purified allergens was used. Results. The highest percentages of sensitization were detected for Poaceae and [i]Ambrosia[/i] pollen allergens. The most abundant airborne pollen types were Urticaceae, [i]Betula[/i], [i]Populus[/i], Fraxinus, Pinus and Poaceae. The length of the pollen season varied. The longest pollen season was that of the [i]Plantago[/i] – 105 days, and the shortest, [i]Corylus[/i] – 20 days. A significant correlation was found between annual total pollen quantity and median sIgE values, especially in 2002. Conclusions. A strong and significant positive correlation was observed between pollen counts, excluding [i]Betula[/i], and sIgE levels in both analysed years. The correlation was weaker and negative in the case of length of pollen season and sIgE values.

Impacts of doping on epitaxial germanium thin film quality and Si-Ge interdiffusion

KAUST Repository

Zhou, Guangnan

2018-04-03

Ge-on-Si structures with three different dopants (P, As and B) and those without intentional doping were grown, annealed and characterized by several different material characterization methods. All samples have a smooth surface (roughness < 1.5 nm), and the Ge films are almost entirely relaxed. B doped Ge films have threading dislocations above 1 × 10 cm, while P and As doping can reduce the threading dislocation density to be less than 10 cm without annealing. The interdiffusion of Si and Ge of different films have been investigated experimentally and theoretically. A quantitative model of Si-Ge interdiffusion under extrinsic conditions across the full x range was established including the dislocationmediated diffusion. The Kirkendall effect has been observed. The results are of technical significance for the structure, doping, and process design of Ge-on-Si based devices, especially for photonic applications.

Impacts of doping on epitaxial germanium thin film quality and Si-Ge interdiffusion

KAUST Repository

Zhou, Guangnan; Lee, Kwang Hong; Anjum, Dalaver H.; Zhang, Qiang; Zhang, Xixiang; Tan, Chuan Seng; Xia, Guangrui

2018-01-01

Ge-on-Si structures with three different dopants (P, As and B) and those without intentional doping were grown, annealed and characterized by several different material characterization methods. All samples have a smooth surface (roughness < 1.5 nm), and the Ge films are almost entirely relaxed. B doped Ge films have threading dislocations above 1 × 10 cm, while P and As doping can reduce the threading dislocation density to be less than 10 cm without annealing. The interdiffusion of Si and Ge of different films have been investigated experimentally and theoretically. A quantitative model of Si-Ge interdiffusion under extrinsic conditions across the full x range was established including the dislocationmediated diffusion. The Kirkendall effect has been observed. The results are of technical significance for the structure, doping, and process design of Ge-on-Si based devices, especially for photonic applications.

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)

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.

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)

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.

Direct growth of transparent conducting Nb-doped anatase TiO2 polycrystalline films on glass

International Nuclear Information System (INIS)

Yamada, Naoomi; Kasai, Junpei; Hitosugi, Taro; Hoang, Ngoc Lam Huong; Nakao, Shoichiro; Hirose, Yasushi; Shimada, Toshihiro; Hasegawa, Tetsuya

2009-01-01

This paper proposes a novel sputter-based method for the direct growth of transparent conducting Ti 1-x Nb x O 2 (TNO) polycrystalline films on glass, without the need for any postdeposition treatments, by the use of an initial seed-layer. Anatase TNO epitaxial films grown on LaAlO 3 (100) substrates under a reducing atmosphere exhibited a low resistivity (ρ) of (3-6)x10 -4 Ω cm. On glass, however, highly resistive rutile phase polycrystalline films (ρ∼100 Ω cm) formed preferentially under the same conditions. These results suggest that epitaxial stabilization of the oxygen-deficient anatase phase occurs on lattice-matched substrates. To produce a similar effect on a glass surface, we deposited a seed-layer of anatase TNO with excellent crystallinity under an increased oxygen atmosphere. As a result, anatase phase TNO polycrystalline films could be grown even under heavily reducing atmospheres. An optimized film exhibited ρ=1.1x10 -3 Ω cm and optical absorption lower than 10% in the visible region. This ρ value is more than one order of magnitude lower than values reported for directly deposited TNO polycrystalline films. This indicates that the seed-layer method has considerable potential for producing transparent conducting TNO polycrystalline films on glass.

Flexible Low-power SiGe HBT Amplifier Circuits for Fast Single-shot Spin Readout

Science.gov (United States)

England, Troy; Lilly, Michael; Curry, Matthew; Carr, Stephen; Carroll, Malcolm

Fast, low-power quantum state readout is one of many challenges facing quantum information processing. Single electron transistors (SETs) are potentially fast, sensitive detectors for performing spin readout of electrons bound to Si:P donors. From a circuit perspective, however, their output impedance and nonlinear conductance are ill suited to drive the parasitic capacitance of coaxial conductors used in cryogenic environments, necessitating a cryogenic amplification stage. We will introduce two new amplifier topologies that provide excellent gain versus power tradeoffs using silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs). The AC HBT allows in-situ adjustment of power dissipation during an experiment and can provide gain in the millikelvin temperature regime while dissipating less than 500 nW. The AC Current Amplifier maximizes gain at nearly 800 A/A. We will also show results of using these amplifiers with SETs at 4 K. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000. Flexible Low-power SiGe HBT Amplifier Circuits for Fast Single-shot Spin Readout.

Effect of Si/Ge ratio on resistivity and thermopower in Gd{sub 5}Si{sub x}Ge{sub 4-x} magnetocaloric compounds

Energy Technology Data Exchange (ETDEWEB)

Raj Kumar, D.M. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Manivel Raja, M., E-mail: mraja@dmrl.drdo.i [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Prabahar, K.; Chandrasekaran, V. [Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad 500058 (India); Poddar, Asok; Ranganathan, R. [Saha Institute of Nuclear Physics, Kolkata 700064 (India); Suresh, K.G. [Indian Institute of Technology Bombay, Mumbai 400076 (India)

2011-07-15

The effect of Si/Ge ratio on resistivity and thermopower behavior has been investigated in the magnetocaloric ferromagnetic Gd{sub 5}Si{sub x}Ge{sub 4-x} compounds with x=1.7-2.3. Microstructural studies reveal the presence of Gd{sub 5}(Si,Ge){sub 4}-matrix phase (5:4-type) along with traces of secondary phases (5:5 or 5:3-type). The x=1.7 and 2.0 samples display the presence of a first order structural transition from orthorhombic to monoclinic phase followed by a magnetic transition of the monoclinic phase. The alloys with x=2.2 and 2.3 display only magnetic transitions of the orthorhombic phase. A low temperature feature apparent in the AC susceptibility and resistivity data below 100 K reflects an antiferromagnetic transition of secondary phase(s) present in these compounds. The resistivity behavior study correlates with microstructural studies. A large change in thermopower of -8 {mu}V/K was obtained at the magneto-structural transition for the x=2 compound. - Research highlights: Effect of Si/Ge ratio on microstructure, magneto-structural transitions, resistivity ({rho}) and thermopower S(T) behaviour has been investigated in Gd{sub 5}Si{sub x}Ge{sub 4-x} compounds with x=1.7, 2.0, 2.2 and 2.3. Microstructural studies reveal the presence of a Gd{sub 5}(Si,Ge){sub 4} -matrix phase (5:4-type) along with traces of secondary phases (5:5 or 5:3-type). The resistivity behaviour has shown good correlation with the microstructural studies. A large change in thermopower of -8{mu}V/K was obtained at the magneto-structural transition for the x=2 compound. The resistivity and change in thermopower values were high for the alloys with Si/Ge ratio {<=}1 compared to that of the alloys with Si/Ge ratio >1.

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...

3D ductile crack propagation within a polycrystalline microstructure using XFEM

Science.gov (United States)

Beese, Steffen; Loehnert, Stefan; Wriggers, Peter

2018-02-01

In this contribution we present a gradient enhanced damage based method to simulate discrete crack propagation in 3D polycrystalline microstructures. Discrete cracks are represented using the eXtended finite element method. The crack propagation criterion and the crack propagation direction for each point along the crack front line is based on the gradient enhanced damage variable. This approach requires the solution of a coupled problem for the balance of momentum and the additional global equation for the gradient enhanced damage field. To capture the discontinuity of the displacements as well as the gradient enhanced damage along the discrete crack, both fields are enriched using the XFEM in combination with level sets. Knowing the crack front velocity, level set methods are used to compute the updated crack geometry after each crack propagation step. The applied material model is a crystal plasticity model often used for polycrystalline microstructures of metals in combination with the gradient enhanced damage model. Due to the inelastic material behaviour after each discrete crack propagation step a projection of the internal variables from the old to the new crack configuration is required. Since for arbitrary crack geometries ill-conditioning of the equation system may occur due to (near) linear dependencies between standard and enriched degrees of freedom, an XFEM stabilisation technique based on a singular value decomposition of the element stiffness matrix is proposed. The performance of the presented methodology to capture crack propagation in polycrystalline microstructures is demonstrated with a number of numerical examples.

Unexpected pressure induced ductileness tuning in sulfur doped polycrystalline nickel metal

Directory of Open Access Journals (Sweden)

Cheng Guo

2018-02-01

Full Text Available The sulfur induced embrittlement of polycrystalline nickel (Ni metal has been a long-standing mystery. It is suggested that sulfur impurity makes ductile Ni metal brittle in many industry applications due to various mechanisms, such as impurity segregation and disorder-induced melting etc. Here we report an observation that the most ductile measurement occurs at a critical sulfur doping concentration, 14 at.% at pressure from 14 GPa up to 29 GPa through texture evolution analysis. The synchrotron-based high pressure texturing measurements using radial diamond anvil cell (rDAC X-ray diffraction (XRD techniques reveal that the activities of slip systems in the polycrystalline nickel metal are affected by sulfur impurities and external pressures, giving rise to the changes in the plastic deformation of the nickel metal. Dislocation dynamics (DD simulation on dislocation density and velocity further confirms the pressure induced ductilization changes in S doped Ni metal. This observation and simulation suggests that the ductilization of the doped polycrystalline nickel metal can be optimized by engineering the sulfur concentration under pressure, shedding a light on tuning the mechanical properties of this material for better high pressure applications.

Unexpected pressure induced ductileness tuning in sulfur doped polycrystalline nickel metal

Science.gov (United States)

Guo, Cheng; Yang, Yan; Tan, Liuxi; Lei, Jialin; Guo, Shengmin; Chen, Bin; Yan, Jinyuan; Yang, Shizhong

2018-02-01

The sulfur induced embrittlement of polycrystalline nickel (Ni) metal has been a long-standing mystery. It is suggested that sulfur impurity makes ductile Ni metal brittle in many industry applications due to various mechanisms, such as impurity segregation and disorder-induced melting etc. Here we report an observation that the most ductile measurement occurs at a critical sulfur doping concentration, 14 at.% at pressure from 14 GPa up to 29 GPa through texture evolution analysis. The synchrotron-based high pressure texturing measurements using radial diamond anvil cell (rDAC) X-ray diffraction (XRD) techniques reveal that the activities of slip systems in the polycrystalline nickel metal are affected by sulfur impurities and external pressures, giving rise to the changes in the plastic deformation of the nickel metal. Dislocation dynamics (DD) simulation on dislocation density and velocity further confirms the pressure induced ductilization changes in S doped Ni metal. This observation and simulation suggests that the ductilization of the doped polycrystalline nickel metal can be optimized by engineering the sulfur concentration under pressure, shedding a light on tuning the mechanical properties of this material for better high pressure applications.

Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: A Car-Parrinello molecular dynamics study

Energy Technology Data Exchange (ETDEWEB)

Ji, Pengfei; Zhang, Yuwen, E-mail: zhangyu@missouri.edu [Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, Missouri 65211 (United States); Yang, Mo [College of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093 (China)

2013-12-21

The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.

Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: A Car-Parrinello molecular dynamics study

International Nuclear Information System (INIS)

Ji, Pengfei; Zhang, Yuwen; Yang, Mo

2013-01-01

The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective

Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: A Car-Parrinello molecular dynamics study

Science.gov (United States)

Ji, Pengfei; Zhang, Yuwen; Yang, Mo

2013-12-01

The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.

Simulation of thermal stress and buckling instability in Si/Ge and Ge/Si core/shell nanowires.

Science.gov (United States)

Das, Suvankar; Moitra, Amitava; Bhattacharya, Mishreyee; Dutta, Amlan

2015-01-01

The present study employs the method of atomistic simulation to estimate the thermal stress experienced by Si/Ge and Ge/Si, ultrathin, core/shell nanowires with fixed ends. The underlying technique involves the computation of Young's modulus and the linear coefficient of thermal expansion through separate simulations. These two material parameters are combined to obtain the thermal stress on the nanowires. In addition, the thermally induced stress is perceived in the context of buckling instability. The analysis provides a trade-off between the geometrical and operational parameters of the nanostructures. The proposed methodology can be extended to other materials and structures and helps with the prediction of the conditions under which a nanowire-based device might possibly fail due to elastic instability.

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.

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.

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)

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

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

Heavy Ion Microbeam- and Broadbeam-Induced Current Transients in SiGe HBTs

Science.gov (United States)

Pellish, Jonathan A.; Reed, R. A.; McMorrow, D.; Vizkelethy, G.; Ferlet-Cavrois, V.; Baggio, J.; Duhamel, O.; Moen, K. A.; Phillips, S. D.; Diestelhorst, R. M.;

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...

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.

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.

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.)

Photoluminescence of epitactical and polycrystalline CuInS2 layers for thin-film solar cells

International Nuclear Information System (INIS)

Eberhardt, J.

2007-01-01

The present thesis deals with one- and polycrystalline CuInS 2 absorber layers for thin-film solar cells and especially with their optical and structural characterization. By means of detailed temperature- and power-dependent photoluminescence measurements in epitactical and polycrystalline absorber layers different radiative transitions could be analyzed and identified. The spectra were dominated by broad luminescence bands of deep perturbing levels. The implantation of hydrogen at low energies led to a passivation of these perturbing levels. On the base of the optical studies on epitactical and polycrystalline absorber layers a new improved defect model for CuInS 2 could be developed. The model contains two donor and two acceptor levels with following ionization energies: D-1=46 meV, D-2=87 meV, A-1=70 meV, and A-2=119 meV

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...

Enhanced thermoelectric properties of polycrystalline Bi2Te3 core fibers with preferentially oriented nanosheets

Directory of Open Access Journals (Sweden)

Min Sun

2018-03-01

Full Text Available Bi2Te3-based materials have been reported to be one of the best room-temperature thermoelectric materials, and it is a challenge to substantially improve their thermoelectric properties. Here novel Bi2Te3 core fibers with borosilicate glass cladding were fabricated utilizing a modified molten core drawing method. The Bi2Te3 core of the fiber was found to consist of hexagonal polycrystalline nanosheets, and polycrystalline nanosheets had a preferential orientation; in other words, the hexagonal Bi2Te3 lamellar cleavage more tended to be parallel to the symmetry axis of the fibers. Compared with a homemade 3-mm-diameter Bi2Te3 rod, the polycrystalline nanosheets’ preferential orientation in the 89-μm-diameter Bi2Te3 core increased its electrical conductivity, but deduced its Seebeck coefficient. The Bi2Te3 core exhibits an ultrahigh ZT of 0.73 at 300 K, which is 232% higher than that of the Bi2Te3 rod. The demonstration of fibers with oriented nano-polycrystalline core and the integration with an efficient fabrication technique will pave the way for the fabrication of high-performance thermoelectric fibers.

Process Research On Polycrystalline Silicon Material (PROPSM). [flat plate solar array project

Science.gov (United States)

Culik, J. S.

1983-01-01

The performance-limiting mechanisms in large-grain (greater than 1 to 2 mm in diameter) polycrystalline silicon solar cells were investigated by fabricating a matrix of 4 sq cm solar cells of various thickness from 10 cm x 10 cm polycrystalline silicon wafers of several bulk resistivities. Analysis of the illuminated I-V characteristics of these cells suggests that bulk recombination is the dominant factor limiting the short-circuit current. The average open-circuit voltage of the polycrystalline solar cells is 30 to 70 mV lower than that of co-processed single-crystal cells; the fill-factor is comparable. Both open-circuit voltage and fill-factor of the polycrystalline cells have substantial scatter that is not related to either thickness or resistivity. This implies that these characteristics are sensitive to an additional mechanism that is probably spatial in nature. A damage-gettering heat-treatment improved the minority-carrier diffusion length in low lifetime polycrystalline silicon, however, extended high temperature heat-treatment degraded the lifetime.

Constitutive model of creep in polycrystalline halite based on workhardening and recovery

International Nuclear Information System (INIS)

Munson, D.E.

1993-01-01

A multimechanism constitutive model of creep has been developed which incorporates the workhardening and recovery transient creep behavior. This model has been applied to the creep of polycrystalline halite. The specific application of the model is in the calculation of the closure of underground rooms in layered salt deposits. Through the use of finite element calculations, this model, with appropriate laboratory material parameters and a Tresca flow potential, has predicted the measured closure of a number of large in situ experimental rooms

Surface and interfacial structural characterization of MBE grown Si/Ge multilayers

International Nuclear Information System (INIS)

Saha, Biswajit; Sharma, Manjula; Sarma, Abhisakh; Rath, Ashutosh; Satyam, P.V.; Chakraborty, Purushottam; Sanyal, Milan K.

2009-01-01

Si/Ge multilayer structures have been grown by solid source molecular beam epitaxy (MBE) on Si (1 1 1) and (1 0 0) substrates and were characterized by high-resolution X-ray diffraction (XRD), atomic force microscopy (AFM), high-depth-resolution secondary ion mass spectroscopy (SIMS) and cross-section high-resolution transmission electron microscopy (HRTEM). A reasonably good agreement has been obtained for layer thickness, interfacial structure and diffusion between SIMS and HRTEM measurements. Epitaxial growth and crystalline nature of the individual layer have been probed using cross-sectional HRTEM and XRD measurements. Surface and interface morphological studies by AFM and HRTEM show island-like growth of both Si and Ge nanostructures.

Characterization of Nanocrystalline SiGe Thin Film Solar Cell with Double Graded-Dead Absorption Layer

Directory of Open Access Journals (Sweden)

Chao-Chun Wang

2012-01-01

Full Text Available The nanocrystalline silicon-germanium (nc-SiGe thin films were deposited by high-frequency (27.12 MHz plasma-enhanced chemical vapor deposition (HF-PECVD. The films were used in a silicon-based thin film solar cell with graded-dead absorption layer. The characterization of the nc-SiGe films are analyzed by scanning electron microscopy, UV-visible spectroscopy, and Fourier transform infrared absorption spectroscopy. The band gap of SiGe alloy can be adjusted between 0.8 and 1.7 eV by varying the gas ratio. For thin film solar cell application, using double graded-dead i-SiGe layers mainly leads to an increase in short-circuit current and therefore cell conversion efficiency. An initial conversion efficiency of 5.06% and the stabilized efficiency of 4.63% for an nc-SiGe solar cell were achieved.

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

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.

A sandwich-like differential B-dot based on EACVD polycrystalline diamond slice

Science.gov (United States)

Xu, P.; Yu, Y.; Xu, L.; Zhou, H. Y.; Qiu, C. J.

2018-06-01

In this article, we present a method of mass production of a standardized high-performance differential B-dot magnetic probe together with the magnetic field measurement in a pulsed current device with the current up to hundreds of kilo-Amperes. A polycrystalline diamond slice produced in an Electron Assisted Chemical Vapor Deposition device is used as the base and insulating material to imprint two symmetric differential loops for the magnetic field measurement. The SP3 carbon bond in the cubic lattice structure of diamond is confirmed by Raman spectra. The thickness of this slice is 20 μm. A gold loop is imprinted onto each surface of the slice by using the photolithography technique. The inner diameter, width, and thickness of each loop are 0.8 mm, 50 μm, and 1 μm, respectively. It provides a way of measuring the pulsed magnetic field with a high spatial and temporal resolution, especially in limited space. This differential magnetic probe has demonstrated a very good common-mode rejection rate through the pulsed magnetic field measurement.

Segregation assisted microtwinning during creep of a polycrystalline L12-hardened Co-base superalloy

International Nuclear Information System (INIS)

Freund, Lisa P.; Messé, Olivier M.D.M.; Barnard, Jonathan S.; Göken, Mathias; Neumeier, Steffen; Rae, Catherine M.F.

2017-01-01

A polycrystalline L1 2 -hardened Co-base superalloy was creep deformed at 750 °C. The investigation of the deformed microstructure in the transmission electron microscope revealed microtwinning to be the prevailing deformation mechanism. The detected twins spanned the entire grain and cut through both, γ and γ′. Detailed high-resolution transmission electron microscopy investigations indicated that twin growth takes place by the slip of single a/6 〈112〉 partial dislocations along the twin boundary. Further analysis of the twin boundaries in the γ′ phase revealed segregation of elements known to decrease the stacking fault energy and a local depletion of γ′ forming elements. We propose that this segregation behavior enables subsequent a/6〈112〉 dislocations to easily slip along the twin boundary and further thicken the twins in the process.

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.

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.)

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

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

International Nuclear Information System (INIS)

Ludwig, W.; Herbig, M.; Ludwig, W.; King, A; Reischig, P.; Marrow, J.; Babout, L.; Mejdal Lauridsen, E.; Proudhon, H.

2011-01-01

Synchrotron radiation X-ray imaging and diffraction techniques offer new possibilities for non-destructive bulk characterization of polycrystalline materials. Minute changes in electron density (different crystallographic phases, cracks, porosities) can be detected using 3D imaging modes exploiting Fresnel diffraction and the coherence properties of third generation synchrotron beams. X-ray diffraction contrast tomography, a technique based on Bragg diffraction imaging, provides access to the 3D shape, orientation and elastic strain state of the individual grains from polycrystalline sample volumes containing several hundred up to a few thousand grains. Combining both imaging modalities allows a comprehensive description of the microstructure of the material at the micrometer length scale. Repeated observations during (interrupted) mechanical tests provide unprecedented insight into crystallographic and grain microstructure related aspects of polycrystal deformation and degradation mechanisms in materials, fulfilling some conditions on grain size and deformation state. (authors)

Microscopic gate-modulation imaging of charge and field distribution in polycrystalline organic transistors

Science.gov (United States)

Matsuoka, Satoshi; Tsutsumi, Jun'ya; Kamata, Toshihide; Hasegawa, Tatsuo

2018-04-01

In this work, a high-resolution microscopic gate-modulation imaging (μ-GMI) technique is successfully developed to visualize inhomogeneous charge and electric field distributions in operating organic thin-film transistors (TFTs). We conduct highly sensitive and diffraction-limit gate-modulation sensing for acquiring difference images of semiconducting channels between at gate-on and gate-off states that are biased at an alternate frequency of 15 Hz. As a result, we observe unexpectedly inhomogeneous distribution of positive and negative local gate-modulation (GM) signals at a probe photon energy of 1.85 eV in polycrystalline pentacene TFTs. Spectroscopic analyses based on a series of μ-GMI at various photon energies reveal that two distinct effects appear, simultaneously, within the polycrystalline pentacene channel layers: Negative GM signals at 1.85 eV originate from the second-derivative-like GM spectrum which is caused by the effect of charge accumulation, whereas positive GM signals originate from the first-derivative-like GM spectrum caused by the effect of leaked gate fields. Comparisons with polycrystalline morphologies indicate that grain centers are predominated by areas with high leaked gate fields due to the low charge density, whereas grain edges are predominantly high-charge-density areas with a certain spatial extension as associated with the concentrated carrier traps. Consequently, it is reasonably understood that larger grains lead to higher device mobility, but with greater inhomogeneity in charge distribution. These findings provide a clue to understand and improve device characteristics of polycrystalline TFTs.

Band structure of Si/Ge core-shell nanowires along the [110] direction modulated by external uniaxial strain

International Nuclear Information System (INIS)

Peng Xihong; Tang Fu; Logan, Paul

2011-01-01

Strain modulated electronic properties of Si/Ge core-shell nanowires along the [110] direction were reported, on the basis of first principles density-functional theory calculations. In particular, the energy dispersion relationship of the conduction/valence band was explored in detail. At the Γ point, the energy levels of both bands are significantly altered by applied uniaxial strain, which results in an evident change of the band gap. In contrast, for the K vectors far away from Γ, the variation of the conduction/valence band with strain is much reduced. In addition, with a sufficient tensile strain (∼1%), the valence band edge shifts away from Γ, which indicates that the band gap of the Si/Ge core-shell nanowires experiences a transition from direct to indirect. Our studies further showed that effective masses of charge carriers can also be tuned using the external uniaxial strain. The effective mass of the hole increases dramatically with tensile strain, while strain shows a minimal effect on tuning the effective mass of the electron. Finally, the relation between strain and the conduction/valence band edge is discussed thoroughly in terms of site-projected wavefunction characters.

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...

Phase-Field Modeling of Polycrystalline Solidification: From Needle Crystals to Spherulites—A Review

Science.gov (United States)

Gránásy, László; Rátkai, László; Szállás, Attila; Korbuly, Bálint; Tóth, Gyula I.; Környei, László; Pusztai, Tamás

2014-04-01

Advances in the orientation-field-based phase-field (PF) models made in the past are reviewed. The models applied incorporate homogeneous and heterogeneous nucleation of growth centers and several mechanisms to form new grains at the perimeter of growing crystals, a phenomenon termed growth front nucleation. Examples for PF modeling of such complex polycrystalline structures are shown as impinging symmetric dendrites, polycrystalline growth forms (ranging from disordered dendrites to spherulitic patterns), and various eutectic structures, including spiraling two-phase dendrites. Simulations exploring possible control of solidification patterns in thin films via external fields, confined geometry, particle additives, scratching/piercing the films, etc. are also displayed. Advantages, problems, and possible solutions associated with quantitative PF simulations are discussed briefly.

A comparative study of transport properties in polycrystalline and epitaxial chromium nitride films

KAUST Repository

Duan, X. F.

2013-01-08

Polycrystalline CrNx films on Si(100) and glass substrates and epitaxial CrNx films on MgO(100) substrates were fabricated by reactive sputtering with different nitrogen gas flow rates (fN2). With the increase of fN2, a lattice phase transformation from metallic Cr2N to semiconducting CrN appears in both polycrystalline and epitaxial CrNx films. At fN2= 100 sccm, the low-temperature conductance mechanism is dominated by both Mott and Efros-Shklovskii variable-range hopping in either polycrystalline or epitaxial CrN films. In all of the polycrystalline and epitaxial films, only the polycrystalline CrNx films fabricated at fN2 = 30 and 50 sccm exhibit a discontinuity in ρ(T) curves at 260-280 K, indicating that both the N-vacancy concentration and grain boundaries play important roles in the metal-insulator transition. © 2013 American Institute of Physics.

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.

Gas cluster ion beam assisted NiPt germano-silicide formation on SiGe

Energy Technology Data Exchange (ETDEWEB)

Ozcan, Ahmet S., E-mail: asozcan@us.ibm.com [IBM Almaden Research Center, 650 Harry Road, San Jose, California 95120 (United States); Lavoie, Christian; Jordan-Sweet, Jean [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States); Alptekin, Emre; Zhu, Frank [IBM Semiconductor Research and Development Center, 2070 Route 52, Hopewell Junction, New York 12533 (United States); Leith, Allen; Pfeifer, Brian D.; LaRose, J. D.; Russell, N. M. [TEL Epion Inc., 900 Middlesex Turnpike, Bldg. 6, Billerica, Massachusetts 01821 (United States)

2016-04-21

We report the formation of very uniform and smooth Ni(Pt)Si on epitaxially grown SiGe using Si gas cluster ion beam treatment after metal-rich silicide formation. The gas cluster ion implantation process was optimized to infuse Si into the metal-rich silicide layer and lowered the NiSi nucleation temperature significantly according to in situ X-ray diffraction measurements. This novel method which leads to more uniform films can also be used to control silicide depth in ultra-shallow junctions, especially for high Ge containing devices, where silicidation is problematic as it leads to much rougher interfaces.

Analysis of twelve-month degradation in three polycrystalline photovoltaic modules

Science.gov (United States)

Lai, T.; Potter, B. G.; Simmons-Potter, K.

2016-09-01

Polycrystalline silicon photovoltaic (PV) modules have the advantage of lower manufacturing cost as compared to their monocrystalline counterparts, but generally exhibit both lower initial module efficiencies and more significant early-stage efficiency degradation than do similar monocrystalline PV modules. For both technologies, noticeable deterioration in power conversion efficiency typically occurs over the first two years of usage. Estimating PV lifetime by examining the performance degradation behavior under given environmental conditions is, therefore, one of continual goals for experimental research and economic analysis. In the present work, accelerated lifecycle testing (ALT) on three polycrystalline PV technologies was performed in a full-scale, industrial-standard environmental chamber equipped with single-sun irradiance capability, providing an illumination uniformity of 98% over a 2 x 1.6m area. In order to investigate environmental aging effects, timedependent PV performance (I-V characteristic) was evaluated over a recurring, compressed day-night cycle, which simulated local daily solar insolation for the southwestern United States, followed by dark (night) periods. During a total test time of just under 4 months that corresponded to a year equivalent exposure on a fielded module, the temperature and humidity varied in ranges from 3°C to 40°C and 5% to 85% based on annual weather profiles for Tucson, AZ. Removing the temperature de-rating effect that was clearly seen in the data enabled the computation of normalized efficiency degradation with time and environmental exposure. Results confirm the impact of environmental conditions on the module long-term performance. Overall, more than 2% efficiency degradation in the first year of usage was observed for all thee polycrystalline Si solar modules. The average 5-year degradation of each PV technology was estimated based on their determined degradation rates.

Effect of strain, substrate surface and growth rate on B-doping in selectively grown SiGe layers

International Nuclear Information System (INIS)

Ghandi, R.; Kolahdouz, M.; Hallstedt, J.; Wise, R.; Wejtmans, Hans; Radamson, H.H.

2008-01-01

In this work, the role of strain and growth rate on boron incorporation in selective epitaxial growth (SEG) of B-doped Si 1-x Ge x (x = 0.15-0.25) layers in recessed or unprocessed (elevated) openings for source/drain applications in CMOS has been studied. A focus has been made on the strain distribution and B incorporation in SEG of SiGe layers

Effect of strain, substrate surface and growth rate on B-doping in selectively grown SiGe layers

Energy Technology Data Exchange (ETDEWEB)

Ghandi, R. [School of Information and Communication Technology, KTH (Royal Institute of Technology), Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden)], E-mail: ghandi@kth.se; Kolahdouz, M.; Hallstedt, J. [School of Information and Communication Technology, KTH (Royal Institute of Technology), Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden); Wise, R.; Wejtmans, Hans [Texas Instrument, 13121 TI Boulevard, Dallas, Tx 75243 (United States); Radamson, H.H. [School of Information and Communication Technology, KTH (Royal Institute of Technology), Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden)

2008-11-03

In this work, the role of strain and growth rate on boron incorporation in selective epitaxial growth (SEG) of B-doped Si{sub 1-x}Ge{sub x} (x = 0.15-0.25) layers in recessed or unprocessed (elevated) openings for source/drain applications in CMOS has been studied. A focus has been made on the strain distribution and B incorporation in SEG of SiGe layers.

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.

A SiGe High Gain and Highly Linear F-Band Single-Balanced Subharmonic Mixer

OpenAIRE

Seyedhosseinzadeh, Neda; Nabavi, Abdolreza; Carpenter, Sona; He, Zhongxia Simon; Bao, Mingquan; Zirath, Herbert

2017-01-01

A compact, broadband, high gain, second-order active down-converter subharmonic mixer is demonstrated using a 130-nm SiGe BiCMOS technology. The mixer adopts a bottom-LO Gilbert topology, on-chip RF and LO baluns and two emitter-follower buffers to realize a high gain wideband operation in both RF and IF frequencies. The measured performance exhibits a flat conversion gain (CG) of about 11 dB from 90 to 130 GHz with an average LO power of +3 dBm and high 2LO-RF isolation better than 60 dB. Th...

High strain amount in recessed junctions induced by selectively deposited boron-doped SiGe layers

International Nuclear Information System (INIS)

Radamson, H.H.; Kolahdouz, M.; Ghandi, R.; Ostling, M.

2008-01-01

This work presents the selective epitaxial growth (SEG) of Si 1-x Ge x (x = 0.15-0.315) layers with high amount of boron (1 x 10 20 -1 x 10 21 cm -3 ) in recessed or unprocessed (elevated) openings for source/drain applications in CMOS has been studied. The influence of the growth rate and strain on boron incorporation has been studied. A focus has been made on the strain distribution and boron incorporation in SEG of SiGe layers

Proper Generalized Decomposition (PGD) for the numerical simulation of polycrystalline aggregates under cyclic loading

Science.gov (United States)

Nasri, Mohamed Aziz; Robert, Camille; Ammar, Amine; El Arem, Saber; Morel, Franck

2018-02-01

The numerical modelling of the behaviour of materials at the microstructural scale has been greatly developed over the last two decades. Unfortunately, conventional resolution methods cannot simulate polycrystalline aggregates beyond tens of loading cycles, and they do not remain quantitative due to the plasticity behaviour. This work presents the development of a numerical solver for the resolution of the Finite Element modelling of polycrystalline aggregates subjected to cyclic mechanical loading. The method is based on two concepts. The first one consists in maintaining a constant stiffness matrix. The second uses a time/space model reduction method. In order to analyse the applicability and the performance of the use of a space-time separated representation, the simulations are carried out on a three-dimensional polycrystalline aggregate under cyclic loading. Different numbers of elements per grain and two time increments per cycle are investigated. The results show a significant CPU time saving while maintaining good precision. Moreover, increasing the number of elements and the number of time increments per cycle, the model reduction method is faster than the standard solver.

