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EBSD characterization of an ECAP deformed Nb single crystal

ZHU, Liang; SANDIM, Hugo R. Z.; SEEFELDT, Marc; VERLINDEN, Bert
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.22%
A niobium single crystal was subjected to equal channel angular pressing (ECAP) at room temperature after orienting the crystal such that [1 -1 -1] ayen ND, [0 1 -1] ayen ED, and [-2 -1 -1] ayen TD. Electron backscatter diffraction (EBSD) was used to characterize the microstructures both on the transverse and the longitudinal sections of the deformed sample. After one pass of ECAP the single crystal exhibits a group of homogeneously distributed large misorientation sheets and a well formed cell structure in the matrix. The traces of the large misorientation sheets match very well with the most favorably oriented slip plane and one of the slip directions is macroscopically aligned with the simple shear plane. The lattice rotation during deformation was quantitatively estimated through comparison of the orientations parallel to three macroscopic axes before and after deformation. An effort has been made to link the microstructure with the initial crystal orientation. Collinear slip systems are believed to be activated during deformation. The full constraints Taylor model was used to simulate the orientation evolution during ECAP. The result matched only partially with the experimental observation.

Influence of the sidewall crystal orientation, HfSiO nitridation and TiN metal gate thickness on n-MuGFETs under analog operation

RODRIGUES, M.; Galeti, Milene; Martino, Joao Antonio; COLLAERT, N.; SIMOEN, E.; CLAEYS, C.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.09%
This work characterizes the analog performance of SOI n-MuGFETs with HfSiO gate dielectric and TiN metal gate with respect to the influence of the high-k post-nitridation. TiN thickness and device rotation. A thinner TiN metal gate is found favorable for improved analog characteristics showing an increase in intrinsic voltage gain. The devices where the high-k material is subjected to a nitridation step indicated a degradation of the Early voltage (V(EA)) values which resulted in a lower voltage gain. The 45 degrees rotated devices have a smaller V(EA) than the standard ones when a HfSiO dielectric is used. However, the higher transconductance of these devices, due to the increased mobility in the (1 0 0) sidewall orientation, compensates this V(EA) degradation of the voltage gain, keeping it nearly equal to the voltage gain values of the standard devices. (C) 2011 Elsevier Ltd. All rights reserved.; CAPES; CNPq/FWO; FAPESP

Efeitos de Superfícies de Contorno na Orientação de Cristais Líquidos Liotrópicos; Boundary Surface Effects on the Liotropic Liquid Crystal Orientation

Bechtold, Ivan Helmuth
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/05/2000 PT
Relevância na Pesquisa
46.15%
Para uso em aplicações tecnológicas os cristais líquidos são geralmente confinados em em celas, onde a interação do cristal líquido com a superfície de contorno é de grande importância para o bom desempenho do dispositivo. Os cristais líquidos liotrópicos em particular, possuem propriedades físicas muito mais complexas que os termotrópicos, que não são conhecidas em sua totalidade. Dessa forma, desenvolvemos um estudo com o objetivo de investigar a influência da superfície na configuração de uma amostra de cristal líquido liotrópico. Utilizamos alguns tratamentos de superfície para alterar as condições de contorno e investigar a orientação induzida ao cristal líquido. Esses tratamentos alteram as propriedades físico-químicas das superfícies, tais como o caráter hidrofílico (utilizando lâminas de vidro) e hidrofóbico (utilizando lâminas de vidro recobertas com polímero). Outro tratamento empregado consiste no esfregamento dos substratos ao longo de uma direção preferencial que pode alterar a topografia das superfícies. Variamos a espessura da amostra para comparar os efeitos devido as interações da superfície em relação as interações entre as moléculas no volume. Efetuamos análise de textura da amostra de cristal líquido liotrópico após colocada nas celas fabricadas com os substratos tratados. Através de medidas de transmitância de um feixe de luz polarizada pela amostra...

