Intergrain Variations of the Chemical and Electronic Surface Structure of Polycrystalline Cu(In,Ga)Se2 Thin-Film Solar Cell Absorbers
Abstract not provided
14 SOLAR ENERGY↗
SEARCH · Engineering Papers
Results for “Polycrystalline structure”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
PolyMicros: A Foundation Model for 3D Polycrystalline Materials Structure
Explore the source record for details and available documents.
Robertson, Andreas Euan [Sandia National Laborator↗
Field strength degradation in Si-SiO2-polycrystalline Si structures
Explore the source record for details and available documents.
Mattauch, R. J.↗
Modeling of Irradiation Hardening of Polycrystalline Materials
High energy particle irradiation of structural polycrystalline materials usually produces irradiation hardening and embrittlement. The development of predict capability for the influence of irradiation on mechanical behavior is very important in materials design for next generation reactors. In this work a multiscale approach was implemented to predict irradiation hardening of body centered cubic (bcc) alpha-iron. The effect of defect density, texture and grain boundary was investigated. In the microscale, dislocation dynamics models were used to predict the critical resolved shear stress from the evolution of local dislocation and defects. In the macroscale, a viscoplastic self-consistent model was applied to predict the irradiation hardening in samples with changes in texture and grain boundary. This multiscale modeling can guide performance evaluation of structural materials used in next generation nuclear reactors.
36 MATERIALS SCIENCE↗
Determining spectral response of the National Ignition Facility particle time of flight diagnostic to x rays
The Particle Time of Flight (PTOF) diagnostic is a chemical vapor deposition diamond detector used for measuring multiple nuclear bang times at the National Ignition Facility. Due to the non-trivial, polycrystalline structure of these detectors, individual characterization and measurement are required to interrogate the sensitivity and behavior of charge carriers. In this paper, a process is developed for determining the x-ray sensitivity of PTOF detectors and relating it to the intrinsic properties of the detector. We demonstrate that the diamond sample measured has a significant non-homogeneity in its properties, with the charge collection well described by a linear model ax + b, where a = 0.63 ± 0.16 V –1 mm –1 and b = 0.00 ± 0.04 V –1 . Finally, we also use this method to confirm an electron to hole mobility ratio of 1.5 ± 1.0 and an effective bandgap of 1.8 eV rather than the theoretical 5.5 eV, leading to a large sensitivity increase.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Methods of growing CdTe-based materials at high rates
Systems and methods for growing high-quality CdTe-based materials at high growth rates are provided. According to an aspect of the invention, a method includes depositing a first CdTe-based layer on a CdTe-based template at a rate of greater than 1 .mu.m/min. Each of the first CdTe-based layer and the CdTe-based template has a single-crystal structure and/or a large-grain polycrystalline structure. The depositing is performed by physical vapor deposition.
36 MATERIALS SCIENCE↗
Synthesis and electrochemical capacitance of long tungsten oxide nanorod arrays grown vertically on substrate
Highlights: ► Growth of long amorphous tungsten oxide nanorods on a substrate. ► Formation of single-crystalline tungsten oxide nanorods by a heat-treatment. ► High electrochemical pseudocapacitance of 2.8 mF cm{sup −2}. ► Excellent cyclability of psuedocapacitance up to 1000 cycles. -- Abstract: Long tungsten oxide nanorods are vertically grown on Al/W/Ti coated silicon substrates using a two-step anodization process. The first anodization of the Al film forms a mesh-like mask of anodic aluminum oxide, and the second anodization of the W film results in the formation of a buffer layer, a bottom nanorod, and a top nanorod of amorphous tungsten oxide. A pore-widening process prior to the second anodization leads to the enhancement of nanorod length above approximately 500 nm. After a heat-treatment, the tungsten oxide nanorods are crystallized to form a single crystalline structure while the buffer layer forms a polycrystalline structure. The crystalline tungsten oxide nanorods show a cyclic voltammogram retaining the quasi-rectangular shape of an electrochemically reversible faradaic redox reaction, i.e., a typical pseudocapacitive behavior. The maximum electrochemical capacitance per apparent surface area reaches approximately 2.8 mF cm{sup −2} at the voltage scan rate of 20 mV s{sup −1}, and the excellent cyclability of charge–discharge process is maintained up to 1000 cycles.