A high linearity SiGe HBT LNA for GPS receiver

International Nuclear Information System (INIS)

Luo Yanbin; Shi Jian; Ma Chengyan; Gan Yebing; Qian Min

2014-01-01

A high linearity 1.575 GHz SiGe:HBT low noise amplifier (LNA) for global positioning system applications is described. The bipolar cascoded with an MOSFET LNA was fabricated in a commercial 0.18 μm SiGe BiCMOS process. A resistor bias feed circuit with a feedback resistor was designed for the LNA input transistor to improve its intermodulation and compression performance. The packaged chip tested on board has displayed a noise figure of 1.11 dB, a power gain of 18 dB, an output 1 dB compression point of +7.8 dBm and an input third-order intercept point of +1.8 dBm. The chip occupies a 500 × 560 μm 2 area and consumes 3.6 mA from a 2.85 V power supply. (semiconductor integrated circuits)

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.)

LAPAS: A SiGe Front End Prototype for the Upgraded ATLAS LAr Calorimeter

CERN Document Server

Dressnandt, N; Rescia, S; Vernon, E

2009-01-01

We have designed and fabricated a very low noise preamplifier and shaper to replace the existing ATLAS Liquid Argon readout for use at the Large Hadron Collider upgrade (sLHC). IBM’s 8WL 130nm SiGe process was chosen for it’s radiation tolerance, low noise bipolar NPN devices, wide voltage rand and potential use in other sLHC detector subsystems. Although the requirements for the final design can not be set at this time, the prototype was designed to accommodate a 16 bit dynamic range. This was accomplished by using a single stage, low noise, wide dynamic range preamp followed by a dual range shaper. The low noise of the preamp is made possible by the low base spreading resistance of the Silicon Germanium NPN bipolar transistors. The relatively high voltage rating of the NPN transistors is exploited to allow a gain of 650V/A in the preamplifier which eases the input voltage noise requirement on the shaper. Each shaper stage is designed as a cascaded differential operational amplifier doublet with a common...

Predicting intragranular misorientation distributions in polycrystalline metals using the viscoplastic self-consistent formulation

DEFF Research Database (Denmark)

Zecevic, Miroslav; Pantleon, Wolfgang; Lebensohn, Ricardo A.

2017-01-01

In a recent paper, we reported the methodology to calculate intragranular fluctuations in the instantaneous lattice rotation rates in polycrystalline materials within the mean-field viscoplastic self-consistent (VPSC) model. This paper is concerned with the time integration and subsequent use......, we calculate intragranular misorientations in face-centered cubic polycrystals deformed in tension and plane-strain compression. These predictions are tested by comparison with corresponding experiments for polycrystalline copper and aluminum, respectively, and with full-field calculations....... It is observed that at sufficiently high strains some grains develop large misorientations that may lead to grain fragmentation and/or act as driving forces for recrystallization. The proposed VPSC-based prediction of intragranular misorientations enables modeling of grain fragmentation, as well as a more...

High strain amount in recessed junctions induced by selectively deposited boron-doped SiGe layers

Energy Technology Data Exchange (ETDEWEB)

Radamson, H.H. [School of Information and Communication Technology, KTH (Royal Institute of Technology) Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden)], E-mail: rad@kth.se; Kolahdouz, M.; Ghandi, R.; Ostling, M. [School of Information and Communication Technology, KTH (Royal Institute of Technology) Isafjordsg. 22-26, Electrum 229, 16640 Kista (Sweden)

2008-12-05

This work presents the selective epitaxial growth (SEG) of Si{sub 1-x}Ge{sub x} (x = 0.15-0.315) layers with high amount of boron (1 x 10{sup 20}-1 x 10{sup 21} cm{sup -3}) in recessed or unprocessed (elevated) openings for source/drain applications in CMOS has been studied. The influence of the growth rate and strain on boron incorporation has been studied. A focus has been made on the strain distribution and boron incorporation in SEG of SiGe layers.

Determining grain resolved stresses in polycrystalline materials using three-dimensional X-ray diffraction

DEFF Research Database (Denmark)

Oddershede, Jette; Schmidt, Søren; Poulsen, Henning Friis

2010-01-01

An algorithm is presented for characterization of the grain resolved (type II) stress states in a polycrystalline sample based on monochromatic X-ray diffraction data. The algorithm is a robust 12-parameter-per-grain fit of the centre-of-mass grain positions, orientations and stress tensors...

Wavelength-tunable waveguides based on polycrystalline organic-inorganic perovskite microwires

Science.gov (United States)

Wang, Ziyu; Liu, Jingying; Xu, Zai-Quan; Xue, Yunzhou; Jiang, Liangcong; Song, Jingchao; Huang, Fuzhi; Wang, Yusheng; Zhong, Yu Lin; Zhang, Yupeng; Cheng, Yi-Bing; Bao, Qiaoliang

2016-03-01

Hybrid organic-inorganic perovskites have emerged as new photovoltaic materials with impressively high power conversion efficiency due to their high optical absorption coefficient and long charge carrier diffusion length. In addition to high photoluminescence quantum efficiency and chemical tunability, hybrid organic-inorganic perovskites also show intriguing potential for diverse photonic applications. In this work, we demonstrate that polycrystalline organic-inorganic perovskite microwires can function as active optical waveguides with small propagation loss. The successful production of high quality perovskite microwires with different halogen elements enables the guiding of light with different colours. Furthermore, it is interesting to find that out-coupled light intensity from the microwire can be effectively modulated by an external electric field, which behaves as an electro-optical modulator. This finding suggests the promising applications of perovskite microwires as effective building blocks in micro/nano scale photonic circuits.

CdTe polycrystalline films on Ni foil substrates by screen printing and their photoelectric performance

International Nuclear Information System (INIS)

Yao, Huizhen; Ma, Jinwen; Mu, Yannan; Su, Shi; Lv, Pin; Zhang, Xiaoling; Zhou, Liying; Li, Xue; Liu, Li; Fu, Wuyou; Yang, Haibin

2015-01-01

Highlights: • The sintered CdTe polycrystalline films by a simple screen printing. • The flexible Ni foil was chose as substrates to reduce the weight of the electrode. • The compact CdTe film was obtained at 550 °C sintering temperature. • The photoelectric activity of the CdTe polycrystalline films was excellent. - Abstract: CdTe polycrystalline films were prepared on flexible Ni foil substrates by sequential screen printing and sintering in a nitrogen atmosphere for the first time. The effect of temperature on the quality of the screen-printed film was investigated in our work. The high-quality CdTe films were obtained after sintering at 550 °C for 2 h. The properties of the sintered CdTe films were characterized by scanning electron microscopy, X-ray diffraction pattern and UV–visible spectroscopy. The high-quality CdTe films have the photocurrent was 2.04 mA/cm 2 , which is higher than that of samples prepared at other temperatures. Furthermore, CdCl 2 treatment reduced the band gap of the CdTe film due to the larger grain size. The photocurrent of photoelectrode based on high crystalline CdTe polycrystalline films after CdCl 2 treatment improved to 2.97 mA/cm 2 , indicating a potential application in photovoltaic devices

Predicting the effective response of bulk polycrystalline ferroelectric ceramics via improved spectral phase field methods

Science.gov (United States)

Vidyasagar, A.; Tan, W. L.; Kochmann, D. M.

2017-09-01

Understanding the electromechanical response of bulk polycrystalline ferroelectric ceramics requires scale-bridging approaches. Recent advances in fast numerical methods to compute the homogenized mechanical response of materials with heterogeneous microstructure have enabled the solution of hitherto intractable systems. In particular, the use of a Fourier-based spectral method as opposed to the traditional finite element method has gained significant interest in the homogenization of periodic microstructures. Here, we solve the periodic, electro-mechanically-coupled boundary value problem at the mesoscale of polycrystalline ferroelectrics in order to extract the effective response of barium titanate (BaTiO3) and lead zirconate titanate (PZT) under applied electric fields. Results include the effective electric hysteresis and the associated butterfly curve of strain vs. electric field for mean stress-free electric loading. Computational predictions of the 3D polycrystalline response show convincing agreement with our experimental electric cycling and strain hysteresis data for PZT-5A. In addition to microstructure-dependent effective physics, we also show how finite-difference-based approximations in the spectral solution scheme significantly reduce instability and ringing phenomena associated with spectral techniques and lead to spatial convergence with h-refinement, which have been major challenges when modeling high-contrast systems such as polycrystals.

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.

Influence of polycrystalline silicon layer on flow through «metal — p-Si» contact

Directory of Open Access Journals (Sweden)

Smyntyna V. A.

2011-11-01

Full Text Available Based on the results of investigations of charge transport in the "metal — p-Si" contacts with different thickness of polycrystalline p-Si layer the mechanisms of charge transport through such structures are shown. It is established that with increasing thickness of the layer of polycrystalline p-Si current transport mechanism changes from a double injection into the drift-diffusion. This change is due to an increase in the drift current component in the space charge zone of "metal — p-Si" contact, which arises as a result of increased surface density of scattering barriers, which are localized at the boundaries of neighboring silicon polycrystals.

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.

Density-functional theory molecular dynamics simulations of a-HfO2/a-SiO2/SiGe and a-HfO2/a-SiO2/Ge with a-SiO2 and a-SiO suboxide interfacial layers

Science.gov (United States)

Chagarov, Evgueni A.; Kavrik, Mahmut S.; Fang, Ziwei; Tsai, Wilman; Kummel, Andrew C.

2018-06-01

Comprehensive Density-Functional Theory (DFT) Molecular Dynamics (MD) simulations were performed to investigate interfaces between a-HfO2 and SiGe or Ge semiconductors with fully-stoichiometric a-SiO2 or sub-oxide SiO interlayers. The electronic structure of the selected stacks was calculated with a HSE06 hybrid functional. Simulations were performed before and after hydrogen passivation of residual interlayer defects. For the SiGe substrate with Ge termination prior to H passivation, the stacks with a-SiO suboxide interlayer (a-HfO2/a-SiO/SiGe) demonstrate superior electronic properties and wider band-gaps than the stacks with fully coordinated a-SiO2 interlayers (a-HfO2/a-SiO2/SiGe). After H passivation, most of the a-HfO2/a-SiO2/SiGe defects are passivated. To investigate effect of random placement of Si and Ge atoms additional simulations with a randomized SiGe slab were performed demonstrating improvement of electronic structure. For Ge substrates, before H passivation, the stacks with a SiO suboxide interlayer (a-HfO2/a-SiO/Ge) also demonstrate wider band-gaps than the stacks with fully coordinated a-SiO2 interlayers (a-HfO2/a-SiO2/Ge). However, even for a-HfO2/a-SiO/Ge, the Fermi level is shifted close to the conduction band edge (CBM) consistent with Fermi level pinning. Again, after H passivation, most of the a-HfO2/a-SiO2/Ge defects are passivated. The stacks with fully coordinated a-SiO2 interlayers have much stronger deformation and irregularity in the semiconductor (SiGe or Ge) upper layers leading to multiple under-coordinated atoms which create band-edge states and decrease the band-gap prior to H passivation.

Thermoelectric performance of spin Seebeck effect in Fe3O4/Pt-based thin film heterostructures

Directory of Open Access Journals (Sweden)

R. Ramos

2016-10-01

Full Text Available We report a systematic study on the thermoelectric performance of spin Seebeck devices based on Fe3O4/Pt junction systems. We explore two types of device geometries: a spin Hall thermopile and spin Seebeck multilayer structures. The spin Hall thermopile increases the sensitivity of the spin Seebeck effect, while the increase in the sample internal resistance has a detrimental effect on the output power. We found that the spin Seebeck multilayers can overcome this limitation since the multilayers exhibit the enhancement of the thermoelectric voltage and the reduction of the internal resistance simultaneously, therefore resulting in significant power enhancement. This result demonstrates that the multilayer structures are useful for improving the thermoelectric performance of the spin Seebeck effect.

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.

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.

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)

Si/Ge intermixing during Ge Stranski–Krastanov growth

Directory of Open Access Journals (Sweden)

Alain Portavoce

2014-12-01

Full Text Available The Stranski–Krastanov growth of Ge islands on Si(001 has been widely studied. The morphology changes of Ge islands during growth, from nucleation to hut/island formation and growth, followed by hut-to-dome island transformation and dislocation nucleation of domes, have been well described, even at the atomic scale, using techniques such as scanning tunneling microscopy and transmission electron microscopy. Although it is known that these islands do not consist of pure Ge (due to Si/Ge intermixing, the composition of the Ge islands is not precisely known. In the present work, atom probe tomography was used to study the composition of buried dome islands at the atomic scale, in the three-dimensional space. The core of the island was shown to contain about 55 atom % Ge, while the Ge composition surrounding this core decreases rapidly in all directions in the islands to reach a Ge concentration of about 15 atom %. The Ge distribution in the islands follows a cylindrical symmetry and Ge segregation is observed only in the {113} facets of the islands. The Ge composition of the wetting layer is not homogeneous, varying from 5 to 30 atom %.

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)

Nanofrictional behavior of amorphous, polycrystalline and textured Y-Cr-O films

International Nuclear Information System (INIS)

Gervacio-Arciniega, J.J.; Flores-Ruiz, F.J.; Diliegros-Godines, C.J.; Broitman, E.; Enriquez-Flores, C.I.; Espinoza-Beltrán, F.J.; Siqueiros, J.; Cruz, M.P.

2016-01-01

Highlights: • Friction coefficient (μ) of ferroelectric textured and polycrystalline YCrO_3 films. • A simple method to evaluate μ from a single AFM image is presented. • The AFM-cantilever spring constant was determined from its dynamic response. • Polycrystalline and amorphous films have a lower μ than textured samples. - Abstract: Differences in friction coefficients (μ) of ferroelectric YCrO_3, textured and polycrystalline films, and non-ferroelectric Y-Cr-O films are analyzed. The friction coefficient was evaluated by atomic force microscopy using a simple quantitative procedure where the dependence of friction force with the applied load is obtained in only one topographical image. A simple code was developed with the MATLAB"® software to analyze the experimental data. The code includes a correction of the hysteresis in the forward and backward scanning directions. The quantification of load exerted on the sample surface was obtained by finite element analysis of the AFM cantilever starting from its experimental dynamic information. The results show that the ferroelectric YCrO_3 film deposited on a Pt(150 nm)/TiO_2(30 nm)/SiO_2/Si (100) substrate is polycrystalline and has a lower friction coefficient than the deposited on SrTiO_3 (110), which is highly textured. From a viewpoint of industrial application in ferroelectric memories, where the writing process is electrical or mechanically achieved by sliding AFM tips on the sample, polycrystalline YCrO_3 films seem to be the best candidates due to their lower μ.

Nanofrictional behavior of amorphous, polycrystalline and textured Y-Cr-O films

Energy Technology Data Exchange (ETDEWEB)

Gervacio-Arciniega, J.J. [Centro de Nanociencias y Nanotecnología (CNyN), Universidad Nacional Autónoma de México (UNAM), km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico); Flores-Ruiz, F.J., E-mail: fcojfloresr@gmail.com [Centro de Nanociencias y Nanotecnología (CNyN), Universidad Nacional Autónoma de México (UNAM), km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico); Diliegros-Godines, C.J. [Centro de Nanociencias y Nanotecnología (CNyN), Universidad Nacional Autónoma de México (UNAM), km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico); Broitman, E. [Thin Film Physics Division, IFM, Linköping University, SE-58183 Linköping (Sweden); Enriquez-Flores, C.I.; Espinoza-Beltrán, F.J. [CINVESTAV Unidad Querétaro, Lib. Norponiente 2000, Real de Juriquilla, 76230 Querétaro, Qro. (Mexico); Siqueiros, J.; Cruz, M.P. [Centro de Nanociencias y Nanotecnología (CNyN), Universidad Nacional Autónoma de México (UNAM), km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico)

2016-08-15

Highlights: • Friction coefficient (μ) of ferroelectric textured and polycrystalline YCrO{sub 3} films. • A simple method to evaluate μ from a single AFM image is presented. • The AFM-cantilever spring constant was determined from its dynamic response. • Polycrystalline and amorphous films have a lower μ than textured samples. - Abstract: Differences in friction coefficients (μ) of ferroelectric YCrO{sub 3}, textured and polycrystalline films, and non-ferroelectric Y-Cr-O films are analyzed. The friction coefficient was evaluated by atomic force microscopy using a simple quantitative procedure where the dependence of friction force with the applied load is obtained in only one topographical image. A simple code was developed with the MATLAB{sup ®} software to analyze the experimental data. The code includes a correction of the hysteresis in the forward and backward scanning directions. The quantification of load exerted on the sample surface was obtained by finite element analysis of the AFM cantilever starting from its experimental dynamic information. The results show that the ferroelectric YCrO{sub 3} film deposited on a Pt(150 nm)/TiO{sub 2}(30 nm)/SiO{sub 2}/Si (100) substrate is polycrystalline and has a lower friction coefficient than the deposited on SrTiO{sub 3} (110), which is highly textured. From a viewpoint of industrial application in ferroelectric memories, where the writing process is electrical or mechanically achieved by sliding AFM tips on the sample, polycrystalline YCrO{sub 3} films seem to be the best candidates due to their lower μ.

A multiscale coupled finite-element and phase-field framework to modeling stressed grain growth in polycrystalline thin films

Energy Technology Data Exchange (ETDEWEB)

Jamshidian, M., E-mail: jamshidian@cc.iut.ac.ir [Department of Mechanical Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Institute of Structural Mechanics, Bauhaus-University Weimar, Marienstrasse 15, 99423 Weimar (Germany); Thamburaja, P., E-mail: prakash.thamburaja@gmail.com [Department of Mechanical & Materials Engineering, Universiti Kebangsaan Malaysia (UKM), Bangi 43600 (Malaysia); Rabczuk, T., E-mail: timon.rabczuk@tdt.edu.vn [Division of Computational Mechanics, Ton Duc Thang University, Ho Chi Minh City (Viet Nam); Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City (Viet Nam)

2016-12-15

A previously-developed finite-deformation- and crystal-elasticity-based constitutive theory for stressed grain growth in cubic polycrystalline bodies has been augmented to include a description of excess surface energy and grain-growth stagnation mechanisms through the use of surface effect state variables in a thermodynamically-consistent manner. The constitutive theory was also implemented into a multiscale coupled finite-element and phase-field computational framework. With the material parameters in the constitutive theory suitably calibrated, our three-dimensional numerical simulations show that the constitutive model is able to accurately predict the experimentally-determined evolution of crystallographic texture and grain size statistics in polycrystalline copper thin films deposited on polyimide substrate and annealed at high-homologous temperatures. In particular, our numerical analyses show that the broad texture transition observed in the annealing experiments of polycrystalline thin films is caused by grain growth stagnation mechanisms. - Graphical abstract: - Highlights: • Developing a theory for stressed grain growth in polycrystalline thin films. • Implementation into a multiscale coupled finite-element and phase-field framework. • Quantitative reproduction of the experimental grain growth data by simulations. • Revealing the cause of texture transition to be due to the stagnation mechanisms.

Generation of uniaxial tensile strain of over 1% on a Ge substrate for short-channel strained Ge n-type Metal–Insulator–Semiconductor Field-Effect Transistors with SiGe stressors

International Nuclear Information System (INIS)

Moriyama, Yoshihiko; Kamimuta, Yuuichi; Ikeda, Keiji; Tezuka, Tsutomu

2012-01-01

Tensile strain of over 1% in Ge stripes sandwiched between a pair of SiGe source-drain stressors was demonstrated. The Metal–Oxide–Semiconductor Field-Effect Transistor (MOSFET)-like structures were fabricated on a (001)-Ge substrate having SiO 2 dummy-gate stripes with widths down to 26 nm. Recess-regions adjacent to the dummy-gate stripes were formed by an anisotropic wet etching technique. A damage-free and well-controlled anisotropic wet etching process is developed in order to avoid plasma-induced damage during a conventional Reactive-ion Etching process. The SiGe stressors were epitaxially grown on the recesses to simulate strained Ge n-channel Metal–Insulator–Semiconductor Field-Effect Transistors (MISFETs) having high electron mobility. A micro-Raman spectroscopy measurement revealed tensile strain in the narrow Ge regions which became higher for narrower regions. Tensile strain of up to 1.2% was evaluated from the measurement under an assumption of uniaxial strain configuration. These results strongly suggest that higher electron mobility than the upper limit for a Si-MOSFET is obtainable in short-channel strained Ge-nMISFETs with the embedded SiGe stressors.

Simulating characteristics of Si/Ge tandem monolithic solar cell with Si1-xGex buffer layer

Directory of Open Access Journals (Sweden)

Gnilenko A. B.

2015-12-01

Full Text Available In spite of many efforts to propose new semiconductor materials and sophisticated constructions of solar cells, crystalline silicone remains the main photovoltaic material widely used up to now. There are various methods to enhance the efficiency of silicone solar cells. One of them is to combine silicone with an additional semiconductor material with the different bandgap to form a tandem construction. For example, the germanium sub-cell used as the bottom cascade for the silicone sub-cell in the tandem monolithic solar cell makes it possible to utilize the "red" sub-band of solar spectra increasing overall solar cell efficiency. The problem of the 4.2% mismatch in lattice constant between Si and Ge can be resolved in such a case by the use of SiGe buffer layer. In the paper the results of the computer simulation for Si/Ge tandem monolithic solar cell with Si1-xGex buffer layer are presented. In the solar cell under consideration, the step graded Si1-xGex buffer layer is located between the top silicone and the bottom germanium cascades to reduce the threading dislocation density in mismatched materials. The cascades are commutated by the use of the germanium tunnel diode between the bottom sub-cell and the buffer layer. For the solar cell modeling, the physically-based device simulator ATLAS of Silvaco TCAD software is employed to predict the electrical behavior of the semiconductor structure and to provide a deep insight into the internal physical processes. The voltage-current characteristic, photovoltaic parameters and the distribution of basic physical values are obtained for the investigated tandem solar cell. The influence of layer thicknesses on the photovoltaic parameters is studied. The calculated efficiency of the tandem solar cell reaches 13% which is a quarter more than the efficiency of a simple silicone solar cell with the same constructive parameters and under the same illumination conditions.

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

Examination Of Si-Ge Heterostructure Nanowire Growth Using Monte Carlo Simulation

International Nuclear Information System (INIS)

Nastovjak, A. G.; Neizvestny, I. G.; Shwartz, N. L.

2011-01-01

The process of Si-Ge heterostructures formation in nanowires (NWs) grown by vapor-liquid-solid mechanism was investigated using Monte Carlo simulation. Dependences of catalyst drop composition on temperature, flux intensity and nanowire diameter were obtained. Periodical oscillations of drop composition near mean value were observed. Oscillation results from layer-by-layer growth at the drop-whisker interface and necessity of supersaturation onset to start new layer formation. It was demonstrated that it is impossible to grow atomically abrupt axial heterojunctions via classical vapor-liquid-solid mechanism due to gradual change of catalyst drop composition when switching the fluxes. This phenomenon is the main reason of heterojunction blurriness. Junction abruptness was found to be dependent on nanowhisker diameter: in adsorption-induced growth mode abruptness of heterojunction decreases with diameter and in diffusion-induced mode it increases.

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

Polycrystalline Mg2Si thin films: A theoretical investigation of their electronic transport properties

International Nuclear Information System (INIS)

Balout, H.; Boulet, P.; Record, M.-C.

2015-01-01

The electronic structures and thermoelectric properties of a polycrystalline Mg 2 Si thin film have been investigated by first-principle density-functional theory (DFT) and Boltzmann transport theory calculations within the constant-relaxation time approximation. The polycrystalline thin film has been simulated by assembling three types of slabs each having the orientation (001), (110) or (111) with a thickness of about 18 Å. The effect of applying the relaxation procedure to the thin film induces disorder in the structure that has been ascertained by calculating radial distribution functions. For the calculations of the thermoelectric properties, the energy gap has been fixed at the experimental value of 0.74 eV. The thermoelectric properties, namely the Seebeck coefficient, the electrical conductivity and the power factor, have been determined at three temperatures of 350 K, 600 K and 900 K with respect to both the energy levels and the p-type and n-type doping levels. The best Seebeck coefficient is obtained at 350 K: the S yy component of the tensor amounts to about ±1000 μV K −1 , depending on the type of charge carriers. However, the electrical conductivity is much too small which results in low values of the figure of merit ZT. Structure–property relationship correlations based on directional radial distribution functions allow us to tentatively draw some explanations regarding the anisotropy of the electrical conductivity. Finally, the low ZT values obtained for the polycrystalline Mg 2 Si thin film are paralleled with those recently reported in the literature for bulk chalcogenide glasses. - Graphical abstract: Structure of the polycrystalline thin film of Mg 2 Si. - Author-Highlights: • Polycrystalline Mg 2 Si film has been modelled by DFT approach. • Thermoelectric properties have been evaluated by semi-classical Boltzmann theory. • The structure was found to be slightly disordered after relaxation. • The highest value of Seebeck

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.)

Self-assembly of InAs and Si/Ge quantum dots on structured surfaces

International Nuclear Information System (INIS)

Patella, F; Sgarlata, A; Arciprete, F; Nufris, S; Szkutnik, P D; Placidi, E; Fanfoni, M; Motta, N; Balzarotti, A

2004-01-01

We discuss the self-aggregation process of InAs and Si-Ge quantum dots (QDs) on natural and patterned GaAs(001) and Si(001) and Si(111) surfaces, with reference to our recent studies with scanning tunnelling and atomic force microscopy and current experimental and theoretical works. Various methods for obtaining naturally structured surfaces are briefly surveyed, as the patterning formed by the surface instability and by the strain in mismatched heteroepitaxy, and the latest methods of pre-patterning and growth at selected sites are discussed. Basic topics are also addressed that determine the final morphology of QDs, such as the wetting layer formation, the elastic strain field and the two-dimensional to three-dimensional phase transition

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.

Silicon-based thin films as bottom electrodes in chalcogenide nonvolatile memories

Energy Technology Data Exchange (ETDEWEB)

Lee, Seung-Yun [IT Convergence and Components Laboratory, Electronics and Telecommunications Research Institute (ETRI), Yuseong-gu, Daejeon 305-350 (Korea, Republic of)], E-mail: seungyun@etri.re.kr; Yoon, Sung-Min; Choi, Kyu-Jeong; Lee, Nam-Yeal; Park, Young-Sam; Ryu, Sang-Ouk; Yu, Byoung-Gon; Kim, Sang-Hoon; Lee, Sang-Heung [IT Convergence and Components Laboratory, Electronics and Telecommunications Research Institute (ETRI), Yuseong-gu, Daejeon 305-350 (Korea, Republic of)

2007-10-31

The effect of the electrical resistivity of a silicon-germanium (SiGe) thin film on the phase transition in a GeSbTe (GST) chalcogenide alloy and the manufacturing aspect of the fabrication process of a chalcogenide memory device employing the SiGe film as bottom electrodes were investigated. While p-type SiGe bottom electrodes were formed using in situ doping techniques, n-type ones could be made in a different manner where phosphorus atoms diffused from highly doped silicon underlayers to undoped SiGe films. The p-n heterojunction did not form between the p-type GST and n-type SiGe layers, and the semiconduction type of the SiGe alloys did not influence the memory device switching. It was confirmed that an optimum resistivity value existed for memory operation in spite of proportionality of Joule heating to electrical resistivity. The very high resistivity of the SiGe film had no effect on the reduction of reset current, which might result from the resistance decrease of the SiGe alloy at high temperatures.

Mixed-signal 0.18μm CMOS and SiGe BiCMOS foundry technologies for ROIC applications

Science.gov (United States)

Kar-Roy, Arjun; Howard, David; Racanelli, Marco; Scott, Mike; Hurwitz, Paul; Zwingman, Robert; Chaudhry, Samir; Jordan, Scott

2010-10-01

Today's readout integrated-circuits (ROICs) require a high level of integration of high performance analog and low power digital logic. TowerJazz offers a commercial 0.18μm CMOS technology platform for mixed-signal, RF, and high performance analog applications which can be used for ROIC applications. The commercial CA18HD dual gate oxide 1.8V/3.3V and CA18HA dual gate oxide 1.8V/5V RF/mixed signal processes, consisting of six layers of metallization, have high density stacked linear MIM capacitors, high-value resistors, triple-well isolation and thick top aluminum metal. The CA18HA process also has scalable drain extended LDMOS devices, up to 40V Vds, for high-voltage sensor applications, and high-performance bipolars for low noise requirements in ROICs. Also discussed are the available features of the commercial SBC18 SiGe BiCMOS platform with SiGe NPNs operating up to 200/200GHz (fT/fMAX frequencies in manufacturing and demonstrated to 270 GHz fT, for reduced noise and integrated RF capabilities which could be used in ROICs. Implementation of these technologies in a thick film SOI process for integrated RF switch and power management and the availability of high fT vertical PNPs to enable complementary BiCMOS (CBiCMOS), for RF enabled ROICs, are also described in this paper.

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.

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...

Control of surface ripple amplitude in ion beam sputtered polycrystalline cobalt films

Energy Technology Data Exchange (ETDEWEB)

Colino, Jose M., E-mail: josemiguel.colino@uclm.es [Institute of Nanoscience, Nanotechnology and Molecular Materials, University of Castilla-La Mancha, Campus de la Fabrica de Armas, Toledo 45071 (Spain); Arranz, Miguel A. [Facultad de Ciencias Quimicas, University of Castilla-La Mancha, Ciudad Real 13071 (Spain)

2011-02-15

We have grown both polycrystalline and partially textured cobalt films by magnetron sputter deposition in the range of thickness (50-200 nm). Kinetic roughening of the growing film leads to a controlled rms surface roughness values (1-6 nm) increasing with the as-grown film thickness. Ion erosion of a low energy 1 keV Ar+ beam at glancing incidence (80{sup o}) on the cobalt film changes the surface morphology to a ripple pattern of nanometric wavelength. The wavelength evolution at relatively low fluency is strongly dependent on the initial surface topography (a wavelength selection mechanism hereby confirmed in polycrystalline rough surfaces and based on the shadowing instability). At sufficiently large fluency, the ripple wavelength steadily increases on a coarsening regime and does not recall the virgin surface morphology. Remarkably, the use of a rough virgin surface makes the ripple amplitude in the final pattern can be controllably increased without affecting the ripple wavelength.

Numerical analysis of the effect of surface roughness on mechanical fields in polycrystalline aggregates

Science.gov (United States)

Guilhem, Yoann; Basseville, Stéphanie; Curtit, François; Stéphan, Jean-Michel; Cailletaud, Georges

2018-06-01

This paper is dedicated to the study of the influence of surface roughness on local stress and strain fields in polycrystalline aggregates. Finite element computations are performed with a crystal plasticity model on a 316L stainless steel polycrystalline material element with different roughness states on its free surface. The subsequent analysis of the plastic strain localization patterns shows that surface roughness strongly affects the plastic strain localization induced by crystallography. Nevertheless, this effect mainly takes place at the surface and vanishes under the first layer of grains, which implies the existence of a critical perturbed depth. A statistical analysis based on the plastic strain distribution obtained for different roughness levels provides a simple rule to define the size of the affected zone depending on the rough surface parameters.

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.

Technics Research on Polycrystalline Cubic Boron Nitride Cutting Tools Dry Turning Ti-6AL-4V Alloy Based on Orthogonal Experimental Design

Directory of Open Access Journals (Sweden)

Jia Yunhai

2018-01-01

Full Text Available Ti-6Al-4V components are the most widely used titanium alloy products not only in the aerospace industry, but also for bio-medical applications. The machine-ability of titanium alloys is impaired by their high temperature chemical reactivity, low thermal conductivity and low modulus of elasticity. Polycrystalline cubic boron nitride represents a substitute tool material for turning titanium alloys due to its high hardness, wear resistance, thermal stability and hot red hardness. For determination of suitable cutting parameters in dry turning Ti-6AL-4V alloy by Polycrystalline cubic boron nitride cutting tools, the samples, 300mm in length and 100mm in diameter, were dry machined in a lathe. The turning suitable parameters, such as cutting speed, feed rate and cut depth were determined according to workpieces surface roughness and tools flank wear based on orthogonal experimental design. The experiment showed that the cutting speed in the range of 160~180 m/min, the feed rate is 0.15 mm/rev and the depth of cut is 0.20mm, ideal workpiece surface roughness and little cutting tools flank wear can be obtained.

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.

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 V_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-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.

