Download or read book Characterization of the Effect of Radiation Damage on the Thin Film Stress Behavior of Nanocrystalline 3C SiC written by Christopher Michael Hardiman and published by . This book was released on 2013 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Radiation Effects in Silicon Carbide written by A.A. Lebedev and published by Materials Research Forum LLC. This book was released on 2017 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book reviews the most interesting research concerning the radiation defects formed in 6H-, 4H-, and 3C-SiC under irradiation with electrons, neutrons, and some kinds of ions. The electrical parameters that make SiC a promising material for applications in modern electronics are discussed in detail. Specific features of the crystal structure of SiC are considered. It is shown that, when wide-bandgap semiconductors are studied, it is necessary to take into account the temperature dependence of the carrier removal rate, which is a standard parameter for determining the radiation hardness of semiconductors. The carrier removal rate values obtained by irradiation of various SiC polytypes with n- and p-type conductivity are analyzed in relation to the type and energy of the irradiating particles. The influence exerted by the energy of charged particles on how radiation defects are formed and conductivity is compensated in semiconductors under irradiation is analyzed. Furthermore, the possibility to produce controlled transformation of silicon carbide polytype is considered. The involvement of radiation defects in radiative and nonradiative recombination processes in SiC is analyzed. Data are also presented regarding the degradation of particular SiC electronic devices under the influence of radiation and a conclusion is made regarding the radiation resistance of SiC. Lastly, the radiation hardness of devices based on silicon and silicon carbide are compared.

Download or read book Electrical Characterization of Radiation Induced Defects in 3C SiC written by Matthew John Cabral and published by . This book was released on 2013 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Radiation Effects in Advanced Semiconductor Materials and Devices written by C. Claeys and published by Springer Science & Business Media. This book was released on 2002-08-21 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: This wide-ranging book summarizes the current knowledge of radiation defects in semiconductors, outlining the shortcomings of present experimental and modelling techniques and giving an outlook on future developments. It also provides information on the application of sensors in nuclear power plants.

Download or read book Radiation Damage in Nanocrystalline Iron written by Gregory Alan Vetterick and published by . This book was released on 2014 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is strong evidence that grain boundaries act as recombination sites for interstitials and vacancies in a polycrystalline material. The prevailing theory is that grain boundaries act to absorb freely mobile interstitials and vacancies as well as sub-microscopic defect clusters, thereby depleting the region adjacent to the grain boundary of sufficient point defects to produce visible defect structures (e.g. stacking fault tetrahedra, voids, and dislocation loops). This theory is the basis for the design of radiation tolerant materials engineered to remove the large non-equilibrium point defect concentration created in cascades under irradiation by high energy particles by introducing a large number of grain boundary sinks. This thesis presents direct experimental evidence for a number of mechanisms operating to remove radiation damage at grain boundaries by in-situ transmission electron microscopy of free standing nanocrystalline iron films. It was found that the size of dislocation loops found in irradiated iron decreases with smaller grain size until a minimum cluster size is reached (about 2-5nm). The number density of defect clusters appears less affected by the presence of a high number of grain boundary sinks, but does vary strongly with the sink strength of the particular boundaries. If a small grain is defined by grain boundaries are capable of producing a very strong denuded zone, the cluster density can be very small. Therefore, the magnitude of this effect is dependent on the grain boundary character well into the nanocrystalline grain size regime. This work also shows that, in addition to the ability of a grain boundary to absorb sub-microscopic defects, the mobility and absorption of microscopic defect structures (i.e. defect clusters and dislocation loops) at grain boundaries has a strong influence on the response of a material to irradiation. Using in-situ TEM we examined the behavior of these microscopic DCs in nanocrystalline iron. The one-dimensional loop hop of b=1/2111 DCs was found totransport DCs to close proximity to GBs where they could annihilate, suggesting a contribution to the long range flux of interstitials to GB sinks. This process had marked effects on the morphology of the irradiated microstructure in nanocrystalline iron, limiting the length of DC strings and reducing the coalescence of DCs into larger defect loops. Furthermore, the research presented in this thesis showed that when large dislocation loops are able to form they may just as easily be lost to grain boundaries: a process which enhances the effect that grain boundary sinks have on the microstructure of the irradiated material. In-situ TEM irradiations in nanocrystalline iron at temperatures from 50K to 773K show that as the temperature of the specimen is increased from cryogenic temperatures (e.g. 50K), the mobility of first b=1/2111 defect clusters, then b=1/2111 dislocation loops, and finally b=100 dislocation loops reaches sufficient levels to enable climb to grain boundaries resulting in absorption. In nanocrystalline materials with a high density of grain boundary sinks this activity results in a small downward shift in the transition temperature between a b=1/2111 dominated microstructure and one that consists primarily of b=100 dislocation loops. At 773K, the microstructure is largely free of any dislocation loops in nanocrystalline iron, a stark change from previous work in microcrystalline iron where the b=100 loops remain stable. The shift in the transition temperature agrees well with initial hypotheses in literature that the nature of the loops remaining in irradiated iron depends on the relative stabilities of the dislocation loops arising due to the elastic anisotropy of iron from thermal magnetic fluctuations, and the high mobility of b=1/2111 dislocation loops compared to b=100 dislocation loops. Using in-situ transmission electron microscopy, the activity of dislocation loops in nanocrystalline iron were directly observed and analyzed using orientation mapping. Bycomparing in-situ TEM results to molecular dynamics simulations, the process of absorption was elucidated for microscopic defect clusters, b=1/2111 dislocation loops, and b=100 dislocation loops.