Exterior orientation of CBERS-2B imagery using multi-feature control and orbital data

Marcato Junior, J.; Tommaselli, A. M G
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 219-225
ENG
Relevância na Pesquisa
46.08%
The major contribution of this paper relates to the practical advantages of combining Ground Control Points (GCPs), Ground Control Lines (GCLs) and orbital data to estimate the exterior orientation parameters of images collected by CBERS-2B (China-Brazil Earth Resources Satellite) HRC (High-resolution Camera) and CCD (High-resolution CCD Camera) sensors. Although the CBERS-2B is no longer operational, its images are still being used in Brazil, and the next generations of the CBERS satellite will have sensors with similar technical features, which motivates the study presented in this paper. The mathematical models that relate the object and image spaces are based on collinearity (for points) and coplanarity (for lines) conditions. These models were created in an in-house developed software package called TMS (Triangulation with Multiple Sensors) with multi-feature control (GCPs and GCLs). Experiments on a block of four CBERS-2B HRC images and on one CBERS-2B CCD image were performed using both models. It was observed that the combination of GCPs and GCLs provided better bundle block adjustment results than conventional bundle adjustment using only GCPs. The results also demonstrate the advantages of using primarily orbital data when the number of control entities is reduced. © 2013 International Society for Photogrammetry and Remote Sensing...

Further investigation of the initial fission-track length and geometry factor in apatite fission-track thermochronology

Soares, Cleber J.; Guedes, Sandro; Tello, Carlos A.; Lixandrão Filho, Arnaldo L.; Osório, Ana M.; Alencar, Igor; Dias, Airton N.C.; Hadler, Julio
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 1381-1392
ENG
Relevância na Pesquisa
36.17%
The external detector method (EDM) is a widely used technique in fission track thermochronology (FTT) in which two different minerals are concomitantly employed: spontaneous tracks are observed in apatite and induced ones in the muscovite external detector. They show intrinsic differences in detection and etching properties that should be taken into account. In this work, new geometry factor values, g, in apatite, were obtained by directly measuring the ρed/ρis ratios and independently determined [GQR]ed/is values through the measurement of projected lengths. Five mounts, two of which were large area prismatic sections and three samples composed of random-orientation pieces have been used to determine the g-values. A side effect of applying EDM is that the value of the initial confined induced fission track, L0, is not measured in routine analyses. The L 0-value is an important parameter to quantify with good confidence the degree of annealing of the spontaneous fission tracks in unknown-age samples, and is essential for accurate thermal history modeling. The impact of using arbitrary L0-values on the inference of sample thermal history is investigated and discussed. The measurement of the L0-value for each sample to be dated using an extra irradiated apatite mount is proposed. This extra mount can be also used for determining the g value as an extension of the ρed/ρis ratio method. Eight apatite samples from crystalline basement...

Effect of crystal orientation on defect production and optical activation of Er-implanted sapphire

Alves, E.; Silva, M.F.; Soares, J.C.; Monteiro, T.; Soares, J.; Santos, L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.01%
Defect production and optical activity of Er-implanted α-Al2O3 were studied as a function of implanted dose and crystal orientation. Erbium fluences in the range of 8×1013–4×1015 Er+/cm2 were implanted into single crystalline samples with either the m-axis or c-axis normal to the surface. The energy of the Er ions was 200 keV. We found that the number of displaced O atoms was about two times higher on samples with the c-axis normal to the surface compared to the m-samples. The annealing stages of the damage follow a similar behaviour for the m-axis and c-axis samples and the complete recovery occurs for temperatures above 1200°C. The reconstruction of the lattice is accompanied by a reduction in the intensity of the photoluminescence signal above 825°C. Since the amount of Er and its lattice site is maintained, it is concluded that the change on its surroundings was responsible for the decrease of optical activity.; Praxis XXI; C/CTM/12067/1998

Alignment of crystal orientations of the multi-domain photonic crystals in Parides sesostris wing scales