A Power Case Study for Monocrystalline and Polycrystalline Solar Panels in Bursa City, Turkey

Directory of Open Access Journals (Sweden)

Ayşegül Taşçıoğlu

2016-01-01

Full Text Available It was intended to reveal the time dependent power generation under different loads for two different solar panels under the conditions of Bursa province in between August 19 and 25, 2014. The testing sets include solar panels, inverter, multimeter, accumulator, regulator, pyranometer, pyrheliometer, temperature sensor, and datalogger. The efficiency of monocrystalline and polycrystalline solar panels was calculated depending on the climatic data’s measurements. As the result of the study, the average performances of monocrystalline and polycrystalline panels are 42.06 and 39.80 Wh, respectively. It was seen that 87.14 W instantaneous power could be obtained from monocrystalline solar panel and that 80.17 W instantaneous power could be obtained from polycrystalline solar panel under maximum total radiation (1001.13 W/m2. Within this frame, it was determined that monocrystalline solar panel is able to operate more efficiently under the conditions of Bursa compared to polycrystalline solar panel. When the multivariate correlations coefficients were examined statistically, a significant relationship in positive direction was detected between total and direct radiation and ambient temperature on energy generation from monocrystalline and polycrystalline panel.

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.

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.

Electrical properties of grain boundaries in polycrystalline materials under intrinsic or low doping

International Nuclear Information System (INIS)

Chowdhury, M H; Kabir, M Z

2011-01-01

An analytical model is developed to study the electrical properties (electric field and potential distributions, potential energy barrier height and polarization phenomenon) of polycrystalline materials at intrinsic or low doping for detector and solar cell applications by considering an arbitrary amount of grain boundary charge and a finite width of grain boundary region. The general grain boundary model is also applicable to highly doped polycrystalline materials. The electric field and potential distributions are obtained by solving Poisson's equation in both depleted grains and grain boundary regions. The electric field and potential distributions across the detector are analysed under various doping, trapping and applied biases. The electric field collapses, i.e. a nearly zero-average electric field region exists in some part of the biased detector at high trapped charge densities at the grain boundaries. The model explains the conditions of existence of a zero-average field region, i.e. the polarization mechanisms in polycrystalline materials. The potential energy barrier at the grain boundary exists if the electric field changes its sign at the opposite side of the grain boundary. The energy barrier does not exist in all grain boundaries in the low-doped polycrystalline detector and it never exists in intrinsic polycrystalline detectors under applied bias condition provided that there is no charge trapping in the grain.

An investigation of group IV alloys and their applications in bipolar transistors

International Nuclear Information System (INIS)

Anteney, I.M.

2000-09-01

This thesis investigates the use of carbon in group IV alloys and their potential uses in bipolar transistors. The first part of the thesis investigates the ability of carbon to suppress transient enhanced diffusion in SiGe heterojunction bipolar transistors, whilst the second part deals with the impact of carbon incorporation on the electrical properties of polycrystalline silicon and silicon-germanium films. A background doping concentration (10 20 cm -3 ) of C has been introduced into the base of SiGe HBTs with the aim of studying the effects of C on TED of B from the base. An electrical method is used to extract the bandgap narrowing in the base of SiGe and SiGe:C HBTs through measurements of the temperature dependence of I c at different C/B reverse biases. The method is very sensitive to small amounts of dopant out-diffusion from the base and hence is ideal for determining the effect of C on TED. Extracted BGN values of 115meV and 173meV were obtained for the SiGe and SiGe:C HBTs respectively, for a C/B reverse bias of 0V. Increasing the C/B reverse bias to 1V increased the extracted BGN of the SiGe HBT to 145meV, but left the SiGe:C value unchanged. This demonstrates that no parasitic energy barrier exists in the SiGe:C HBT and that TED has been suppressed. The effect of carbon position and concentration has been studied by introducing a peak C concentration of 10 20 cm -3 in the collector and 1.1x10 19 cm -3 or 1.5x10 19 cm -3 C in the base. From these measurements it has been shown that TED is only suppressed in the device with 1.5x10 19 cm -3 C in the base, indicating that a C concentration of 1.5x10 19 cm -3 is needed to suppress TED and that the C needs to be co-located with the B profile. The effects of carbon on the electrical properties of polycrystalline Si and SiGe films have been investigated. The resistivity, Hall mobility (μ H ) and effective carrier concentration (N EFF ) of n- and p-type polySi 1-y C y and polySi 0.82-y Ge 0.18 C y layers

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)

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)

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.

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.

Tunable band structures of polycrystalline graphene by external and mismatch strains

Institute of Scientific and Technical Information of China (English)

Jiang-Tao Wu; Xing-Hua Shi; Yu-Jie Wei

2012-01-01

Lacking a band gap largely limits the application of graphene in electronic devices.Previous study shows that grain boundaries (GBs) in polycrystalline graphene can dramatically alter the electrical properties of graphene.Here,we investigate the band structure of polycrystalline graphene tuned by externally imposed strains and intrinsic mismatch strains at the GB by density functional theory (DFT) calculations.We found that graphene with symmetrical GBs typically has zero band gap even with large uniaxial and biaxial strain.However,some particular asymmetrical GBs can open a band gap in graphene and their band structures can be substantially tuned by external strains.A maximum band gap about 0.19 eV was observed in matched-armchair GB (5,5) | (3,7) with a misorientation of θ =13° when the applied uniaxial strain increases to 9％.Although mismatch strain is inevitable in asymmetrical GBs,it has a small influence on the band gap of polycrystalline graphene.

Influence of ammonia flow rate for improving properties of polycrystalline GaN

Science.gov (United States)

Ariff, A.; Ahmad, M. A.; Hassan, Z.; Zainal, N.

2018-06-01

Post-annealing treatment in ammonia ambient is widely accepted for GaN material, but less works have been done to investigate the influence of the ammonia (NH3) flow rate for reducing the N-deficiency as well as improving the quality of the material. In this work, we investigated the influence of NH3 flow rate at 1, 2, 3, and 4 slm in improving properties of a ∼1 μm thick polycrystalline GaN layer. Our simulation work suggested that the uniformity of temperature and pressure gradient of the NH3 gas did not lead to the reduction of N-deficiency of the polycrystalline GaN layer. Instead, it was found that the mitigation of the N-deficiency was strongly influenced by the fluid velocity of the NH3 gas, which had passed over the layer. Either at lower or higher fluid velocity, the chance for the active N atoms to incorporate into the GaN lattice structure was low. Therefore, the N-deficiency on the polycrystalline GaN layer could not be minimized under these conditions. As measured by EDX, the N atoms incorporation was the most effective when the NH3 flow rate at 3 slm, suggesting the flow rate significantly improved the N-deficiency of the polycrystalline GaN layer. Furthermore, it favored the formation of larger hexagonal faceted grains, with the smallest FWHM of XRD peaks from the GaN diffractions in (10 1 bar 0), (0002) and (10 1 bar 1) orientations, while allowing the polycrystalline GaN layer to show sharp and intense emissions peak of NBE in a PL spectrum.

Thermal conductivity of nanocrystalline SiGe alloys using molecular dynamics simulations

Science.gov (United States)

Abs da Cruz, Carolina; Katcho, Nebil A.; Mingo, Natalio; Veiga, Roberto G. A.

2013-10-01

We have studied the effect of nanocrystalline microstructure on the thermal conductivity of SiGe alloys using molecular dynamics simulations. Nanograins are modeled using both the coincidence site lattice and the Voronoi tessellation methods, and the thermal conductivity is computed using the Green-Kubo formalism. We analyze the dependence of the thermal conductivity with temperature, grain size L, and misorientation angle. We find a power dependence of L1/4 of the thermal conductivity with the grain size, instead of the linear dependence shown by non-alloyed nanograined systems. This dependence can be derived analytically underlines the important role that disorder scattering plays even when the grains are of the order of a few nm. This is in contrast to non-alloyed systems, where phonon transport is governed mainly by the boundary scattering. The temperature dependence is weak, in agreement with experimental measurements. The effect of angle misorientation is also small, which stresses the main role played by the disorder scattering.

Intrinsic Compressive Stress in Polycrystalline Films is Localized at Edges of the Grain Boundaries

Science.gov (United States)

Vasco, Enrique; Polop, Celia

2017-12-01

The intrinsic compression that arises in polycrystalline thin films under high atomic mobility conditions has been attributed to the insertion or trapping of adatoms inside grain boundaries. This compression is a consequence of the stress field resulting from imperfections in the solid and causes the thermomechanical fatigue that is estimated to be responsible for 90% of mechanical failures in current devices. We directly measure the local distribution of residual intrinsic stress in polycrystalline thin films on nanometer scales, using a pioneering method based on atomic force microscopy. Our results demonstrate that, at odds with expectations, compression is not generated inside grain boundaries but at the edges of gaps where the boundaries intercept the surface. We describe a model wherein this compressive stress is caused by Mullins-type surface diffusion towards the boundaries, generating a kinetic surface profile different from the mechanical equilibrium profile by the Laplace-Young equation. Where the curvatures of both profiles differ, an intrinsic stress is generated in the form of Laplace pressure. The Srolovitz-type surface diffusion that results from the stress counters the Mullins-type diffusion and stabilizes the kinetic surface profile, giving rise to a steady compression regime. The proposed mechanism of competition between surface diffusions would explain the flux and time dependency of compressive stress in polycrystalline thin films.

Feasibility Study of Thin Film Thermocouple Piles

Science.gov (United States)

Sisk, R. C.

2001-01-01

Historically, thermopile detectors, generators, and refrigerators based on bulk materials have been used to measure temperature, generate power for spacecraft, and cool sensors for scientific investigations. New potential uses of small, low-power, thin film thermopiles are in the area of microelectromechanical systems since power requirements decrease as electrical and mechanical machines shrink in size. In this research activity, thin film thermopile devices are fabricated utilizing radio frequency sputter coating and photoresist lift-off techniques. Electrical characterizations are performed on two designs in order to investigate the feasibility of generating small amounts of power, utilizing any available waste heat as the energy source.

Suspended mid-infrared fiber-to-chip grating couplers for SiGe waveguides

Science.gov (United States)

Favreau, Julien; Durantin, Cédric; Fédéli, Jean-Marc; Boutami, Salim; Duan, Guang-Hua

2016-03-01

Silicon photonics has taken great importance owing to the applications in optical communications, ranging from short reach to long haul. Originally dedicated to telecom wavelengths, silicon photonics is heading toward circuits handling with a broader spectrum, especially in the short and mid-infrared (MIR) range. This trend is due to potential applications in chemical sensing, spectroscopy and defense in the 2-10 μm range. We previously reported the development of a MIR photonic platform based on buried SiGe/Si waveguide with propagation losses between 1 and 2 dB/cm. However the low index contrast of the platform makes the design of efficient grating couplers very challenging. In order to achieve a high fiber-to-chip efficiency, we propose a novel grating coupler structure, in which the grating is locally suspended in air. The grating has been designed with a FDTD software. To achieve high efficiency, suspended structure thicknesses have been jointly optimized with the grating parameters, namely the fill factor, the period and the grating etch depth. Using the Efficient Global Optimization (EGO) method we obtained a configuration where the fiber-to-waveguide efficiency is above 57 %. Moreover the optical transition between the suspended and the buried SiGe waveguide has been carefully designed by using an Eigenmode Expansion software. Transition efficiency as high as 86 % is achieved.

$^{31}$Si Self-Diffusion in Si-Ge Alloys and Si-(B-)C-N Ceramics and Diffusion Studies for Al and Si Beam Developments

CERN Multimedia

Nylandsted larsen, A; Voss, T L; Strohm, A

2002-01-01

An invaluable method for studying diffusion in solids is the radiotracer technique. However, its applicability had been restricted to radiotracer atoms with half-lives $t_{1/2}$ of about 1~d or longer. Within the framework of IS372 a facility was developed in which short-lived radiotracer atoms ( 5min $\\scriptstyle{\\lesssim}$ $t_{1/2}\\scriptstyle{\\lesssim}$1 d ) can be used. For the implantation of the short-lived tracers the facility is flanged to the ISOLDE beamline, and all post-implantation steps required in the radiotracer technique are done in situ.\\\\ After successful application of this novel technique in diffusion studies of $^{11}$C ($t_{1/2}$ = 20.3 min), this experiment aims at performing self-diffusion studies of $^{31}$Si ($t_{1/2}$ = 2.6~h) in Si--Ge alloys and in amorphous Si--(B--)C--N ceramics.\\\\ Our motivation for measuring diffusion in Si--Ge alloys is their recent technological renaissance as well as the purpose to test the prediction that in these alloys the self-diffusion mechanism chang...

Adjoint-based optimization of mechanical performance in polycrystalline materials and structures through texture control

Energy Technology Data Exchange (ETDEWEB)

Gu, Grace [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brown, Judith Alice [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bishop, Joseph E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-08-01

The texture of a polycrystalline material refers to the preferred orientation of the grains within the material. In metallic materials, texture can significantly affect the mechanical properties such as elastic moduli, yield stress, strain hardening, and fracture toughness. Recent advances in additive manufacturing of metallic materials offer the possibility in the not too distant future of controlling the spatial variation of texture. In this work, we investigate the advantages, in terms of mechanical performance, of allowing the texture to vary spatially. We use an adjoint-based gradient optimization algorithm within a finite element solver (COMSOL) to optimize several engineering quantities of interest in a simple structure (hole in a plate) and loading (uniaxial tension) condition. As a first step to general texture optimization, we consider the idealized case of a pure fiber texture in which the homogenized properties are transversely isotropic. In this special case, the only spatially varying design variables are the three Euler angles that prescribe the orientation of the homogenized material at each point within the structure. This work paves a new way to design metallic materials for tunable mechanical properties at the microstructure level.

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...

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

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

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.

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.

Calculation of Debye-Scherrer diffraction patterns from highly stressed polycrystalline materials

Energy Technology Data Exchange (ETDEWEB)

MacDonald, M. J., E-mail: macdonm@umich.edu [Applied Physics Program, University of Michigan, Ann Arbor, Michigan 48109 (United States); SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Vorberger, J. [Helmholtz Zentrum Dresden-Rossendorf, 01328 Dresden (Germany); Gamboa, E. J.; Glenzer, S. H.; Fletcher, L. B. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Drake, R. P. [Climate and Space Sciences and Engineering, Applied Physics, and Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2016-06-07

Calculations of Debye-Scherrer diffraction patterns from polycrystalline materials have typically been done in the limit of small deviatoric stresses. Although these methods are well suited for experiments conducted near hydrostatic conditions, more robust models are required to diagnose the large strain anisotropies present in dynamic compression experiments. A method to predict Debye-Scherrer diffraction patterns for arbitrary strains has been presented in the Voigt (iso-strain) limit [Higginbotham, J. Appl. Phys. 115, 174906 (2014)]. Here, we present a method to calculate Debye-Scherrer diffraction patterns from highly stressed polycrystalline samples in the Reuss (iso-stress) limit. This analysis uses elastic constants to calculate lattice strains for all initial crystallite orientations, enabling elastic anisotropy and sample texture effects to be modeled directly. The effects of probing geometry, deviatoric stresses, and sample texture are demonstrated and compared to Voigt limit predictions. An example of shock-compressed polycrystalline diamond is presented to illustrate how this model can be applied and demonstrates the importance of including material strength when interpreting diffraction in dynamic compression experiments.

EPR of gamma-irradiated polycrystalline alanine-in-glass dosimeter

International Nuclear Information System (INIS)

Al-Karmi, Anan M.; Morsy, M.A.

2008-01-01

This study attempts to overcome some of the reported discrepancies in alanine-EPR reproducibility that may be related to alanine dosimeter preparation and/or EPR spectrometer settings. The dosimeters were prepared by packing pure polycrystalline L-α-alanine directly as supplied by the manufacturer in glass tubes. This dosimeter production scheme avoids any possible contribution to the EPR signal from a binding material. The dosimeters were irradiated with gamma ray to low-dose ranges typical for medical therapy (0-20 Gy). Special attention has been paid to the study of minimum detectable dose, measurement repeatability and reproducibility, and post-irradiation stability. The dosimeter exhibited a linear dose response in the dose range from 0.1 to 20 Gy. These positive properties favor the polycrystalline alanine-in-glass tube as a radiation dosimeter

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.

Development of a theoretical model for polycrystalline superconducting anisotropic using the effective medium approximation

International Nuclear Information System (INIS)

Cruz-García, A.; Muné, P; Govea-Alcaide, E.

2008-01-01

Full text: In this paper, is a study of the transport properties in anisotropic polycrystalline superconducting. The presence of certain order of orientation of grains in polycrystalline superconducting (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O 10+delta , is modeled by introducing a probability of orientation, gamma factor. In addition, is included in the model the concentration c, which characterize the contribution of porosity to the decrease in the conductivity of the Crystal, transparent. Assumes that pores and pimples are ellipsoid flattened with similar dimensions and takes into account the values of conductivity of beads in each direction. The calculation is based on the application of a generalization of the approximation of the effective way to the study of heterogeneous media, which is called coherent potential approximation (APC). The results are compared with an empirical model developed recently for samples of YBa 2 Cu 3 O 7 -delta (YBCO) which enriches its employment and applied to ceramic superconducting in general. (author)

Micromechanical modeling of stress-induced strain in polycrystalline Ni–Mn–Ga by directional solidification

International Nuclear Information System (INIS)

Zhu, Yuping; Shi, Tao; Teng, Yao

2015-01-01

Highlights: • A micromechanical model of directional solidification Ni–Mn–Ga is developed. • The stress–strain curves in different directions are tested. • The martensite Young’s moduli in different directions are predicted. • The macro reorientation strains in different directions are investigated. - Abstract: Polycrystalline ferromagnetic shape memory alloy Ni–Mn–Ga produced by directional solidification possess unique properties. Its compressive stress–strain behaviors in loading–unloading cycle show nonlinear and anisotropic. Based on the self-consistent theory and thermodynamics principle, a micromechanical constitutive model of polycrystalline Ni–Mn–Ga by directional solidification is developed considering the generating mechanism of the macroscopic strain and anisotropy. Then, the stress induced strains at different angles to solidification direction are calculated, and the results agree well with the experimental data. The predictive curves of martensite Young’s modulus and macro reorientation strain in different directions are investigated. It may provide theoretical guidance for the design and use of ferromagnetic shape memory alloy

PECVD Tekniği ile Büyütülmüş İnce Filmlerde Oluşan Ge ve SiGe Nanokristallerin Geçirgen Elektron Mikroskobu (TEM) ,Raman ve Fotoışıma Spektroskopisi Teknikleri ile İncelenmesi

OpenAIRE

Şahin, Bünyamin; Ağan, Sedat

2009-01-01

We report an experimental study, optical properties of Ge and SiGe nanocrystals in SiOx structures are investigated by using Transmission Electron Microscopy (TEM), Raman and Photlüminescence Spectroscopy techniques. Ge nanocrystals in silicon oxide thin films have been grown with different annealing time by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. The aim of our work is to determine size and size distiributions Ge, SiGe nanocrystals in SiOx martix due to annealing process...

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

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

Reliability of high mobility SiGe channel MOSFETs for future CMOS applications

CERN Document Server

Franco, Jacopo; Groeseneken, Guido

2014-01-01

Due to the ever increasing electric fields in scaled CMOS devices, reliability is becoming a showstopper for further scaled technology nodes. Although several groups have already demonstrated functional Si channel devices with aggressively scaled Equivalent Oxide Thickness (EOT) down to 5Å, a 10 year reliable device operation cannot be guaranteed anymore due to severe Negative Bias Temperature Instability. This book focuses on the reliability of the novel (Si)Ge channel quantum well pMOSFET technology. This technology is being considered for possible implementation in next CMOS technology nodes, thanks to its benefit in terms of carrier mobility and device threshold voltage tuning. We observe that it also opens a degree of freedom for device reliability optimization. By properly tuning the device gate stack, sufficiently reliable ultra-thin EOT devices with a 10 years lifetime at operating conditions are demonstrated. The extensive experimental datasets collected on a variety of processed 300mm wafers and pr...

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

Electromagnetic Component Research

Science.gov (United States)

2009-12-01

19 15: (a) 94 GHz Antenna Feeds Suspended Resistor (b) Thermopile Test Structure (c) Thermopile DC Voltage-Power Response...EMTs by implementing a fully coupled electro-mechanical formulation based upon the piezoe lectric constitutive equations for stress and electric... resistor , thermally isolated from the underlying substrate by micromachining. Energy received by the antenna is dissipated in the resistor causing the

Reconstruction of the domain orientation distribution function of polycrystalline PZT ceramics using vector piezoresponse force microscopy.

Science.gov (United States)

Kratzer, Markus; Lasnik, Michael; Röhrig, Sören; Teichert, Christian; Deluca, Marco

2018-01-11

Lead zirconate titanate (PZT) is one of the prominent materials used in polycrystalline piezoelectric devices. Since the ferroelectric domain orientation is the most important parameter affecting the electromechanical performance, analyzing the domain orientation distribution is of great importance for the development and understanding of improved piezoceramic devices. Here, vector piezoresponse force microscopy (vector-PFM) has been applied in order to reconstruct the ferroelectric domain orientation distribution function of polished sections of device-ready polycrystalline lead zirconate titanate (PZT) material. A measurement procedure and a computer program based on the software Mathematica have been developed to automatically evaluate the vector-PFM data for reconstructing the domain orientation function. The method is tested on differently in-plane and out-of-plane poled PZT samples, and the results reveal the expected domain patterns and allow determination of the polarization orientation distribution function at high accuracy.

Polycrystalline Si nanoparticles and their strong aging enhancement of blue photoluminescence

Science.gov (United States)

Yang, Shikuan; Cai, Weiping; Zeng, Haibo; Li, Zhigang

2008-07-01

Nearly spherical polycrystalline Si nanoparticles with 20 nm diameter were fabricated based on laser ablation of silicon wafer immersed in sodium dodecyl sulfate aqueous solution. Such Si nanoparticles consist of disordered areas and ultrafine grains of 3 nm in mean size and exhibit significant photoluminescence in blue region. Importantly, aging at ambient air leads to continuing enhancement of the emission (more than 130 times higher in 16 weeks) showing stable and strong blue emission. This aging enhancement is attributed to progressive passivation of nonradiative Pb centers corresponding to silicon dangling bonds on the particles' surface. This study could be helpful in pushing Si into optoelectronic field and Si-based full color display, biomedical tagging, and flash memories.

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....

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

Young’s Modulus of Polycrystalline Titania Microspheres Determined by In Situ Nanoindentation and Finite Element Modeling

Directory of Open Access Journals (Sweden)

Peida Hao

2014-01-01

Full Text Available In situ nanoindentation was employed to probe the mechanical properties of individual polycrystalline titania (TiO2 microspheres. The force-displacement curves captured by a hybrid scanning electron microscope/scanning probe microscope (SEM/SPM system were analyzed based on Hertz’s theory of contact mechanics. However, the deformation mechanisms of the nano/microspheres in the nanoindentation tests are not very clear. Finite element simulation was employed to investigate the deformation of spheres at the nanoscale under the pressure of an AFM tip. Then a revised method for the calculation of Young’s modulus of the microspheres was presented based on the deformation mechanisms of the spheres and Hertz’s theory. Meanwhile, a new force-displacement curve was reproduced by finite element simulation with the new calculation, and it was compared with the curve obtained by the nanoindentation experiment. The results of the comparison show that utilization of this revised model produces more accurate results. The calculated results showed that Young’s modulus of a polycrystalline TiO2 microsphere was approximately 30% larger than that of the bulk counterpart.

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

Tracking performance of a single-crystal and a polycrystalline diamond pixel-detector

Energy Technology Data Exchange (ETDEWEB)

Menasce, D.; et al.

2013-06-01

We present a comparative characterization of the performance of a single-crystal and a polycrystalline diamond pixel-detector employing the standard CMS pixel readout chips. Measurements were carried out at the Fermilab Test Beam Facility, FTBF, using protons of momentum 120 GeV/c tracked by a high-resolution pixel telescope. Particular attention was directed to the study of the charge-collection, the charge-sharing among adjacent pixels and the achievable position resolution. The performance of the single-crystal detector was excellent and comparable to the best available silicon pixel-detectors. The measured average detection-efficiency was near unity, ε = 0.99860±0.00006, and the position-resolution for shared hits was about 6 μm. On the other hand, the performance of the polycrystalline detector was hampered by its lower charge collection distance and the readout chip threshold. A new readout chip, capable of operating at much lower threshold (around 1 ke^$-$), would be required to fully exploit the potential performance of the polycrystalline diamond pixel-detector.

Influence of alloy disorder scattering on the hole mobility of SiGe nanowires

Energy Technology Data Exchange (ETDEWEB)

Martinez-Blanque, Celso; Ruiz, Francisco G., E-mail: franruiz@ugr.es; Godoy, Andres, E-mail: agodoy@ugr.es; Marin, Enrique G.; Donetti, Luca; Gámiz, Francisco [Dpto. de Electrónica y Tecnología de Computadores, Facultad de Ciencias, Universidad de Granada, Av. Fuentenueva S/N, 18071 Granada (Spain)

2014-12-28

In this work, we analyze the influence of the alloy disorder (AD) scattering on the low-field hole mobility of Si{sub 1-x}Ge{sub x} nanowires (NWs). To do it, the electrostatic description is achieved through a self-consistent solution of the Poisson equation and the six-band k⋅p method in the cross section of the NW. The momentum relaxation time approximation is used to calculate the hole mobility, including alloy disorder and phonon scattering mechanisms, and the use of approximations to calculate the overlap integrals for the scattering matrix elements is discussed. We study the influence of the alloy disorder scattering on the total mobility compared to the phonon contribution, for different values of the AD scattering parameter proposed in the literature, and analyze the performance of SiGe NWs as a function of the Ge molar fraction for both low and high inversion charge densities.

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.

Stress-strain relationship and XRD line broadening in [0001] textured hexagonal polycrystalline materials

International Nuclear Information System (INIS)

Yokoyama, Ryouichi

2011-01-01

Stress analysis with X-ray diffraction (XRD) for hexagonal polycrystalline materials in the Laue classes 6/mmm and 6/m has been studied on the basis of the crystal symmetry of the constituent crystallites which was proposed by R. Yokoyama and J. Harada ['Re-evaluation of formulae for X-ray stress analysis in polycrystalline specimens with fibre texture', Journal of Applied Crystallography, Vol.42, pp.185-191 (2009)]. The relationship between the stress and strain observable by XRD in a hexagonal polycrystalline material with [0001] fibre texture was formulated in terms of the elastic compliance defined for its single crystal. As a result, it was shown that the average strains obtained in the crystallites for both symmetries of 6/mmm and 6/m are different from each other under the triaxial or biaxial stress field. Then, it turned out that the line width of XRD changes depending on the measurement direction. (author)

CdCl2 passivation of polycrystalline CdMgTe and CdZnTe absorbers for tandem photovoltaic cells

Science.gov (United States)

Swanson, Drew E.; Reich, Carey; Abbas, Ali; Shimpi, Tushar; Liu, Hanxiao; Ponce, Fernando A.; Walls, John M.; Zhang, Yong-Hang; Metzger, Wyatt K.; Sampath, W. S.; Holman, Zachary C.

2018-05-01

As single-junction silicon solar cells approach their theoretical limits, tandems provide the primary path to higher efficiencies. CdTe alloys can be tuned with magnesium (CdMgTe) or zinc (CdZnTe) for ideal tandem pairing with silicon. A II-VI/Si tandem holds the greatest promise for inexpensive, high-efficiency top cells that can be quickly deployed in the market using existing polycrystalline CdTe manufacturing lines combined with mature silicon production lines. Currently, all high efficiency polycrystalline CdTe cells require a chloride-based passivation process to passivate grain boundaries and bulk defects. This research examines the rich chemistry and physics that has historically limited performance when extending Cl treatments to polycrystalline 1.7-eV CdMgTe and CdZnTe absorbers. A combination of transmittance, quantum efficiency, photoluminescence, transmission electron microscopy, and energy-dispersive X-ray spectroscopy clearly reveals that during passivation, Mg segregates and out-diffuses, initially at the grain boundaries but eventually throughout the bulk. CdZnTe exhibits similar Zn segregation behavior; however, the onset and progression is localized to the back of the device. After passivation, CdMgTe and CdZnTe can render a layer that is reduced to predominantly CdTe electro-optical behavior. Contact instabilities caused by inter-diffusion between the layers create additional complications. The results outline critical issues and paths for these materials to be successfully implemented in Si-based tandems and other applications.

Mn-implanted, polycrystalline indium tin oxide and indium oxide films

International Nuclear Information System (INIS)

Scarlat, Camelia; Vinnichenko, Mykola; Xu Qingyu; Buerger, Danilo; Zhou Shengqiang; Kolitsch, Andreas; Grenzer, Joerg; Helm, Manfred; Schmidt, Heidemarie

2009-01-01

Polycrystalline conducting, ca. 250 nm thick indium tin oxide (ITO) and indium oxide (IO) films grown on SiO 2 /Si substrates using reactive magnetron sputtering, have been implanted with 1 and 5 at.% of Mn, followed by annealing in nitrogen or in vacuum. The effect of the post-growth treatment on the structural, electrical, magnetic, and optical properties has been studied. The roughness of implanted films ranges between 3 and 15 nm and XRD measurements revealed a polycrystalline structure. A positive MR has been observed for Mn-implanted and post-annealed ITO and IO films. It has been interpreted by considering s-d exchange. Spectroscopic ellipsometry has been used to prove the existence of midgap electronic states in the Mn-implanted ITO and IO films reducing the transmittance below 80%.

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.

Device model for pixelless infrared image up-converters based on polycrystalline graphene heterostructures

Science.gov (United States)

Ryzhii, V.; Shur, M. S.; Ryzhii, M.; Karasik, V. E.; Otsuji, T.

2018-01-01

We developed a device model for pixelless converters of far/mid-infrared radiation (FIR/MIR) images into near-infrared/visible (NIR/VIR) images. These converters use polycrystalline graphene layers (PGLs) immersed in the van der Waals materials integrated with a light emitting diode (LED). The PGL serves as an element of the PGL infrared photodetector (PGLIP) sensitive to the incoming FIR/MIR due to the interband absorption. The spatially non-uniform photocurrent generated in the PGLIP repeats (mimics) the non-uniform distribution (image) created by the incident FIR/MIR. The injection of the nonuniform photocurrent into the LED active layer results in the nonuniform NIR/VIR image reproducing the FIR/MIR image. The PGL and the entire layer structure are not deliberately partitioned into pixels. We analyze the characteristics of such pixelless PGLIP-LED up-converters and show that their image contrast transfer function and the up-conversion efficiency depend on the PGL lateral resistivity. The up-converter exhibits high photoconductive gain and conversion efficiency when the lateral resistivity is sufficiently high. Several teams have successfully demonstrated the large area PGLs with the resistivities varying in a wide range. Such layers can be used in the pixelless PGLIP-LED image up-converters. The PGLIP-LED image up-converters can substantially surpass the image up-converters based on the quantum-well infrared photodetector integrated with the LED. These advantages are due to the use of the interband FIR/NIR absorption and a high photoconductive gain in the GLIPs.

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

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

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

Practice guidelines on the use of esophageal manometry - A GISMAD-SIGE-AIGO medical position statement.

Science.gov (United States)

Savarino, Edoardo; de Bortoli, Nicola; Bellini, Massimo; Galeazzi, Francesca; Ribolsi, Mentore; Salvador, Renato; Savarino, Vincenzo; Penagini, Roberto

2016-10-01

Patients with esophageal symptoms potentially associated to esophageal motor disorders such as dysphagia, chest pain, heartburn and regurgitation, represent one of the most frequent reasons for referral to gastroenterological evaluation. The utility of esophageal manometry in clinical practice is: (1) to accurately define esophageal motor function, (2) to identify abnormal motor function, and (3) to establish a treatment plan based on motor abnormalities. With this in mind, in the last decade, investigations and technical advances, with the introduction of high-resolution esophageal manometry, have enhanced our understanding and management of esophageal motility disorders. The following recommendations were developed to assist physicians in the appropriate use of esophageal manometry in modern patient care. They were discussed and approved after a comprehensive review of the medical literature pertaining to manometric techniques and their recent application. This position statement created under the auspices of the Gruppo Italiano di Studio per la Motilità dell'Apparato Digerente (GISMAD), Società Italiana di Gastroenterologia ed Endoscopia Digestiva (SIGE) and Associazione Italiana Gastroenterologi ed Endoscopisti Digestivi Ospedalieri (AIGO) is intended to help clinicians in applying manometric studies in the most fruitful manner within the context of their patients with esophageal symptoms. Copyright © 2016 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.

Influence of irradiation on mechanical properties of Si-Ge alloys

Energy Technology Data Exchange (ETDEWEB)

Sichinava, Avtandil; Bokuchava, Guram; Chubinidze, Giorgi; Archuadze, Giorgi [Ilia Vekua Sukhumi Institute of Physics and Technology, Tbilisi (Georgia); Gapishvili, Nodar [Ilia Vekua Sukhumi Institute of Physics and Technology, Tbilisi (Georgia); Georgian Technical University, Tbilisi (Georgia)

2017-07-15

Impact of various irradiation (Ar and He ions, high energy electrons) on microhardness and indentation of monocrystalline Si{sub 0,98}Ge{sub 0,02} alloy is studied. Samples of Si and SiGe alloy are obtained by Czochralski (CZ) method in the [111] direction in the atmosphere of high purity Ar. High energy electron irradiation with fluence of ∝10{sup 12} cm{sup -2} is conducted at the Clinac 2100iX. Ar and He ion implantation is performed on modernized ''VEZUVI-3M'' plant. It is shown that for all types of irradiation the microhardness and indentation modulus versus load are characterized by reverse indentation size effect (ISE). With the increase of fluences of Ar and He ions, the maximum value of the effect increases. At high values of loading force impact on the indenter the mechanical characteristics slowly decrease. Impact of isochronous thermal annealing on mechanical properties of high energy electron irradiated samples is studied. Non-monotonic changes of microhardness and indentation modulus are revealed in the temperature range of 200-260 C. It is proposed that such changes are caused by radiation defects transformation. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Computer studies of the scattering of low energy hydrogen ions from polycrystalline solids

International Nuclear Information System (INIS)

Oen, O.S.; Robinson, M.T.