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1998 with total page 920 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanical Characterization of Polycrystalline 3C Silicon Carbide Thin Films written by Sharvani Nagappa and published by . This book was released on 2007 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metals Abstracts written by and published by . This book was released on 1992 with total page 1516 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Growth and Characterization of Thin Film Nanocrystalline Silicon Materials and Solar Cells written by Solomon Nwabueze Agbo and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physics Briefs written by and published by . This book was released on 1993 with total page 1058 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Growth and Characterization of Silicon Carbide Thin Films and Nanowires written by Lunet Estefany Luna and published by . This book was released on 2016 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon carbide (SiC) based electronics and sensors hold promise for pushing past the limits of current technology to achieve small, durable devices that can function in high-temperature, high-voltage, corrosive, and biological environments. SiC is an ideal material for such conditions due to its high mechanical strength, excellent chemical stability, and its biocompatibility. Consequently, SiC thin films and nanowires have attracted interest in applications such as micro- and nano-electromechanical systems, biological sensors, field emission cathodes, and energy storage devices. In terms of high-temperature microdevices, maintaining low-resistance electrical contact between metal and SiC remains a challenge. Although SiC itself maintains structural and electrical stability at high temperatures, the metallization schemes on SiC can suffer from silicide formation and oxidation when exposed to air. The second chapter presents efforts to develop stable metallization schemes to SiC. A stack consisting of Ni-induced solid-state graphitization of SiC and an atomic layer deposited layer of alumina is shown to yield low contact resistivity of Pt/Ti to polycrystalline n-type 3C-SiC films that is stable in air at 450 oC for 500 hours. The subsequent chapters focus on the growth and structural characterization of SiC nanowires. In addition to its structural stability in harsh-environments, there is interest in controlling SiC crystal structure or polytype formation. Over 200 different polytypes have been reported for SiC, with the most common being 3C, 4H, and 2H. In terms of SiC nanowire growth, the 3C or cubic phase is the most prevalent. However, as the stacking fault energy for SiC is on the order of a few meV, it is common to have a high density of stacking faults within a given SiC crystal structure. Thus, to enable reliable performance of SiC nanowires, a growth method that can promote a specific polytype or reduce stacking faults is of importance. Ni-catalyzed chemical vapor deposition method is employed for the growth of the nanowires. The effects of substrate structure and quality as well as the various growth parameters such as temperature, pressure, and post-deposition annealing are investigated. Most significant has been the growth and characterization of vertically aligned hexagonal phase (or 4H-like) SiC nanowires grown on commercially available 4H-SiC (0001). The studies presented in this thesis tackle issues in SiC metallization and nanowire growth in efforts to expand the versatility of SiC as a material platform for novel devices.

