Nm For Different Samples Research Articles

Effect of varying the vanadium thickness layer of V2O5/V/V2O5 film on its microstructural and thermochromic properties

In this study, V2O5/V/V2O5 sandwich-structured films were deposited on glass substrates by electron beam evaporation. The thickness of the first (bottom) V2O5 layer was 40 nm and the last (top) layer was 20 nm, while that of the sandwiched vanadium layer varied up to 12 nm for different samples. The effects of varying the thickness of the sandwiched vanadium layer on microstructural and thermochromic properties of the as-deposited and thermal annealed films were investigated. Ultrahigh-resolution scanning electron microscopy revealed the presence of nanostructures with various irregular shapes on the surfaces of all films. Also, the atomic force microscopy revealed an average roughness of ∼10–38 nm for increasing thickness of the sandwiched vanadium layer. X-ray powder diffraction measurements showed the presence of the monoclinic VO2 (M) crystal structure of the films with (011) preferred orientation at 27.94° for both 7 and 12 nm thicknesses of the sandwiched vanadium layers. The varying thickness of the sandwiched vanadium layers enhanced phase transition temperature values to ∼33.92 and ∼29.11 °C for both 7 and 12 nm thicknesses of the sandwiched layers, respectively. These enhanced transition temperature values, as a result of thickness variation of the sandwiched vanadium layers, pointed toward utilization of this method in the successful synthesis of VO2 films for thermochromic windows application and optoelectronics.

CdSe nanocrystalline thin films: composition, structure and optical properties

Nanocrystalline CdSe semiconductor thin films of different crystalline sizes have been synthesized by cathodic electrodeposition onto indium tin oxide glass and titanium electrodes. The composition of as-grown films, their crystalline structure and band gap were evaluated as a function of deposition current density and temperature. Particle induced X-ray emission and Rutherford backscattering spectrometric analysis indicate that the samples are free from any foreign impurity and the Cd to Se ratio changes at very low electrolysis current density. Crystalline size estimated from Grazing angle X-ray diffraction (GXRD) is found to be varied between 7 and 19 nm for different samples. A lattice contraction of 1.00% has been estimated from the GXRD measurement. Optical absorption shows size quantization effect marked by a blue shift by 0.52 eV from its standard bulk band gap value 1.7 eV . Crystalline size estimated from the blue shift is found to be much smaller compared to that determined from GXRD. Both GXRD and transmission electro microscopy (TEM) studies of CdSe nanocrystals reveal the cubic phase of the samples and the sizes estimated from both GXRD and TEM analysis are found to be comparable.

High-resolution X-ray scattering from CdMnTe/CdTe multiple quantum well structures

Cd1−xMnxTe/CdTe multiple quantum well structures have been investigated by high-resolution X-ray diffraction methods. Reciprocal space maps of the scattering distribution around the 004 reciprocal point and individual transverse scans showed that the crystalline quality of the epitaxial layers was high. The peak widths, at both the half maximum and one tenth maximum, of transverse scans along theqx direction at differentqz positions, showed no systematic variation with satellite order. Analysis of the X-ray diffraction profiles around the 004 reciprocal lattice point indicated the presence of an interfacial phase, of thickness between 0.2 and 0.6 nm for different samples, between the InSb substrate and CdTe buffer layer. This interfacial phase mainly influences the secondary interference fringes and high-angle tails in the diffraction profiles.