Physics

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Shiv Nadar University

Ion implantation is a promising route for doping quartz with luminescent impurity atoms and growing photoactive nanoparticles of them. The present work focuses on cathodoluminescence (CL) and epitaxy during or after Na, Rb, Cs, Ge, and Ba ion implantation as well as Rb/Ge double implantation in crystalline α-quartz, under the conditions of dynamic, chemical or laser epitaxy. In addition to the known intrinsic sub-bands in the CL spectra, which have been associated with specific defects in the silica matrix, very intense blue or violet bands were found. They are correlated with the implanted ion species and follow their thermal behaviour. The quantum efficiency and possible origins of the blue/violet CL emission for various ions and processing treatments will be discussed. The case of double Rb/Ge implantation appears to be very promising with respect to a combination of a high CL output and full chemical epitaxy. © 2006 Elsevier B.V. All rights reserved.

World University root node

(SoNS) School of Natural Sciences

Physica B: Condensed Matter

Luminescence and epitaxy of ion-implanted α-quartz

4H-SiC samples implanted with 1020 Al were annealed at various temperatures with a BN/AIN or graphite cap, and there morphological, structural, and electrical properties are compared. No blow holes were observed in either cap. Some Si out-diffuses through the graphite cap which results in a rougher surface and a structurally modified region near the surface. The BN/AlN cap annealed at 1800°C cannot be readily removed, whereas the graphite cap can be removed easily after any annealing temperature. The sheet resistances for both types of samples were about the same.

Materials Science Forum

Comparison of graphite and BN/AIN annealing caps for ion implanted SiC

2007 International Semiconductor Device Research Symposium, ISDRS

Evolution of annealed undoped single crystal ZnO surfaces and implications for Schottky barrier height

Physical Review Letters

Condensed Matter: Electronic Properties, etc.-Importance of Van Der Waals Interaction for Organic Molecule-Metal Junctions: Adsorption of Thiophene on Cu (110) as a Prototype

We report on the structural, electrical, and optical properties of 5% niobium doped TiO2 thin films grown on various substrates by pulsed laser deposition. The epitaxial anatase Nb: TiO2 film on LaAlO3 is shown to be an intrinsic transparent metal and its metallic property arises from Nb substitution into Ti site as evidenced by the Rutherford backscattering channeling result. In contrast, the rutile Nb: TiO2 thin films show insulating behaviors with 2-3 orders higher room temperature electrical resistivity and ∼30 times lower mobility. A blueshift in the optical absorption edge is observed in both phases, though of differing magnitude. © 2007 American Institute of Physics.

Fulltext

Journal of Applied Physics

Niobium doped TiO2: Intrinsic transparent metallic anatase versus highly resistive rutile phase

The structure and magnetism of ZnO-based solid solutions, dilute magnetic semiconductors, with nickel solute were obtained via a solvothermal method. Compared with previous methods for solid solution DMSs, our synthesis method was really facile and economical. The one-dimensional solid solution of Zn 1-xNixO nanostructures were grown in a alcoholic solution. Moreover, the percentage of doped nickel can be easily controlled. The X-ray diffraction, transmission electron micrograph and magnetization hysteresis loops of nickel-doped ZnO nanocrystals were presented to confirm that the nickel impurities are embedded inside the nanocrystal. {\textcopyright} 2007 Materials Research Society.

Materials Research Society Symposium Proceedings

Synthesis and characterization of nickel-doped ZnO nanocrystals

Physical Review B

Large-scale correlated calculations of linear optical absorption and low-lying excited states of polyacenes: Pariser-Parr-Pople Hamiltonian

In this work, we describe the homo- and hetero-epitaxial growth of hexagonal and cubic MgxZn1-xO thin films on lattice matched substrates of c-Al2O3, ZnO, MgO and SrTiO 3. The crystalline quality, composition and epitaxial nature of the alloy films are obtained by x-ray diffraction and Rutherford backscattering spectroscopy (RBS) techniques. The RBS channeling yields are in the range 3-8% for homoepitaxial and hetero-epitaxial thin films. The metal-semiconductor-metal and ultraviolet detectors were fabricated on hexagonal and cubic Mg xZn1-xO thin films and the leakage current and UV-visible rejection ratio are correlated with the epitaxial relationship between the film and substrates. © 2007 IOP Publishing Ltd.

Journal of Physics D: Applied Physics

Homo- and hetero-epitaxial growth of hexagonal and cubic Mg xZn1-x O alloy thin films by pulsed laser deposition technique

The authors performed a systematic study of the structural and electrical properties of Nb:Ti O2 thin films by varying the substrate temperature (TS) and oxygen partial pressure (P O2). Niobium is found to incorporate easily and substitutionally into titanium lattice site as indicated by its low activation energy. By increasing TS, the carrier concentration (n) increases in the same way that niobium substitution fraction (s) increases, and the mobility increases as the structural quality is improved. With increasing P O2, n decreases dramatically though s does not change considerably. This may indicate that a large number of p -type native defects form, which "kill" the electrons produced by the Nb donors. © 2007 American Institute of Physics.

Applied Physics Letters

Growth parameter-property phase diagram for pulsed laser deposited transparent oxide conductor anatase Nb:Ti O2

Physical Review-Section B-Condensed Matter

Electronic structure: Wide-band, narrow-band, and strongly correlated systems-Structural and electronic properties of Mg, Zn, and Cd from Hartree-Fock and density functional calculations including