1976-02-01

Reflection of 50 eV to 10 keV H atoms from polycrystalline Cu, Nb and Au targets has been calculated using the binary collision cascade program MARLOWE. The fractions of particles and energy reflected (backscattered) increase with increasing atomic number of the target and decrease with increasing incident energy. The results indicate that the effects of polycrystallinity are modest, reducing the amorphous reflection coefficients by about 25 percent. The calculations agree quite well with the experimental data for Cu and Au, but are about a factor of two larger than is observed for Nb

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

Degradation of Au–Ti contacts of SiGe HBTs during electromagnetic field stress

International Nuclear Information System (INIS)

Alaeddine, A; Genevois, C; Cuvilly, F; Daoud, K; Kadi, M

2011-01-01

This paper addresses electromagnetic field stress effects on SiGe heterojunction bipolar transistors (HBTs)' reliability issues, focusing on the relationship between the stress-induced current and device structure degradations. The origin of leakage currents and electrical parameter shifts in failed transistors has been studied by complementary failure analysis techniques. Characterization of the structure before and after ageing was performed by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). For the stressed samples, interface deformations of the titanium (Ti) thin film around all gold (Au) contacts have been clearly detected. These degradations include localized interface reaction between Au and Ti layers as well as their lateral atomic migration causing a significant reduction of Ti thickness. EDS analysis of the disordered region which is near the Si 3 N 4 interface has shown significant signals from Au. These observations could be attributed to the coupling between high current densities induced by stress and thermal effects due to local heating effects

Diffusion Mechanisms and Lattice Locations of Thermal-Equilibrium Defects in Si-Ge Alloys

CERN Multimedia

Lyutovich, K; Touboltsev, V; Laitinen, P O; Strohm, A

2002-01-01

It is generally accepted that Ge and Si differ considerably with respect to intrinsic-point-defect-mediated diffusion. In Ge, the native point defects dominating under thermal-equilibium conditions at all solid-state temperatures accessible in diffusion experiments are vacancies, and therefore Ge self-diffusion is vacancy-controlled. In Si, by contrast, self-interstitials and vacancies co-exist in thermal equilibrium. Whereas in the most thoroughly investigated temperature regime above about 1000$^\\circ$C Si self-diffusion is self-interstitial-controlled, it is vacancy-controlled at lower temperatures. According to the scenario displayed above, self-diffusion in Si-Ge alloys is expected to change from an interstitialcy mechanism on the Si side to a vacancy mechanism on the Ge side. Therefore, $^{71}$Ge self-diffusion experiments in Si$_{1- \\it y}$Ge$_{\\it y}$ as a function of composition Y are highly interesting. In a first series of experiments the diffusion of Ge in 0.4 to 10 $\\mu$m thick, relaxed, low-disl...

High temperature deformation of polycrystalline NiO and CoO

International Nuclear Information System (INIS)

Krishnamachari, V.; Notis, M.R.

1977-01-01

High temperature creep of polycrystalline NiO appears to be controlled by oxygen lattice diffusion at temperatures between 1273 and 1373 K and at stress levels from 34.5 to 79.8 MPa (5 to 11 ksi). Experimentally observed creep rates agree well with predictions obtained from deformation maps based on self-diffusion data. TEM examination indicates that dislocations present in crept NiO specimens are predominantly glide-type rather than climb-type dislocations as found in CoO. The difference in creep behavior of these materials is believed to be due to the difference in stacking fault energies and the nature of charge associated with lattice defects. 2 tables. 7 figs., 34 references

TU-FG-209-03: Exploring the Maximum Count Rate Capabilities of Photon Counting Arrays Based On Polycrystalline Silicon

Energy Technology Data Exchange (ETDEWEB)

Liang, A K; Koniczek, M; Antonuk, L E; El-Mohri, Y; Zhao, Q [University of Michigan, Ann Arbor, MI (United States)

2016-06-15

Purpose: Photon counting arrays (PCAs) offer several advantages over conventional, fluence-integrating x-ray imagers, such as improved contrast by means of energy windowing. For that reason, we are exploring the feasibility and performance of PCA pixel circuitry based on polycrystalline silicon. This material, unlike the crystalline silicon commonly used in photon counting detectors, lends itself toward the economic manufacture of radiation tolerant, monolithic large area (e.g., ∼43×43 cm2) devices. In this presentation, exploration of maximum count rate, a critical performance parameter for such devices, is reported. Methods: Count rate performance for a variety of pixel circuit designs was explored through detailed circuit simulations over a wide range of parameters (including pixel pitch and operating conditions) with the additional goal of preserving good energy resolution. The count rate simulations assume input events corresponding to a 72 kVp x-ray spectrum with 20 mm Al filtration interacting with a CZT detector at various input flux rates. Output count rates are determined at various photon energy threshold levels, and the percentage of counts lost (e.g., due to deadtime or pile-up) is calculated from the ratio of output to input counts. The energy resolution simulations involve thermal and flicker noise originating from each circuit element in a design. Results: Circuit designs compatible with pixel pitches ranging from 250 to 1000 µm that allow count rates over a megacount per second per pixel appear feasible. Such rates are expected to be suitable for radiographic and fluoroscopic imaging. Results for the analog front-end circuitry of the pixels show that acceptable energy resolution can also be achieved. Conclusion: PCAs created using polycrystalline silicon have the potential to offer monolithic large-area detectors with count rate performance comparable to those of crystalline silicon detectors. Further improvement through detailed circuit

Tailoring of in-plane magnetic anisotropy in polycrystalline cobalt thin films by external stress

Energy Technology Data Exchange (ETDEWEB)

Kumar, Dileep, E-mail: dkumar@csr.res.in [UGC-DAE Consortium for Scientic Research, Khandwa Road, Indore 452001 (India); Singh, Sadhana [UGC-DAE Consortium for Scientic Research, Khandwa Road, Indore 452001 (India); Vishawakarma, Pramod [School of Nanotechnology, RGPV, Bhopal 462036 (India); Dev, Arun Singh; Reddy, V.R. [UGC-DAE Consortium for Scientic Research, Khandwa Road, Indore 452001 (India); Gupta, Ajay [Amity Center for Spintronic Materials, Amity University, Sector 125, Noida 201303 (India)

2016-11-15

Polycrystalline Co films of nominal thickness ~180 Å were deposited on intentionally curved Si substrates. Tensile and compressive stresses of 100 MPa and 150 MPa were induced in the films by relieving the curvature. It has been found that, within the elastic limit, presence of stress leads to an in-plane magnetic anisotropy in the film and its strength increases with increasing stress. Easy axis of magnetization in the films is found to be parallel/ transverse to the compressive /tensile stresses respectively. The origin of magnetic anisotropy in the stressed films is understood in terms of magneto- elastic coupling, where the stress try to align the magnetic moments in order to minimize the magneto-elastic as well as anisotropy energy. Tensile stress is also found to be responsible for the surface smoothening of the films, which is attributed to the movement of the atoms associated with the applied stress. The present work provides a possible way to tailor the magnetic anisotropy and its direction in polycrystalline and amorphous films using external stress. - Highlights: • Tensile and compressive stresses were induced in Co films by removing the bending force from the substrates after film deposition. • Controlled external mechanical stress is found to be responsible for magnetic anisotropies in amorphous and polycrystalline thin films, where crystalline anisotropy is absent. • Tensile stress leads to surface smoothening of the polycrystalline Co films.

Reduction in the formation temperature of Poly-SiGe alloy thin film in Si/Ge system

Science.gov (United States)

Tah, Twisha; Singh, Ch. Kishan; Madapu, K. K.; Sarguna, R. M.; Magudapathy, P.; Ilango, S.

2018-04-01

The role of deposition temperature in the formation of poly-SiGe alloy thin film in Si/Ge system is reported. For the set ofsamples deposited without any intentional heating, initiation of alloying starts upon post annealingat ˜ 500 °C leading to the formation of a-SiGe. Subsequently, poly-SiGe alloy phase could formonly at temperature ≥ 800 °C. Whereas, for the set of samples deposited at 500 °C, in-situ formation of poly-SiGe alloy thin film could be observed. The energetics of the incoming evaporated atoms and theirsubsequent diffusionsin the presence of the supplied thermal energy is discussed to understand possible reasons for lowering of formation temperature/energyof the poly-SiGe phase.

Synthesis and characterization of silicon-doped polycrystalline GaN ...

Indian Academy of Sciences (India)

Silicon-doped polycrystalline GaN films were successfully deposited at temperatures ranging from 300 to 623 K on fused silica and silicon substrates by radio frequency (r.f.) magnetron sputtering at a system pressure of ~ 5 Pa. The films were characterized by optical as well as microstructural measurements. The optical ...

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

Influence of lattice distortion on phase transition properties of polycrystalline VO{sub 2} thin film

Energy Technology Data Exchange (ETDEWEB)

Lin, Tiegui [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Wang, Langping, E-mail: aplpwang@hit.edu.cn [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Wang, Xiaofeng; Zhang, Yufen [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Yu, Yonghao, E-mail: yhyu@hit.edu.cn [Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, Harbin 150001 (China)

2016-08-30

Highlights: • Polycrystalline VO{sub 2} thin films were fabricated by high power impulse magnetron sputtering. • The reported lowest phase transition temperature for undoped polycrystalline VO{sub 2} thin film was reduced to 32 °C by this research. • XRD patterns at varied temperatures revealed that the main structual change was a gradual shift in interplanar spacing with temperature. - Abstract: In this work, high power impulse magnetron sputtering was used to control the lattice distortion in polycrystalline VO{sub 2} thin film. SEM images revealed that all the VO{sub 2} thin films had crystallite sizes of below 20 nm, and similar configurations. UV–vis-near IR transmittance spectra measured at different temperatures showed that most of the as-deposited films had a typical metal–insulator transition. Four-point probe resistivity results showed that the transition temperature of the films varied from 54.5 to 32 °C. The X-ray diffraction (XRD) patterns of the as-deposited films revealed that most were polycrystalline monoclinic VO{sub 2}. The XRD results also confirmed that the lattice distortions in the as-deposited films were different, and the transition temperature decreased with the difference between the interplanar spacing of the as-deposited thin film and standard rutile VO{sub 2}. Furthermore, a room temperature rutile VO{sub 2} thin film was successfully synthesized when this difference was small enough. Additionally, XRD patterns measured at varied temperatures revealed that the phase transition process of the polycrystalline VO{sub 2} thin film was a coordinative deformation between grains with different orientations. The main structural change during the phase transition was a gradual shift in interplanar spacing with temperature.

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...

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 ...

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

Research on electrodischarge drilling of polycrystalline diamond with increased gap voltage

Science.gov (United States)

Skoczypiec, Sebastian; Bizoń, Wojciech; Żyra, Agnieszka

2018-05-01

This paper presents an experimental investigation of the machining characteristics of polycrystalline diamond (PCD). Machining of PCD by conventional technologies is not an effective solution. Due to presence of cobalt this material can be machined by application of electrical discharges. On the other side, electrical conductivity of PCD is on the limit of electrodischarge machining (EDM) possibilities. Proposed paper reports experimental investigation on electrodischarge drilling of PCD samples. The test were carried out with application on of high-voltage (up to 550 V) pulse power unit for two kinds of dielectrics: carbon based (Exxsol D80) and de-ionized water. As output parameters machining accuracy (side gap), material removal rate were selected. Also, based on SEM photographs and energy dispersive X-ray spectroscopy (EDS) analysis, a qualitative evaluation of the obtained results was presented.

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

The X-ray sensitivity of semi-insulating polycrystalline CdZnTe thick films

International Nuclear Information System (INIS)

Won, Jae Ho; Kim, Ki Hyun; Suh, Jong Hee; Cho, Shin Hang; Cho, Pyong Kon; Hong, Jin Ki; Kim, Sun Ung

2008-01-01

The X-ray sensitivity is one of the important parameters indicating the detector performance. The X-ray sensitivity of semi-insulating polycrystalline CdZnTe:Cl thick films was investigated as a function of electric field, mean photon energy, film thickness, and charge carrier transport parameters and, compared with another promising detector materials. The X-ray sensitivities of the polycrystalline CdZnTe films with 350 μm thickness were about 2.2 and 6.2 μC/cm 2 /R in the ohmic-type and Schottky-type detector at 0.83 V/μm, respectively

ANNEALING OF POLYCRYSTALLINE THIN FILM SILICON SOLAR CELLS IN WATER VAPOUR AT SUB-ATMOSPHERIC PRESSURES

Directory of Open Access Journals (Sweden)

Peter Pikna

2014-10-01

Full Text Available Thin film polycrystalline silicon (poly-Si solar cells were annealed in water vapour at pressures below atmospheric pressure. PN junction of the sample was contacted by measuring probes directly in the pressure chamber filled with steam during passivation. Suns-VOC method and a Lock-in detector were used to monitor an effect of water vapour to VOC of the solar cell during whole passivation process (in-situ. Tested temperature of the sample (55°C – 110°C was constant during the procedure. Open-circuit voltage of a solar cell at these temperatures is lower than at room temperature. Nevertheless, voltage response of the solar cell to the light flash used during Suns-VOC measurements was good observable. Temperature dependences for multicrystalline wafer-based and polycrystalline thin film solar cells were measured and compared. While no significant improvement of thin film poly-Si solar cell parameters by annealing in water vapour at under-atmospheric pressures was observed up to now, in-situ observation proved required sensitivity to changing VOC at elevated temperatures during the process.

SiGe-based re-engineering of electronic warfare subsystems

CERN Document Server

Lambrechts, Wynand

2017-01-01

This book equips readers with a thorough understanding of the applicability of new-generation silicon-germanium (SiGe) electronic subsystems for the military purposes of electronic warfare and defensive countermeasures. The theoretical and technical background is extensively explained and all aspects of the integration of SiGe as an enabling technology for maritime, land, and airborne (including space) electronic warfare are addressed, including research, design, development, and implementation. The coverage is supported by mathematical derivations, informative illustrations, practical examples, and case studies. While SiGe technology provides speed, performance, and price advantages in many markets, sharing of information on its use in electronic warfare systems has to date been limited, especially in developing nations. This book will therefore be warmly welcomed as an engineering guideline that focuses especially on the speed and reliability of current-generation SiGe circuits and highlights emerging innov...

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

Single-fabrication-step Ge nanosphere/SiO2/SiGe heterostructures: a key enabler for realizing Ge MOS devices

Science.gov (United States)

Liao, P. H.; Peng, K. P.; Lin, H. C.; George, T.; Li, P. W.

2018-05-01

We report channel and strain engineering of self-organized, gate-stacking heterostructures comprising Ge-nanosphere gate/SiO2/SiGe-channels. An exquisitely-controlled dynamic balance between the concentrations of oxygen, Si, and Ge interstitials was effectively exploited to simultaneously create these heterostructures in a single oxidation step. Process-controlled tunability of the channel length (5–95 nm diameters for the Ge-nanospheres), gate oxide thickness (2.5–4.8 nm), as well as crystal orientation, chemical composition and strain engineering of the SiGe-channel was achieved. Single-crystalline (100) Si1‑x Ge x shells with Ge content as high as x = 0.85 and with a compressive strain of 3%, as well as (110) Si1‑x Ge x shells with Ge content of x = 0.35 and corresponding compressive strain of 1.5% were achieved. For each crystal orientation, our high Ge-content, highly-stressed SiGe shells feature a high degree of crystallinity and thus, provide a core ‘building block’ required for the fabrication of Ge-based MOS devices.

Systematic study of polycrystalline flow during tension test of sheet 304 austenitic stainless steel at room temperature

International Nuclear Information System (INIS)

Muñoz-Andrade, Juan D.

2013-01-01

By systematic study the mapping of polycrystalline flow of sheet 304 austenitic stainless steel (ASS) during tension test at constant crosshead velocity at room temperature was obtained. The main results establish that the trajectory of crystals in the polycrystalline spatially extended system (PCSES), during irreversible deformation process obey a hyperbolic motion. Where, the ratio between the expansion velocity of the field and the velocity of the field source is not constant and the field lines of such trajectory of crystals become curved, this accelerated motion is called a hyperbolic motion. Such behavior is assisted by dislocations dynamics and self-accommodation process between crystals in the PCSES. Furthermore, by applying the quantum mechanics and relativistic model proposed by Muñoz-Andrade, the activation energy for polycrystalline flow during the tension test of 304 ASS was calculated for each instant in a global form. In conclusion was established that the mapping of the polycrystalline flow is fundamental to describe in an integral way the phenomenology and mechanics of irreversible deformation processes

Systematic study of polycrystalline flow during tension test of sheet 304 austenitic stainless steel at room temperature

Energy Technology Data Exchange (ETDEWEB)

Muñoz-Andrade, Juan D., E-mail: jdma@correo.azc.uam.mx [Departamento de Materiales, División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana Unidad Azcapotzalco, Av. San Pablo No. 180, Colonia Reynosa Tamaulipas, C.P. 02200, México Distrito Federal (Mexico)

2013-12-16

By systematic study the mapping of polycrystalline flow of sheet 304 austenitic stainless steel (ASS) during tension test at constant crosshead velocity at room temperature was obtained. The main results establish that the trajectory of crystals in the polycrystalline spatially extended system (PCSES), during irreversible deformation process obey a hyperbolic motion. Where, the ratio between the expansion velocity of the field and the velocity of the field source is not constant and the field lines of such trajectory of crystals become curved, this accelerated motion is called a hyperbolic motion. Such behavior is assisted by dislocations dynamics and self-accommodation process between crystals in the PCSES. Furthermore, by applying the quantum mechanics and relativistic model proposed by Muñoz-Andrade, the activation energy for polycrystalline flow during the tension test of 304 ASS was calculated for each instant in a global form. In conclusion was established that the mapping of the polycrystalline flow is fundamental to describe in an integral way the phenomenology and mechanics of irreversible deformation processes.

A batch process micromachined thermoelectric energy harvester: fabrication and characterization

International Nuclear Information System (INIS)

Su, J; Goedbloed, M; Van Andel, Y; De Nooijer, M C; Elfrink, R; Wang, Z; Vullers, R J M; Leonov, V

2010-01-01

Micromachined thermopiles are considered as a cost-effective solution for energy harvesters working at a small temperature difference and weak heat flows typical for, e.g., the human body. They can be used for powering autonomous wireless sensor nodes in a body area network. In this paper, a micromachined thermoelectric energy harvester with 6 µm high polycrystalline silicon germanium (poly-SiGe) thermocouples fabricated on a 6 inch wafer is presented. An open circuit voltage of 1.49 V and an output power of 0.4 µW can be generated with 3.5 K temperature difference in a model of a wearable micromachined energy harvester of the discussed design, which has a die size of 1.0 mm × 2.5 mm inside a watch-size generator

Resistivity and morphology of TiSi2 formed on Xe+-implanted polycrystalline silicon

International Nuclear Information System (INIS)

Kuwano, H.; Phillips, J.R.; Mayer, J.W.

1990-01-01

Xe ion irradiation of polycrystalline silicon before Ti deposition is found to affect subsequent silicide formation. Silicide films were prepared by implanting 60, 100, or 240 keV Xe + ions into 500-nm-thick undoped polycrystalline silicon before depositing Ti and annealing in vacuum. Preimplantation altered the subsequent silicide resistivity, x-ray diffraction patterns, and morphology as compared to films prepared on unimplanted polycrystalline Si substrates. We found that minimal TiSi 2 resistivities were achieved at lower temperatures with preimplantation, indicating that the Xe-implanted substrate promotes a lower temperature transition from the metastable C49 phase to the low-resistivity equilibrium C54 phase of TiSi 2 . X-ray diffraction results confirmed the lower temperature formation of the C54 phase with preimplantation. Low-temperature annealing (650 degree C, 30 min) of 6x10 16 cm -2 , 240 keV Xe + -implanted samples yielded low-resistivity (∼22 μΩ cm) silicide films, while simultaneously annealed samples without preimplantation had resistivity five times higher. Lower doses were effective at lower implant energies, with low resistivity achieved after 725 degree C, 30 min annealing for 2x10 15 cm -2 , 60 keV Xe + preimplantation

3-D growth of a short fatigue crack within a polycrystalline microstructure studied using combined diffraction and phase-contrast X-ray tomography

DEFF Research Database (Denmark)

Herbig, M.; King, Andrew; Reischig, Peter

2011-01-01

X-ray diffraction contrast tomography is a recently developed, non-destructive synchrotron imaging technique which characterizes microstructure and grain orientation in polycrystalline materials in three dimensions. By combining it with propagation-based phase-contrast tomography it is possible t...

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)

Structure and magnetoresistive properties of current-perpendicular-to-plane pseudo-spin valves using polycrystalline Co2Fe-based Heusler alloy films

International Nuclear Information System (INIS)

Nakatani, T.M.; Du, Ye; Takahashi, Y.K.; Furubayashi, T.; Hono, K.

2013-01-01

We report current-perpendicular-to-plane giant magnetoresistance (CPP–GMR) of pseudo-spin valves (PSVs) with polycrystalline Co 2 Fe(Al 0.5 Si 0.5 ) (CFAS) and Co 2 Fe(Ga 0.5 Ge 0.5 ) (CFGG) Heusler alloy films. Strongly [0 1 1] textured polycrystalline Heusler alloy films grew on the Ta/Ru/Ag underlayer. Relatively large CPP–GMR values of ΔRA up to 4 mΩ μm 2 and ΔR/R up to 10% were obtained with 5 nm thick Heusler alloy films and Ag spacer layer by annealing CFAS PSV at 450 °C and CFGG PSV at 350 °C. Transmission electron microscopy revealed a flat and sharp interface between the [0 1 1] textured CFAS layers and the [1 1 1] textured Ag spacer layer. Annealing above an optimal temperature for each PSV led to reductions in MR values as a result of the thickening of the spacer layer induced by the Ag diffusion from the outer Ag layers

The enhancement of the interdiffusion in Si/Ge amorphous artificial multilayers by additions of B and Au

International Nuclear Information System (INIS)

Park, B.; Spaepen, F.; Poate, J.M.; Jacobson, D.C.

1990-01-01

Amorphous Si/amorphous Ge artificial multilayers were prepared by ion beam sputtering. Boron or gold impurities were introduced into the Si/Ge multilayers by ion implantation or during the sputtering deposition. Diffusion coefficients were determined by measuring the decrease in the intensity of the first order X-ray diffraction peak resulting from the composition modulation. It was found that the interdiffusion of Si and Ge in their amorphous phase can be enhanced by doping. The enhancement factor is independent of the degree of structural relaxation, as observed by the decrease of diffusivity with annealing time, of the amorphous phase. A model is proposed that describes this behavior in terms of electronic effects, introduced by the dopants, on the pre-existing structural defects governing diffusion

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)

Photonic metasurface made of array of lens-like SiGe Mie resonators formed on (100) Si substrate via dewetting

Science.gov (United States)

Poborchii, Vladimir; Shklyaev, Alexander; Bolotov, Leonid; Uchida, Noriyuki; Tada, Tetsuya; Utegulov, Zhandos N.

2017-12-01

Metasurfaces consisting of arrays of high-index Mie resonators concentrating/redirecting light are important for integrated optics, photodetectors, and solar cells. Herein, we report the optical properties of low-Ge-content SiGe lens-like Mie resonator island arrays fabricated via dewetting during Ge deposition on a Si(100) surface at approximately 900 °C. We observe enhancement of the Si interaction with light owing to the efficient island-induced light concentration in the submicron-depth Si layer, which is mediated by both near-field Mie resonance leaking into the substrate and far-field light focusing. Such metasurfaces can improve the Si photodetector and solar-cell performance.

Weak antilocalization and low-temperature characterization of sputtered polycrystalline bismuth selenide

Science.gov (United States)

Sahu, Protyush; Chen, Jun-Yang; Myers, Jason C.; Wang, Jian-Ping

2018-03-01

We report a thorough crystal and transport characterization of sputtered polycrystalline BixSe1 -x (20 nm), grown on a thermally oxidized silicon substrate. The crystal and grain structures of the sample are characterized by transmission electron microscopy. Selected-area electron diffraction shows a highly polycrystalline structure. Transport measurements suggest semiconducting behavior of the BixSe1 -x film with a very high carrier concentration (˜1020 cm3) and low mobility [˜8 cm2/(V s)]. High-field magnetoresistance measurements reveal weak antilocalization, to which both the low mobility and the angular dependence suggest an impurity-dominated contribution. Fitting parameters are obtained from 2D magnetoconductivity using the Hikami-Larkin-Nagaoka equation. The variation of the phase coherence length with temperature suggests electron-electron scattering for phase decoherence. Electron-electron interaction theory is used to analyze the low-temperature conductivity.

Oxygen deficiency in MoO{sub 3} polycrystalline nanowires and nanotubes

Energy Technology Data Exchange (ETDEWEB)

Varlec, Ana, E-mail: ana.varlec@ijs.si [Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Arčon, Denis [Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Faculty of Mathematics and Physics, University of Ljubljana, Jadranska cesta 19, SI-1000 Ljubljana (Slovenia); Škapin, Srečo D. [Advanced Materials Department, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Remškar, Maja [Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia)

2016-02-15

We report on the synthesis of polycrystalline molybdenum oxide (MoO{sub 3}) nanowires via oxidation of molybdenum-sulfur-iodine (Mo{sub 6}S{sub 2}I{sub 8}) nanowires. This unique synthesis route results in an interesting morphology comprising porous nanowires and nanotubes. We found the nanowires to have the orthorhombic MoO{sub 3} structure. The structure is slightly oxygen deficient which results in the appearance of a new resonant Raman band (1004 cm{sup −1}) and paramagnetic defects (Mo{sup 5+}) of both the point and crystallographic shear plane nature. - Highlights: • Polycrystalline MoO{sub 3} nanowires were obtained via oxidation of Mo{sub 6}S{sub 2}I{sub 8} nanowires. • Nanowires are porous and tubular with either filled or empty interior. • Nanowires are slightly oxygen deficient which leads to a new Raman band.

Role of interfacial defect creation-annihilation processes at grain boundaries on the diffusional creep of polycrystalline alumina

International Nuclear Information System (INIS)

Ikuma, Y.; Gordon, R.S.

1981-01-01

It is generally assumed in the diffusional creep of a polycrystalline solid that grain boundaries act as perfect sources and sinks for lattice defects. However, if this assumption is not valid, then diffusional creep can become rate limited by interfacial defect reactions at grain boundaries. Steady state diffusional creep data will be presented at 1450 to 1500 0 C for polycrystalline alumina doped with Ti and a Mg-Ti co-dopant, which are consistent with interfacial controlled kinetics over an intermediate grain size range. A new type of creep deformation map will be presented which reveals the range of grain sizes and impurity concentrations over which interfacial defect creation and/or annihilation processes are important in the steady state creep of polycrystalline alumina

Thermal boundary resistance at Si/Ge interfaces by molecular dynamics simulation

Directory of Open Access Journals (Sweden)

Tianzhuo Zhan

2015-04-01

Full Text Available In this study, we investigated the temperature dependence and size effect of the thermal boundary resistance at Si/Ge interfaces by non-equilibrium molecular dynamics (MD simulations using the direct method with the Stillinger-Weber potential. The simulations were performed at four temperatures for two simulation cells of different sizes. The resulting thermal boundary resistance decreased with increasing temperature. The thermal boundary resistance was smaller for the large cell than for the small cell. Furthermore, the MD-predicted values were lower than the diffusion mismatch model (DMM-predicted values. The phonon density of states (DOS was calculated for all the cases to examine the underlying nature of the temperature dependence and size effect of thermal boundary resistance. We found that the phonon DOS was modified in the interface regions. The phonon DOS better matched between Si and Ge in the interface region than in the bulk region. Furthermore, in interface Si, the population of low-frequency phonons was found to increase with increasing temperature and cell size. We suggest that the increasing population of low-frequency phonons increased the phonon transmission coefficient at the interface, leading to the temperature dependence and size effect on thermal boundary resistance.

Thin SiGe virtual substrates for Ge heterostructures integration on silicon

International Nuclear Information System (INIS)

Cecchi, S.; Chrastina, D.; Frigerio, J.; Isella, G.; Gatti, E.; Guzzi, M.; Müller Gubler, E.; Paul, D. J.

2014-01-01

The possibility to reduce the thickness of the SiGe virtual substrate, required for the integration of Ge heterostructures on Si, without heavily affecting the crystal quality is becoming fundamental in several applications. In this work, we present 1 μm thick Si 1−x Ge x buffers (with x > 0.7) having different designs which could be suitable for applications requiring a thin virtual substrate. The rationale is to reduce the lattice mismatch at the interface with the Si substrate by introducing composition steps and/or partial grading. The relatively low growth temperature (475 °C) makes this approach appealing for complementary metal-oxide-semiconductor integration. For all the investigated designs, a reduction of the threading dislocation density compared to constant composition Si 1−x Ge x layers was observed. The best buffer in terms of defects reduction was used as a virtual substrate for the deposition of a Ge/SiGe multiple quantum well structure. Room temperature optical absorption and photoluminescence analysis performed on nominally identical quantum wells grown on both a thick graded virtual substrate and the selected thin buffer demonstrates a comparable optical quality, confirming the effectiveness of the proposed approach

Silicon germanium as a novel mask for silicon deep reactive ion etching

KAUST Repository

Serry, Mohamed Y.

2013-10-01

This paper reports on the use of p-type polycrystalline silicon germanium (poly-Si1-xGex) thin films as a new masking material for the cryogenic deep reactive ion etching (DRIE) of silicon. We investigated the etching behavior of various poly-Si1-xGex:B (0SiGe mask for silicon depends strongly on three factors: Ge content; boron concentration; and etching temperature. Compared to conventional SiO2 and SiN masks, the proposed SiGe masking material exhibited several advantages, including high etching selectivity to silicon (>1:800). Furthermore, the SiGe mask was etched in SF6/O2 plasma at temperatures ≥ - 80°C and at rates exceeding 8 μm/min (i.e., more than 37 times faster than SiO2 or SiN masks). Because of the chemical and thermodynamic stability of the SiGe film as well as the electronic properties of the mask, it was possible to deposit the proposed film at CMOS backend compatible temperatures. The paper also confirms that the mask can easily be dry-removed after the process with high etching-rate by controlling the ICP and RF power and the SF6 to O2 ratios, and without affecting the underlying silicon substrate. Using low ICP and RF power, elevated temperatures (i.e., > - 80°C), and an adjusted O2:SF6 ratio (i.e., ~6%), we were able to etch away the SiGe mask without adversely affecting the final profile. Ultimately, we were able to develop deep silicon- trenches with high aspect ratio etching straight profiles. © 1992-2012 IEEE.

Homogeneous SiGe crystal growth in microgravity by the travelling liquidus-zone method

International Nuclear Information System (INIS)

Kinoshita, K; Arai, Y; Inatomi, Y; Sakata, K; Takayanagi, M; Yoda, S; Miyata, H; Tanaka, R; Sone, T; Yoshikawa, J; Kihara, T; Shibayama, H; Kubota, Y; Shimaoka, T; Warashina, Y

2011-01-01

Homogeneous SiGe crystal growth experiments will be performed on board the ISS 'Kibo' using a gradient heating furnace (GHF). A new crystal growth method invented for growing homogeneous mixed crystals named 'travelling liquidus-zone (TLZ) method' is evaluated by the growth of Si 0.5 Ge 0.5 crystals in space. We have already succeeded in growing homogeneous 2mm diameter Si 0.5 Ge 0.5 crystals on the ground but large diameter homogeneous crystals are difficult to be grown due to convection in a melt. In microgravity, larger diameter crystals can be grown with suppressing convection. Radial concentration profiles as well as axial profiles in microgravity grown crystals will be measured and will be compared with our two-dimensional TLZ growth model equation and compositional variation is analyzed. Results are beneficial for growing large diameter mixed crystals by the TLZ method on the ground. Here, we report on the principle of the TLZ method for homogeneous crystal growth, results of preparatory experiments on the ground and plan for microgravity experiments.

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

Synthesis and optical properties of polycrystalline Li{sub 2}Al{sub 2}B{sub 2}O{sub 7} (LABO)

Energy Technology Data Exchange (ETDEWEB)

Dagdale, S. R., E-mail: shiva.dagdale68@gmail.com; Muley, G. G., E-mail: gajananggm@yahoo.co.in [Department of Physics Sant Gadge Baba Amravati University, Amravati, Maharashtra, India-444602 (India)

2016-05-06

A polycrystalline lithium aluminum borate (Li{sub 2}Al{sub 2}B{sub 2}O{sub 7}, LABO) has been synthesized by using simple solid-state technique. The obtained LABO polycrystalline was characterized by powder X-ray diffraction; Fourier transform infrared (FT-IR) spectroscopy and second harmonic generation (SHG) efficiency measurement. The functional groups were identified using the FT-IR spectroscopic data. The SHG efficiency of the polycrystalline material was obtained by the classic Kurtz powder technique using a fundamental wavelength 1064 nm of Nd:YAG laser and it is found to be 1.4 times that of potassium dihydrogen phosphate (KDP).