Yoshioka, S.; Fujita, H.; Kinoshita, S.; Matsuhana, B.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
Publicado em 06/03/2014 EN
Relevância na Pesquisa
36.2%
It is known that the wing scales of the emerald-patched cattleheart butterfly, Parides sesostris, contain gyroid-type photonic crystals, which produce a green structural colour. However, the photonic crystal is not a single crystal that spreads over the entire scale, but it is separated into many small domains with different crystal orientations. As a photonic crystal generally has band gaps at different frequencies depending on the direction of light propagation, it seems mysterious that the scale is observed to be uniformly green under an optical microscope despite the multi-domain structure. In this study, we have carefully investigated the structure of the wing scale and discovered that the crystal orientations of different domains are not perfectly random, but there is a preferred crystal orientation that is aligned along the surface normal of the scale. This finding suggests that there is an additional factor during the developmental process of the microstructure that regulates the crystal orientation.

Magnetite Crystal Orientation in Magnetosome Chains

Körnig, André; Winklhofer, Michael; Baumgartner, Jens; Gonzalez, Teresa Perez; Fratzl, Peter; Faivre, Damien
Fonte: BlackWell Publishing Ltd Publicador: BlackWell Publishing Ltd
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.09%
One-dimensional magnetic nanostructures have magnetic properties superior to non-organized materials due to strong uniaxial shape anisotropy. Magnetosome chains in magnetotactic bacteria represent a biological paradigm of such magnet, where magnetite crystals synthesized in organelles called magnetosomes are arranged into linear chains. Two-dimensional synchrotron X-ray diffraction (XRD) is applied to cells of magnetotactic bacteria that are pre-aligned with a magnetic field to determine the crystallographic orientation of magnetosomes relative to the chain axis. The obtained pole figure patterns reveal a [111] fiber texture along the chain direction for magnetospirilla strains MSR-1 and AMB-1, whereas a [100] fiber texture is measured for Desulfovibrio magneticus strain RS-1. The [100] axis appears energetically unfavorable because it represents a magnetic hard axis in magnetite, but can be turned into an effective easy axis by particle elongation along [100] for aspect ratios higher than 1.25, consistent with aspect ratios in RS-1 magnetosomes determined earlier. The pronounced fiber textures can be explained either by a strain-specific biological control on crystal orientation at the chain level or by physical alignment effects due to intra-chain magnetic interactions. In this case...

Structural integrity of enamel: experimental and modeling

Xie, Z.; Swain, M.; Hoffman, M.
Fonte: Inter Amer Assoc Dental Research Publicador: Inter Amer Assoc Dental Research
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
46.01%
Tooth enamel is the hardest tissue in the human body and is directly responsible for dental function. Due to its non-regenerative nature, enamel is unable to heal and repair itself biologically after damage. We hypothesized that with its unique microstructure, enamel possesses excellent resistance to contact-induced damage, regardless of loading direction. By combining instrumented indentation tests with microstructural analysis, we report that enamel can absorb indentation energy through shear deformation within its protein layers between apatite crystallites. Moreover, a near-isotropic inelastic response was observed when we analyzed indentation data in directions either perpendicular or parallel to the path of enamel prisms. An "effective" crystal orientation angle, 33 degrees -34 degrees, was derived for enamel microstructure, independent of the loading direction. These findings will help guide the design of the nanostructural architecture of dental restorative materials.; Z. Xie, M.V. Swain and M.J. Hoffman

