Optical and electrical properties of hydrided palladium thin films studied by an inversion approach from transmittance measurements

• Published in: Thin solid films Vol. 496; no. 2; pp. 189 - 196
• Main Authors: Vargas, W.E., Rojas, I., Azofeifa, D.E., Clark, N.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 21.02.2006; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Hydrides; Materials science; Metals, semimetals, and alloys; Methods of deposition of films and coatings; film growth and epitaxy; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Palladium; Physics; Vapor phase epitaxy; growth from vapor phase; Visible and ultraviolet spectra; 42.25.Bs; 78.66.-w; Optical properties; Hydrides; Palladium; 81.15.Ef; 72.80.Ga; Ultrathin films; Polarization; Inorganic compounds; Pressure effects; Interband transitions; Crystal growth from vapors; Experimental study; 81.15.Ef Optical properties; Transmittance; Optimization; Optical conductivity; Thin films; Free carrier; Dielectric function; Quantity ratio; Transition elements; Permittivity; Electron beam evaporation
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2005.08.346

Palladium (Pd) thin films have been deposited by electron beam evaporation, and exposed to increasing hydrogen pressures. Transmittance spectra in the range of visible light have been measured to obtain from them, by means of a spectral projected gradient method, the wavelength dependence of the dielectric function. The decreasing metallic character of Pd with hydrogen absorption is displayed. This effect is more pronounced when Pd is deposited on metallic substrates, and there is a correlation with an increase in the effective polarization of the core electrons determining the optical dielectric constant value. Another optimization approach is devised to separate the contribution of the free carriers and of the interband transitions to the optical conductivity and to the dielectric function. Very good agreement is found between the optimized parameters characterizing the free carrier contribution and the corresponding values reported in the literature and obtained by independent experimental methods.