LAPAS: A SiGe Front End Prototype for the Upgraded ATLAS LAr

CERN Document Server

Rescia, S; Newcomer, F M; Dressnandt, N

2009-01-01

We have designed and fabricated a very low noise preamplifier and shaper with a (RC)2 – CR response to replace the existing ATLAS Liquid Argon readout for use at SLHC. IBM’s 8WL 130nm SiGe process was chosen for its radiation tolerance wide voltage range and potential for use in other LHC detector subsystems. The required dynamic range of 15 bits is accomplished by utilization of a single stage, low noise, wide dynamic range preamp connected to a dual range shaper. The low noise of the preamp (~.01nA / √Hz) is achieved by utilizing the process Silicon Germanium bipolar transistors. The relatively high voltage rating of the npn transistors is exploited to allow a gain of 650V/A. With this gain the equivalent input voltage noise requirement on the shaper to about 2.2nV/ √Hz. Each shaper stage is designed as a cascaded differential op amp doublet with a common mode operating point regulated by an internal feedback loop. The shaper outputs are designed to be compatible with the 130nm CMOS ADC being develo...

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

Visible and ultraviolet emission from pulse irradiated amorphous and polycrystalline H2O ice

International Nuclear Information System (INIS)

Freeman, C.G.; Quickenden, T.I.; Litjens, R.A.J.; Sangster, D.F.

1984-01-01

Luminescence peaking at 405 nm was observed when thin films of amorphous or polycrystalline ice at 97 K were irradiated with a pulsed beam of 0.53 MeV electrons. These emissions differed from the luminescence emitted by crystalline ice in that memory effects were not observed; the peak wavelengths were red shifted by approx.20 nm; and the half-lives were 6--9 ns instead of approx.400 ns. The emission spectra of polycrystalline ice samples produced by rapid deposition or by annealing amorphous ice were similar, but both had substantially lower intensities than amorphous ice spectra

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.

Synthesis of 1D, 2D, and 3D ZnO Polycrystalline Nanostructures Using the Sol-Gel Method

Directory of Open Access Journals (Sweden)

Yung-Kuan Tseng

2012-01-01

Full Text Available This study employed various polyol solvents to synthesize zinc oxide polycrystalline nanostructures in the form of fibers (1D, rhombic flakes (2D, and spheres (3D. The synthetic process primarily involved the use of zinc acetate dihydrate in polyol solutions, which were used to derive precursors of zinc alkoxides. Following hydrolysis at 160°C, the zinc alkoxide particles self-assembled into polycrystalline nanostructures with different morphologies. Following calcination at 500°C for 1 h, polycrystalline ZnO with good crystallinity was obtained. FE-SEM explored variations in surface morphology; XRD was used to analyze the crystalline structures and crystallinity of the products, which were confirmed as ZnO wurtzite structures. FE-TEM verified that the ZnO nanostructures were polycrystalline. Furthermore, we employed TGA/DSC to observe the phase transition. According to the results of property analyses, we proposed models of the relevant formation mechanisms. Finally, various ZnO structures were applied in the degradation of methylene blue to compare their photocatalytic efficiency.

Laser-beam-induced current mapping evaluation of porous silicon-based passivation in polycrystalline silicon solar cells

Energy Technology Data Exchange (ETDEWEB)

Rabha, M. Ben; Bessais, B. [Laboratoire de Nanomateriaux et des Systemes pour l' Energie, Centre de Recherches et des Technologies de l' Energie - Technopole de Borj-Cedria BP 95, 2050 Hammam-Lif (Tunisia); Dimassi, W.; Bouaicha, M.; Ezzaouia, H. [Laboratoire de photovoltaique, des semiconducteurs et des nanostructures, Centre de Recherches et des Technologies de l' Energie - Technopole de Borj-Cedria BP 95, 2050 Hammam-Lif (Tunisia)

2009-05-15

In the present work, we report on the effect of introducing a superficial porous silicon (PS) layer on the performance of polycrystalline silicon (pc-Si) solar cells. Laser-beam-induced current (LBIC) mapping shows that the PS treatment on the emitter of pc-Si solar cells improves their quantum response and reduce the grain boundaries (GBs) activity. After the porous silicon treatment, mapping investigation shows an enhancement of the LBIC and the internal quantum efficiency (IQE), due to an improvement of the minority carrier diffusion length and the passivation of recombination centers at the GBs as compared to the reference substrate. It was quantitatively shown that porous silicon treatment can passivate both the grains and GBs. (author)

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

Preparation and characterization of carbonate terminated polycrystalline Al2O3/Al films

International Nuclear Information System (INIS)

Tornow, C.; Noeske, P.-L.M.; Dieckhoff, S.; Wilken, R.; Gaertner, K.

2005-01-01

X-ray photoelectron spectroscopy (XPS) was applied to investigate the surface reactivity of polycrystalline Al films in contact with a gas mixture of carbon dioxide and oxygen at room temperature. Based on the characterization of interactions between these substrates and the individual gases at selected exposures, various surface functionalities were identified. Simultaneously dosing both carbon dioxide and oxygen is shown to create surface-terminating carbonate species, which contribute to inhibiting the formation of an Al 2 O 3 layer. Finally, a reaction scheme is suggested to account for the observed dependence of surface group formation on the dosing conditions

On elastic moduli and elastic anisotropy in polycrystalline martensitic NiTi

International Nuclear Information System (INIS)

Qiu, S.; Clausen, B.; Padula, S.A.; Noebe, R.D.; Vaidyanathan, R.

2011-01-01

A combined experimental and computational effort was undertaken to provide insight into the elastic response of B19' martensitic NiTi variants as they exist in bulk, polycrystalline aggregate form during monotonic tensile and compressive loading. The experimental effort centered on using in situ neutron diffraction during loading to measure elastic moduli in several directions along with an average Young's modulus and a Poisson's ratio. The measurements were compared with predictions from a 30,000 variant, self-consistent polycrystalline deformation model that accounted for the elastic intergranular constraint, and also with predictions of single crystal behavior from previously published ab initio studies. Variant conversion and detwinning processes that influenced the intergranular constraint occurred even at stresses where the macroscopic stress-strain response appeared linear. Direct evidence of these processes was revealed in changes in texture, which were captured in inverse pole figures constructed from the neutron diffraction measurements.

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.

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

Photoluminescence of epitactical and polycrystalline CuInS{sub 2} layers for thin-film solar cells; Photolumineszenz epitaktischer und polykristalliner CuInS{sub 2}-Schichten fuer Duennschichtsolarzellen

Energy Technology Data Exchange (ETDEWEB)

Eberhardt, J.

2007-12-18

The present thesis deals with one- and polycrystalline CuInS{sub 2} absorber layers for thin-film solar cells and especially with their optical and structural characterization. By means of detailed temperature- and power-dependent photoluminescence measurements in epitactical and polycrystalline absorber layers different radiative transitions could be analyzed and identified. The spectra were dominated by broad luminescence bands of deep perturbing levels. The implantation of hydrogen at low energies led to a passivation of these perturbing levels. On the base of the optical studies on epitactical and polycrystalline absorber layers a new improved defect model for CuInS{sub 2} could be developed. The model contains two donor and two acceptor levels with following ionization energies: D-1=46 meV, D-2=87 meV, A-1=70 meV, and A-2=119 meV.

High-Performance Silicon-Germanium-Based Thermoelectric Modules for Gas Exhaust Energy Scavenging

Science.gov (United States)

Romanjek, K.; Vesin, S.; Aixala, L.; Baffie, T.; Bernard-Granger, G.; Dufourcq, J.

2015-06-01

Some of the energy used in transportation and industry is lost as heat, often at high-temperatures, during conversion processes. Thermoelectricity enables direct conversion of heat into electricity, and is an alternative to the waste-heat-recovery technology currently used, for example turbines and other types of thermodynamic cycling. The performance of thermoelectric (TE) materials and modules has improved continuously in recent decades. In the high-temperature range ( T hot side > 500°C), silicon-germanium (SiGe) alloys are among the best TE materials reported in the literature. These materials are based on non-toxic elements. The Thermoelectrics Laboratory at CEA (Commissariat à l'Energie Atomique et aux Energies Alternatives) has synthesized n and p-type SiGe pellets, manufactured TE modules, and integrated these into thermoelectric generators (TEG) which were tested on a dedicated bench with hot air as the source of heat. SiGe TE samples of diameter 60 mm were created by spark-plasma sintering. For n-type SiGe doped with phosphorus the peak thermoelectric figure of merit reached ZT = 1.0 at 700°C whereas for p-type SiGe doped with boron the peak was ZT = 0.75 at 700°C. Thus, state-of-the-art conversion efficiency was obtained while also achieving higher production throughput capacity than for competing processes. A standard deviation high reproducibility. A silver-paste-based brazing technique was used to assemble the TE elements into modules. This assembly technique afforded low and repeatable electrical contact resistance (high temperatures (up to 600°C), and thirty 20 mm × 20 mm TE modules were produced and tested. The results revealed the performance was reproducible, with power output reaching 1.9 ± 0.2 W for a 370 degree temperature difference. When the temperature difference was increased to 500°C, electrical power output increased to >3.6 W. An air-water heat exchanger was developed and 30 TE modules were clamped and connected electrically

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.)

Front buried metallic contacts and thin porous silicon combination for efficient polycrystalline silicon solar cells

International Nuclear Information System (INIS)

Ben Rabha, M.; Boujmil, M.F.; Meddeb, N.; Saadoun, M.; Bessais, B.

2006-01-01

We investigate the impacts of achieving buried grid metallic contacts (BGMC), with and without application of a front porous silicon (PS) layer, on the photovoltaic properties of polycrystalline silicon (pc-Si) solar cells. A grooving method based on Chemical Vapor Etching (CVE) was used to perform buried grid contacts on the emitter of pc-Si solar cells. After realizing the n + /p junction using a phosphorus diffusion source, BGMCs were realized using the screen printing technique. We found that the buried metallic contacts improve the short circuit current from 16 mA/cm 2 (for reference cell without buried contacts) to about 19 mA/cm 2 . After application of a front PS layer on the n + emitter, we observe an enhancement of the short circuit current from 19 to 24 mA/cm 2 with a decrease of the reflectivity by about 40% of its initial value. The dark I-V characteristics of the pc-Si cells with PS-based emitter show an important reduction of the reverse current together with an improvement of the rectifying behaviour. Spectral response measurements performed at a wavelength range of 400-1100 nm showed a significant increase in the quantum efficiency, particularly at shorter wavelength (400-650 nm). These results indicate that the BGMCs improve the carrier collection and that the PS layer acts as an antireflective coating that reduces reflection losses and passivates the front surface. This low cost and simple technology based on the CVE technique could enable preparing efficient polycrystalline silicon solar cells

Compound polycrystalline solar cells. Recent progress and Y2K perspective

Energy Technology Data Exchange (ETDEWEB)

Birkmire, R.W. [Institute of Energy Conversion, University of Delaware, DE 19716 Newark (United States)

2001-01-01

A historical perspective on the development of polycrystalline thin-film solar cells based on CdTe and CuInSe{sub 2} is presented, and recent progress of these thin-film technologies is discussed. Impressive improvements in the efficiency of laboratory scale devices has not been easy to translate to the manufacturing environment, principally due to our lack of understanding of the basic science and engineering of these materials and devices. 'Next-generation' high-performance thin-film solar cells utilizing multijunction device configurations should achieve efficiencies of more than 25% within ten years. However, our cost-effective manufacturing of these more complex devices will be problematic unless the science and engineering issues associated with processing of thin-film PV devices are addressed.

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

Characterisation of electrodeposited polycrystalline uranium dioxide thin films on nickel foil for industrial applications

International Nuclear Information System (INIS)

Adamska, A.M.; Bright, E. Lawrence; Sutcliffe, J.; Liu, W.; Payton, O.D.; Picco, L.; Scott, T.B.

2015-01-01

Polycrystalline uranium dioxide thin films were grown on nickel substrates via aqueous electrodeposition of a precursor uranyl salt. The arising semiconducting uranium dioxide thin films exhibited a tower-like morphology, which may be suitable for future application in 3D solar cell applications. The thickness of the homogenous, tower-like films reached 350 nm. Longer deposition times led to the formation of thicker (up to 1.5 μm) and highly porous films. - Highlights: • Electrodeposition of polycrystalline UO_2 thin films • Tower-like morphology for 3D solar cell applications • Novel technique for separation of heavy elements from radioactive waste streams

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. 

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

Studies on the polycrystalline silicon/SiO2 stack as front surface field for IBC solar cells by two-dimensional simulations

International Nuclear Information System (INIS)

Jiang Shuai; Jia Rui; Tao Ke; Hou Caixia; Sun Hengchao; Li Yongtao; Yu Zhiyong

2017-01-01

Interdigitated back contact (IBC) solar cells can achieve a very high efficiency due to its less optical losses. But IBC solar cells demand for high quality passivation of the front surface. In this paper, a polycrystalline silicon/SiO 2 stack structure as front surface field to passivate the front surface of IBC solar cells is proposed. The passivation quality of this structure is investigated by two dimensional simulations. Polycrystalline silicon layer and SiO 2 layer are optimized to get the best passivation quality of the IBC solar cell. Simulation results indicate that the doping level of polycrystalline silicon should be high enough to allow a very thin polycrystalline silicon layer to ensure an effective passivation and small optical losses at the same time. The thickness of SiO 2 should be neither too thin nor too thick, and the optimal thickness is 1.2 nm. Furthermore, the lateral transport properties of electrons are investigated, and the simulation results indicate that a high doping level and conductivity of polycrystalline silicon can improve the lateral transportation of electrons and then the cell performance. (paper)

Aluminum-doped Zn O polycrystalline films prepared by co-sputtering of a Zn O-Al target

Energy Technology Data Exchange (ETDEWEB)

Becerril, M.; Silva L, H.; Guillen C, A.; Zelaya A, O. [Instituto Politecnico Nacional, Centro de Investigacion y de Estudios Avanzados, Departamento de Fisica, Apdo. Postal 14-740, 07000 Mexico D. F. (Mexico)

2014-07-01

Aluminum-doped Zinc oxide polycrystalline thin films (Azo) were grown on 7059 Corning glass substrates at room temperature by co-sputtering from a Zn O-Al target. The target was designed as follows, high purity elemental Aluminum was evaporated onto a Zn O target covering small areas. The structural, optical and electrical properties were analyzed as a function of Al content. The Al doped Zn O polycrystalline films showed an n-type conductivity. It was found that the electrical resistivity drops and the carrier concentration increases as a consequence of Al incorporation within the Zn O lattice. In both cases, the changes are of several orders of magnitude. From the results, we conclude that, using these Zn O-Al targets, n-type Al doped Zn O polycrystalline films with high transmittance and low resistivity can be obtained. The crystalline structure of the films was determined by X-ray diffraction. Atomic Force Microscopy images were obtained with an Auto probe C P (Veeco Metrology Group) Microscope. (Author)

On elastic moduli and elastic anisotropy in polycrystalline martensitic NiTi

Energy Technology Data Exchange (ETDEWEB)

Qiu, S. [Advanced Materials Processing and Analysis Center (AMPAC), Mechanical, Materials and Aerospace Engineering Department, University of Central Florida, Orlando, FL 32816 (United States); Clausen, B. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Padula, S.A.; Noebe, R.D. [NASA Glenn Research Center, Cleveland, OH 44135 (United States); Vaidyanathan, R., E-mail: raj@mail.ucf.edu [Advanced Materials Processing and Analysis Center (AMPAC), Mechanical, Materials and Aerospace Engineering Department, University of Central Florida, Orlando, FL 32816 (United States)

2011-08-15

A combined experimental and computational effort was undertaken to provide insight into the elastic response of B19' martensitic NiTi variants as they exist in bulk, polycrystalline aggregate form during monotonic tensile and compressive loading. The experimental effort centered on using in situ neutron diffraction during loading to measure elastic moduli in several directions along with an average Young's modulus and a Poisson's ratio. The measurements were compared with predictions from a 30,000 variant, self-consistent polycrystalline deformation model that accounted for the elastic intergranular constraint, and also with predictions of single crystal behavior from previously published ab initio studies. Variant conversion and detwinning processes that influenced the intergranular constraint occurred even at stresses where the macroscopic stress-strain response appeared linear. Direct evidence of these processes was revealed in changes in texture, which were captured in inverse pole figures constructed from the neutron diffraction measurements.

In vitro study of color stability of polycrystalline and monocrystalline ceramic brackets.

Science.gov (United States)

de Oliveira, Cibele Braga; Maia, Luiz Guilherme Martins; Santos-Pinto, Ary; Gandini Junior, Luiz Gonzaga

2014-01-01

The aim of this in vitro study was to analyze color stability of monocrystalline and polycrystalline ceramic brackets after immersion in dye solutions. 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 spectrophotometer. Data were assessed by Multivariate Profile Analysis, Analysis of Variance (ANOVA) and Multiple Comparison Tests of means. There was a perceptible change of color in all ceramic brackets immersed in coffee (ΔE* Allure = 7.61, Inspire Ice = 6.09, Radiance = 6.69, Transcend = 7.44), black tea (ΔE* Allure = 6.24, Inspire Ice = 5.21, Radiance = 6.51, Transcend = 6.14) and red wine (ΔE* Allure = 6.49, Inspire Ice = 4.76, Radiance = 5.19, Transcend = 5.64), but no change was noticed in Coke and artificial saliva (ΔE brackets undergo color change when exposed to solutions of coffee, black tea and red wine. However, the same crystalline structure, either monocrystalline or polycrystalline, do not follow the same or a similar pattern in color change, varying according to the bracket fabrication, which shows a lack of standardization in the manufacturing process. Coffee dye produced the most marked color changes after 21 days of immersion for most ceramic brackets evaluated.

Elasticity and hardness of nano-polycrystalline boron nitrides: The apparent Hall-Petch effect

International Nuclear Information System (INIS)

Nagakubo, A.; Ogi, H.; Hirao, M.; Sumiya, H.

2014-01-01

Nano-polycrystalline boron nitride (BN) is expected to replace diamond as a superhard and superstiff material. Although its hardening was reported, its elasticity remains unclear and the as-measured hardness could be significantly different from the true value due to the elastic recovery. In this study, we measured the longitudinal-wave elastic constant of nano-polycrystalline BNs using picosecond ultrasound spectroscopy and confirmed the elastic softening for small-grain BNs. We also measured Vickers and Knoop hardness for the same specimens and clarified the relationship between hardness and stiffness. The Vickers hardness significantly increased as the grain size decreased, while the Knoop hardness remained nearly unchanged. We attribute the apparent increase in Vickers hardness to the elastic recovery and propose a model to support this insight.

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.

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

Recent developments using TowerJazz SiGe BiCMOS platform for mmWave and THz applications

Science.gov (United States)

Kar-Roy, Arjun; Howard, David; Preisler, Edward J.; Racanelli, Marco

2013-05-01

In this paper, we report on the highest speed 240GHz/340GHz FT/FMAX NPN which is now available for product designs in the SBC18H4 process variant of TowerJazz's mature 0.18μm SBC18 silicon germanium (SiGe) BiCMOS technology platform. NFMIN of ~2dB at 50GHz has been obtained with these NPNs. We also describe the integration of earlier generation NPNs with FT/FMAX of 240GHz/280GHz into SBC13H3, a 0.13μm SiGe BiCMOS technology platform. Next, we detail the integration of the deep silicon via (DSV), through silicon via (TSV), high-resistivity substrate, sub-field stitching and hybrid-stitching capability into the 0.18μm SBC18 technology platform to enable higher performance and highly integrated product designs. The integration of SBC18H3 into a thick-film SOI substrate, with essentially unchanged FT and FMAX, is also described. We also report on recent circuit demonstrations using the SBC18H3 platform: (1) a 4-element phased-array 70-100GHz broadband transmit and receive chip with flat saturated power greater than 5dBm and conversion gain of 33dB; (2) a fully integrated W-band 9-element phase-controllable array with responsivity of 800MV/W and receiver NETD is 0.45K with 20ms integration time; (3) a 16-element 4x4 phased-array transmitter with scanning in both the E- and H-planes with maximum EIRP of 23-25 dBm at 100-110GHz; (4) a power efficient 200GHz VCO with -7.25dBm output power and tuning range of 3.5%; and (5) a 320GHz 16-element imaging receiver array with responsivity of 18KV/W at 315GHz, a 3dB bandwidth of 25GHz and a low NEP of 34pW/Hz1/2. Wafer-scale large-die implementation of the phased-arrays and mmWave imagers using stitching in TowerJazz SBC18 process are also discussed.

Simulation of inter- and transgranular crack propagation in polycrystalline aggregates due to stress corrosion cracking

International Nuclear Information System (INIS)

Musienko, Andrey; Cailletaud, Georges

2009-01-01

The motivation of the study is the development of a coupled approach able to account for the interaction between environment and plasticity in a polycrystalline material. The paper recalls first the constitutive equations used to describe the behavior of the grain core and of the grain boundary (GB). The procedure that is applied to generate synthetic polycrystalline aggregates with an explicit representation of the grain boundary area by 2D or 3D finite elements is then described. The approach is applied to the modeling of iodine-assisted stress corrosion cracking (IASCC) in Zircaloy tubes used in nuclear power plants.

Advanced single-wafer sequential multiprocessing techniques for semiconductor device fabrication

International Nuclear Information System (INIS)

Moslehi, M.M.; Davis, C.

1989-01-01

Single-wafer integrated in-situ multiprocessing (SWIM) is recognized as the future trend for advanced microelectronics production in flexible fast turn- around computer-integrated semiconductor manufacturing environments. The SWIM equipment technology and processing methodology offer enhanced equipment utilization, improved process reproducibility and yield, and reduced chip manufacturing cost. They also provide significant capabilities for fabrication of new and improved device structures. This paper describes the SWIM techniques and presents a novel single-wafer advanced vacuum multiprocessing technology developed based on the use of multiple process energy/activation sources (lamp heating and remote microwave plasma) for multilayer epitaxial and polycrystalline semiconductor as well as dielectric film processing. Based on this technology, multilayer in-situ-doped homoepitaxial silicon and heteroepitaxial strained layer Si/Ge x Si 1 - x /Si structures have been grown and characterized. The process control and the ultimate interfacial abruptness of the layer-to-layer transition widths in the device structures prepared by this technology will challenge the MBE techniques in multilayer epitaxial growth applications

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)

Zeeman perturbed nuclear quadrupole spin echo envelope modulations for spin 3/2 nuclei in polycrystalline specimens

Science.gov (United States)

Ramachandran, R.; Narasimhan, P. T.

The results of theoretical and experimental studies of Zeeman-perturbed nuclear quadrupole spin echo envelope modulations (ZSEEM) for spin 3/2 nuclei in polycrystalline specimens are presented. The response of the Zeeman-perturbed spin ensemble to resonant two pulse excitations has been calculated using the density matrix formalism. The theoretical calculation assumes a parallel orientation of the external r.f. and static Zeeman fields and an arbitrary orientation of these fields to the principal axes system of the electric field gradient. A numerical powder averaging procedure has been adopted to simulate the response of the polycrystalline specimens. Using a coherent pulsed nuclear quadrupole resonance spectrometer the ZSEEM patterns of the 35Cl nuclei have been recorded in polycrystalline specimens of potassium chlorate, barium chlorate, mercuric chloride (two sites) and antimony trichloride (two sites) using the π/2-τ-π/2 sequence. The theoretical and experimental ZSEEM patterns have been compared. In the case of mercuric chloride, the experimental 35Cl ZSEEM patterns are found to be nearly identical for the two sites and correspond to a near-zero value of the asymmetry parameter, η, of the electric field gradient tensor. The difference in the η values for the two 35Cl sites (η ˜0·06 and η˜0·16) in antimony trichloride is clearly reflected in the experimental and theoretical ZSEEM patterns. The present study indicates the feasibility of evaluating η for spin 3/2 nuclei in polycrystalline specimens from ZSEEM investigations.

Strain Amount Dependent Grain Size and Orientation Developments during Hot Compression of a Polycrystalline Nickel Based Superalloy

Directory of Open Access Journals (Sweden)

Guoai He

2017-02-01

Full Text Available Controlling grain size in polycrystalline nickel base superalloy is vital for obtaining required mechanical properties. Typically, a uniform and fine grain size is required throughout forging process to realize the superplastic deformation. Strain amount occupied a dominant position in manipulating the dynamic recrystallization (DRX process and regulating the grain size of the alloy during hot forging. In this article, the high-throughput double cone specimen was introduced to yield wide-range strain in a single sample. Continuous variations of effective strain ranging from 0.23 to 1.65 across the whole sample were achieved after reaching a height reduction of 70%. Grain size is measured to be decreased from the edge to the center of specimen with increase of effective strain. Small misorientation tended to generate near the grain boundaries, which was manifested as piled-up dislocation in micromechanics. After the dislocation density reached a critical value, DRX progress would be initiated at higher deformation region, leading to the refinement of grain size. During this process, the transformations from low angle grain boundaries (LAGBs to high angle grain boundaries (HAGBs and from subgrains to DRX grains are found to occur. After the accomplishment of DRX progress, the neonatal grains are presented as having similar orientation inside the grain boundary.

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

Accelerated diffusion controlled creep of polycrystalline materials. Communication 1. Model of diffusion controlled creep acceleration

International Nuclear Information System (INIS)

Smirnova, E.S.; Chuvil'deev, V.N.

1998-01-01

The model is suggested which describes the influence of large-angle grain boundary migration on a diffusion controlled creep rate in polycrystalline materials (Coble creep). The model is based on the concept about changing the value of migrating boundary free volume when introducing dislocations distributed over the grain bulk into this boundary. Expressions are obtained to calculate the grain boundary diffusion coefficient under conditions of boundary migration and the parameter, which characterized the value of Coble creep acceleration. A comparison is made between calculated and experimental data for Cd, Co and Fe

Direct imaging of dopant distribution in polycrystalline ZnO films

Czech Academy of Sciences Publication Activity Database

Lorenzo, F.; Aebersold, A.B.; Morales-Masis, M.; Ledinský, Martin; Escrig, S.; Vetushka, Aliaksi; Alexander, D.T.L.; Hessler-Wyser, A.; Fejfar, Antonín; Hébert, C.; Nicolay, S.; Ballif, C.

2017-01-01

Roč. 9, č. 8 (2017), s. 7241-7248 ISSN 1944-8244 R&D Projects: GA ČR GC16-10429J Institutional support: RVO:68378271 Keywords : dopant distribution * film polarity * grain boundaries * NanoSIMS * polycrystalline film * zinc oxide Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 7.504, year: 2016

Investigation of high mobility pseudomorphic SiGe p-channels in Si MOSFETS at low and high electric fields

International Nuclear Information System (INIS)

Palmer, Martin John

2001-01-01

Silicon Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) for high speed, high current applications are rapidly approaching the physical and financial limits of the technology. This opens opportunities for the incorporation of materials with intrinsically better transport characteristics. An alloy of silicon and germanium is one such material that is gaining much recognition as the active component of MOSFETs and as the secondary structures (such as the gate electrode). This work examines a batch of buried channel Si 0.64 Ge 0.36 p-MOSFETs, with a minimum effective length of 0.35 μm, under different bias conditions and at different temperatures. High current and transconductance enhancements are apparent at long gate lengths. The carrier mobility is up to a factor of 2.5 times that of silicon at room temperature and 7.5 times at 4 K. A clear trend of decreasing peak mobility with decreasing silicon cap thickness is evident. Simulations show that scattering caused by the roughness of the SiO 2 /Si interface dominates, rather than alloy scattering or Si/SiGe roughness, even for a buried channel. This scattering increases with the proximity of the carriers to the interface. An increase of interface trap density with decreasing cap thickness, demonstrates that segregated germanium exists some distance into the cap and interferes with the oxidation process. This will increase scattering through increased SiO 2 /Si roughness and increased trapped charge. The short channel, high field results are comparable or slightly worse than those of silicon due to lower saturation drift velocity. However, fitting to a drift-diffusion model shows an apparent increase in saturation velocity for short channels, especially at low temperatures. This effect correlates with the low field mobility and is greater for devices containing SiGe. This is an indication of velocity overshoot, which may enhance the performance of SiGe MOSFETs at deep submicron gate lengths. (author)

Vapor transport deposition of large-area polycrystalline CdTe for radiation image sensor application

Energy Technology Data Exchange (ETDEWEB)

Yang, Keedong; Cha, Bokyung; Heo, Duchang; Jeon, Sungchae [Korea Electrotechnology Research Institute, 111 Hanggaul-ro, Ansan-si, Gyeonggi-do 426-170 (Korea, Republic of)

2014-07-15

Vapor transport deposition (VTD) process delivers saturated vapor to substrate, resulting in high-throughput and scalable process. In addition, VTD can maintain lower substrate temperature than close-spaced sublimation (CSS). The motivation of this work is to adopt several advantages of VTD for radiation image sensor application. Polycrystalline CdTe films were obtained on 300 mm x 300 mm indium tin oxide (ITO) coated glass. The polycrystalline CdTe film has columnar structure with average grain size of 3 μm ∝ 9 μm, which can be controlled by changing the substrate temperature. In order to analyze electrical and X-ray characteristics, ITO-CdTe-Al sandwich structured device was fabricated. Effective resistivity of the polycrystalline CdTe film was ∝1.4 x 10{sup 9}Ωcm. The device was operated under hole-collection mode. The responsivity and the μτ product estimated to be 6.8 μC/cm{sup 2}R and 5.5 x 10{sup -7} cm{sup 2}/V. The VTD can be a process of choice for monolithic integration of CdTe thick film for radiation image sensor and CMOS/TFT circuitry. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

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.

The effect of crystal symmetry on the maximum polarization of polycrystalline ferroelectric materials

International Nuclear Information System (INIS)

Jones, Jacob L.

2010-01-01

In polycrystalline ceramics, the degree of domain orientation in all possible crystal orientations contributes to the total realizable polarization. The extent to which domains are oriented towards an applied field can be described by a polarization distribution function. Such representations are calculated and presented in the present work for several different crystal systems including monoclinic symmetries that exhibit a polarization rotation mechanism. The relationship between the polarization distribution functions and the attainable macroscopic polarization is also developed for polycrystalline ceramics that are initially randomly oriented. In these cases, polarization rotation allows a significant degree of preferred orientation parallel to the electric field (>1000 multiples of a random distribution). However, the fraction of single crystal polarization that can be achieved (97.5%) is only marginally better than those of higher crystal symmetry.

Modeling elasto-plastic behavior of polycrystalline grain structure of steels at mesoscopic level

International Nuclear Information System (INIS)

Kovac, Marko; Cizelj, Leon

2005-01-01

The multiscale model is proposed to explicitly account for the inhomogeneous structure of polycrystalline materials. Grains and grain boundaries are modeled explicitly using Voronoi tessellation. The constitutive model of crystal grains utilizes anisotropic elasticity and crystal plasticity. Commercially available finite element code is applied to solve the boundary value problem defined at the macroscopic scale. No assumption regarding the distribution of the mesoscopic strain and stress fields is used, apart the finite element discretization. The proposed model is then used to estimate the minimum size of polycrystalline aggregate of selected reactor pressure vessel steel (22 NiMoCr 3 7), above which it can be considered macroscopically homogeneous. Elastic and rate-independent plastic deformation modes are considered. The results are validated by the experimental and simulation results from the literature

Optical and electrical properties of polycrystalline and amorphous Al-Ti thin films

DEFF Research Database (Denmark)

Canulescu, Stela; Borca, C. N.; Rechendorff, Kristian

2016-01-01

The structural, optical, and transport properties of sputter-deposited Al-Ti thin films have been investigated as a function of Ti alloying with a concentration ranging from 2% to 46%. The optical reflectivity of Al-Ti films at visible and near-infrared wavelengths decreases with increasing Ti...... content. Xray absorption fine structure measurements reveal that the atomic ordering around Ti atoms increases with increasing Ti content up to 20% and then decreases as a result of a transition from a polycrystalline to amorphous structure. The transport properties of the Al-Ti films are influenced...... by electron scattering at the grain boundaries in the case of polycrystalline films and static defects, such as antisite effects and vacancies in the case of the amorphous alloys. The combination of Ti having a real refractive index (n) comparable with the extinction coefficient (k) and Al with n much smaller...

Natural occurrence of pure nano-polycrystalline diamond from impact crater

Science.gov (United States)

Ohfuji, Hiroaki; Irifune, Tetsuo; Litasov, Konstantin D.; Yamashita, Tomoharu; Isobe, Futoshi; Afanasiev, Valentin P.; Pokhilenko, Nikolai P.

2015-10-01

Consolidated bodies of polycrystalline diamond with grain sizes less than 100 nm, nano-polycrystalline diamond (NPD), has been experimentally produced by direct conversion of graphite at high pressure and high temperature. NPD has superior hardness, toughness and wear resistance to single-crystalline diamonds because of its peculiar nano-textures, and has been successfully used for industrial and scientific applications. Such sintered nanodiamonds have, however, not been found in natural mantle diamonds. Here we identified natural pure NPD, which was produced by a large meteoritic impact about 35 Ma ago in Russia. The impact diamonds consist of well-sintered equigranular nanocrystals (5-50 nm), similar to synthetic NPD, but with distinct [111] preferred orientation. They formed through the martensitic transformation from single-crystal graphite. Stress-induced local fragmentation of the source graphite and subsequent rapid transformation to diamond in the limited time scale result in multiple diamond nucleation and suppression of the overall grain growth, producing the unique nanocrystalline texture of natural NPD. A huge amount of natural NPD is expected to be present in the Popigai crater, which is potentially important for applications as novel ultra-hard material.