Effect of microstructure upon elastic behaviour of human tooth enamel

Xie, Z.; Swain, M.; Swadener, G.; Munroe, P.; Hoffman, M.
Fonte: Elsevier Sci Ltd Publicador: Elsevier Sci Ltd
Tipo: Artigo de Revista Científica
Publicado em //2009 EN
Relevância na Pesquisa
46.01%
Tooth enamel is the stiffest tissue in the human body with a well-organized microstructure. Developmental diseases, such as enamel hypomineralisation, have been reported to cause marked reduction in the elastic modulus of enamel and consequently impair dental function. We produce evidence, using site-specific transmission electron microscopy (TEM), of difference in microstructure between sound and hypomineralised enamel. Built upon that, we develop a mechanical model to explore the relationship of the elastic modulus of the mineral-protein composite structure of enamel with the thickness of protein layers and the direction of mechanical loading. We conclude that when subject to complex mechanical loading conditions, sound enamel exhibits consistently high stiffness, which is essential for dental function. A marked decrease in stiffness of hypomineralised enamel is caused primarily by an increase in the thickness of protein layers between apatite crystals and to a lesser extent by an increase in the effective crystal orientation angle.; Z.-H. Xie, M.V. Swain, G. Swadener, P. Munroe, M. Hoffman

Electron paramagnetic resonance studies of molecular orientation and nuclear exchange in single crystals of morphine N-oxide.

Weerts, Gary Lee
Fonte: Monterey, California ; Naval Postgraduate School Publicador: Monterey, California ; Naval Postgraduate School
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
36.29%
Approved for public release; distribution unlimited.; Low temperature (-150°C) EPR spectra of the nitroxide generated photolytically in a single crystal of N-nitromorpholine are complicated by the presence of two magnetically distinct orientations of the N-0 bond within the crystal. As the temperature is raised, the spectra are further complicated by motional effects. Since at -150° the molecule is essentially frozen in the crystal lattice with respect to the time of the EPR interaction, and since the nitrogen coupling tensor is markedly anisotropic, the observed EPR spectrum varies widely as the orientation of the applied field changes. The anisotropy of the nitrogen coupling tensor made it possible to unequivocally determine the orientation of the crystal with respect to the applied magnetic field. A series of experimental spectra was then obtained for several combinations of crystal orientation and temperature.In addition, computer programs were developed which simulate low, intermediate, and high temperature EPR spectra. By using a combination of experimental spectra and these programs, it was possible to determine the angle between the two orientations of the N-0 bond in the crystal and also to determine the energy barrier to exchange.

Size effects in LiF plasticity: new insights into the lattice resistance contribution

Soler Arnedo, Rafael
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
36.27%
Previous studies on the mechanical response under compression of single-crystal micropillars suggest that the effect of sample size on the flow stress is material dependent. This investigation addresses the role of the intrinsic lattice resistance of the material on this dependency. In particular, the objective of this study is to ascertain whether different slip systems can be characterized individually using micro-compression and to see how size effects differ as a function of the bulk critical resolved shear stress of the operative slip system. For this, LiF was chosen as the model material as it presents a marked plastic anisotropy as a result of the large difference in the critical resolved shear stress between the “soft" {110}{110} and the “hard" {100}{110} active slip systems, and because their operative slip systems depend strongly on the micropillar crystallographic orientation. Plasticity in LiF was evaluated in terms of crystal orientation and slip system activation by means of crystal plasticity finite element simulations, focusing on the distinctive response of two micropillar crystallographic orientations, the [100]- and the [111]-orientation, where only the “soft" and the “hard" slip systems activate...

A Crystal Plasticity Model of Fatigue of Dissimilar Magnesium Alloy Bi-Crystals

Knight, SIMON
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
36.29%
A crystal plasticity finite element (CPFE) model was applied to the fatigue deformation of dissimilar Mg alloy bi-crystals. The mesoscopic stress-strain and microscopic slip and twinning behaviour of the model were first validated with experimental tension and compression data of pure Mg single crystals. High-cycle fatigue (HCF) simulations up to 1000 cycles were then used to systematically examine the effect of different textures on the cyclic deformation behavior of Mg AZ31-AZ80 bi-crystals at room-temperature. Fatigue behaviour was characterized in terms of the mesoscopic average stress-strain response and the evolution of the microscopic deformation (slip/twin activity). The model captures load asymmetry, cyclic hardening/softening and ratcheting. However, the model did not capture stress concentrations at the grain boundary (GB) for the grain shapes considered. Either basal slip or tensile twinning was activated for any given orientation. When the soft AZ31 grain is oriented for basal slip almost all the shear strain is contained in that grain and has approximately ten times more accumulated shear strain than the other orientations. The results reveal there is a strong effect from orientation combinations on the cyclic deformation wherein a “hard” orientation shields a “soft” orientation from strain. When the AZ80 grain is oriented for basal slip and the AZ31 grain is oriented for tensile twinning the bi-crystal is soft...

