166 research outputs found
Growth and formation of inverse GaP and InP opals
Opals consist of an ordered array of SiO2 spheres. This leads to a modulation of the refractive index and hence photonic stop bands behaviour over the visible/IR range of the electro-magnetic spectrum. The exact position of the stop bands depends on the size of the silica spheres. However, the refractive index contrast between the SiO2 spheres and air spaces is not great enough to open up a full photonic band gap (PBG), only the pseudogap. To increase the contrast the air spaces are filled with a material of high refractive index such as InP or GaP. To further increase the contrast the SiO2 is removed leaving a III-V framework as the inverse opal structure.
By use of MOCVD we have been able to infill opals with InP and GaP to such a level that has supported the inversion of the composite forming a structure of air holes within a III-V lattice. XRD and Raman confirmed the quality of the III-V infill, while the extent of the infill was studied by SEM and reflectance measurements
An evolutionary perspective on glutathione transferases inferred from class-theta glutathione transferase cDNA sequences
Large magnetoelectric coupling in nanoscale BiFeO from direct electrical measurements
We report the results of direct measurement of remanent hysteresis loops on
nanochains of BiFeO at room temperature under zero and 20 kOe
magnetic field. We noticed a suppression of remanent polarization by nearly
40\% under the magnetic field. The powder neutron diffraction data reveal
significant ion displacements under a magnetic field which seems to be the
origin of the suppression of polarization. The isolated nanoparticles,
comprising the chains, exhibit evolution of ferroelectric domains under dc
electric field and complete 180 switching in switching-spectroscopy
piezoresponse force microscopy. They also exhibit stronger ferromagnetism with
nearly an order of magnitude higher saturation magnetization than that of the
bulk sample. These results show that the nanoscale BiFeO exhibits
coexistence of ferroelectric and ferromagnetic order and a strong
magnetoelectric multiferroic coupling at room temperature comparable to what
some of the type-II multiferroics show at a very low temperature.Comment: 7 pages with 5 figures, published in Phys. Rev.
Energy barriers at interfaces between (100) InxGa1-xAs (0 <= x <= 0.53) and atomic-layer deposited Al2O3 and HfO2
The electron energy band alignment at interfaces of InxGa1-xAs (0 <= x <= 0.53) with atomic-layer deposited insulators Al2O3 and HfO2 is characterized using internal photoemission and photoconductivity experiments. The energy of the InxGa1-xAs valence band top is found to be only marginally influenced by the semiconductor composition. This result suggests that the known bandgap narrowing from 1.42 to 0.75 eV when the In content increases from 0 to 0.53 occurs mostly through downshift of the semiconductor conduction band bottom. It finds support from both electron and hole photoemission data. Similarly to the GaAs case, electron states originating from the interfacial oxidation of InxGa1-xAs lead to reduction in the electron barrier at the semiconductor/oxide interface. (C) 2009 American Institute of Physics. (DOI: 10.1063/1.3137187
Energy barriers at interfaces of (100)GaAs with atomic layer deposited Al2O3 and HfO2
Band alignment at the interfaces of (100)GaAs with Al2O3 and HfO2 grown using atomic layer deposition is determined using internal photoemission and photoconductivity measurements. Though the inferred conduction and valence band offsets for both insulators were found to be close to or larger than 2 eV, the interlayer grown by concomitant oxidation of GaAs reduces the barrier for electrons by approximately 1 eV. The latter may pose significant problems associated with electron injection from GaAs into the oxide. (C) 2008 American Institute of Physics. (DOI: 10.1063/1.3021374
Human glutathione S-transferase theta (GSTT1): cDNA cloning and the characterization of a genetic polymorphism
Polymorphisms of cytochrome P450 1A1, glutathione s-transferases M1 and T1 genes in Ouangolodougou (Northern Ivory Coast)
In this study, the frequencies of CYP1A1, GSTM1, and GSTT1 gene polymorphisms were determined in 133 healthy individuals from Ouangolodougou, a small rural town situated in the north of the Ivory Coast. As appeared in several published studies, ethnic differences in these frequencies have been found to play an important role in the metabolism of a relevant number of human carcinogens. In the studied sample, the frequencies of Ile/Ile (wild type), Ile/Val (heterozygous variant), and Val/Val (homozygous variant) CYP1A1 genotypes were 0.271, 0.692, and 0.037, respectively. Frequencies of GSTM1 and GSTT1 null genotypes were 0.361 and 0.331, respectively. No significant differences were noted between men and women. In contrast to published data for Africans, CYP1A1 *Val Allele frequency (0.383) was significantly high (p < 0.001) in this specific population. For the GSTT1 null genotype, no differences were found between the studied and other African populations, the contrary to what occurred for the GSTM1 null genotype in relation to Gambia and Egypt
Atomic layer deposition of Cu with a carbene-stabilized Cu (i) silylamide
The metal–organic Cu(I) complex 1,3-diisopropyl-imidazolin-2-ylidene copper hexamethyl disilazide has been tested as a novel oxygen-free precursor for atomic layer deposition of Cu with molecular hydrogen. Being a strong Lewis base, the carbene stabilizes the metal centre to form a monomeric compound that can be vaporised and transported without visible degradation. A significant substrate dependence of the growth process not only with respect to the film material but also to the structure of the films was observed. On Pd surfaces continuous films are grown and no phase boundary can be observed between the Cu film and the Pd, while island growth is observed on Ru substrates, which as a consequence requires thicker films in order to achieve a fully coalesced layer. Island growth is also observed for ultra-thin (<10 nm) Pd layers on Si substrates. Possible explanations for the different growth modes observed are discussed
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