Determination of electronic structure by impedance spectroscopy

• Published in: Journal of non-crystalline solids Vol. 356; no. 11; pp. 705 - 709
• Main Authors: Niklasson, Gunnar A., Malmgren, Sara, Green, Sara, Backholm, Jonas
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier B.V 01.04.2010; Elsevier
• Subjects: Band structure; Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dielectric properties; Electric modulus; Electrochemical properties; Electron states and collective excitations in thin films, multilayers, quantum wells, mesoscopic and nanoscale systems; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Engineering Science with specialization in Solid State Physics; Exact sciences and technology; Inorganic chemistry; Kemi; NATURAL SCIENCES; NATURVETENSKAP; Oorganisk kemi; Physics; Relaxation; TECHNOLOGY; TEKNIKVETENSKAP; Teknisk fysik med inriktning mot fasta tillståndets fysik; Thin films and multilayers; Band structure; Relaxation; Electrochemical properties; Electric modulus; Dielectric properties; Localized states; Charge carriers; Iridium Tantalum Oxides Mixed; Intercalation compounds; Amorphous state; Electronic density of states; Thin films; Complex impedance; Tungsten oxide; Investigation method; Capacitance; Iridium oxide; Permittivity
• ISSN: 0022-3093; 1873-4812; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2009.06.053

We present a novel method, based on electrochemical intercalation and impedance spectroscopy, to determine the electronic density of states of disordered transition metal oxides. Specifically, we have determined the “electrochemical density of states” of tungsten and iridium oxide thin films over energy ranges as wide as 1–2 eV. Our experimental results show a number of qualitative features exhibited by state-of-the-art band structure computations. Differences in details are probably due to the disordered, porous and sometimes amorphous nature of our films. The results suggest that the impedance spectroscopy method can be used to obtain the density of states only if the conduction band states are localized. The electrochemical density of states is often smaller than the computed one due to kinetic effects, i.e. very slow relaxations of the charge carriers. Nevertheless, our sensitive method opens new vistas for studying the electronic structure of disordered materials.