36 MATERIALS SCIENCE↗
Structure of Ultrathin Polycrystalline Iron Films Grown on SiO{sub 2}/Si(001)
The structure of polycrystalline Fe films grown on an oxidized Si(001) surface at room temperature has been studied by the technique of high-energy electron diffraction. It has been found that the grain orientation in the films depends of the amount of deposited iron. In Fe films less than 5 nm thick, grains have been found to be randomly oriented. Fe films more than 5 nm in thickness exhibit the (111) texture with an axis coinciding with the surface normal. The angular dispersion of the [111] direction in the Fe lattice from the surface normal is ±25°. It has been found that as the Fe films become thicker, the (111) texture changes to the (110) texture.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Electrical properties of silicon schottky diodes containing metal films of various compositions
Au{sub x}Ti{sub 100{sub -}} {sub x}/n-Si Schottky diodes are fabricated and studied; in addition, the electrical properties of diodes containing metal films with varying composition (x = 0, 14, 30, 38, 60, 80, and 100) are also studied. Using X-ray phase analysis, it is established that the film of Au{sub 38}Ti{sub 62} composition has the amorphous structure, while the remaining films Au{sub x}Ti{sub 100-x} possess the polycrystalline structure. The main parameters of the Schottky diodes are determined in relation to the composition and structure of the metal films. As a result, it is shown that the electrical properties of Au{sub x}Ti{sub 100-x}/n-Si Schottky diodes are related to variations in the composition and structure of metal films.
36 MATERIALS SCIENCE↗
A Hierarchical Upscaling Method for Predicting Strength of Materials under Thermal, Radiation and Mechanical loading - Irradiation Strengthening Mechanisms in Stainless Steels
Stainless steels based on Fe-Cr-Ni alloys are the most popular structural materials used in reactors. High energy particle irradiation of in this kind of polycrystalline structural materials usually produces irradiation hardening and embrittlement. The development of predictive capability for the influence of irradiation on mechanical behavior is very important in materials design for next-generation reactors. Irradiation hardening is related to structural information crossing different length scale, such as composition, dislocation, crystal orientation distribution and so on. To predict the effective hardening, the influence factors along different length scales should be considered. A multiscale approach was implemented in this work to predict irradiation hardening of iron based structural materials. Three length scales are involved in this multiscale model: nanometer, micrometer and millimeter. In the microscale, molecular dynamics (MD) was utilized to predict on the edge dislocation mobility in body centered cubic (bcc) Fe and its Ni and Cr alloys. On the mesoscale, dislocation dynamics (DD) models were used to predict the critical resolved shear stress from the evolution of local dislocation and defects. In the macroscale, a viscoplastic self-consistent (VPSC) model was applied to predict the irradiation hardening in samples with changes in texture. The effects of defect density and texture were investigated. Simulated evolution of yield strength with irradiation agrees well with the experimental data of irradiation strengthening of stainless steel 304L, 316L and T91. This multiscale model we developed in this project can provide a guidance tool in performance evaluation of structural materials for next-generation nuclear reactors. Combining with other tools developed in the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program, the models developed will have more impact in improving the reliability of current reactors and affordability of new reactors.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
A method for polycrystalline silicon delineation applicable to a double-diffused MOS transistor
Method is simple and eliminates requirement for unreliable special etchants. Structure is graded in resistivity to prevent punch-through and has very narrow channel length to increase frequency response. Contacts are on top to permit planar integrated circuit structure. Polycrystalline shield will prevent creation of inversion layer in isolated region.
Halsor, J. L.↗
Structural and optical properties of nano-structured CdS thin films prepared by chemical bath deposition
Cadmium sulfide (CdS) thin films have been deposited on conducting glass substrates by chemical bath deposition (CBD) technique. The effect of precursor concentration on the structural, morphological, compositional, and optical properties of the CdS films has been studied. Crystal structure of these CdS films is characterized by X-ray diffraction (XRD) and it reveals polycrystalline structure with mixture of cubic and wurtzite phases with grain size decreasing as precursor concentration is increased. Optical studies reveal that the CdS thin films have high transmittance in visible spectral region reaching 90% and the films possess direct optical band gap that decreases from 2.46 to 2.39 eV with decreasing bath concentration. Our study suggests that growth is nucleation controlled.
