The structure of ultrathin Langmuir-Blodgett films of cadmium behenate.
Grazing incidence x-ray-diffraction investigations of the structures of Langmuir-Blodgett films of cadmium behenate with 1, 2, 3, 5, and 21 monolayers are reported. The single monolayer film, deposited on a hydrophilic substrate, showed a hexagonal structure, whereas the bilayer film, deposited on a hydrophobic substrate, had a rectangular structure with herringbone orientation of the acyl chains. With multilayer films formed on a hydrophilic substrate, it was possible to detect that the hexagonal structure of the first layer was retained when additional layers were deposited and that the additional layers had the same rectangular structure as the bilayer.
Superstructures and correlated metal ion layers in Langmuir-Blodgett films of cadmium soaps observed with grazing incidence X-ray diffraction
The structures of Langmuir−Blodgett films of cadmium soaps have been investigated using grazing incidence synchrotron X-ray diffraction and imaging plate detection. It was found that the cadmium atoms in the films are arranged with a monoclinic (C) symmetry, while the chains have the same monoclinic structure as that of the metal atoms but without the centered symmetry. The chains are perpendicular to the film surface and arranged in a herringbone pattern. For the first time with X-ray diffraction, a 5 × 1 superstructure present in the film plane and commensurate with the local structure was observed. The meridional diffraction shows a pattern from a set of wide slits, from which thicknesses corresponding to both a monolayer and a bilayer of the cadmium soap films were determined.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.