Bandgap Materials (bandgap + material)

Distribution by Scientific Domains


Selected Abstracts


Proceedings of the E-MRS 2003 Fall Meeting , Symposia A and C

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004
Marek Godlewski
This volume contains the proceedings of Symposium A: Novel Wide Bandgap Materials for Optoelectronic and Electronic Applications and Symposium C: 5th International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology at the E-MRS 2003 Fall Meeting, organized by the European Materials Research Society for the first time in Warsaw, Poland, 15,19 September 2003. Symposium A reviewed recent progress in the studies of wide bandgap materials such as nitrides and ZnO, as well as in relevant experimental techniques, whereas Symposium C was devoted to the current trends in physics and technology of MBE and MOCVD. [source]


E-MRS 2003 Fall Meeting Symposium A: Novel Wide Bandgap Materials for Optoelectronic and Electronic Applications

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004
Marek Godlewski
No abstract is available for this article. [source]


UV emission on a Si substrate: Optical and structural properties of ,-CuCl on Si grown using liquid phase epitaxy techniques

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009
A. Cowley
Abstract Considerable research is being carried out in the area of wide band gap semiconductor materials for light emission in the 300,400 nm spectral range. Current materials being used for such devices are typically based on II,VI and III-nitride compounds and variants thereof. However, one of the major obstacles to the successful fabrication of III-N devices is lattice mismatch-induced high dislocation densities for epitaxially grown layers on non-native substrates. ,-CuCl is a direct bandgap material and an ionic wide bandgap I,VII semiconductor with a room temperature free exciton binding energy of ,190 meV (compared to ,25 meV and ,60 meV for GaN and ZnO, respectively) and has a band gap of 3.4 eV (, , 366 nm). The lattice constant of ,-CuCl (0.541 nm) is closely matched to that of Si (0.543 nm). This could, in principle, lead to the development of optoelectronic systems based on CuCl grown on Si. Research towards this end has successfully yielded polycrystalline ,-CuCl on Si(100) and Si(111) using vacuum-based deposition techniques [1]. We report on developments towards achieving single crystal growth of CuCl from solution via Liquid Phase Epitaxy (LPE) based techniques. Work is being carried out using alkali halide flux compounds to depress the liquidus temperature of the CuCl below its solid phase wurtzite-zincblende transition temperature (407 C [2]) for solution based epitaxy on Si substrates. Initial results show that the resulting KCl flux-driven deposition of CuCl onto the Si substrate has yielded superior photoluminescence (PL) and X-ray excited optical luminescence (XEOL) behavior relative to comparitively observed spectra for GaN or polycrystalline CuCl. This enhancement is believed to be caused by an interaction between the KCl and CuCl material subsequent to the deposition process, perhaps involving a reduction in Cl vacancy distributions in CuCl. This paper presents a detailed discussion of a CuCl LPE growth system as well as the characterization of deposited materials using X-ray diffraction (XRD), room temperature and low temperature PL, and XEOL. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Nanomorphology and Charge Generation in Bulk Heterojunctions Based on Low-Bandgap Dithiophene Polymers with Different Bridging Atoms

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2010
Mauro Morana
Abstract Carbon bridged (C-PCPDTBT) and silicon-bridged (Si-PCPDTBT) dithiophene donor,acceptor copolymers belong to a promising class of low bandgap materials. Their higher field-effect mobility, as high as 10,2,cm2 V,1,s,1 in pristine films, and their more balanced charge transport in blends with fullerenes make silicon-bridged materials better candidates for use in photovoltaic devices. Striking morphological changes are observed in polymer:fullerene bulk heterojunctions upon the substitution of the bridging atom. XRD investigation indicates increased ,,, stacking in Si-PCPDTBT compared to the carbon-bridged analogue. The fluorescence of this polymer and that of its counterpart C-PCPDTBT indicates that the higher photogeneration achieved in Si-PCPDTBT:fullerene films (with either [C60]PCBM or [C70]PCBM) can be correlated to the inactivation of a charge-transfer complex and to a favorable length of the donor,acceptor phase separation. TEM studies of Si-PCPDTBT:fullerene blended films suggest the formation of an interpenetrating network whose phase distribution is comparable to the one achieved in C-PCPDTBT:fullerene using 1,8-octanedithiol as an additive. In order to achieve a balanced hole and electron transport, Si-PCPDTBT requires a lower fullerene content (between 50 to 60,wt%) than C-PCPDTBT (more than 70,wt%). The Si-PCPDTBT:[C70]PCBM OBHJ solar cells deliver power conversion efficiencies of over 5%. [source]


Structure Determination in Colloidal Crystal Photonic Bandgap Structures

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2002
John Ballato
Structure/optical property relationships in photonic bandgap structures are evaluated by a novel combination of sample sectioning, microscopy, and image analysis. Disordered colloidal crystals of solution-derived, monosized SiO2 particles were sectioned by focused ion beam (FIB) milling and then imaged using field emission scanning electron microscopy (FE-SEM). Pair correlation and radial distribution functions of the particulate arrangement were generated directly from a binary color scale rendering of the FE-SEM images, therein defining the level of order or disorder in the structure. These experimentally obtained spatial correlation functions were used to compute the scattering spectral properties in an analogous, although inverse (i.e., solving the inverse scattering problem), method to that used in X-ray diffraction for structure determination. Using a first-order approximation to the scattering from a disordered structure, the bandwidth and midgap values for the colloidal crystal photonic bandgap materials were within 15% of those measured. This new methodology promises to provide a simple and direct approach for quantifying the structure/optical property relationships in ordered and disordered photonic crystals directly from standard microstructural imaging techniques. [source]


Proceedings of the E-MRS 2003 Fall Meeting , Symposia A and C

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2004
Marek Godlewski
This volume contains the proceedings of Symposium A: Novel Wide Bandgap Materials for Optoelectronic and Electronic Applications and Symposium C: 5th International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology at the E-MRS 2003 Fall Meeting, organized by the European Materials Research Society for the first time in Warsaw, Poland, 15,19 September 2003. Symposium A reviewed recent progress in the studies of wide bandgap materials such as nitrides and ZnO, as well as in relevant experimental techniques, whereas Symposium C was devoted to the current trends in physics and technology of MBE and MOCVD. [source]