Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5145466 | International Journal of Hydrogen Energy | 2017 | 6 Pages |
Abstract
We report measurements of the optical transmission, between 240 and 1040Â nm, and electrical resistivity of polycrystalline zirconium thin films as they absorb hydrogen. Both are measured as H2 pressure is increased up to 880Â mbar, at room temperature. Films, 20-22Â nm thick, are deposited on fused quartz substrates by e-beam evaporation at 5.3Â ÃÂ 10â7Â mbar base pressure and covered with a 8.0Â nm Pd over-coat. The morphology of the films is studied by means of AFM images. The complex refractive indices of Zr and Pd are extracted numerically from the transmission spectra by using a spectral projected gradient method for different hydrogen pressures. The corresponding dielectric functions for various Zr hydrogen concentrations are described with the parametric Drude-Lorentz and Brendel-Bormann (DL & BB) models. The Acceptance-Probability-Controlled Simulated Annealing approach is applied to calculate the parameters of the DL & BB model. This allows us to describe the effect of increasing hydrogen absorption on these parameters and in derived quantities, like the relaxation time and the effective mass of conduction electrons, the electrical resistance, the Fermi energy, and the electronic density of states at the Fermi level.
Related Topics
Physical Sciences and Engineering
Chemistry
Electrochemistry
Authors
Daniel E. Azofeifa, Neville Clark, William E. Vargas, Hugo Solis, E. Avendano, Michael Cambronero, Diana Valverde-Mendez,