Laüe back-reflection method for crystallographic orientation of a martensitic Cu-Zn-Al single crystal of the monoclinic system

Zambrano,Uíslei Carlos; Blanco,Matildes; Barelli,Nilso; Benedetti,Assis Vicente; Fernández,Javier
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
Relevância na Pesquisa
46.22%
A martensitic single crystal Cu-23.95Zn-3.62(wt.%)Al alloy was obtained melting pure Cu, Zn and Al using Bridgman's method. The martensitic phase (monoclinic) can present up to 24 variants, and orienting the surface according to a certain plane is a very hard task. The single crystal was submitted to 8 tons of tension (stress) along the longitudinal direction to reduce the number of variants and facilitate the surface orientation according to the desired plane. This single crystal was oriented using the Laüe back-reflection method to give surfaces with the following oriented crystallographic planes: (010), (120) and (130). It was observed that the tension stress was applied along the [010] direction.

The evolution of machining-induced surface of single-crystal FCC copper via nanoindentation

Zhang, Lin; Huang, Hu; Zhao, Hongwei; Ma, Zhichao; Yang, Yihan; Hu, Xiaoli
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 04/05/2013 EN
Relevância na Pesquisa
36.21%
The physical properties of the machining-induced new surface depend on the performance of the initial defect surface and deformed layer in the subsurface of the bulk material. In this paper, three-dimensional molecular dynamics simulations of nanoindentation are preformed on the single-point diamond turning surface of single-crystal copper comparing with that of pristine single-crystal face-centered cubic copper. The simulation results indicate that the nucleation of dislocations in the nanoindentation test on the machining-induced surface and pristine single-crystal copper is different. The dislocation embryos are gradually developed from the sites of homogeneous random nucleation around the indenter in the pristine single-crystal specimen, while the dislocation embryos derived from the vacancy-related defects are distributed in the damage layer of the subsurface beneath the machining-induced surface. The results show that the hardness of the machining-induced surface is softer than that of pristine single-crystal copper. Then, the nanocutting simulations are performed along different crystal orientations on the same crystal surface. It is shown that the crystal orientation directly influences the dislocation formation and distribution of the machining-induced surface. The crystal orientation of nanocutting is further verified to affect both residual defect generations and their propagation directions which are important in assessing the change of mechanical properties...

Nanoconfinement induced crystal orientation and large piezoelectric coefficient in vertically aligned P(VDF-TrFE) nanotube array

Liew, Weng Heng; Mirshekarloo, Meysam Sharifzadeh; Chen, Shuting; Yao, Kui; Tay, Francis Eng Hock
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 12/05/2015 EN
Relevância na Pesquisa
46.2%
Vertically aligned piezoelectric P(VDF-TrFE) nanotube array comprising nanotubes embedded in anodized alumina membrane matrix without entanglement has been fabricated. It is found that the crystallographic polar axes of the P(VDF-TrFE) nanotubes are oriented along the nanotubes long axes. Such a desired crystal orientation is due to the kinetic selection mechanism for lamellae growth confined in the nanopores. The preferred crystal orientation in nanotubes leads to huge piezoelectric coefficients of the P(VDF-TrFE). The piezoelectric strain and voltage coefficients of P(VDF-TrFE) nanotube array are observed to be 1.97 and 3.40 times of those for conventional spin coated film. Such a significant performance enhancement is attributed to the well-controlled polarization orientation, the elimination of the substrate constraint, and the low dielectric constant of the nanotube array. The P(VDF-TrFE) nanotube array exhibiting the unique structure and outstanding piezoelectric performance is promising for wide applications, including various electrical devices and electromechanical sensors and transducers.

