scholarly journals Characterization of Structural Defects in (Cd,Zn)Te Crystals Grown by the Travelling Heater Method

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1402
Author(s):  
Jiaona Zou ◽  
Alex Fauler ◽  
Alexander S. Senchenkov ◽  
Nikolai N. Kolesnikov ◽  
Lutz Kirste ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Defect Formation ◽  
Growth Parameters ◽  
Structural Defects ◽  
Dislocation Slip ◽  
Growth Interface ◽  
Space Experiments ◽  
Compositional Uniformity ◽  
Resistivity Variation ◽  
High Degree

Structural defects and compositional uniformity remain the major problems affecting the performance of (Cd, Zn)Te (CZT) based detector devices. Understanding the mechanism of growth and defect formation is therefore fundamental to improving the crystal quality. In this frame, space experiments for the growth of CZT by the Travelling Heater Method (THM) under microgravity are scheduled. A detailed ground-based program was performed to determine experimental parameters and three CZT crystals were grown by the THM. The structural defects, compositional homogeneity and resistivity of these ground-based crystals were investigated. A ZnTe content variation was observed at the growth interface and a high degree of stress associated with extensive dislocation networks was induced, which propagated into the grown crystal region according to the birefringence and X-ray White Beam Topography (XWBT) results. By adjusting the growth parameters, the ZnTe variations and the resulting stress were efficiently reduced. In addition, it was revealed that large inclusions and grain boundaries can generate a high degree of stress, leading to the formation of dislocation slip bands and subgrain boundaries. The dominant defects, including grain boundaries, dislocation networks and cracks in the interior of crystals, led to the resistivity variation in the crystals. The bulk resistivity of the as-grown crystals ranged from 109 Ωcm to 1010 Ωcm.

scholarly journals Simultaneous X-ray radiography and diffraction topography imaging applied to silicon for defect analysis during melting and crystallization

2019 ◽  
Vol 52 (6) ◽  
pp. 1312-1320 ◽  
Author(s):  
Maike Becker ◽  
Gabrielle Regula ◽  
Guillaume Reinhart ◽  
Elodie Boller ◽  
Jean-Paul Valade ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Grain Boundaries ◽  
Growth Process ◽  
Defect Formation ◽  
Simultaneous Recording ◽  
European Synchrotron Radiation Facility ◽  
Crystal Defects ◽  
Structural Defects ◽  
X Ray

One of the key issues to be resolved to improve the performance of silicon solar cells is to reduce crystalline defect formation and propagation during the growth-process fabrication step. For this purpose, the generation of structural defects such as grain boundaries and dislocations in silicon must be understood and characterized. Here, in situ X-ray diffraction imaging, historically named topography, is combined with radiography imaging to analyse the development of crystal defects before, during and after crystallization. Two individual indirect detector systems are implemented to record simultaneously the crystal structure (topographs) and the solid–liquid morphology evolution (radiographs) at high temperature. This allows for a complete synchronization of the images and for an increased image acquisition rate compared with previous studies that used X-ray sensitive films to record the topographs. The experiments are performed with X-ray synchrotron radiation at beamline ID19 at the European Synchrotron Radiation Facility. In situ observations of the heating, melting, solidification and holding stages of silicon samples are presented, to demonstrate that with the upgraded setup detailed investigations of time-dependent phenomena are now possible. The motion of dislocations is recorded throughout the experiment, so that their interaction with grain boundaries and their multiplication through the activation of Frank–Read sources can be observed. Moreover, the capability to record with two camera-based detectors allows for the study of the relationship between strain distribution, twinning and nucleation events. In conclusion, the simultaneous recording of topographs and radiographs has great potential for further detailed investigations of the interaction and generation of grains and defects that influence the growth process and the final crystalline structure in silicon and other crystalline materials.

scholarly journals Effect of Crystallographic Orientation and Grain Boundaries on Martensitic Transformation and Superelastic Response of Oligocrystalline Fe–Mn–Al–Ni Shape Memory Alloys

2021 ◽  
Author(s):  
A. Bauer ◽  
M. Vollmer ◽  
T. Niendorf
Keyword(s):  
Martensitic Transformation ◽  
Grain Boundary ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Grain Boundaries ◽  
Tensile Tests ◽  
Image Correlation ◽  
Stress Concentrations ◽  
Grain Orientations ◽  
High Degree

AbstractIn situ tensile tests employing digital image correlation were conducted to study the martensitic transformation of oligocrystalline Fe–Mn–Al–Ni shape memory alloys in depth. The influence of different grain orientations, i.e., near-〈001〉 and near-〈101〉, as well as the influence of different grain boundary misorientations are in focus of the present work. The results reveal that the reversibility of the martensite strongly depends on the type of martensitic evolving, i.e., twinned or detwinned. Furthermore, it is shown that grain boundaries lead to stress concentrations and, thus, to formation of unfavored martensite variants. Moreover, some martensite plates seem to penetrate the grain boundaries resulting in a high degree of irreversibility in this area. However, after a stable microstructural configuration is established in direct vicinity of the grain boundary, the transformation begins inside the neighboring grains eventually leading to a sequential transformation of all grains involved.