36 MATERIALS SCIENCE↗
Microstructural, nanomechanical, and microtribological properties of Pb thin films prepared by pulsed laser deposition and thermal evaporation techniques
In this work, the authors compare the morphological, structural, nanomechanical, and microtribological properties of Pb films deposited by thermal evaporation (TE) and pulsed laser deposition (PLD) techniques onto Si (111) substrates. Films were investigated by scanning electron microscopy, surface probe microscopy, and x-ray diffraction in θ-2θ geometry to determine their morphology, root-mean-square (RMS) roughness, and microstructure, respectively. TE films showed a percolated morphology with densely packed fibrous grains while PLD films had a granular morphology with a columnar and tightly packed structure in accordance with the zone growth model of Thornton. Moreover, PLD films presented a more polycrystalline structure with respect to TE films, with RMS roughness of 14 and 10 nm, respectively. Hardness and elastic modulus vary from 2.1 to 0.8 GPa and from 14 to 10 GPa for PLD and TE films, respectively. A reciprocal friction test has shown that PLD films have lower friction coefficient and wear rate than TE films. Our study has demonstrated for first time that, at the microscale, Pb films do not show the same simple lubricious properties measured at the macroscale.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Structural and magnetic characterization of as-prepared and annealed FeCoCu nanowire arrays in ordered anodic aluminum oxide templates
Herein, we report on the preparation, structure, and magnetic characterization of FeCoCu nanowire arrays grown by DC electrodeposition inside self-assembled ordered nanopores of anodic aluminum oxide templates. A systematic study of their structure has been performed both in as-prepared samples and after annealing in the temperature range up to 800 °C, although particular attention has been paid to annealing at 700 °C after which maximum magnetic hardening is achieved. The obtained nanowires have a diameter of 40 nm and their Fe{sub 0.28}Co{sub 0.67}Cu{sub 0.05} composition was confirmed by energy dispersive X-ray spectroscopy (EDS). Focused ion-beam lamellas of two samples (as-prepared and annealed at 700 °C) were prepared for their imaging in the high-resolution transmission electron microscopy (HRTEM) perpendicularly to the electron beam, where the obtained EDS compositional mappings show a homogeneous distribution of the elements. X-ray diffraction analysis, and selected area electron diffraction (SAED) patterns confirm that nanowires exhibit a bcc cubic structure (space group Im-3m). In addition, bright-dark field images show that the nanowires have a polycrystalline structure that remains essentially the same after annealing, but some modifications were observed: (i) an overall increase and sharpening of recrystallized grains, and (ii) an apparent shrinkage of the nanowires diameter. Obtained SAED patterns also show strong textured components with determined <111> and <112> crystalline directions parallel to the wires growth direction. The presence of both directions was also confirmed in the HRTEM images doing Fourier transform analyses. Magnetic measurements show strong magnetic anisotropy with magnetization easy axis parallel to the nanowires in as-prepared and annealed samples. The magnetic properties are tuned by suitable thermal treatments so that, maximum enhanced coercivity (∼2.7 kOe) and normalized remanence (∼0.91 Ms) values are achieved after annealing at temperature of 700 °C. The contribution of the changes in the crystalline structure, induced by the heat treatment, to the magnetic hardening of the FeCoCu nanowires is discussed.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Structural and growth aspects of electron beam physical vapor deposited NiO-CeO{sub 2} nanocomposite films
Deposition of composite materials as thin film by electron beam physical vapor deposition technique (EB-PVD) still remains as a challenge. Here, the authors report the deposition of NiO-CeO{sub 2} (30/70 wt. %) composites on quartz substrate by EB-PVD. Two NiO-CeO{sub 2} nanocomposite targets—one as green compact and the other after sintering at 1250 °C—were used for the deposition. Though the targets varied with respect to physical properties such as crystallite size (11–45 nm) and relative density (44% and 96%), the resultant thin films exhibited a mean crystallite size in the range of 20–25 nm underlining the role of physical nature of deposition. In spite of the crystalline nature of the targets and similar elemental concentration, a transformation from amorphous to crystalline structure was observed in thin films on using sintered target. Postannealing of the as deposited film at 800 °C resulted in a polycrystalline structure consisting of CeO{sub 2} and NiO. Deposition using pure CeO{sub 2} or NiO as target resulted in the preferential orientation toward (111) and (200) planes, respectively, showing the influence of adatoms on the evaporation and growth process of NiO-CeO{sub 2} composite. The results demonstrate the influence of electron beam gun power on the adatom energy for the growth process of composite oxide thin films.
