Study of vanadium doped ZnO films prepared by dc reactive magnetron sputtering at different substrate temperatures

ZnO films doped with vanadium (ZnO:V) have been prepared by dc reactive magnetron sputtering technique at different substrate temperatures (RT–500 C). The effects of the substrate temperature on ZnO:V films properties have been studied. XRD measurements show that only ZnO polycrystalline structure has been obtained, no V2O5 or VO2 crystal phase can be observed. It has been found that the film prepared at low substrate temperature has a preferred orientation along the (002) direction. As the substrate temperature is increased, the (002) peak intensity decreases. When the substrate temperature reaches the 500 ºC, the film shows a random orientation. SEM measurements show a clear formation of the nano-grains in the sample surface when the substrate temperature is higher than 400 º C. The optical properties of the films have been studied by measuring the specular transmittance. The refractive index has been calculated by fitting the transmittance spectra using OJL model combined with harmonic oscillator

Effect of the deposition rate on ITO thin films properties prepared by ion beam assisted deposition (IBAD) technique

Indium tin oxide (ITO) thin films have been deposited onto glass substrates at room temperature by ion beam assisted deposition technique at different deposition rates (0.1 -- 0.3 nm/s). The effects of the deposition rate on the structural, optical and electrical properties of the deposited films have been studied. The optical constants of the deposited films were calculated by fitting the transmittance spectra using the semi-quantum model. Considering the application for the electromagnetic wave shielding which needs a high IR reflectance, the optimising deposition rate is 0.2 nm/s. The films prepared at this deposition rate shows a relative high IR reflectance (60%), a good electrical conductivity (5 x 10-3 -cm), and a reasonable transmittance in the visible region (over 80%)

Symbolic Computation of Variational Symmetries in Optimal Control

We use a computer algebra system to compute, in an efficient way, optimal control variational symmetries up to a gauge term. The symmetries are then used to obtain families of Noether's first integrals, possibly in the presence of nonconservative external forces. As an application, we obtain eight independent first integrals for the sub-Riemannian nilpotent problem (2,3,5,8).Comment: Presented at the 4th Junior European Meeting on "Control and Optimization", Bialystok Technical University, Bialystok, Poland, 11-14 September 2005. Accepted (24-Feb-2006) to Control & Cybernetic

Study of indium tin oxide thin films deposited on acrylics substrates by Ion beam assisted deposition technique

Indium tin oxide (ITO) thin films have been deposited onto acrylics (PMMA) substrates by ion beam assisted deposition technique at different oxygen flows. The structural, optical and electrical properties of the deposited films have been characterized by X-ray diffraction, transmittance, FTIR, ellipometry and Hall effect measurements. The optical constants of the deposited films have been calculated by fitting the ellipsometric spectra. The effects of the oxygen flow on the properties of the deposited films have been studied. It has been found that 40 sccm oxygen flow is an optimum value for getting the films with good transmittance and low electrical resistivity

Random walk on random walks

In this paper we study a random walk in a one-dimensional dynamic random environment consisting of a collection of independent particles performing simple symmetric random walks in a Poisson equilibrium with density ¿¿(0,8). At each step the random walk performs a nearest-neighbour jump, moving to the right with probability p° when it is on a vacant site and probability p· when it is on an occupied site. Assuming that p°¿(0,1) and p·¿12, we show that the position of the random walk satisfies a strong law of large numbers, a functional central limit theorem and a large deviation bound, provided ¿ is large enough. The proof is based on the construction of a renewal structure together with a multiscale renormalisation argument

Random walk on random walks

In this paper we study a random walk in a one-dimensional dynamic random environment consisting of a collection of independent particles performing simple symmetric random walks in a Poisson equilibrium with density ¿¿(0,8). At each step the random walk performs a nearest-neighbour jump, moving to the right with probability p° when it is on a vacant site and probability p· when it is on an occupied site. Assuming that p°¿(0,1) and p·¿12, we show that the position of the random walk satisfies a strong law of large numbers, a functional central limit theorem and a large deviation bound, provided ¿ is large enough. The proof is based on the construction of a renewal structure together with a multiscale renormalisation argument