Grain Boundary Structures and Properties in Polycrystalline Silicon

1981 ◽  
Vol 5 ◽  
Author(s):  
Y.S. Tsuo ◽  
J.B. Milstein ◽  
T. Surek
Keyword(s):  
Grain Boundaries ◽  
Polycrystalline Silicon ◽  
Physical Vapor Deposition ◽  
Growth Parameters ◽  
Defect Structures ◽  
Photovoltaic Properties ◽  
Structures And Properties ◽  
Silicon Materials ◽  
Silicon Sheet ◽  
Ribbon Growth

ABSTRACTThe method of preparation of polycrystalline silicon can have a strong influence on the types and distributions of grain boundaries, and thereby influence the electrical properties of devices made from such materials. Examples of methods employed in the preparation of polycrystalline silicon for solar cell applications include directional solidification (Czochralski pulling and various casting techniques), ribbon growth techniques (ribbon-to-ribbon, edgedefined film-fed growth, low-angle silicon sheet growth, edge supported pulling, silicon-on-ceramic), chemical and physical vapor deposition (CVD and PVD) on silicon and foreign substrates, recrystallization techniques (laser, electron beam), and others such as graphoepitaxy and electrodeposition. This paper reviews the important morphological features such as grain size and defect structures of the various polycrystalline silicon materials and the influence of growth parameters on these features. The effects of grain boundaries on the electrical and photovoltaic properties of various polycrystalline silicon materials will also be discussed.

scholarly journals Nonequilibrium evolution thermodynamic of poly- and two-components alloys affected by severe plastic deformation

2021 ◽  
Vol 2052 (1) ◽  
pp. 012026
Author(s):  
L Metlov ◽  
M Gordey
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
Kinetic Equations ◽  
Copper Matrix ◽  
Structural Defects ◽  
Two Component ◽  
Diffusion Phase ◽  
Qualitative Phase ◽  
And Diffusion

Abstract The nonequilibrium evolutionary thermodynamics approach is generalized to the case of alloys prone to structural martensitic and diffusion phase transitions in them. A system of kinetic equations is written out to describe the evolution of the density of structural defects, grain boundaries, dislocations and point defects, as well as for the order parameter in the processing of these alloys by the severe plastic deformation way. The approach is illustrated by the numerical experiments results on a specific example of two-component copper-based alloys. Kinetic curves of the evolution of the grain boundaries, dislocations and atoms dissolved in a copper matrix are obtained, qualitative phase diagrams are constructed.

Entropy of Nanostructures

2017 ◽  
pp. 600-614
Author(s):  
Ottorino Ori ◽  
Franco Cataldo ◽  
Mihai V. Putz
Keyword(s):  
Mechanical Properties ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Defect Formation ◽  
Vacancy Concentration ◽  
Structural Evolution ◽  
Point Of View ◽  
Structural Defects ◽  
Formation Mechanisms ◽  
Topological Invariants

Recent advances in graphene studies deal with the influence of structural defects on graphene chemical, electrical, magnetic and mechanical properties. Here the complex mechanisms leading to the formation of clusters of vacancies in 2D honeycomb HD lattices are described by a pure topological point of view, aiming to correlate the variation of specific topological invariants, sensible to vacancy concentration, to the structural evolution of the defective networks driven by the topo-thermodynamical Gibbs free energy. Interesting predictions on defect formation mechanisms add details on the topological mechanisms featured by the graphenic structures with defects. Future roles of bondonic particles in defective HD materials are also envisaged.

scholarly journals X-ray Based in Situ Investigation of Silicon Growth Mechanism Dynamics—Application to Grain and Defect Formation

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 555 ◽  
Author(s):  
Hadjer Ouaddah ◽  
Maike Becker ◽  
Thècle Riberi-Béridot ◽  
Maria Tsoutsouva ◽  
Vasiliki Stamelou ◽  
...  
Keyword(s):  
High Temperature ◽  
Defect Formation ◽  
Imaging Techniques ◽  
Original System ◽  
Bragg Diffraction ◽  
Grain Structure ◽  
Structural Defects ◽  
X Ray ◽  
In Situ Investigation

To control the final grain structure and the density of structural crystalline defects in silicon (Si) ingots is still a main issue for Si used in photovoltaic solar cells. It concerns both innovative and conventional fabrication processes. Due to the dynamic essence of the phenomena and to the coupling of mechanisms at different scales, the post-mortem study of the solidified ingots gives limited results. In the past years, we developed an original system named GaTSBI for Growth at high Temperature observed by Synchrotron Beam Imaging, to investigate in situ the mechanisms involved during solidification. X-ray radiography and X-ray Bragg diffraction imaging (topography) are combined and implemented together with the running of a high temperature (up to 2073 K) solidification furnace. The experiments are conducted at the European Synchrotron Radiation Facility (ESRF). Both imaging techniques provide in situ and real time information during growth on the morphology and kinetics of the solid/liquid (S/L) interface, as well as on the deformation of the crystal structure and on the dynamics of structural defects including dislocations. Essential features of twinning, grain nucleation, competition, strain building, and dislocations during Si solidification are characterized and allow a deeper understanding of the fundamental mechanisms of its growth.