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....

On the evolution of surface roughness during deformation of polycrystalline aluminum alloys

NARCIS (Netherlands)

Vellinga, WP; van Tijum, Redmer; de Hosson, JTM

Surface roughening of polycrystalline Al-Mg alloys during tensile deformation is investigated using white light confocal microscopy. Materials are tested that differ only in grain size. A height-height correlation technique is used to analyze the data. The surface obeys self-affine scaling on length

A macroscopic constitutive model of temperature-induced phase transition of polycrystalline Ni2MnGa by directional solidification

International Nuclear Information System (INIS)

Zhu, Yuping; Gu, Yunling; Liu, Hongguang

2015-01-01

Directional solidification technology has been widely used to improve the properties of polycrystalline Ni 2 MnGa materials. Mechanical training can adjust the internal organizational structures of the materials, reduce the stress of twin boundaries motion, and then result in larger strain at lower outfield levels. In this paper, we test the microscopic structure of Ni 2 MnGa polycrystalline ferromagnetic shape memory alloy produced by directional solidification and compress it along two axes successively for mechanical training. The influences of pre-compressive stresses on the temperature-induced strains are analyzed. The macroscopic mechanical behaviors show anisotropy. According to the generating mechanism of the macroscopic strain, a three-dimensional constitutive model is established. Based on thermodynamic method, the kinetic equations of the martensitic transformation and inverse transformation are presented considering the driving force and energy dissipation. The prediction curves of temperature-induce strains along two different directions are investigated. And the results coincide well with the experiment data. It well explains the macroscopic anisotropy mechanical behaviors and fits for using in engineering

Thermally stimulated currents in α-HgI2 polycrystalline films

International Nuclear Information System (INIS)

Shiu, Y.-T.; Huang, T.-J.; Shih, C.-T.; Su, C.-F.; Lan, S.-M.; Chiu, K.-C.

2007-01-01

A study of thermally stimulated currents (TSC) is applied to α-HgI 2 polycrystalline films grown by physical vapour deposition with various thermal boundary conditions. Five TSC peaks are clearly observed and numerically fitted. The activation energy and the density of the trapping centre that corresponds to each TSC peak are then calculated. Finally, the effects of the deposition conditions on the TSC results are discussed

Magnetic field induced enhancement of resistance in polycrystalline ZrTe5

Science.gov (United States)

Behera, Prakash; Bera, Sumit; Patidar, Manju Mishra; Singh, Durgesh; Mishra, A. K.; Krishnan, M.; Gangrade, M.; Deshpande, U. P.; Venkatesh, R.; Ganesan, V.

2018-04-01

Transport properties of the polycrystalline ZrTe5 showing a considerable positive Magneto-Resistance (MR) in the intermediate temperatures has been reported. Substantial shift of peak temperature by approximately 65 K with an applied magnetic field of 13.5 Tesla has been observed. Magneto resistance of this polycrystalline sample (˜100%) is comparable with its single crystalline counterpart reported in literature. The peak intensity scales with peak temperature and obeys reasonably the Dionne relationship that is a clear indication of polaron mediated conduction in this system. Magneto Resistance (MR) in this system is attributed to the two carrier polaronic conduction model similar to the Holstein's approach. The results are further complemented with the Peak shift in magnetic field expected for a system having a fraction of localized carrier density. This observation places this famous thermoelectric material that displays a topological Dirac to Weyl transition in magnetic field in to the family of materials that have potential technological applications in the liquid nitrogen temperature range viz. 85-150 K.

A model-reduction approach to the micromechanical analysis of polycrystalline materials

Science.gov (United States)

Michel, Jean-Claude; Suquet, Pierre

2016-03-01

The present study is devoted to the extension to polycrystals of a model-reduction technique introduced by the authors, called the nonuniform transformation field analysis (NTFA). This new reduced model is obtained in two steps. First the local fields of internal variables are decomposed on a reduced basis of modes as in the NTFA. Second the dissipation potential of the phases is replaced by its tangent second-order (TSO) expansion. The reduced evolution equations of the model can be entirely expressed in terms of quantities which can be pre-computed once for all. Roughly speaking, these pre-computed quantities depend only on the average and fluctuations per phase of the modes and of the associated stress fields. The accuracy of the new NTFA-TSO model is assessed by comparison with full-field simulations on two specific applications, creep of polycrystalline ice and response of polycrystalline copper to a cyclic tension-compression test. The new reduced evolution equations is faster than the full-field computations by two orders of magnitude in the two examples.

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.

Misoriented dislocation substructures and the fracture of polycrystalline Cu-Al alloys

Science.gov (United States)

Koneva, N. A.; Trishkina, L. I.; Cherkasova, T. V.; Kozlov, E. V.

2016-10-01

The evolution of the dislocation substructure in polycrystalline Cu-Al alloys with various grain sizes is studied during deformation to failure. A relation between the fracture of the alloys and the forming misorientation dislocation substructures is revealed. Microcracks in the alloy are found to form along grain boundaries and the boundaries of misoriented dislocation cells and microtwins.

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

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.

Dominant pinning mechanisms in YBa2Cu3O7-x films on single and polycrystalline yttria stabilized zirconia substrates

Science.gov (United States)

Harshavardhan, K. S.; Rajeswari, M.; Hwang, D. M.; Chen, C. Y.; Sands, T.; Venkatesan, T.; Tkaczyk, J. E.; Lay, K. W.; Safari, A.

1992-04-01

Critical-current densities have been measured in YBa2Cu3O7-x films deposited on (100) yttria stabilized zirconia (YSZ) and polycrystalline YSZ substrates as a function of temperature (4.5-88 K), magnetic field (0-1 T) and orientation relative to the applied field. The results indicate that in films on polycrystalline substrates, surface and interface pinning play a dominant role at high temperatures. In films on (100) YSZ, pinning is mainly due to intrinsic layer pinning as well as extrinsic pinning associated with the interaction of the fluxoids with point defects and low energy planar (2D) boundaries. The differences are attributed to the intrinsic rigidity of single fluxoids which is reduced in films on polycrystalline substrates thereby weakening the intrinsic layer pinning.

Zinc-substituted ZIF-67 nanocrystals and polycrystalline membranes for propylene/propane separation

KAUST Repository

Wang, Chongqing

2016-09-09

Continuous ZIF-67 polycrystalline membranes with effective propylene/propane separation performances were successfully fabricated through the incorporation of zinc ions into the ZIF-67 framework. The separation factor increases from 1.4 for the pure ZIF-67 membrane to 50.5 for the 90% zinc-substituted ZIF-67 membrane.

Method of making quasi-grain boundary-free polycrystalline solar cell structure and solar cell structure obtained thereby

Science.gov (United States)

Gonzalez, Franklin N.; Neugroschel, Arnost

1984-02-14

A new solar cell structure is provided which will increase the efficiency of polycrystalline solar cells by suppressing or completely eliminating the recombination losses due to the presence of grain boundaries. This is achieved by avoiding the formation of the p-n junction (or other types of junctions) in the grain boundaries and by eliminating the grain boundaries from the active area of the cell. This basic concept can be applied to any polycrystalline material; however, it will be most beneficial for cost-effective materials having small grains, including thin film materials.

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)

Preparation and characterization of carbonate terminated polycrystalline Al{sub 2}O{sub 3}/Al films

Energy Technology Data Exchange (ETDEWEB)

Tornow, C. [Fraunhofer-Institute for Manufacturing Technology and Applied Materials Research (IFAM), Adhesive Bonding Technology and Surfaces, Wiener Str. 12, D-28359 Bremen (Germany); Fachhochschule Oldenburg/Ostfriesland/Wilhelmshaven, University of Applied Sciences, Faculty of Technology, Department of Applied Natural Sciences, Engineering Physics, Constantiaplatz 4, D-26723 Emden (Germany); Noeske, P.-L.M. [Fraunhofer-Institute for Manufacturing Technology and Applied Materials Research (IFAM), Adhesive Bonding Technology and Surfaces, Wiener Str. 12, D-28359 Bremen (Germany); Dieckhoff, S. [Fraunhofer-Institute for Manufacturing Technology and Applied Materials Research (IFAM), Adhesive Bonding Technology and Surfaces, Wiener Str. 12, D-28359 Bremen (Germany); Wilken, R. [Fraunhofer-Institute for Manufacturing Technology and Applied Materials Research (IFAM), Adhesive Bonding Technology and Surfaces, Wiener Str. 12, D-28359 Bremen (Germany)]. E-mail: rw@ifam.fraunhofer.de; Gaertner, K. [Fachhochschule Oldenburg/Ostfriesland/Wilhelmshaven, University of Applied Sciences, Faculty of Technology, Department of Applied Natural Sciences, Engineering Physics, Constantiaplatz 4, D-26723 Emden (Germany)

2005-12-15

X-ray photoelectron spectroscopy (XPS) was applied to investigate the surface reactivity of polycrystalline Al films in contact with a gas mixture of carbon dioxide and oxygen at room temperature. Based on the characterization of interactions between these substrates and the individual gases at selected exposures, various surface functionalities were identified. Simultaneously dosing both carbon dioxide and oxygen is shown to create surface-terminating carbonate species, which contribute to inhibiting the formation of an Al{sub 2}O{sub 3} layer. Finally, a reaction scheme is suggested to account for the observed dependence of surface group formation on the dosing conditions.

Effect of high temperature annealing on the thermoelectric properties of GaP doped SiGe

Science.gov (United States)

Vandersande, Jan W.; Wood, Charles; Draper, Susan

1987-01-01

Silicon-germanium alloys doped with GaP are used for thermoelectric energy conversion in the temperature range 300-1000 C. The conversion efficiency depends on Z = S-squared/rho lambda, a material's parameter (the figure of merit), where S is the Seebeck coefficient, rho is the electrical resistivity and lambda is the thermal conductivity. The annealing of several samples in the temperature range of 1100-1300 C resulted in the power factor P (= S-squared/rho) increasing with increased annealing temperature. This increase in P was due to a decrease in rho which was not completely offset by a drop in S-squared suggesting that other changes besides that in the carrier concentration took place. SEM and EDX analysis of the samples indicated the formation of a Ga-P-Ge rich phase as a result of the annealing. It is speculated that this phase is associated with the improved properties. Several reasons which could account for the improvement in the power factor of annealed GaP doped SiGe are given.

New opportunities for 3D materials science of polycrystalline materials at the micrometre lengthscale by combined use of X-ray diffraction and X-ray imaging

Energy Technology Data Exchange (ETDEWEB)

Ludwig, W., E-mail: ludwig@esrf.fr [Universite de Lyon, INSA-Lyon, MATEIS CNRS UMR 5510, 69621Villeurbanne (France); European Synchrotron Radiation Facility, BP220, 38043 Grenoble (France); King, A. [European Synchrotron Radiation Facility, BP220, 38043 Grenoble (France); School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom); Reischig, P. [European Synchrotron Radiation Facility, BP220, 38043 Grenoble (France); Herbig, M. [Universite de Lyon, INSA-Lyon, MATEIS CNRS UMR 5510, 69621Villeurbanne (France); Lauridsen, E.M.; Schmidt, S. [Riso National Laboratory for Sustainable Energy, Technical University of Denmark, P.O. Box 49, DK-4000 Roskilde (Denmark); Proudhon, H.; Forest, S. [MINES ParisTech, Centre des materiaux, CNRS UMR 7633, BP 87, 91003 Evry Cedex (France); Cloetens, P.; Roscoat, S. Rolland du [European Synchrotron Radiation Facility, BP220, 38043 Grenoble (France); Buffiere, J.Y. [Universite de Lyon, INSA-Lyon, MATEIS CNRS UMR 5510, 69621Villeurbanne (France); Marrow, T.J. [School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom); Poulsen, H.F. [Riso National Laboratory for Sustainable Energy, Technical University of Denmark, P.O. Box 49, DK-4000 Roskilde (Denmark)

2009-10-25

Non-destructive, three-dimensional (3D) characterization of the grain structure in mono-phase polycrystalline materials is an open challenge in material science. Recent advances in synchrotron based X-ray imaging and diffraction techniques offer interesting possibilities for mapping 3D grain shapes and crystallographic orientations for certain categories of polycrystalline materials. Direct visualisation of the three-dimensional grain boundary network or of two-phase (duplex) grain structures by means of absorption and/or phase contrast techniques may be possible, but is restricted to specific material systems. A recent extension of this methodology, termed X-ray diffraction contrast tomography (DCT), combines the principles of X-ray diffraction imaging, three-dimensional X-ray diffraction microscopy (3DXRD) and image reconstruction from projections. DCT provides simultaneous access to 3D grain shape, crystallographic orientation and local attenuation coefficient distribution. The technique applies to the larger range of plastically undeformed, polycrystalline mono-phase materials, provided some conditions on grain size and texture are fulfilled. The straightforward combination with high-resolution microtomography opens interesting new possibilities for the observation of microstructure related damage and deformation mechanisms in these materials.

New opportunities for 3D materials science of polycrystalline materials at the micrometre lengthscale by combined use of X-ray diffraction and X-ray imaging

International Nuclear Information System (INIS)

Ludwig, W.; King, A.; Reischig, P.; Herbig, M.; Lauridsen, E.M.; Schmidt, S.; Proudhon, H.; Forest, S.; Cloetens, P.; Roscoat, S. Rolland du; Buffiere, J.Y.; Marrow, T.J.; Poulsen, H.F.

2009-01-01

Non-destructive, three-dimensional (3D) characterization of the grain structure in mono-phase polycrystalline materials is an open challenge in material science. Recent advances in synchrotron based X-ray imaging and diffraction techniques offer interesting possibilities for mapping 3D grain shapes and crystallographic orientations for certain categories of polycrystalline materials. Direct visualisation of the three-dimensional grain boundary network or of two-phase (duplex) grain structures by means of absorption and/or phase contrast techniques may be possible, but is restricted to specific material systems. A recent extension of this methodology, termed X-ray diffraction contrast tomography (DCT), combines the principles of X-ray diffraction imaging, three-dimensional X-ray diffraction microscopy (3DXRD) and image reconstruction from projections. DCT provides simultaneous access to 3D grain shape, crystallographic orientation and local attenuation coefficient distribution. The technique applies to the larger range of plastically undeformed, polycrystalline mono-phase materials, provided some conditions on grain size and texture are fulfilled. The straightforward combination with high-resolution microtomography opens interesting new possibilities for the observation of microstructure related damage and deformation mechanisms in these materials.

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.

SiGe HBT cryogenic preamplification for higher bandwidth donor spin read-out

Science.gov (United States)

Curry, Matthew; Carr, Stephen; Ten-Eyck, Greg; Wendt, Joel; Pluym, Tammy; Lilly, Michael; Carroll, Malcolm

2014-03-01

Single-shot read-out of a donor spin can be performed using the response of a single-electron-transistor (SET). This technique can produce relatively large changes in current, on the order of 1 (nA), to distinguish between the spin states. Despite the relatively large signal, the read-out time resolution has been limited to approximately 100 (kHz) of bandwidth because of noise. Cryogenic pre-amplification has been shown to extend the response of certain detection circuits to shorter time resolution and thus higher bandwidth. We examine a SiGe HBT circuit configuration for cryogenic preamplification, which has potential advantages over commonly used HEMT configurations. Here we present 4 (K) measurements of a circuit consisting of a Silicon-SET inline with a Heterojunction-Bipolar-Transistor (HBT). We compare the measured bandwidth with and without the HBT inline and find that at higher frequencies the signal-to-noise-ratio (SNR) with the HBT inline exceeds the SNR without the HBT inline. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. The work was supported by the Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.

Polycrystalline oxides formation during transient oxidation of (001) Cu-Ni binary alloys studied by in situ TEM and XRD

International Nuclear Information System (INIS)

Yang, J.C.; Li, Z.Q.; Sun, L.; Zhou, G.W.; Eastman, J.A.; Fong, D.D.; Fuoss, P.H.; Baldo, P.M.; Rehn, L.E.; Thompson, L.J.

2009-01-01

The nucleation and growth of Cu 2 O and NiO islands due to oxidation of Cu x Ni 1-x (001) films were monitored, at various temperatures, by in situ ultra-high vacuum (UHV) transmission electron microscopy (TEM) and in situ synchrotron X-ray diffraction (XRD). In remarkable contrast to our previous observations of Cu and Cu-Au oxidation, irregular-shaped polycrystalline oxide islands formed with respect to the Cu-Ni alloy film, and an unusual second oxide nucleation stage was noted. In situ XRD experiments revealed that NiO formed first epitaxially, then other orientations appeared, and finally polycrystalline Cu 2 O developed as the oxidation pressure was increased. The segregation of Ni and Cu towards or away, respectively, from the alloy surface during oxidation could disrupt the surface and cause polycrystalline oxide formation.

Total dose effects on the shallow-trench isolation leakage current characteristics in a 0.35microm SiGe BiCMOS technology

International Nuclear Information System (INIS)

Niu, G.; Mathew, S.J.; Banerjee, G.; Cressler, J.D.; Clark, S.D.; Palmer, M.J.; Subbanna, S.

1999-01-01

The effects of gamma irradiation on the Shallow-Trench Isolation (STI) leakage currents in a SiGe BiCMOS technology are investigated for the first time, and shown to be strongly dependent on the irradiation gate bias and operating substrate bias. A positive irradiation gate bias significantly enhances the STI leakage, suggesting a strong field assisted nature of the charge buildup process in the STI. Numerical simulations also suggest the existence of fixed positive charges deep in the bulk along the STI/Si interface. A negative substrate bias, however, effectively suppresses the STI leakage, and can be used to eliminate the leakage produced by the charges deep in the bulk under irradiation

Anomalous magnetoresistance in antiferromagnetic polycrystalline materials R2Ni3Si5 (R=rare earth)

International Nuclear Information System (INIS)

Mazumdar, C.; Nigam, A.K.; Nagarajan, R.; Gupta, L.C.; Chandra, G.; Padalia, B.D.; Godart, C.; Vijayaraghaven, R.

1997-01-01

Magnetoresistance (MR) studies on polycrystalline R 2 Ni 3 Si 5 , (R=Y, rare earth) which order antiferromagnetically at low temperatures, are reported here. MR of the Nd, Sm, and Tb members of the series exhibit positive giant magnetoresistance, largest among polycrystalline materials (85%, 75%, and 58% for Tb 2 Ni 3 Si 5 , Sm 2 Ni 3 Si 5 , and Nd 2 Ni 3 Si 5 , respectively, at 4.4 K in a field of 45 kG). These materials have, to the best of our knowledge, the largest positive GMR reported ever for any bulk polycrystalline compounds. The magnitude of MR does not correlate with the rare earth magnetic moments. We believe that the structure of these materials, which can be considered as a naturally occurring multilayer of wavy planes of rare earth atoms separated by Ni endash Si network, plays a role. The isothermal MR of other members of this series (R=Pr,Dy,Ho) exhibits a maximum and a minimum, below their respective T N close-quote s. We interpret these in terms of a metamagnetic transition and short-range ferromagnetic correlations. The short-range ferromagnetic correlations seem to be dominant in the temperature region just above T N . copyright 1997 American Institute of Physics

Enhanced spectroscopic gas sensors using in-situ grown carbon nanotubes

Energy Technology Data Exchange (ETDEWEB)

De Luca, A.; Cole, M. T.; Milne, W. I. [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom); Hopper, R. H.; Boual, S.; Ali, S. Z. [Cambridge CMOS Sensors Ltd., Deanland House, 160 Cowley Road, Cambridge CB4 0DL (United Kingdom); Warner, J. H.; Robertson, A. R. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Udrea, F. [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom); Cambridge CMOS Sensors Ltd., Deanland House, 160 Cowley Road, Cambridge CB4 0DL (United Kingdom); Gardner, J. W. [School of Engineering, University of Warwick, Coventry CV4 7AL (United Kingdom)

2015-05-11

In this letter, we present a fully complementary-metal-oxide-semiconductor (CMOS) compatible microelectromechanical system thermopile infrared (IR) detector employing vertically aligned multi-walled carbon nanotubes (CNT) as an advanced nano-engineered radiation absorbing material. The detector was fabricated using a commercial silicon-on-insulator (SOI) process with tungsten metallization, comprising a silicon thermopile and a tungsten resistive micro-heater, both embedded within a dielectric membrane formed by a deep-reactive ion etch following CMOS processing. In-situ CNT growth on the device was achieved by direct thermal chemical vapour deposition using the integrated micro-heater as a micro-reactor. The growth of the CNT absorption layer was verified through scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The functional effects of the nanostructured ad-layer were assessed by comparing CNT-coated thermopiles to uncoated thermopiles. Fourier transform IR spectroscopy showed that the radiation absorbing properties of the CNT adlayer significantly enhanced the absorptivity, compared with the uncoated thermopile, across the IR spectrum (3 μm–15.5 μm). This led to a four-fold amplification of the detected infrared signal (4.26 μm) in a CO{sub 2} non-dispersive-IR gas sensor system. The presence of the CNT layer was shown not to degrade the robustness of the uncoated devices, whilst the 50% modulation depth of the detector was only marginally reduced by 1.5 Hz. Moreover, we find that the 50% normalized absorption angular profile is subsequently more collimated by 8°. Our results demonstrate the viability of a CNT-based SOI CMOS IR sensor for low cost air quality monitoring.

Modeling and simulation of the deposition/relaxation processes of polycrystalline diatomic structures of metallic nitride films

Science.gov (United States)

García, M. F.; Restrepo-Parra, E.; Riaño-Rojas, J. C.

2015-05-01

This work develops a model that mimics the growth of diatomic, polycrystalline thin films by artificially splitting the growth into deposition and relaxation processes including two stages: (1) a grain-based stochastic method (grains orientation randomly chosen) is considered and by means of the Kinetic Monte Carlo method employing a non-standard version, known as Constant Time Stepping, the deposition is simulated. The adsorption of adatoms is accepted or rejected depending on the neighborhood conditions; furthermore, the desorption process is not included in the simulation and (2) the Monte Carlo method combined with the metropolis algorithm is used to simulate the diffusion. The model was developed by accounting for parameters that determine the morphology of the film, such as the growth temperature, the interacting atomic species, the binding energy and the material crystal structure. The modeled samples exhibited an FCC structure with grain formation with orientations in the family planes of , and . The grain size and film roughness were analyzed. By construction, the grain size decreased, and the roughness increased, as the growth temperature increased. Although, during the growth process of real materials, the deposition and relaxation occurs simultaneously, this method may perhaps be valid to build realistic polycrystalline samples.

Technology of uncooled fast polycrystalline PbSe focal plane arrays in systems for muzzle flash detection

Science.gov (United States)

Kastek, Mariusz; PiÄ tkowski, Tadeusz; Polakowski, Henryk; Barela, Jaroslaw; Firmanty, Krzysztof; Trzaskawka, Piotr; Vergara, German; Linares, Rodrigo; Gutierrez, Raul; Fernandez, Carlos; Montojo Supervielle, Maria Teresa

2014-05-01

The paper presents some aspects of muzzle flash detection using low resolution polycrystalline PbSe 32×32 and 80×80 detectors FPA operating at room temperature (uncooled performance). These sensors, which detect in MWIR (3 - 5 microns region) and are manufactured using proprietary technology from New Infrared Technologies (VPD PbSe - Vapor Phase Deposition of polycrystalline PbSe), can be applied to muzzle flash detection. The system based in the uncooled 80×80 FPA monolithically integrated with the CMOS readout circuitry has allowed image recording with frame rates over 2000 Hz (true snapshot acquisition), whereas the lower density, uncooled 32×32 FPA is suitable for being used in low cost infrared imagers sensitive in the MWIR band with frame rates above 1000 Hz. The FPA detector, read-out electronics and processing electronics (allows the implementation of some algorithms for muzzle flash detection) of both systems are presented. The systems have been tested at field test ground. Results of detection range measurement with two types of optical systems (wide and narrow field of view) have been shown. The theoretical analysis of possibility detection of muzzle flash and initial results of testing of some algorithms for muzzle flash detection have been presented too.

Environmental aging in polycrystalline-Si photovoltaic modules: comparison of chamber-based accelerated degradation studies with field-test data

Science.gov (United States)

Lai, T.; Biggie, R.; Brooks, A.; Potter, B. G.; Simmons-Potter, K.

2015-09-01

Lifecycle degradation testing of photovoltaic (PV) modules in accelerated-degradation chambers can enable the prediction both of PV performance lifetimes and of return-on-investment for installations of PV systems. With degradation results strongly dependent on chamber test parameters, the validity of such studies relative to fielded, installed PV systems must be determined. In the present work, accelerated aging of a 250 W polycrystalline silicon module is compared to real-time performance degradation in a similar polycrystalline-silicon, fielded, PV technology that has been operating since October 2013. Investigation of environmental aging effects are performed in a full-scale, industrial-standard environmental chamber equipped with single-sun irradiance capability providing illumination uniformity of 98% over a 2 x 1.6 m area. Time-dependent, photovoltaic performance (J-V) is evaluated over a recurring, compressed night-day cycle providing representative local daily solar insolation for the southwestern United States, followed by dark (night) cycling. This cycle is synchronized with thermal and humidity environmental variations that are designed to mimic, as closely as possible, test-yard conditions specific to a 12 month weather profile for a fielded system in Tucson, AZ. Results confirm the impact of environmental conditions on the module long-term performance. While the effects of temperature de-rating can be clearly seen in the data, removal of these effects enables the clear interpretation of module efficiency degradation with time and environmental exposure. With the temperature-dependent effect removed, the normalized efficiency is computed and compared to performance results from another panel of similar technology that has previously experienced identical climate changes in the test yard. Analysis of relative PV module efficiency degradation for the chamber-tested system shows good comparison to the field-tested system with ~2.5% degradation following

ESR and spin-trapping study of room-temperature radicals in γ-irradiated polycrystalline pyrimidine nucleotides

International Nuclear Information System (INIS)

Zhang, Z.; Kuwabara, M.; Yoshii, G.

1983-01-01

Free radicals produced in γ-irradiated polycrystalline 5'-dCMP (free acid and 2Na), 3'-CMP (free acid and Li), and 5'-UMP (2Na) were studied by ESR and spin-trapping. The results were compared with those of previous single-crystal studies. Furthermore, attempts to identify free radicals in γ-irradiated 5'-dUMP (2Na), 5'-CMP (free acid and 2Na), and 3'-UMP (Na), which have not been the subject of single-crystal studies to date, were made. After γ-irradiation at room temperature to a dose of 100 kGy, the polycrystalline samples were dissolved in aqueous solutions of t-nitrosobutane in the presence or absence of oxygen. The presence or absence of oxygen was helpful in analyzing the presence of more than one radical species. Thus two types of radicals could be established for all samples. Radical -C 5 H-C 6 H 2 -, formed by H addition to the double bond of the base, was observed in the presence of oxygen, and radical -C/sub 5'/H 2 , formed by the transformation of the radical due to loss of an H atom at the C/sub 5'/ position of the sugar moiety, was observed in the absence of oxygen. In some cases, radicals located at the C/sub 1'/, C/sub 4'/, and C/sub 5'/ of the sugar moiety were tentatively identified. For the ESR spectrum associated with radical at C/sub 1'/ the possibility of another explanation was also discussed in relation to the spectrum due to radical at C 5 of the base. Radical -C 5 H 2 -C 6 H-, formed by H addition to the double bond of the base, was not identified

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.

Diffusion phenomena in polycrystalline chromium near the upper homological temperature of intercrystalline diffusion manifestation

International Nuclear Information System (INIS)

Kajgorodov, V.N.; Klothman, S.M.; Kurkin, M.I.; Dyakin, V.V.; Zherebthov, D.V.

1997-01-01

A study is made into the temperature dependences of density of states in a zone of intercrystalline diffusion of atomic probes 57 Co in polycrystalline chromium as well as in the temperature dependences of isomer shift and line width in Moessbauer spectra near the upper temperature boundary of manifestation of intercrystalline diffusion. In polycrystalline chromium the release of states in the core of the crystallite conjugation region (CCR) takes place only at high temperatures due to the fact that a stationary zone of high point defect concentration in the vicinity of CCR is conserved up to high temperatures. The atomic probe escape from the core of CCR starts at the temperatures at which the equilibrium vacancy concentration in the bulk of crystallite is equal to that in a stationary zone of high defect concentration

Comparison of Deformation in High-Purity Single/Large Grain and Polycrystalline Niobium Superconducting Cavities

International Nuclear Information System (INIS)

Ganapati Rao Myneni; Peter Kneisel

2005-01-01

The current approach for the fabrication of superconducting radio frequency (SRF) cavities is to roll and deep draw sheets of polycrystalline high-purity niobium. Recently, a new technique was developed at Jefferson Laboratory that enables the fabrication of single-crystal high-purity Nb SRF cavities. To better understand the differences between SRF cavities fabricated out of fine-grained polycrystalline sheet in the standard manner and single crystal cavities fabricated by the new technique, two half-cells were produced according to the two different procedures and compared using a variety of analytical techniques including optical microscopy, scanning laser confocal microscopy, profilometry, and X-ray diffraction. Crystallographic orientations, texture, and residual stresses were determined in the samples before and after forming and this poster presents the results of this ongoing study

Faraday effect of polycrystalline bismuth iron garnet thin film prepared by mist chemical vapor deposition method

International Nuclear Information System (INIS)

Yao, Situ; Kamakura, Ryosuke; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa

2017-01-01

We have synthesized polycrystalline thin film composed of a single phase of metastable bismuth iron garnet, Bi_3Fe_5O_1_2, on a fused silica substrate, one of the most widely utilized substrates in the solid-state electronics, by using mist chemical vapor deposition (mist CVD) method. The phase purity and stoichiometry are confirmed by X-ray diffraction and Rutherford backscattering spectrometry. The resultant thin film shows a small surface roughness of 3.251 nm. The saturation magnetization at room temperature is 1200 G, and the Faraday rotation angle at 633 nm reaches −5.2 deg/μm. Both the magnetization and the Faraday rotation angles are somewhat higher than those of polycrystalline BIG thin films prepared by other methods. - Highlights: • Thin film of polycrystalline Bi_3Fe_5O_1_2 was prepared by the mist CVD method. • Optimized conditions were found for the synthesis of single phase of Bi_3Fe_5O_1_2. • The Faraday rotation angle at 633 nm is –5.2 deg/μm at room temperature. • The Faraday rotation is interpreted by the electronic transitions of Fe"3"+ ions.

A macroscopic constitutive model of temperature-induced phase transition of polycrystalline Ni{sub 2}MnGa by directional solidification

Energy Technology Data Exchange (ETDEWEB)

Zhu, Yuping, E-mail: zhuyuping@126.com; Gu, Yunling; Liu, Hongguang

2015-02-25

Directional solidification technology has been widely used to improve the properties of polycrystalline Ni{sub 2}MnGa materials. Mechanical training can adjust the internal organizational structures of the materials, reduce the stress of twin boundaries motion, and then result in larger strain at lower outfield levels. In this paper, we test the microscopic structure of Ni{sub 2}MnGa polycrystalline ferromagnetic shape memory alloy produced by directional solidification and compress it along two axes successively for mechanical training. The influences of pre-compressive stresses on the temperature-induced strains are analyzed. The macroscopic mechanical behaviors show anisotropy. According to the generating mechanism of the macroscopic strain, a three-dimensional constitutive model is established. Based on thermodynamic method, the kinetic equations of the martensitic transformation and inverse transformation are presented considering the driving force and energy dissipation. The prediction curves of temperature-induce strains along two different directions are investigated. And the results coincide well with the experiment data. It well explains the macroscopic anisotropy mechanical behaviors and fits for using in engineering.

Effect of texture on grain boundary misorientation distributions in polycrystalline high temperature superconductors

International Nuclear Information System (INIS)

Goyal, A.; Specht, E.D.; Kroeger, D.M.; Mason, T.A.

1996-01-01

Computer simulations were performed to determine the most probable grain boundary misorientation distribution (GBMD) in model polycrystalline superconductors. GBMDs in polycrystalline superconductors can be expected to dictate the macroscopic transport critical current density, J c . Calculations were performed by simulating model polycrystals and then determining the GBMD. Such distributions were calculated for random materials having cubic, tetragonal, and orthorhombic crystal symmetry. In addition, since most high temperature superconductors are tetragonal or pseudotetragonal, the effect of macroscopic uniaxial and biaxial grain orientation texture on the GBMD was determined for tetragonal materials. It is found that macroscopic texture drastically alters the grain boundary misorientation distribution. The fraction of low angle boundaries increases significantly with uniaxial and biaxial texture. The results of this study are important in correlating the macroscopic transport J c with the measured grain orientation texture as determined by x-ray diffraction copyright 1996 American Institute of Physics

Fabrication and Testing of Thermoelectric CMOS-MEMS Microgenerators with CNCs Film

Directory of Open Access Journals (Sweden)

Yu-Wei Chen

2018-06-01

Full Text Available Manufacturing and testing of a TMG (thermoelectric microgenerator with CNCs (carbon nanocapsules film fabricated utilizing a CMOS (complementary metal oxide semiconductor technology are investigated. The microgenerator includes a CNCs layer, thermopiles, and thermometers. CNCs, a heat absorbing material, are coated on the microgenerator, so that the TD (temperature difference of HP (hot part and CP (cold part in the thermopiles increases, resulting in an enhancement of the microgenerator OP (output power. Thermometers fabricated in the microgenerator are employed to detect the HP and CP temperature in thermopiles. In order to enhance thermopiles’ TD, the HP in thermopiles was manufactured as suspension structures isolating heat dissipation, and the CP in thermopiles was made on a silicon substrate to increase the heat sink. Experiments showed that the microgenerator OV (output voltage was 3.3 mV and its output power was 125 pW at TD 3 K. Voltage and power factors of TMG were 0.71 mV/K/mm2 and 9.04 pW/K2/mm2, respectively.