Crystal orientation and thickness dependence of superconductivity on tetragonal FeSe1-x thin films

Wang, M. J.; Luo, J. Y.; Huang, T. W.; Chang, H. H.; Chen, T. K.; Hsu, F. C.; Wu, C. T; Wu, P. M.; Chang, A. M.; Wu, M. K.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/04/2009
Relevância na Pesquisa
46.01%
Superconductivity was recently found in the simple tetragonal FeSe structure. Recent studies suggest that FeSe is unconventional, with the symmetry of the superconducting pairing state still under debate. To tackle these problems, clean single crystals and thin films are required. Here we report the fabrication of superconducting beta-phase FeSe1-x thin films on different substrates using a pulsed laser deposition (PLD) technique. Quite interestingly, the crystal orientation, and thus, superconductivity in these thin films is sensitive to the growth temperature. At 320C, films grow preferably along c-axis, but the onset of superconductivity depends on film thickness. At 500C, films grow along (101), with little thickness dependence. These results suggest that the low temperature structural deformation previously found is crucial to the superconductivity of this material.

Measurements of charge carrier mobilities and drift velocity saturation in bulk silicon of <111> and <100> crystal orientation at high electric fields

Becker, Julian; Fretwurst, Eckhart; Klanner, Robert
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.15%
The mobility of electrons and holes in silicon depends on many parameters. Two of them are the electric field and the temperature. It has been observed previously that the mobility in the transition region between ohmic transport and saturation velocities is a function of the orientation of the crystal lattice. This paper presents a new set of parameters for the mobility as function of temperature and electric field for <111> and <100> crystal orientation. These parameters are derived from time of flight measurements of drifting charge carriers in planar p^+nn^+ diodes in the temperature range between -30{\deg}C and 50{\deg}C and electric fields of 2x10^3 V/cm to 2x10^4 V/cm.; Comment: revised version after peer review

The Effect of Crystal Orientation on Thermal Shock-induced Fracture and Properties of Ion Implated Sapphire

Gurarie, V N; Otsuka, P H; Jamieson, David Norman; Williams, James; Conway, Martin
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.08%
Ion beam modification of thermal shock resistance of sapphire single crystals with various crystallographic faces is experimentally investigated. The temperature threshold of fracture is determined in both implanted and unimplanted crystals by measuring the fragment contraction on cooling from fracture temperature. Optical and SEM microscopy are used to analyse fracture morphology and thermal shock behaviour on the (0 0 0 1), (1 1̄ 0 2) and (1 1 2̄ 0) faces in sapphire crystals implanted with 70 keV Si- ions and then subjected to thermal stress testing using pulsed plasma. The most stable crystal faces in terms of stress resistance are established. Ion implantation is shown to reduce the temperature threshold of fracture for all faces tested. The (1 1̄ 0 2) face proved to be the most stable for both implanted and unimplanted crystals. The results are discussed on the basis of fracture mechanics principles and the implantation-induced crack nucleation process.

The influence of crystal orientation on surface passivation in multi-crystalline silicon

Sio, Hang Cheong (Kelvin); Phang, Sieu Pheng; Wan, Yimao; Liang, Wensheng; Trupke, T; Cao, Sheng; Hu, Dongli; Wan, Yuepeng; MacDonald, Daniel
Fonte: IEEE Publicador: IEEE
Tipo: Conference paper
Relevância na Pesquisa
46.01%
We present an approach to study the variation of the surface recombination velocity in multi-crystalline silicon wafers through photoluminescence imaging for thin, passivated and mirror polished wafers. The influence of crystal orientation on surface pass