Download or read book Radiation Effects in Interfaces and Thin Films written by Alexander Mairov and published by . This book was released on 2016 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the key approaches to developing materials with greater radiation damage resistance is to introduce a large fraction of internal interfaces. Interfaces act as sinks for recombination of radiation-induced defects and as sites for accumulation of helium bubbles, thereby diverting them away from grain boundaries, where they can induce embrittlement. The beneficial role of interfaces in mitigating radiation damage has been demonstrated in nanoscale multilayered structures and in nanograined materials. Another more common example is oxide dispersion strengthened (ODS) steels and nanostructured ferritic alloys (NFA) where a fine distribution of particles (clusters) of varying stoichiometries (e.g., Y2Ti2O7, Y2TiO5, Y2O3, TiO2 and Y-Ti-O non-stoichiometric oxides) not only confer high creep strength, but also high radiation damage tolerance due to the large area of metal/oxide interfaces. However, the efficacy of these interfaces to act as defect sinks depends on their compositional and physical stability under radiation. With this background, this work focused on the stability of interfaces between Ti, TiO2, and Y2O3 thin film deposited on Fe-12%Cr substrates after irradiation with 5MeV Ni+2 ions at various temperatures. TEM and STEM-EDS methods were used to understand the compositional changes at the interfaces. Additionally, accumulation of implanted helium at epitaxial and non-epitaxial Fe/Y2O3 interfaces was also studied. Finally, the study was extended to study irradiation effects (up to 150 dpa) in novel Al2O3 nanoceramic films with immediate potential applications as coatings for corrosion protection in the harsh high temperature environments of Gen IV reactors. This research is expected to have implications in the development of radiation damage tolerant nanostructured alloys for nuclear reactors while also expanding the scientific knowledge-base in the area of radiation stability of interfaces in solids and protective coatings.

Download or read book Radiation Damage in Nanostructured Metallic Films written by Kaiyuan Yu and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High energy neutron and charged particle radiation cause microstructural and mechanical degradation in structural metals and alloys, such as phase segregation, void swelling, embrittlement and creep. Radiation induced damages typically limit nuclear materials to a lifetime of about 40 years. Next generation nuclear reactors require materials that can sustain over 60 - 80 years. Therefore it is of great significance to explore new materials with better radiation resistance, to design metals with favorable microstructures and to investigate their response to radiation. The goals of this thesis are to study the radiation responses of several nanostructured metallic thin film systems, including Ag/Ni multilayers, nanotwinned Ag and nanocrystalline Fe. Such systems obtain high volume fraction of boundaries, which are considered sinks to radiation induced defects. From the viewpoint of nanomechanics, it is of interest to investigate the plastic deformation mechanisms of nanostructured films, which typically show strong size dependence. By controlling the feature size (layer thickness, twin spacing and grain size), it is applicable to picture a deformation mechanism map which also provides prerequisite information for subsequent radiation hardening study. And from the viewpoint of radiation effects, it is of interest to explore the fundamentals of radiation response, to examine the microstructural and mechanical variations of irradiated nanometals and to enrich the design database. More importantly, with the assistance of in situ techniques, it is appealing to examine the defect generation, evolution, annihilation, absorption and interaction with internal interfaces (layer interfaces, twin boundaries and grain boundaries). Moreover, well-designed nanostructures can also verify the speculation that radiation induced defect density and hardening show clear size dependence. The focus of this thesis lies in the radiation response of Ag/Ni multilayers and nanotwinned Ag subjected to charged particles. The radiation effects in irradiated nanograined Fe are also investigated for comparison. Radiation responses in these nanostructured metallic films suggest that immiscible incoherent Ag/Ni multilayers are more resistant to radiation in comparison to their monolithic counterparts. Their mechanical properties and radiation response show strong layer thickness dependence in terms of radiation hardening and defect density. Coherent twin boundaries can interact with stacking fault tetrahedral and remove them effectively. Twin boundaries can actively absorb radiation induced defects and defect clusters resulting in boundary migration. Size dependence is also found in nanograins where fewer defects exhibit in films with smaller grains. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149359