scholarly journals Recrystallization processes, microstructure and crystallographic preferred orientation evolution in polycrystalline ice during high-temperature simple shear

2019 ◽  
Vol 13 (5) ◽  
pp. 1495-1511 ◽  
Author(s):  
Baptiste Journaux ◽  
Thomas Chauve ◽  
Maurine Montagnat ◽  
Andrea Tommasi ◽  
Fabrice Barou ◽  
...  
Keyword(s):  
High Temperature ◽  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Simple Shear ◽  
Shear Plane ◽  
Preferred Orientation ◽  
Dislocation Slip ◽  
Crystallographic Preferred Orientation ◽  
Polycrystalline Ice

Abstract. Torsion experiments were performed in polycrystalline ice at high temperature (0.97 Tm) to reproduce the simple shear kinematics that are believed to dominate in ice streams and at the base of fast-flowing glaciers. As clearly documented more than 30 years ago, under simple shear ice develops a two-maxima c axis crystallographic preferred orientation (CPO), which evolves rapidly into a single cluster CPO with a c axis perpendicular to the shear plane. Dynamic recrystallization mechanisms that occur in both laboratory conditions and naturally deformed ice are likely candidates to explain the observed CPO evolution. In this study, we use electron backscatter diffraction (EBSD) and automatic ice texture analyzer (AITA) to characterize the mechanisms accommodating deformation, the stress and strain heterogeneities that form under torsion of an initially isotropic polycrystalline ice sample at high temperature, and the role of dynamic recrystallization in accommodating these heterogeneities. These analyses highlight an interlocking microstructure, which results from heterogeneity-driven serrated grain boundary migration, and sub-grain boundaries composed of dislocations with a [c]-component Burgers vector, indicating that strong local stress heterogeneity develops, in particular, close to grain boundaries, even at high temperature and high finite shear strain. Based on these observations, we propose that nucleation by bulging, assisted by sub-grain boundary formation and followed by grain growth, is a very likely candidate to explain the progressive disappearance of the c axis CPO cluster at low angle to the shear plane and the stability of the one normal to it. We therefore strongly support the development of new polycrystal plasticity models limiting dislocation slip on non-basal slip systems and allowing for efficient accommodation of strain incompatibilities by an association of bulging and formation of sub-grain boundaries with a significant [c] component.

Structural Defects of Silicon Epitaxy and Epi/Substrate Interface Related to Improper In-Situ Surface Cleaning at Low Temperatures

1990 ◽  
Vol 202 ◽  
Author(s):  
Tri-Rung Yew ◽  
Rafael Reif
Keyword(s):  
Defect Formation ◽  
Chemical Vapor ◽  
Deposition Process ◽  
Surface Cleaning ◽  
Structural Defects ◽  
Plasma Cleaning ◽  
Substrate Interface ◽  
Silicon Epitaxy ◽  
Pressure Chemical

ABSTRACTThis paper investigates the defect formation at the epi/substrate interface and epitaxial layers due to an improper in–situ Ar or Ar/H2 plasma cleaning at 500–800 °C Deposition process was carried out immediately after the in–situ cleaning process by ultralow pressure chemical vapor deposition process (ULPCVD) from SiH4/H2. Characteristics of the defects and their relationship with damage or impurity contaminations at the interface are presented. Finally, an optimum cleaning condition which ensures high quality epitaxial growth is addressed.

Defect-induced vibrational response of multi-walled carbon nanotubes using resonance Raman spectroscopy

2005 ◽  
Vol 20 (12) ◽  
pp. 3368-3373 ◽  
Author(s):  
S.A. Curran ◽  
J.A. Talla ◽  
D. Zhang ◽  
D.L. Carroll
Keyword(s):  
Carbon Nanotubes ◽  
Raman Spectroscopy ◽  
Acid Treatment ◽  
Defect Formation ◽  
Double Resonance ◽  
Resonance Raman ◽  
The Body ◽  
Structural Defects ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

We systematically introduced defects onto the body of multi-walled carbon nanotubes through an acid treatment, and the evolution of these defects was examined by Raman spectroscopy using different excitation wavelengths. The D and D′ modes are most prominent and responsive to defect formation caused by acid treatment and exhibit dispersive behavior upon changing the excitation wavelengths as expected from the double resonance Raman (DRR) mechanism. Several weaker Raman resonances including D″ and L1 (L2) + D′ modes were also observed at the lower excitation wavelengths (633 and 785 nm). In addition, specific structural defects including the typical pentagon-heptagon structure (Stone–Wales defects) were identified by Raman spectroscopy. In a closer analysis we also observed Haeckelite structures, specifically Ag mode response in R5,7 and O5,6,7.

Sign in / Sign up

Export Citation Format

Share Document