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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Defect Complexes in Silicon: Electronic Structures and Positron

Hakala, Mikko 00 December 1900 (has links) (PDF)
No description available.

Point defects in selected B2 phases

Song, Flossie Li-Sheng. January 1982 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 136-142).

X-ray diffraction from point-like imperfection /

He, Baoping, January 1992 (has links)
Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 203-208). Also available via the Internet.

The effects of point defect structure on the flotation of lead sulphide

Funk, Robert Melvin, 1941- January 1965 (has links)
No description available.

Theory of defect interactions in metals

Thetford, Roger January 1989 (has links)
The static relaxation program DEVIL has been updated to use N-body Finnis-Sinclair potentials. Initial calculations of self-interstitial and monovacancy formation energies confirm that the modified program is working correctly. An extra repulsive pair potential (constructed to leave the original fitting unaltered) overcomes some deficiencies in the published Finnis-Sinclair potentials. The modified potentials are used to calculate interstitial energies and relaxations in the b.c.c. transition metals vanadium, niobium, tantalum, molybdenum and tungsten. Further adaptation enables DEVIL to model dislocations running parallel to any lattice vector. Periodic boundary conditions are applied in the direction of the dislocation line, giving an infinite straight dislocation. The energies per unit length of two different dislocations are compared with experiment. A study of migration of point defects in the perfect lattice provides information on the mobility of interstitials and vacancies. The possible reorientation of split dumbbell interstitials in a migration step comes under scrutiny. The total energy needed to form and migrate an interstitial is compared with that required for a vacancy. The interaction between point defects and dislocations is studied in detail. Binding energies for both sclf-intcrstitials and monovacancies at edge dislocations are calculated for the five metals mentioned above. Formation energies of the point defects in the neighbourhood of the edge dislocation are calculated for niobium, and the extent of the regions from which the defects are spontaneously absorbed are found. For split dumbbell interstilials, the size and shape of the absorption region depends on the orientation of the dumbbell. Migration of both interstitials and vacancies into the absorption zone is studied; the presence of the dislocation has a particularly dramatic effect on vacancy migration. The results on absorption zones are related to the dislocation sink strengths vital in radiation damage theory.

Atomic level diffusion mechanisms in silicon

De Souza, Maria Merlyne January 1993 (has links)
No description available.

Defects and dopants in carbon related materials

Pinto, Hugo Manuel January 2012 (has links)
This thesis presents theoretical studies of the optical and electronic properties of defects in diamond and of the mechanisms of doping graphene. The birefringence of the four petalled defect commonly observed in CVD diamond is explained by four linear arrays of dislocations along ⟨110⟩ directions with ⟨110⟩ Burgers vectors. Such an arrangement of dislocations reproduces the extension and the features of the birefringence patterns observed experimentally. Density functional theory via the AIMPRO code was used to study the electronic and optical properties of different nitrogen-related point defects in diamond. It was found that the zero-phonon luminescence line of the NV− defects can split in the presence of a surface or other NV− defects. Since VNH and VN2 are expected to have similar optical properties, the optical transi- tions for VN2 were used to correct the transitions for VNH calculated by local density approximation. The absorption band at 2.38 eV (520 nm) observed in CVD diamond is then attributed to an internal transition of VNH. The weak zero-phonon line and broad vibronic sidebands for VN− and VN−2 and its absence for VNH− is explained by the large structural change when the defect is excited. Finally, different mechanisms for doping graphene were considered. The calculations predict the electropositive metals, such as Ti and Cr, act as donors, while molecules with strong electron affinity, such as F4-TCNQ, act as acceptors in graphene. An unexpected mechanism of doping graphene was shown by Au which dopes bilayer graphene but not single layer. In the presence of water, electrochemical reactions on the graphene can also lead to p or n-type doping.

Chemical state and luminescence imaging of natural and synthetic diamond

Jones, Geraint Owen January 2011 (has links)
This thesis presents work undertaken using Synchrotron and Laboratory based techniques in parallel on the Chemical State and Luminescence Imaging of Natural and Synthetic Diamond. X-ray absorption spectroscopy (XAS) techniques have revealed information on the chemical structure and bonding within brown and variegated type Ia, IIa, CVD and high-pressure, high-temperature (HPHT) treated diamonds. XAS, Raman, X-ray Excited Optical Luminescence (XEOL) and Photoluminescence (PL) are some of the techniques that have been applied to characterise and investigate the cause of the brown colouration. The XAS measurements have been undertaken in imaging mode with the capabilities of correlating the luminescence image with the brown regions in partial luminescence yield (PLY) and total luminescence yield (TLY). OD-XAS spectrums have been obtained at non-brown and brown regions and have revealed a higher concentration of sp2-bonded carbon present at the brown sites. Raman spectroscopy utilized in imaging mode also supports this discovery.

Characterization of point defects in nonlinear optical materials

Chirila, Madalina M. January 2003 (has links)
Thesis (Ph. D.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xi, 125 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 121-125).

Evolution of point defect clusters during ion irradiation and thermal annealing

Fedorov, Alexander Valerievich, January 2000 (has links)
Thesis (doctoral)--Technische Universiteit Delft, 2000. / Includes bibliographical references (p. 123-130).

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