Download or read book Radiation Effects in Silicon Carbide SiC Micro Nanoelectromechanical Systems M NEMS written by Hailong Chen and published by . This book was released on 2020 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation is of great importance in both fundamental science (e.g., understanding black holes, exploring the time evolution and the origin of the universe) and technological applications (e.g., diagnosing and treating diseases in medicine, and producing electricity at nuclear plant). Among all the radiation studies, radiation in semiconductor materials attracts the most attention in the information era with numerous semiconductor devices operating in space and on earth. Although silicon (Si) still dominates the semiconductor industry, a number of wide bandgap (WBG) semiconductors have demonstrated advantages in harsh environment applications. Among them, silicon carbide (SiC), with a family of polytypes and excellent properties such as wide bandgap (2.3-3.2 eV), high displacement energies (20-35 eV), excellent elastic modulus (~200-700 GPa) and outstanding thermal conductivity (~500 W m-1K-1), has shown great potential for high temperature, high power, and radiation resistant applications. A quite large body of work has been performed during recent decades to understand the radiation effects in the SiC electronic devices, such as field effect transistors (FETs), bipolar junction transistors (BJTs), and diodes. Meantime, while micro/nanoelectromechanical systems (M/NEMS) have gained tremendous advancements and made great impact on many important applications including inertial sensing (e.g., gyroscopes, accelerators), radio-frequency (RF) signal processing and communication, radiation study in M/NEMS has been quite limited, especially for those based on beyond-Si materials. This dissertation makes an initial thrust toward investigating radiation effects in SiC M/NEMS. First, we develop an innovative 3D integrated MEMS platform, by exploiting a scheme consisting of an array of vertically stacked SiC thin diaphragms (and Si ones for comparison). This integrated design and configuration not only scientifically enables probing different radiation effects (with clear reference and control samples) in a 3D fashion, but also economically evades very expensive, repetitive tests on individual devices. Further, we demonstrate cantilever-shaped 3C-SiC multimode MEMS resonators for real-time detection of ultraviolet (UV) radiation. In parallel, we have also developed Si counterparts of the SiC devices to help elucidate how SiC behaves differently from Si for radiation sensing and detecting. Finally, we explore the displacement and ionizing irradiation effects in SiC NEMS switching devices to gain comprehensive and in-depth understanding of the science behind the radiation effects in nanoscale structures made of thin SiC on SiO2. The investigation of NEMS switches before, during, and after proton and X-ray irradiation reveals how energetic particles cause threshold voltage modification, due to the dislocation damage in SiC crystal and how ionizing effects may affect the performance of these nanoscale devices.

Download or read book Radiation Effects and Micromechanics of SiC written by and published by . This book was released on 1992 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The basic displacement damage process in SiC has been fully explored, and the mechanisms identified. Major modifications have been made to the theory of damage dosimetry in Fusion, Fission and Ion Simulation studies of Sic. For the first time, calculations of displacements per atoms in SiC can be made in any irradiation environment. Applications to irradiations in fusion first wall neutron spectra (ARIES and PROMETHEUS) as well as in fission spectra (HIFIR and FFTF) are given. Nucleation of helium-filled cavities in SiC was studied, using concepts of stability theory to determine the size of the critical nucleus under continuous generation of helium and displacement damage. It is predicted that a bimodal distribution of cavity sizes is likely to occur in heavily irradiated SiC. A study of the chemical compatibility of SiC composite structures with fusion reactor coolants at high-temperatures was undertaken. It was shown that SiC itself is chemically very stable in helium coolants in the temperature range 500--1000[degree]C. However, current fiber/matrix interfaces, such as C and BN are not. The fracture mechanics of high-temperature matrix cracks with bridging fibers is now in progress. A fundamentally unique approach to study the propagation and interaction of cracks in a composite was initiated. The main focus of our research during the following period will be : (1) Theory and experiments for the micro-mechanics of high-temperature failure; and (2) Analysis of radiation damage and microstructure evolution.

Download or read book X ray Double Crystal and X ray Topographic Characterization of 3C silicon Carbide Thin Films on Silicon Titanium Carbide 6H silicon Carbide and Aluminum Nitride sapphire Substrates written by Rajender Reddy Thokala and published by . This book was released on 1994 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Interfacial Radiation Damage Resistance in Oxide Thin Film Heterojunctions Atomic Perspective written by Michel Sassi and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Improving the understanding of radiation damage mechanisms at the nanoscale level is important for the development of advanced in-core sensors and robust oxide-based waste forms. In this study, a suite of atomic-scale experimental techniques, coupled with ab initio simulations, has been used to examine and characterize the evolution of radiation damage at the La2Ti2-xZrxO7 / SrTiO3 thin film heterojunctions after irradiation with 1 MeV Zr+ ions to simulate fission fragment damage. We probe the onset of amorphization at the nanoscale using aberration-corrected scanning transmission electron microscopy (STEM) and position-averaged convergent beam electron diffraction (PACBED), finding that the oxide interface exhibits markedly improved damage resistance, in contrast to the bulk of the film or substrate. A combination of energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) has been performed before and after irradiation to examine associated chemical and local electronic changes, and to identify the salient features mediating the interfacial enhanced damage response. Ab initio molecular dynamics simulations of bulk La2Ti2-xZrxO7 show that the accommodation of electronic-type damage (comprising half of the total damage energy of 1 MeV Zr+) can be related to the bandgap of the crystal, as well as the ability of the octahedral network to accommodate distortions. In addition, we present atomistic density functional theory calculations of the interface and discuss possible atomic-scale mechanisms for the observed radiation damage resistance. Our study indicates that the engineering of oxide interfaces may offer a means to tune both functional properties and damage resistance, with potential implications for device design in extreme environments.