High-Efficiency Polycrystalline CdS/CdTe Solar Cells on Buffered Commercial TCO-Coated Glass

Science.gov (United States)

Colegrove, E.; Banai, R.; Blissett, C.; Buurma, C.; Ellsworth, J.; Morley, M.; Barnes, S.; Gilmore, C.; Bergeson, J. D.; Dhere, R.; Scott, M.; Gessert, T.; Sivananthan, Siva

2012-10-01

Multiple polycrystalline CdS/CdTe solar cells with efficiencies greater than 15% were produced on buffered, commercially available Pilkington TEC Glass at EPIR Technologies, Inc. (EPIR, Bolingbrook, IL) and verified by the National Renewable Energy Laboratory (NREL). n-CdS and p-CdTe were grown by chemical bath deposition (CBD) and close space sublimation, respectively. Samples with sputter-deposited CdS were also investigated. Initial results indicate that this is a viable dry-process alternative to CBD for production-scale processing. Published results for polycrystalline CdS/CdTe solar cells with high efficiencies are typically based on cells using research-grade transparent conducting oxides (TCOs) requiring high-temperature processing inconducive to low-cost manufacturing. EPIR's results for cells on commercial glass were obtained by implementing a high-resistivity SnO2 buffer layer and by optimizing the CdS window layer thickness. The high-resistivity buffer layer prevents the formation of CdTe-TCO junctions, thereby maintaining a high open-circuit voltage and fill factor, whereas using a thin CdS layer reduces absorption losses and improves the short-circuit current density. EPIR's best device demonstrated an NREL-verified efficiency of 15.3%. The mean efficiency of hundreds of cells produced with a buffer layer between December 2010 and June 2011 is 14.4%. Quantum efficiency results are presented to demonstrate EPIR's progress toward NREL's best-published results.

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.

The three-dimensional microstructure of polycrystalline materials unravelled by synchrotron light; La microstructure 3D des materiaux polycristallins vue sous la lumiere synchrotron

Energy Technology Data Exchange (ETDEWEB)

Ludwig, W.; Herbig, M. [Universite de Lyon, INSA-Lyon, MATEIS, UMR 5510 CNRS, LyonTech Campus, Bat. Saint-Exupery, 25 avenue Jean Capelle, F-69621 Villeurbanne Cedex (France); Ludwig, W.; King, A; Reischig, P. [European Synchrotron Radiation Facility, 6 rue J. Horowitz, BP 220, F-38043 Grenoble (France); Marrow, J. [University of Oxford, Department of Materiels, Parks road, Oxford OX1 3PH (United Kingdom); Babout, L. [Computer Engineering Department, Technical University of Lodz, ul. Stefanowskiego 18/22, PL-90- 537 Lodz (Poland); Mejdal Lauridsen, E. [Materials Research Department, Riso National Laboratory for Sustainable Energy, Technical University of Denmark (DTU), Building 228, PO Box 49, DK-4000 Roskilde (Denmark); Proudhon, H. [MINES ParisTech, Centre des Materiaux, UMR 7633 CNRS, BP 87, F-91003 Evry Cedex (France)

2011-07-01

Synchrotron radiation X-ray imaging and diffraction techniques offer new possibilities for non-destructive bulk characterization of polycrystalline materials. Minute changes in electron density (different crystallographic phases, cracks, porosities) can be detected using 3D imaging modes exploiting Fresnel diffraction and the coherence properties of third generation synchrotron beams. X-ray diffraction contrast tomography, a technique based on Bragg diffraction imaging, provides access to the 3D shape, orientation and elastic strain state of the individual grains from polycrystalline sample volumes containing several hundred up to a few thousand grains. Combining both imaging modalities allows a comprehensive description of the microstructure of the material at the micrometer length scale. Repeated observations during (interrupted) mechanical tests provide unprecedented insight into crystallographic and grain microstructure related aspects of polycrystal deformation and degradation mechanisms in materials, fulfilling some conditions on grain size and deformation state. (authors)

Magnetoelectric coupling effect in transition metal modified polycrystalline BiFeO3 thin films

International Nuclear Information System (INIS)

Sreenivas Puli, Venkata; Kumar Pradhan, Dhiren; Gollapudi, Sreenivasulu; Coondoo, Indrani; Panwar, Neeraj; Adireddy, Shiva; Chrisey, Douglas B.; Katiyar, Ram S.

2014-01-01

Rare-earth (Sm) and transition metal (Co) modified polycrystalline BiFeO 3 (BFO) thin films have been deposited on Pt/TiO 2 /SiO 2 /Si substrate successfully through pulsed laser deposition (PLD) technique. Piezoelectric, leakage current and temperature dependent dielectric and magnetic behaviour were investigated for the films. Typical “butterfly-shaped” loop were observed in BSFCO films with an effective piezoelectric constant (d 33 ) ∼94 pm/V at 0.6 MV/cm. High dielectric constant ∼900 and low dielectric loss ∼0.25 were observed at room temperature. M–H loops have shown relatively high saturation magnetization ∼35 emu/cm 3 at a maximum field of H ∼20 kOe. Enhanced magnetoelectric coupling response is observed under applied magnetic field. The multiferroic, piezoelectric, leakage current behaviours were explored. Such studies should be helpful in designing multiferroic materials based on BSFCO films. - Highlights: • Transition metal modified polycrystalline BiFeO 3 thin films prepared using PLD. • High ME-coupling response was observed in co-substituted BiFeO 3 thin films. • High magnetization ∼35 emu/cm 3 at a maximum field of H ∼20 kOe. • Low leakage current might be due to co-substitution in BiFeO 3 thin films. • A notable piezoelectric constant d 33 ∼94 pm/V was found in BiFeO 3 thin films

Large-Scale PV Module Manufacturing Using Ultra-Thin Polycrystalline Silicon Solar Cells: Annual Subcontract Report, 1 October 2003--30 September 2004

Energy Technology Data Exchange (ETDEWEB)

Wohlgemuth, J.; Narayanan, M.

2005-03-01

The major objectives of this program are to continue the advancement of BP Solar polycrystalline silicon manufacturing technology. The program includes work in the following areas: Efforts in the casting area to increase ingot size, improve ingot material quality, and improve handling of silicon feedstock as it is loaded into the casting stations; developing wire saws to slice 100- m-thick silicon wafers on 290- m centers; developing equipment for demounting and subsequent handling of very thin silicon wafers; developing cell processes using 100- m-thick silicon wafers that produce encapsulated cells with efficiencies of at least 15.4% at an overall yield exceeding 95%; expanding existing in-line manufacturing data reporting systems to provide active process control; establishing a 50-MW (annual nominal capacity) green-field Mega-plant factory model template based on this new thin polycrystalline silicon technology; facilitating an increase in the silicon feedstock industry's production capacity for lower-cost solar-grade silicon feedstock.

A comparative study of transport properties in polycrystalline and epitaxial chromium nitride films

KAUST Repository

Duan, X. F.; Mi, Wenbo; Guo, Zaibing; Bai, Haili

2013-01-01

Polycrystalline CrNx films on Si(100) and glass substrates and epitaxial CrNx films on MgO(100) substrates were fabricated by reactive sputtering with different nitrogen gas flow rates (fN2). With the increase of fN2, a lattice phase transformation

Fabricating ordered functional nanostructures onto polycrystalline substrates from the bottom-up

International Nuclear Information System (INIS)

Torres, María; Pardo, Lorena; Ricote, Jesús; Fuentes-Cobas, Luís E.; Rodriguez, Brian J.; Calzada, M. Lourdes

2012-01-01

Microemulsion-mediated synthesis has emerged as a powerful bottom-up procedure for the preparation of ferroelectric nanostructures onto substrates. However, periodical order has yet to be achieved onto polycrystalline Pt-coated Si substrates. Here, we report a new methodology that involves microemulsion-mediated synthesis and the controlled modification of the surface of the substrate by coating it with a template-layer of water-micelles. This layer modifies the surface tension of the substrate and yields a periodic arrangement of ferroelectric crystalline nanostructures. The size of the nanostructures is decreased to the sub-50 nm range and they show a hexagonal order up to the third neighbors, which corresponds to a density of 275 Gb in −2 . The structural analysis of the nanostructures by synchrotron X-ray diffraction confirms that the nanostructures have a PbTiO 3 perovskite structure, with lattice parameters of a = b = 3.890(0) Å and c = 4.056(7) Å. Piezoresponse force microscopy confirmed the ferro-piezoelectric character of the nanostructures. This simple methodology is valid for the self-assembly of other functional oxides onto polycrystalline substrates, enabling their reliable integration into micro/nano devices.

Modeling the thermal deformation of TATB-based explosives. Part 1: Thermal expansion of “neat-pressed” polycrystalline TATB

Energy Technology Data Exchange (ETDEWEB)

Luscher, Darby J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-05-08

We detail a modeling approach to simulate the anisotropic thermal expansion of polycrystalline (1,3,5-triamino-2,4,6-trinitrobenzene) TATB-based explosives that utilizes microstructural information including porosity, crystal aspect ratio, and processing-induced texture. This report, the first in a series, focuses on nonlinear thermal expansion of “neat-pressed” polycrystalline TATB specimens which do not contain any binder; additional complexities related to polymeric binder and irreversible ratcheting behavior are briefly discussed, however detailed investigation of these aspects are deferred to subsequent reports. In this work we have, for the first time, developed a mesoscale continuum model relating the thermal expansion of polycrystal TATB specimens to their microstructural characteristics. A self-consistent homogenization procedure is used to relate macroscopic thermoelastic response to the constitutive behavior of single-crystal TATB. The model includes a representation of grain aspect ratio, porosity, and crystallographic texture attributed to the consolidation process. A quantitative model is proposed to describe the evolution of preferred orientation of graphitic planes in TATB during consolidation and an algorithm constructed to develop a discrete representation of the associated orientation distribution function. Analytical and numerical solutions using this model are shown to produce textures consistent with previous measurements and characterization for isostatic and uniaxial “die-pressed” specimens. Predicted thermal strain versus temperature for textured specimens are shown to be in agreement with corresponding experimental measurements. Using the developed modeling approach, several simulations have been run to investigate the influence of microstructure on macroscopic thermal expansion behavior. Results from these simulations are used to identify qualitative trends. Implications of the identified trends are discussed in the context of

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

Non-destructive identification of unknown minor phases in polycrystalline bulk alloys using three-dimensional X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Yang, Yiming, E-mail: yangyiming1988@outlook.com [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Xu, Liang [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Wang, Yudan; Du, Guohao [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Yang, Sam [Commonwealth Scientific and Industrial Research Organization, Melbourne, VIC 3168 (Australia); Xiao, Tiqiao, E-mail: tqxiao@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

2017-02-15

Minor phases make considerable contributions to the mechanical and physical properties of metals and alloys. Unfortunately, it is difficult to identify unknown minor phases in a bulk polycrystalline material using conventional metallographic methods. Here, a non-destructive method based on three-dimensional X-ray diffraction (3DXRD) is developed to solve this problem. Simulation results demonstrate that this method is simultaneously able to identify minor phase grains and reveal their positions, orientations and sizes within bulk alloys. According to systematic simulations, the 3DXRD method is practicable for an extensive sample set, including polycrystalline alloys with hexagonal, orthorhombic and cubic minor phases. Experiments were also conducted to confirm the simulation results. The results for a bulk sample of aluminum alloy AA6061 show that the crystal grains of an unexpected γ-Fe (austenite) phase can be identified, three-dimensionally and nondestructively. Therefore, we conclude that the 3DXRD method is a powerful tool for the identification of unknown minor phases in bulk alloys belonging to a variety of crystal systems. This method also has the potential to be used for in situ observations of the effects of minor phases on the crystallographic behaviors of alloys. - Highlights: •A method based on 3DXRD is developed for identification of unknown minor phase. •Grain position, orientation and size, is simultaneously acquired. •A systematic simulation demonstrated the applicability of the proposed method. •Experimental results on a AA6061 sample confirmed the practicability of the method.

Amorphous-crystalline interface evolution during Solid Phase Epitaxy Regrowth of SiGe films amorphized by ion implantation

International Nuclear Information System (INIS)

D'Angelo, D.; Piro, A.M.; Mirabella, S.; Bongiorno, C.; Romano, L.; Terrasi, A.; Grimaldi, M.G.

2007-01-01

Transmission Electron Microscopy was combined with Time Resolved Reflectivity to study the amorphous-crystalline (a-c) interface evolution during Solid Phase Epitaxy Regrowth (SPER) of Si 0.83 Ge 0.17 films deposited on Si by Molecular Beam Epitaxy and amorphized with Ge + ion implantation. Starting from the Si/SiGe interface, a 20 nm thick layer regrows free of defects with the same SPER rate of pure Si. The remaining SiGe regrows with planar defects and dislocations, accompanied by a decrease of the SPER velocity. The sample was also studied after implantation with B or P. In these cases, the SPER rate raises following the doping concentration profile, but no difference in the defect-free layer thickness was observed compared to the un-implanted sample. On the other hand, B or P introduction reduces the a-c interface roughness, while B-P co-implantation produces roughness comparable to the un-implanted sample

Quantum interference magnetoconductance of polycrystalline germanium films in the variable-range hopping regime

Science.gov (United States)

Li, Zhaoguo; Peng, Liping; Zhang, Jicheng; Li, Jia; Zeng, Yong; Zhan, Zhiqiang; Wu, Weidong

2018-06-01

Direct evidence of quantum interference magnetotransport in polycrystalline germanium films in the variable-range hopping (VRH) regime is reported. The temperature dependence of the conductivity of germanium films fulfilled the Mott VRH mechanism with the form of ? in the low-temperature regime (?). For the magnetotransport behaviour of our germanium films in the VRH regime, a crossover, from negative magnetoconductance at the low-field to positive magnetoconductance at the high-field, is observed while the zero-field conductivity is higher than the critical value (?). In the regime of ?, the magnetoconductance is positive and quadratic in the field for some germanium films. These features are in agreement with the VRH magnetotransport theory based on the quantum interference effect among random paths in the hopping process.

Strain-Induced Rolled Thin Films for Lightweight Tubular Thermoelectric Generators

KAUST Repository

Singh, Devendra

2017-11-24

Thermoelectric generators (TEGs) are interesting energy harvesters of otherwise wasted heat. Here, a polymer-assisted generic process and its mechanics to obtain sputtered thermoelectric (TE) telluride material-based 3D tubular structures with unprecedented length (up to seamless 4 cm and further expandable) are shown. This length allows for large temperature differences between the hot and the cold ends, a critical but untapped enabler for high power generation. Compared with a flat slab, better area efficiency is observed for a rolled tube and compared with a solid rod architecture, a rolled tube uses less material (thus making it lightweight and cost effective) and has competitive performance advantage due to a smaller contact area. It is also shown that a tubular architecture thermopile-based TEG is able to generate up to 5 μW of power (eight pairs of p- and n-type thermopiles) through a temperature difference of 60 °C. The demonstrated process can play an important role in transforming 2D atomic crystal structure TE materials into 3D tubular thermopiles for effective TEG application, which can maintain higher temperature differences by longer distances between hot and cold ends.

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

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.

Impact of Joule heating, roughness, and contaminants on the relative hardness of polycrystalline gold

International Nuclear Information System (INIS)

Freeze, Christopher R; Ji, Xiaoyin; Irving, Douglas L; Kingon, Angus I

2013-01-01

Asperities play a central role in the mechanical and electrical properties of contacting surfaces. Changes in trends of uniaxial compression of an asperity tip in contact with a polycrystalline substrate as a function of substrate geometry, compressive stress and applied voltage are investigated here by implementation of a coupled continuum and atomistic approach. Surprisingly, an unmodified Au polycrystalline substrate is found to be softer than one containing a void for conditions of high stress and an applied voltage of 0.2 V. This is explained in terms of the temperature distribution and weakening of Au as a function of temperature. The findings in this communication are important to the design of materials for electrical contacts because applied conditions may play a role in reversing relative hardness of the materials for conditions experienced during operation. (fast track communication)

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

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

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.

Comparisons of Fabric Strength and Development in Polycrystalline Ice at Atmospheric and Basal Hydrostatic Pressures

Science.gov (United States)

Breton, Daniel; Baker, Ian; Cole, David

2013-04-01

Understanding and predicting the flow of polycrystalline ice is crucial to ice sheet modeling and paleoclimate reconstruction from ice cores. Ice flow rates depend strongly on the fabric (i.e. the distribution of grain sizes and crystallographic orientations) which evolves over time and enhances the flow rate in the direction of applied stress. The mechanisms for fabric evolution in ice have been extensively studied at atmospheric pressures, but little work has been done to observe these processes at the high pressures experienced deep within ice sheets where long-term changes in ice rheology are expected to have significance. We conducted compressive creep tests to ~10% strain on 917 kg m-3, initially randomly-oriented polycrystalline ice specimens at 0.1 (atmospheric) and 20 MPa (simulating ~2,000 m depth) hydrostatic pressures, performing microstructural analyses on the resulting deformed specimens to characterize the evolution and strength of crystal fabric. Our microstructural analysis technique simultaneously collects grain shape and size data from Scanning Electron Microscope (SEM) micrographs and obtains crystallographic orientation data via Electron BackScatter Diffraction (EBSD). Combining these measurements allows rapid analysis of the ice fabric over large numbers of grains, yielding statistically useful numbers of grain size and orientation data. We present creep and microstructural data to demonstrate pressure-dependent effects on the mechanical and microstructural evolution of polycrystalline ice and discuss possible mechanisms for the observed differences.

Thermodynamic model for grain boundary effects on hydrogen solubility, diffusivity and permeability in poly-crystalline tungsten

Energy Technology Data Exchange (ETDEWEB)

Oda, Takuji, E-mail: oda@snu.ac.kr

2016-11-15

Highlights: • A thermodynamic model to simulate grain boundary effects on hydrogen behaviors in poly-crystalline W was established. • With this model, the effective solubility, diffusivity and permeability of hydrogen are calculated as a function of grain size. • Grain boundary significantly change the hydrogen behaviors in poly-crystalline W up to around 1000 K. - Abstract: A thermodynamic model to evaluate effects of grain boundary (GB) on hydrogen behaviors in poly-crystalline tungsten is established. With this model, the effective solubility, diffusivity and permeability of hydrogen in tungsten equilibrated with surrounding H{sub 2} gas can be calculated as a function of grain size, temperature and H{sub 2} partial pressure. By setting 1.0 eV to the binding energy of hydrogen to GBs and 0.4 eV to the diffusion barrier of hydrogen along GBs, the model reasonably reproduces some experimental data on the effective diffusivity and permeability. Comparisons between calculation results by the model and available experimental data show that GBs significantly affect the hydrogen behaviors up to around 1000 K or higher in practical materials. Therefore, the effects of GBs need to be considered in analysis of experimental results, for which the present model can be utilized, and in prediction of tritium inventory and leakage in fusion reactors.

Faraday effect of polycrystalline bismuth iron garnet thin film prepared by mist chemical vapor deposition method

Energy Technology Data Exchange (ETDEWEB)

Yao, Situ; Kamakura, Ryosuke; Murai, Shunsuke; Fujita, Koji; Tanaka, Katsuhisa, E-mail: tanaka@dipole7.kuic.kyoto-u.ac.jp

2017-01-15

We have synthesized polycrystalline thin film composed of a single phase of metastable bismuth iron garnet, Bi{sub 3}Fe{sub 5}O{sub 12}, on a fused silica substrate, one of the most widely utilized substrates in the solid-state electronics, by using mist chemical vapor deposition (mist CVD) method. The phase purity and stoichiometry are confirmed by X-ray diffraction and Rutherford backscattering spectrometry. The resultant thin film shows a small surface roughness of 3.251 nm. The saturation magnetization at room temperature is 1200 G, and the Faraday rotation angle at 633 nm reaches −5.2 deg/μm. Both the magnetization and the Faraday rotation angles are somewhat higher than those of polycrystalline BIG thin films prepared by other methods. - Highlights: • Thin film of polycrystalline Bi{sub 3}Fe{sub 5}O{sub 12} was prepared by the mist CVD method. • Optimized conditions were found for the synthesis of single phase of Bi{sub 3}Fe{sub 5}O{sub 12}. • The Faraday rotation angle at 633 nm is –5.2 deg/μm at room temperature. • The Faraday rotation is interpreted by the electronic transitions of Fe{sup 3+} ions.

Measurement, modeling, and simulation of cryogenic SiGe HBT amplifier circuits for fast single spin readout

Science.gov (United States)

England, Troy; Curry, Matthew; Carr, Steve; Swartzentruber, Brian; Lilly, Michael; Bishop, Nathan; Carrol, Malcolm

2015-03-01

Fast, low-power quantum state readout is one of many challenges facing quantum information processing. Single electron transistors (SETs) are potentially fast, sensitive detectors for performing spin readout of electrons bound to Si:P donors. From a circuit perspective, however, their output impedance and nonlinear conductance are ill suited to drive the parasitic capacitance typical of coaxial conductors used in cryogenic environments, necessitating a cryogenic amplification stage. We will discuss calibration data, as well as modeling and simulation of cryogenic silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) circuits connected to a silicon SET and operating at 4 K. We find a continuum of solutions from simple, single-HBT amplifiers to more complex, multi-HBT circuits suitable for integration, with varying noise levels and power vs. bandwidth tradeoffs. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.

High-aspect-ratio and high-flatness Cu3(SiGe) nanoplatelets prepared by chemical vapor deposition.

Science.gov (United States)

Klementová, Mariana; Palatinus, Lukás; Novotný, Filip; Fajgar, Radek; Subrt, Jan; Drínek, Vladislav

2013-06-01

Cu3(SiGe) nanoplatelets were synthesized by low-pressure chemical vapor deposition of a SiH3C2H5/Ge2(CH3)6 mixture on a Cu-substrate at 500 degrees C, total pressure of 110-115 Pa, and Ge/Si molar ratio of 22. The nanoplatelets with composition Cu76Si15Ge12 are formed by the 4'-phase, and they are flattened perpendicular to the [001] direction. Their lateral dimensions reach several tens of micrometers in size, but they are only about 50 nm thick. Their surface is extremely flat, with measured root mean square roughness R(q) below 0.2 nm. The nanoplatelets grow via the non-catalytic vapor-solid mechanism and surface growth. In addition, nanowires and nanorods of various Cu-Si-Ge alloys were also obtained depending on the experimental conditions. Morphology of the resulting Cu-Si-Ge nanoobjects is very sensitive to the experimental parameters. The formation of nanoplatelets is associated with increased amount of Ge in the alloy.

Large-Scale PV Module Manufacturing Using Ultra-Thin Polycrystalline Silicon Solar Cells: Annual Subcontract Report, 1 April 2002--30 September 2003 (Revised)

Energy Technology Data Exchange (ETDEWEB)

Wohlgemuth, J.; Shea, S. P.

2004-04-01

The goal of BP Solar's Crystalline PVMaT program is to improve the present polycrystalline silicon manufacturing facility to reduce cost, improve efficiency, and increase production capacity. Key components of the program are: increasing ingot size; improving ingot material quality; improving material handling; developing wire saws to slice 100 ..mu..m thick silicon wafers on 200 ..mu..m centers; developing equipment for demounting and subsequent handling of very thin silicon wafers; developing cell processes using 100 ..mu..m thick silicon wafers that produce encapsulated cells with efficiencies of at least 15.4% at an overall yield exceeding 95%; expanding existing in-line manufacturing data reporting systems to provide active process control; establishing a 50 MW (annual nominal capacity) green-field Mega plant factory model template based on this new thin polycrystalline silicon technology; and facilitating an increase in the silicon feedstock industry's production capacity for lower-cost solar-grade silicon feedstock.

Low temperature magnetron sputter deposition of polycrystalline silicon thin films using high flux ion bombardment

International Nuclear Information System (INIS)

Gerbi, Jennifer E.; Abelson, John R.

2007-01-01

We demonstrate that the microstructure of polycrystalline silicon thin films depends strongly on the flux of low energy ions that bombard the growth surface during magnetron sputter deposition. The deposition system is equipped with external electromagnetic coils which, through the unbalanced magnetron effect, provide direct control of the ion flux independent of the ion energy. We report the influence of low energy ( + on the low temperature ( + ions to silicon neutrals (J + /J 0 ) during growth by an order of magnitude (from 3 to 30) enables the direct nucleation of polycrystalline Si on glass and SiO 2 coated Si at temperatures below 400 degree sign C. We discuss possible mechanisms for this enhancement of crystalline microstructure, including the roles of enhanced adatom mobility and the formation of shallow, mobile defects

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.

Effects of crystal structure and grain orientation on the roughness of deformed polycrystalline metals

NARCIS (Netherlands)

Wouters, Onne; Vellinga, WP; van Tijum, Redmer; De Hosson, JTM

Surface roughening during tensile deformation of polycrystalline aluminum, iron and zinc is investigated using white light confocal microscopy and orientation imaging microscopy. A height-height correlation technique is used to analyze the data. The surface obeys self-affine scaling on length scales

Formation of polycrystalline MgB2 synthesized by powder in sealed tube method with different initial boron phase

Science.gov (United States)

Yudanto, Sigit Dwi; Imaduddin, Agung; Kurniawan, Budhy; Manaf, Azwar

2018-04-01

Magnesium diboride, MgB2 is a new high critical temperature superconductor that discovered in the beginning of the 21st century. The MgB2 has a simple crystal structure and a high critical temperature, which can be manufactured in several forms like thin films, tapes, wires including bulk in the large scale. For that reason, the MgB2 has good prospects for various applications in the field of electronic devices. In the current work, we have explored the synthesis of MgB2 polycrystalline using powder in a sealed tube method. Different initial boron phase for the synthesized of MgB2 polycrystalline were used. These were, in addition to magnesium powders, crystalline boron, amorphous boron and combination both of them were respectively fitted in the synthesis. The raw materials were mixed in a stoichiometric ratio of Mg: B=1:2, ground using agate mortar, packed into stainless steel SS304. The pack was then sintered at temperature of 800°C for 2 hours in air atmosphere. Phase formation of MgB2 polycrystalline in difference of initial boron phase was characterized using XRD and SEM. Referring to the diffraction pattern and microstructure observation, MgB2 polycrystalline was formed, and the formation was effective when using the crystalline Mg and fully amorphous B as the raw materials. The critical temperature of the specimen was evaluated by the cryogenic magnet. The transition temperature of the MgB2 specimen synthesized using crystalline magnesium and full amorphous boron is 42.678 K (ΔTc = 0.877 K).

Performance of in-pixel circuits for photon counting arrays (PCAs) based on polycrystalline silicon TFTs

International Nuclear Information System (INIS)

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

2016-01-01

Photon counting arrays (PCAs), defined as pixelated imagers which measure the absorbed energy of x-ray photons individually and record this information digitally, are of increasing clinical interest. A number of PCA prototypes with a 1 mm pixel-to-pixel pitch have recently been fabricated with polycrystalline silicon (poly-Si)—a thin-film technology capable of creating monolithic imagers of a size commensurate with human anatomy. In this study, analog and digital simulation frameworks were developed to provide insight into the influence of individual poly-Si transistors on pixel circuit performance—information that is not readily available through empirical means. The simulation frameworks were used to characterize the circuit designs employed in the prototypes. The analog framework, which determines the noise produced by individual transistors, was used to estimate energy resolution, as well as to identify which transistors contribute the most noise. The digital framework, which analyzes how well circuits function in the presence of significant variations in transistor properties, was used to estimate how fast a circuit can produce an output (referred to as output count rate). In addition, an algorithm was developed and used to estimate the minimum pixel pitch that could be achieved for the pixel circuits of the current prototypes. The simulation frameworks predict that the analog component of the PCA prototypes could have energy resolution as low as 8.9% full width at half maximum (FWHM) at 70 keV; and the digital components should work well even in the presence of significant thin-film transistor (TFT) variations, with the fastest component having output count rates as high as 3 MHz. Finally, based on conceivable improvements in the underlying fabrication process, the algorithm predicts that the 1 mm pitch of the current PCA prototypes could be reduced significantly, potentially to between ∼240 and 290 μm. (paper)

Magnetoelectric coupling effect in transition metal modified polycrystalline BiFeO{sub 3} thin films

Energy Technology Data Exchange (ETDEWEB)

Sreenivas Puli, Venkata, E-mail: pvsri123@gmail.com [Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118 (United States); Department of Physics and Institute of Functional Nanomaterials, University of Puerto Rico, San Juan, PR 00936 (United States); Kumar Pradhan, Dhiren [Department of Physics and Institute of Functional Nanomaterials, University of Puerto Rico, San Juan, PR 00936 (United States); Gollapudi, Sreenivasulu [Department of Physics, Oakland University, Rochester, MI 48309-4401 (United States); Coondoo, Indrani [Department of Materials and Ceramic and CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Panwar, Neeraj [Department of Physics, Central University of Rajasthan, Bandar Sindri, Kishangarh 305801, Rajasthan (India); Adireddy, Shiva; Chrisey, Douglas B. [Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118 (United States); Katiyar, Ram S. [Department of Physics and Institute of Functional Nanomaterials, University of Puerto Rico, San Juan, PR 00936 (United States)

2014-11-15

Rare-earth (Sm) and transition metal (Co) modified polycrystalline BiFeO{sub 3} (BFO) thin films have been deposited on Pt/TiO{sub 2}/SiO{sub 2}/Si substrate successfully through pulsed laser deposition (PLD) technique. Piezoelectric, leakage current and temperature dependent dielectric and magnetic behaviour were investigated for the films. Typical “butterfly-shaped” loop were observed in BSFCO films with an effective piezoelectric constant (d{sub 33}) ∼94 pm/V at 0.6 MV/cm. High dielectric constant ∼900 and low dielectric loss ∼0.25 were observed at room temperature. M–H loops have shown relatively high saturation magnetization ∼35 emu/cm{sup 3} at a maximum field of H ∼20 kOe. Enhanced magnetoelectric coupling response is observed under applied magnetic field. The multiferroic, piezoelectric, leakage current behaviours were explored. Such studies should be helpful in designing multiferroic materials based on BSFCO films. - Highlights: • Transition metal modified polycrystalline BiFeO{sub 3} thin films prepared using PLD. • High ME-coupling response was observed in co-substituted BiFeO{sub 3} thin films. • High magnetization ∼35 emu/cm{sup 3} at a maximum field of H ∼20 kOe. • Low leakage current might be due to co-substitution in BiFeO{sub 3} thin films. • A notable piezoelectric constant d{sub 33} ∼94 pm/V was found in BiFeO{sub 3} thin films.

Observations of Fabric Development in Polycrystalline Ice at Basal Pressures: Methods and Initial Results

Science.gov (United States)

Breton, D. J.; Baker, I.; Cole, D. M.

2012-12-01

Understanding and predicting the flow of polycrystalline ice is crucial to ice sheet modeling and paleoclimate reconstruction from ice cores. Ice flow rates depend strongly on the fabric (i.e. the distribution of grain sizes and crystallographic orientations) which evolves over time and enhances the flow rate in the direction of applied stress. The mechanisms for fabric evolution in ice have been extensively studied at atmospheric pressures, but little work has been done to observe these processes at the high pressures experienced deep within ice sheets where long-term changes in ice rheology are expected to have significance. We conducted compressive creep tests on a 917 kg m-3 polycrystalline ice specimen at 20 MPa hydrostatic pressure, thus simulating ~2,000 m depth. Initial specimen grain orientations were random, typical grain diameters were 1.2 mm, and the applied creep stress was 0.3 MPa. Subsequent microstructural analyses on the deformed specimen and a similarly prepared, undeformed specimen allowed characterization of crystal fabric evolution under pressure. Our microstructural analysis technique simultaneously collected grain shape and size data from Scanning Electron Microscope (SEM) micrographs and obtained crystallographic orientation data via Electron BackScatter Diffraction (EBSD). Combining these measurements allows rapid analysis of the ice fabric over large numbers of grains, yielding statistically useful numbers of grain size and full c- and a-axis grain orientation data. The combined creep and microstructural data demonstrate pressure-dependent effects on the mechanical and microstructural evolution of polycrystalline ice. We discuss possible mechanisms for the observed phenomena, and future directions for hydrostatic creep testing.