36 MATERIALS SCIENCE↗
Effect of carbon content on solidification behaviors and morphological characteristics of the constituent phases in Cr-Fe-C alloys
A combination of transmission electron microscopy, electron backscatter diffraction and wavelength dispersive spectrum has been used to identify crystal structure, grain boundary characteristic and chemical composition of the constituent phases in Cr-Fe-C alloys with three different carbon concentrations. Depending on the three different carbon concentrations, the solidification structures are found to consist of primary {alpha}-phase and [{alpha} + (Cr,Fe){sub 23} C{sub 6}] eutectic in Cr-18.4Fe-2.3 C alloy; primary (Cr,Fe){sub 23} C{sub 6} and [{alpha} + (Cr,Fe){sub 23} C{sub 6}] eutectic in Cr-24.5Fe-3.8 C alloy and primary (Cr,Fe){sub 7} C{sub 3} and [{alpha} + (Cr,Fe){sub 7} C{sub 3}] eutectic in Cr-21.1Fe-5.9 C alloy, respectively. The grain boundary analysis is useful to understand growth mechanism of the primary phase. The morphologies of primary (Cr,Fe){sub 23} C{sub 6} and (Cr,Fe){sub 7} C{sub 3} carbides are faceted structures with polygonal shapes, different from primary {alpha}-phase with dendritic shape. The primary (Cr,Fe){sub 23} C{sub 6} and (Cr,Fe){sub 7} C{sub 3} carbides with strong texture exist a single crystal structure and contain a slight low angle boundary, resulting in the polygonal growth mechanism. Nevertheless, the primary {alpha}-phase with relative random orientation exhibits a polycrystalline structure and comprises a massive high-angle boundary, caused by the dendritic growth mechanism. - Highlights: Black-Right-Pointing-Pointer Microstructures of the as-clad Cr-based alloys are characterized by TEM. Black-Right-Pointing-Pointer EBSD technique has been use to characterize the grain boundary of primary phases. Black-Right-Pointing-Pointer We examine transitions in morphology about the primary phases. Black-Right-Pointing-Pointer Morphologies of primary carbides are polygonal different from primary {alpha}-phase. Black-Right-Pointing-Pointer Solidification structures rely on C concentrations in Cr-Fe-C alloy.
36 MATERIALS SCIENCE↗
Characterization of CuO/n–Si pn junction synthesized by successive ionic layer adsorption and reaction method
Transparent conducting Copper oxide CuO thin films were successfully synthesized on glass and n-type Silicon substrates by successive ionic layer adsorption and reaction method. The crystal structure, surface texture, optical and electrical properties were studied. The results revealed that the deposited CuO thin films at different cycles number (5, 10, 15), have polycrystalline structure nature with monoclinic phase, and the crystallite size increases with the increase of cycles number. The average roughness and the root mean square values increase with increasing cycles number. The optical energy band gap and Urbach energy was decrement from 2.33 eV and 1.2 eV for 5 cycles to 2.1 eV and 0.82 eV for 15 cycles. The electrical properties of Ni/CuO/n–Si pn junction were studied using current–voltage (I–V) measurements. The barrier heights (Φ{sub B}) of Ni/CuO/n–Si thin films were calculated and its values are (0.716, 0.736, 0.723) eV, for 5, 10 and 15 cycles respectively with an applied bias voltage of 3 V.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Study of Se and Cl segregation in poly-crystalline CdSeTe
CdTe based thin film solar cells have shown to be competitive in terms of efficiency and low cost, but the polycrystalline structure and low minority carrier lifetime constrain CdTe based devices from reaching the theoretical efficiency limit. In this work, the effect of Se and Cl segregation in polycrystalline CdSeTe photovoltaic devices was studied. We demonstrated using two-photon time-resolved photoluminescence (TRPL) that the Se alloyed CdSeTe absorber layer shows high minority carrier lifetime, and used density functional theory (DFT) calculations to explain the origin of such high lifetime.
cadmium compounds↗