Development of sensor system for indoor location based service implementation

Energy Technology Data Exchange (ETDEWEB)

Cha, Joo Heon; Lee, Kyung Ho [Kookmin Univ., Seoul (Korea, Republic of)

2012-11-15

This paper introduces a sensor system based on indoor locations in order to implement the Building Energy Management System. This system consists of a thermopile sensor and an ultrasonic sensor. The sensor module is rotated by 360 .deg. and yawed up and down by two electric motors. Therefore, it can simultaneously detect the number and location of the inhabitants in the room. It uses wireless technology to communicate with the building manager or the smart home server, and it can save electric energy by controlling the lighting system or heating/air conditioning equipment automatically. We also demonstrate the usefulness of the proposed system by applying it to a real environment.

Development of sensor system for indoor location based service implementation

International Nuclear Information System (INIS)

Cha, Joo Heon; Lee, Kyung Ho

2012-01-01

This paper introduces a sensor system based on indoor locations in order to implement the Building Energy Management System. This system consists of a thermopile sensor and an ultrasonic sensor. The sensor module is rotated by 360 .deg. and yawed up and down by two electric motors. Therefore, it can simultaneously detect the number and location of the inhabitants in the room. It uses wireless technology to communicate with the building manager or the smart home server, and it can save electric energy by controlling the lighting system or heating/air conditioning equipment automatically. We also demonstrate the usefulness of the proposed system by applying it to a real environment

X-ray photoelectron spectroscopy study of CO2 reaction with polycrystalline uranium surface

International Nuclear Information System (INIS)

Liu Kezhao; Yu Yong; Zhou Juesheng; Wu Sheng; Wang Xiaolin; Fu Yibei

1999-10-01

The adsorption of CO 2 on 'clean' depleted polycrystalline uranium metal surface has been studied by X-ray photoelectron spectroscopy (XPS) at 300 K. The 'clean' surface were prepared by Ar + ion sputtering under ultra-high vacuum (UHV) condition with a base pressure 6.7 x 10 -8 Pa. The result s shows that adsorption of CO 2 on 'clean' uranium metal took place in total dissociation, and leads to the formation of uranium dioxide, uranium carbides and free carbon. The total dissociation of CO 2 produced carbon, oxygen species, CO 2 2- and CO 3 2- species. The diffusion tendency of carbon was much stronger than that of oxygen, and led to form a carbide in oxide-metal interface while the oxygen remained on their surface as an oxide

Recovery Act : Near-Single-Crystalline Photovoltaic Thin Films on Polycrystalline, Flexible Substrates

Energy Technology Data Exchange (ETDEWEB)

Venkat Selvamanickam; Alex Freundlich

2010-11-29

III-V photovoltaics have exhibited efficiencies above 40%, but have found only a limited use because of the high cost of single crystal substrates. At the other end of the spectrum, polycrystalline and amorphous thin film solar cells offer the advantage of low-cost fabrication, but have not yielded high efficiencies. Our program is based on single-crystalline-like thin film photovoltaics on polycrystalline substrates using biaxially-textured templates made by Ion Beam-Assisted Deposition (IBAD). MgO templates made by IBAD on flexible metal substrate have been successfully used for epitaxial growth of germanium films. In spite of a 4.5% lattice mismatch, heteroepitaxial growth of Ge was achieved on CeO2 that was grown on IBAD MgO template. Room temperature optical bandgap of the Ge films was identified at 0.67 eV indicating minimal residual strain. Refraction index and extinction coefficient values of the Ge films were found to match well with that measured from a reference Ge single crystal. GaAs has been successfully grown epitaxially on Ge on metal substrate by molecular beam epitaxy. RHEED patterns indicate self annihilation of antiphase boundaries and the growth of a single domain GaAs. The GaAs is found to exhibit strong photoluminescence signal and, an existence of a relatively narrow (FWHM~20 meV) band-edge excitons measured in this film indicates a good optoelectronic quality of deposited GaAs. While excellent epitaxial growth has been achieved in GaAs on flexible metal substrates, the defect density of the films as measured by High Resolution X-ray Diffraction and etch pit experiments showed a high value of 5 * 10^8 per cm^2. Cross sectional transmission electron microscopy of the multilayer architecture showed concentration of threading dislocations near the germanium-ceria interface. The defect density was found decrease as the Ge films were made thicker. The defects appear to originate from the MgO layer presumably because of large lattice mismatches

Solvent-free synthesis of nanosized hierarchical sodalite zeolite with a multi-hollow polycrystalline structure

KAUST Repository

Zeng, Shangjing

2016-08-03

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 is investigated by adding an organosilane surfactant as a mesopore-generating agent.

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

Laser-induced surface recrystallization of polycrystalline PbI2 thick films for X-ray detector application

Science.gov (United States)

Sun, Hui; Zhao, Beijun; Zhu, Xinghua; Zhu, Shifu; Yang, Dingyu; Wangyang, Peihua; Gao, Xiuyin

2018-01-01

In this work, laser-induced surface recrystallization process was developed to improve the surface properties and device performance of the polycrystalline PbI2 thick films prepared by using close space vapor deposition method. A continuous polycrystalline PbI2 recrystallized layer with a better mechanical strength and reflectivity improved from 2% to 4%-6% was obtained by this recrystallization process for the films with mechanical pretreatment. Other polytypes is absent in the recrystallized layer with the 2H-polytype remaining before and after treatment and obtaining improved electrical and X-ray photoelectric response performance. The pretreatment such as mechanical cutting/polishing and hydrogenation is necessary to lower the non-wetting crystallization behavior during the recrystallization process due to the rough surface state and oxygen contamination.

Investigation of the chlorine A-Center in polycrystalline CdTe layers by photoluminescence spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Kraft, Christian; Metzner, Heiner; Haedrich, Mathias [Institut fuer Festkoerperphysik, Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Schley, Pascal [Institut fuer Physik, Technische Universitaet Ilmenau, 98684 Ilmenau (Germany); Goldhahn, Ruediger [Institut fuer Experimentelle Physik, Universitaet Magdeburg, 39016 Magdeburg (Germany)

2012-07-01

Polycrystalline CdTe is a well known absorber material for thin film solar cells. However, the improvement of CdTe-based solar cells for industrial application is mainly based on empirical enhancements of certain process steps which are not concerning the absorber itself. Hence, the defect structure of CdTe is still not understood in detail. One of the most discussed defects in CdTe is the so called chlorine A-center. In general, the A-Center describes a defect complex of the intrinsic cadmium vacancy defect and an extrinsic impurity. By means of photoluminescence spectroscopy at temperatures of 5 K we investigated the behavior of the chlorine A-center under different CdTe activation techniques. Therefore, we were able to determine the electronic level of that defect and to analyze its influence on the crystal quality and the functionality of solar cells that were prepared of the corresponding samples.

Thermally-activated deformation in dispersion-hardened polycrystalline iron at room temperature

DEFF Research Database (Denmark)

Singh, Bachu Narain; Cotteril, P.

1970-01-01

The activation volume and dislocation velocity exponent have been obtained for polycrystalline iron in the extruded, extruded and annealed, and cold-rolled and annealed condition containing various amounts of alumina or zirconia particles, using the strain rate-change technique. It is found that ...... to the thermally activated flow stress contribution at room temperature. The dislocation velocity exponent also explains the yield-drop and Lüder's strain and is in a good agreement with Hahn's model....

A new and inexpensive pyranometer for the visible spectral range.

Science.gov (United States)

Martínez, Miguel A; Andújar, José M; Enrique, Juan M

2009-01-01

This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm), whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulation, cosine error minimisation and all this at a very low cost, tens of times lower than that of commercial thermopile-based devices. This new photodiode-based pyranometer overcomes traditional problems in this type of device and offers similar characteristics to those of thermopile-based pyranometers and, therefore, can be used in any installation where reliable measurement of solar irradiance is necessary, especially in those where cost is a deciding factor in the choice of a meter. This new pyranometer has been registered in the Spanish Patent and Trademark Office under the number P200703162.

A New and Inexpensive Pyranometer for the Visible Spectral Range

Directory of Open Access Journals (Sweden)

Miguel A. Martínez

2009-06-01

Full Text Available This paper presents the design, construction and testing of a new photodiode-based pyranometer for the visible spectral range (approx. 400 to 750 nm, whose principal characteristics are: accuracy, ease of connection, immunity to noise, remote programming and operation, interior temperature regulation, cosine error minimisation and all this at a very low cost, tens of times lower than that of commercial thermopile-based devices. This new photodiode-based pyranometer overcomes traditional problems in this type of device and offers similar characteristics to those of thermopile-based pyranometers and, therefore, can be used in any installation where reliable measurement of solar irradiance is necessary, especially in those where cost is a deciding factor in the choice of a meter. This new pyranometer has been registered in the Spanish Patent and Trademark Office under the number P200703162.

Evolutionary selection growth of two-dimensional materials on polycrystalline substrates

Science.gov (United States)

Vlassiouk, Ivan V.; Stehle, Yijing; Pudasaini, Pushpa Raj; Unocic, Raymond R.; Rack, Philip D.; Baddorf, Arthur P.; Ivanov, Ilia N.; Lavrik, Nickolay V.; List, Frederick; Gupta, Nitant; Bets, Ksenia V.; Yakobson, Boris I.; Smirnov, Sergei N.

2018-03-01

There is a demand for the manufacture of two-dimensional (2D) materials with high-quality single crystals of large size. Usually, epitaxial growth is considered the method of choice1 in preparing single-crystalline thin films, but it requires single-crystal substrates for deposition. Here we present a different approach and report the synthesis of single-crystal-like monolayer graphene films on polycrystalline substrates. The technological realization of the proposed method resembles the Czochralski process and is based on the evolutionary selection2 approach, which is now realized in 2D geometry. The method relies on `self-selection' of the fastest-growing domain orientation, which eventually overwhelms the slower-growing domains and yields a single-crystal continuous 2D film. Here we have used it to synthesize foot-long graphene films at rates up to 2.5 cm h-1 that possess the quality of a single crystal. We anticipate that the proposed approach could be readily adopted for the synthesis of other 2D materials and heterostructures.

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

Anisotropic etching of polycrystalline silicon with a hot Cl2 molecular beam

International Nuclear Information System (INIS)

Suzuki, K.; Hiraoka, S.; Nishimatsu, S.

1988-01-01

A hot Cl 2 molecular (Cl/sup */ 2 ) beam was successfully applied to achieve highly anisotropic, highly selective, and almost damage-free etching of polycrystalline Si. The anisotropy, the ratio of etch rates in vertical and horizontal directions, was larger than 25. The selectivity, the ratio of polycrystalline Si and SiO 2 etch rates, was larger than 1000. The Cl/sup */ 2 beam was produced by free jet expansion of a Cl 2 gas heated in a graphite furnace. The furnace temperature was 830 0 C. The substrate temperature was 180 0 C. The average total energy (0.38 eV) of a Cl/sup */ 2 molecule impinging on a substrate surface is much lower than the critical energy (approximately 10 eV) to displace the atoms of the etched material and to cause surface damage. This is the essential reason why this highly selective and almost damage-free etching has been achieved. The highly anisotropic etching mechanism is explained by a model taking into account the directional incidence of Cl/sup */ 2 molecules to the surface, and the deactivation process of the Cl/sup */ 2 molecules on a cold surface

Large-Scale PV Module Manufacturing Using Ultra-Thin Polycrystalline Silicon Solar Cells: Final Subcontract Report, 1 April 2002--28 February 2006

Energy Technology Data Exchange (ETDEWEB)

Wohlgemuth, J.; Narayanan, M.

2006-07-01

The major objectives of this program were to continue advances of BP Solar polycrystalline silicon manufacturing technology. The Program included work in the following areas. (1) Efforts in the casting area to increase ingot size, improve ingot material quality, and improve handling of silicon feedstock as it is loaded into the casting stations. (2) Developing wire saws to slice 100-..mu..m-thick silicon wafers on 290-..mu..m-centers. (3) Developing equipment for demounting and subsequent handling of very thin silicon wafers. (4) Developing cell processes using 100-..mu..m-thick silicon wafers that produce encapsulated cells with efficiencies of at least 15.4% at an overall yield exceeding 95%. (5) Expanding existing in-line manufacturing data reporting systems to provide active process control. (6) Establishing a 50-MW (annual nominal capacity) green-field Mega-plant factory model template based on this new thin polycrystalline silicon technology. (7) Facilitating an increase in the silicon feedstock industry's production capacity for lower-cost solar-grade silicon feedstock..

Comparison of the nonradiative deep levels in silicon solar cells made of monocrystalline, polycrystalline and amorphous silicon using deep level transient spectroscopy (DLTS)

International Nuclear Information System (INIS)

Hammadeh, H.; Darwich, R.

2005-03-01

The aim of this work is to study the defects in solar cells fabricated from crystalline, polycrystalline and amorphous silicon. Using Deep Level Transient Spectroscopy technique, (DLTS), we have determined their activation energies, concentrations and their effect on the solar cell efficiency. Our results show a DLTS peak in crystalline silicon which we could attribute to tow peaks originating from iron contamination. In the polycrystalline based solar cells we observed a series of non conventional DLTS peaks while in amorphous silicon we observed a peak using low measurement frequencies (between 8 kHz and 20 kHz). We studied these defects and determined their activation energies as well as the capture cross section for one of them. We suggest a possible configuration of these defects. We cannot able to study the effect of these defects on the solar cell efficiency because we have not the experimental set-up which measure the solar cell efficiency. (Authors)

Time-resolved x-ray diffraction techniques for bulk polycrystalline materials under dynamic loading

Energy Technology Data Exchange (ETDEWEB)

Lambert, P. K.; Hustedt, C. J.; Zhao, M.; Ananiadis, A. G.; Hufnagel, T. C. [Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Vecchio, K. S. [Department of NanoEngineering, University of California San Diego, La Jolla, California 92093 (United States); Huskins, E. L. [Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37830 (United States); US Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, Maryland 21005 (United States); Casem, D. T. [US Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, Maryland 21005 (United States); Gruner, S. M. [Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853 (United States); Kavli Institute at Cornell for Nanoscale Science, Cornell University, Ithaca, New York 14853 (United States); Tate, M. W.; Philipp, H. T.; Purohit, P.; Weiss, J. T. [Department of Physics, Cornell University, Ithaca, New York 14853 (United States); Woll, A. R. [Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853 (United States); Kannan, V.; Ramesh, K. T. [Department of Mechanical Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Kenesei, P.; Okasinski, J. S.; Almer, J. [X-ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2014-09-15

We have developed two techniques for time-resolved x-ray diffraction from bulk polycrystalline materials during dynamic loading. In the first technique, we synchronize a fast detector with loading of samples at strain rates of ∼10{sup 3}–10{sup 4} s{sup −1} in a compression Kolsky bar (split Hopkinson pressure bar) apparatus to obtain in situ diffraction patterns with exposures as short as 70 ns. This approach employs moderate x-ray energies (10–20 keV) and is well suited to weakly absorbing materials such as magnesium alloys. The second technique is useful for more strongly absorbing materials, and uses high-energy x-rays (86 keV) and a fast shutter synchronized with the Kolsky bar to produce short (∼40 μs) pulses timed with the arrival of the strain pulse at the specimen, recording the diffraction pattern on a large-format amorphous silicon detector. For both techniques we present sample data demonstrating the ability of these techniques to characterize elastic strains and polycrystalline texture as a function of time during high-rate deformation.

Cyclic voltammetric response of nicotinic acid and nicotinamide on a polycrystalline gold electrode

International Nuclear Information System (INIS)

Wang Xiaoxia; Yang Nianjun; Wan Qijin

2006-01-01

The oxidation of nicotinic acid and nicotinamide on a polycrystalline gold electrode occurred at almost same potentials but their reduction did at different peak potentials. The redox reaction mechanisms of nicotinic acid and nicotinamide were rationalized by the formation/disappearance of the new nitrogen-oxygen bonds in the pyridine rings by means of cyclic voltammetry and bulk electrolysis. The anodic currents of nicotinic acid and nicotinamide were controlled by diffusion, while the cathodic ones by adsorption. The difference in the cathodic peak potentials of nicotinic acid and nicotinamide on the polycrystalline gold electrode is attributed to the effect of the electron densities of remote substituents on the pyridine rings. The cathodic peak currents at about 0.20 V were linear with their concentrations in the range of 2.4 mM to 2.7 μM and 2.4 mM to 3.3 μM with detection limits of 0.27 and 0.33 μM for nicotinic acid and nicotinamide, respectively. Voltammetry was then adopted for the selective monitoring the content of nicotinic acid and nicotinamide in pharmaceuticals

Mechanical properties of polycrystalline RuSr2GdCu2O8 superconductor

International Nuclear Information System (INIS)

Brum Leite Gusmao Pinheiro, Lincoln; Serbena, Francisco Carlos; Foerster, Carlos Eugenio; Rodrigues, Pedro Junior; Jurelo, Alcione Roberto; Chinelatto, Adilson Luiz; Junior, Jorge Luiz Pimentel

2011-01-01

Research highlights: → Hardness and elastic modulus of Ru-1212 phase measured by instrumented indentation are reported. → Polycrystalline samples were produced by a solid state reaction technique. → Samples were also characterized by SEM, XRD and electrical resistivity measurements. → Hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. → These values are comparable with those of Y-123. - Abstract: The main objective of this paper is to report the room temperature hardness and elastic modulus of the RuSr 2 GdCu 2 O 8 superconductor phase by instrumented indentation. Polycrystalline samples were produced by a solid state reaction technique. The samples were also characterized by scanning electron microscopy, X-ray diffraction and electrical resistivity measurements. The influence of porosity on the mechanical properties was avoided by considering only those indentations inside the grains. The hardness and elastic modulus were 8.6 GPa and 145 GPa, respectively. These values are comparable with those of Y-123. The indentation fracture toughness evaluated after conventional Vickers indentation was 1.9 MPa m 1/2 .

Fast polycrystalline CdTe detectors for bunch-by-bunch luminosity monitoring in the LHC

CERN Document Server

Brambilla, A; Jolliot, M; Bravin, E

2008-01-01

The luminosity at the four interaction points of the Large Hadron Collider (LHC) must be continuously monitored in order to provide an adequate tool for the control and optimisation of beam parameters. Polycrystalline cadmium telluride (CdTe) detectors have previously been tested, showing their high potential to fulfil the requirements of luminosity measurement in the severe environment of the LHC interaction regions. Further, the large signal yield and the fast response time should allow bunch-by-bunch measurement of the luminosity at 40 MHz with high accuracy. Four luminosity monitors with two rows of five polycrystalline CdTe detectors each have been fabricated and will be installed at both sides of the low-luminosity interaction points ALICE and LHC-b. A detector housing was specially designed to meet the mechanical constraints in the LHC. A series of elementary CdTe detectors were fabricated and tested, of which 40 were selected for the luminosity monitors. A sensitivity of 104 electrons per minimum ioni...

Magnetoresistance and anomalous Hall effect of reactive sputtered polycrystalline Ti1 - XCrxN films

KAUST Repository

Duan, Xiaofei

2013-09-01

The reactive-sputtered polycrystalline Ti1 - xCrxN films with 0.17 ≤ x ≤ 0.51 are ferromagnetic and at x = 0.47 the Curie temperature TC shows a maximum of ~ 120 K. The films are metallic at 0 ≤ x ≤ 0.47, while the films with x = 0.51 and 0.78 are semiconducting-like. The upturn of resistivity below 70 K observed in the films with 0.10 ≤ x ≤ 0.47 is from the effects of the electron-electron interaction and weak localization. The negative magnetoresistance (MR) of the films with 0.10 ≤ x ≤ 0.51 is dominated by the double-exchange interaction, while at x = 0.78, MR is related to the localized magnetic moment scattering at the grain boundaries. The scaling ρxyA/n ∝ ρxx2.19 suggests that the anomalous Hall effect in the polycrystalline Ti1 - xCrxN films is scattering-independent. © 2013 Elsevier B.V. All rights reserved.

Experimental study of stress-induced localized transformation plastic zones in tetragonal zirconia polycrystalline ceramics

International Nuclear Information System (INIS)

Sun, Q.; Zhao, Z.; Chen, W.; Qing, X.; Xu, X.; Dai, F.

1994-01-01

Stress-induced martensitic transformation plastic zones in ceria-stabilized tetragonal zirconia polycrystalline ceramics (Ce-TZP), under loading conditions of uniaxial tension, compression, and three-point bending, are studied by experiments. The transformed monoclinic phase volume fraction distribution and the corresponding plastic strain distribution and the surface morphology (surface uplift) are measured by means of moire interferometry, Raman microprobe spectroscopy, and the surface measurement system. The experimental results from the above three kinds of specimens and methods consistently show that the stress-induced transformation at room temperature of the above specimen is not uniform within the transformation zone and that the plastic deformation is concentrated in some narrow band; i.e., macroscopic plastic flow localization proceeds during the initial stage of plastic deformation. Flow localization phenomena are all observed in uniaxial tension, compression, and three-point bending specimens. Some implications of the flow localization to the constitutive modeling and toughening of transforming thermoelastic polycrystalline ceramics are explored

Comparison of the top-down and bottom-up approach to fabricate nanowire-based Silicon/Germanium heterostructures

International Nuclear Information System (INIS)

Wolfsteller, A.; Geyer, N.; Nguyen-Duc, T.-K.; Das Kanungo, P.; Zakharov, N.D.; Reiche, M.; Erfurth, W.; Blumtritt, H.; Werner, P.; Goesele, U.

2010-01-01

Silicon nanowires (NWs) and vertical nanowire-based Si/Ge heterostructures are expected to be building blocks for future devices, e.g. field-effect transistors or thermoelectric elements. In principle two approaches can be applied to synthesise these NWs: the 'bottom-up' and the 'top-down' approach. The most common method for the former is the vapour-liquid-solid (VLS) mechanism which can also be applied to grow NWs by molecular beam epitaxy (MBE). Although MBE allows a precise growth control under highly reproducible conditions, the general nature of the growth process via a eutectic droplet prevents the synthesis of heterostructures with sharp interfaces and high Ge concentrations. We compare the VLS NW growth with two different top-down methods: The first is a combination of colloidal lithography and metal-assisted wet chemical etching, which is an inexpensive and fast method and results in large arrays of homogenous Si NWs with adjustable diameters down to 50 nm. The second top-down method combines the growth of Si/Ge superlattices by MBE with electron beam lithography and reactive ion etching. Again, large and homogeneous arrays of NWs were created, this time with a diameter of 40 nm and the Si/Ge superlattice inside.

Effect of high-temperature annealing on the microstructure and thermoelectric properties of GaP doped SiGe. M.S. Thesis

Science.gov (United States)

Draper, Susan L.

1987-01-01

Annealing of GaP doped SiGe will significantly alter the thermoelectric properties of the material resulting in increased performance as measured by the figure of merit Z and the power factor P. The microstructures and corresponding thermoelectric properties after annealing in the 1100 to 1300 C temperature range have been examined to correlate performance improvement with annealing history. The figure of merit and power factor were both improved by homogenizing the material and limiting the amount of cross-doping. Annealing at 1215 C for 100 hr resulted in the best combination of thermoelectric properties with a resultant figure of merit exceeding 1x10 to the -3 deg C to the -1 and a power factor of 44 microW/cm/deg C sq for the temperature range of interest for space power: 400 to 1000 C.

An integrated 12.5-Gb/s optoelectronic receiver with a silicon avalanche photodetector in standard SiGe BiCMOS technology.

Science.gov (United States)

Youn, Jin-Sung; Lee, Myung-Jae; Park, Kang-Yeob; Rücker, Holger; Choi, Woo-Young

2012-12-17

An optoelectronic integrated circuit (OEIC) receiver is realized with standard 0.25-μm SiGe BiCMOS technology for 850-nm optical interconnect applications. The OEIC receiver consists of a Si avalanche photodetector, a transimpedance amplifier with a DC-balanced buffer, a tunable equalizer, and a limiting amplifier. The fabricated OEIC receiver successfully detects 12.5-Gb/s 2(31)-1 pseudorandom bit sequence optical data with the bit-error rate less than 10(-12) at incident optical power of -7 dBm. The OEIC core has 1000 μm x 280 μm chip area, and consumes 59 mW from 2.5-V supply. To the best of our knowledge, this OEIC receiver achieves the highest data rate with the smallest sensitivity as well as the best power efficiency among integrated OEIC receivers fabricated with standard Si technology.

An All-Solid-State pH Sensor Employing Fluorine-Terminated Polycrystalline Boron-Doped Diamond as a pH-Insensitive Solution-Gate Field-Effect Transistor.

Science.gov (United States)

Shintani, Yukihiro; Kobayashi, Mikinori; Kawarada, Hiroshi

2017-05-05

A fluorine-terminated polycrystalline boron-doped diamond surface is successfully employed as a pH-insensitive SGFET (solution-gate field-effect transistor) for an all-solid-state pH sensor. The fluorinated polycrystalline boron-doped diamond (BDD) channel possesses a pH-insensitivity of less than 3mV/pH compared with a pH-sensitive oxygenated channel. With differential FET (field-effect transistor) sensing, a sensitivity of 27 mv/pH was obtained in the pH range of 2-10; therefore, it demonstrated excellent performance for an all-solid-state pH sensor with a pH-sensitive oxygen-terminated polycrystalline BDD SGFET and a platinum quasi-reference electrode, respectively.

'Observation' of dislocation motion in single crystal and polycrystalline aluminum during uniaxial deformation using photoemission technique

International Nuclear Information System (INIS)

Cai, M.; Levine, L.E.; Langford, S.C.; Dickinson, J.T.

2005-01-01

We report measurements of photostimulated electron emission (PSE) from single-crystalline aluminum (99.995%) and high-purity polycrystalline aluminum (>99.9%) during uniaxial tensile deformation. Photoelectron intensities are sensitive to changes in surface morphology accompanying deformation, including slip line and slip band formation. In the single crystalline material, the PSE intensity increases linearly with strain. In the polycrystalline material, the PSE intensity increases exponentially with strain. In both materials, time-resolved PSE measurements show step-like increases in intensity consistent with the heterogeneous nucleation and growth of slip bands during tensile deformation. In this sense, we have 'observed' dislocation motion by this technique. Slip bands on the surfaces of deformed samples were subsequently imaged by atomic-force microscopy (AFM). Photoelectron measurements can provide reliable, quantitative information for dislocation dynamics

Overcoming challenges to the formation of high-quality polycrystalline TiO{sub 2}:Ta transparent conducting films by magnetron sputtering

Energy Technology Data Exchange (ETDEWEB)

Neubert, M.; Cornelius, S.; Fiedler, J. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany); Gebel, T.; Liepack, H. [DTF Technology GmbH, 01108 Dresden (Germany); Kolitsch, A. [Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany); HZDR Innovation GmbH, 01328 Dresden (Germany); Vinnichenko, M. [Fraunhofer-Institut für Keramische Technologien und Systeme, 01277 Dresden (Germany)

2013-08-28

The work is focused on understanding the physical processes responsible for the modification of the structure, electrical and optical properties of polycrystalline TiO{sub 2}:Ta films formed by annealing of initially amorphous films grown by direct current magnetron sputtering of electrically conductive ceramic targets. It is shown that fine tuning of the oxygen content during deposition of amorphous TiO{sub 2}:Ta films is critical to achieving low resistivity and high optical transmittance after annealing. Increasing the total pressure during magnetron sputter deposition is shown to decrease the sensitivity of the annealed films to the oxygen flow variation during deposition of the initially amorphous layers. Polycrystalline anatase TiO{sub 2}:Ta films of low electrical resistivity (ρ{sub H} = 1.5 × 10{sup −3}Ω cm), high free electron mobility (μ{sub H} = 8 cm{sup 2}/Vs), and low extinction (k{sub 550nm} = 0.006) are obtained in this way at a total pressure of 2 Pa. The dependence of the polycrystalline film electrical properties on the oxygen content is discussed in terms of Ta dopant electrical activation/deactivation taking into account the formation of compensating defects at different oxygen pressures. The temperature-dependent transport of the polycrystalline anatase TiO{sub 2}:Ta films is investigated showing the dominant role of the optical phonon scattering in the case of films with an optimum Ti/O ratio.

Bi surfactant mediated growth for fabrication of Si/Ge nanostructures and investigation of Si/Ge intermixing by STM

Energy Technology Data Exchange (ETDEWEB)

Paul, N.

2007-10-26

In the thesis work presented here, we show that Bi is more promising surfactant material than Sb. We demonstrate that by using Bi as a terminating layer on Ge/Si surface, it is possible to distinguish between Si and Ge in Scanning tunnelling microscope (STM). Any attempt to utilize surfactant mediated growth must be preceded by a thorough study of its effect on the the system being investigated. Thus, the third chapter of this thesis deals with an extensive study of the Bi surfactant mediated growth of Ge on Si(111) surface as a function of Ge coverage. The growth is investigated from the single bilayer Ge coverage till the Ge coverage of about 15 BL when the further Ge deposition leads to two-dimensional growth. In the fourth chapter, the unique property of Bi terminating layer on Ge/Si surface to result in an STM height contrast between Si and Ge is explained with possible explanations given for the reason of this apparent height contrast. The controlled fabrication of Ge/Si nanostructures such as nanowires and nanorings is demonstrated. A study on Ge-Si diffusion in the surface layers by a direct method such as STM was impossible previously because of the similar electronic structure of Ge and Si. Since with the Bi terminating surface layer, one is able to distinguish between Ge and Si, the study of intermixing between them is also possible using STM. This method to distinguish between Si and Ge allows one to study intermixing on the nanoscale and to identify the fundamental diffusion processes giving rise to the intermixing. In Chapter 5 we discuss how this could prove useful especially as one could get a local probe over a very narrow Ge-Si interface. A new model is proposed to estimate change in the Ge concentration in the surface layer with time. The values of the activation energies of Ge/Si exchange and Si/Ge exchange are estimated by fitting the experimental data with the model. The Ge/Si intermixing has been studied on a surface having 1 ML Bi ({radical

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.

Carrier transport in polycrystalline silicon thin films solar cells grown on a highly textured structure

Czech Academy of Sciences Publication Activity Database

Honda, Shinya; Takakura, H.; Hamakawa, Y.; Muhida, R.; Kawamura, T.; Harano, T.; Toyama, T.; Okamoto, H.

2004-01-01

Roč. 43, 9A (2004), s. 5955-5959 ISSN 0021-4922 Institutional research plan: CEZ:AV0Z1010914 Keywords : polycrystalline silicon thin film * solar cells * substrate texture Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.142, year: 2004

Low-temperature internal friction in high-purity monocrystalline and impure polycrystalline niobium after plastic deformation

International Nuclear Information System (INIS)

Wasserbaech, W.; Thompson, E.

2001-01-01

The internal friction Q -1 of plastically deformed, high-purity monocrystalline and impure polycrystalline niobium specimens was measured in the temperature range between 65 mK and about 2 K. Plastic deformation has a pronounced effect on the internal friction Q -1 of the high-purity monocrystalline specimens, and the effect has been found to be almost temperature independent. By contrast, surprisingly, the internal friction Q -1 of the impure polycrystalline specimens was found to be almost independent of the extent of plastic deformation. Comparison of the experimental results with different models of a dynamic scattering of acoustic phonons by dislocations leads to the conclusion that the results cannot be explained with the two-level tunneling model. Instead it is suggested that a strong interaction between acoustic phonons and geometrical kinks in non-screw dislocations is responsible for the observed internal friction Q -1 . (orig.)

Passivation of defects in polycrystalline Cu2O thin films by hydrogen or cyanide treatment

International Nuclear Information System (INIS)

Ishizuka, S.; Kato, S.; Okamoto, Y.; Sakurai, T.; Akimoto, K.; Fujiwara, N.; Kobayashi, H.

2003-01-01

The effects of the passivation of defects in polycrystalline nitrogen-doped cuprous oxide (Cu 2 O) thin films with hydrogen or cyanide treatment were studied. In the photoluminescence (PL) measurements, although the emission was not observed before treatment, luminescence of Cu 2 O at around 680 nm was observed after each treatment. This improvement in the luminescence property may be due to the passivation of non-radiative recombination centers by H or CN. The hole carrier concentration increased from the order of 10 16 to 10 17 cm -3 with hydrogen or cyanide treatment. From these results, both the hydrogen and cyanide treatments were found to be very effective to passivate defects and improve the optical and electrical properties of polycrystalline Cu 2 O thin films. The thermal stability of the passivation effects by the cyanide treatment is, however, superior to that by the hydrogen treatment

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).

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.

Fabrication of polycrystalline diamond refractive X-ray lens by femtosecond laser processing

Energy Technology Data Exchange (ETDEWEB)

Kononenko, T.V.; Ralchenko, V.G.; Ashkinazi, E.E.; Konov, V.I. [General Physics Institute of Russian Academy of Sciences, Moscow (Russian Federation); National Research Nuclear University ' ' MEPhI' ' , Moscow (Russian Federation); Polikarpov, M.; Ershov, P. [Immanuel Kant Baltic Federal University, Functional Nanomaterials, Kaliningrad (Russian Federation); Kuznetsov, S.; Yunkin, V. [Institute of Microelectronics Technology RAS, Chernogolovka, Moscow region (Russian Federation); Snigireva, I. [European Synchrotron Radiation Facility, Grenoble (France)

2016-03-15

X-ray planar compound refractive lenses were fabricated from a polycrystalline diamond plate grown by chemical vapor deposition, by precise through cutting with femtosecond laser pulses. The lens geometry and the surface morphology were investigated with optical and scanning electron microscopy, while the material structure modification was analyzed by Raman spectroscopy. The results of the preliminary lens test at 9.25-keV X-rays are presented. (orig.)