@article{23870,
  keywords = {Electrochromism, D.C. magnetron sputtering, Niobia, Optical properties, Sol-gel deposition},
  author = {Nilgün Özer and Carl M Lampert and Michael D Rubin},
  title = {Optical and Electrochemical Characteristics of Niobium Oxide Films Prepared by Sol-Gel Process and Magnetron Sputtering: A Comparison},
  abstract = {<p>Electrochromic niobia (Nb<sub>2</sub>0<sub>5</sub>) coatings were prepared by the sot-gel spin-coating and d.c. magnetron sputtering techniques. Parameters were investigated for the process fabrication of sol-gel spin coated Nb<sub>2</sub>0<sub>5</sub> films exhibiting high coloration efficiency comparable with that d.c. magnetron sputtered niobia films. X-ray diffraction studies (XRD) showed that the sot-gel deposited and magnetron sputtered films heat treated at temperatures below 450°C, were amorphous, whereas those heat treated at higher temperatures were slightly crystalline. X-ray photoelectron spectroscopy (XPS) studies showed that the stoichiometry of the films was Nb<sub>2</sub>0<sub>5</sub>. The refractive index and electrochromic coloration were found to depend on the preparation technique. Both films showed low absorption and high transparency in the visible range. We found that the <em>n</em>, <em>k</em> values of the sot-gel deposited films to be lower than for the sputtered films. The <em>n</em> and <em>k</em> values were <em>n</em> = 1.82 and <em>k</em> = 3 × 10<sup>−3</sup>, and <em>n</em> = 2.28 and <em>k</em> = 4 × 10<sup>−3</sup> at 530 urn for sot-gel deposited and sputtered films, respectively. The electrochemical behavior and structural changes were investigated in 1 M LiC10<sub>4</sub>/propylene carbonate solution. Using the electrochemical measurements and X-ray photoelectron spectroscopy, the probable electrode reaction with the lithiation and delithiation is Nb<sub>2</sub>O<sub>5</sub> + <em>x</em> Li<sup>+</sup> + <em>x</em> e<sup>−</sup> ↔ Li<sub>x</sub>Nb<sub>2</sub>0<sub>5</sub>. Cyclic voltametric (CV) measurements showed that both Nb<sub>2</sub>0<sub>5</sub> films exhibits electrochemical reversibility beyond 1200 cycles without change in performance. “In situ” optical measurement revealed that those films exhibit an electrochromic effect in the spectral range 300 &lt; λ &lt; 2100 nm but remain unchanged in the infrared spectral range. The change in visible transmittance was 40% for 250 nm thick electrodes. Spectroelectrochemical measurements showed that spin coated films were essentially electrochemically equivalent to those prepared by d.c. magnetron sputter deposition.</p>},
  year = {1995},
  journal = {Solar Energy Materials and Solar Cells},
  volume = {40},
  number = {4},
  pages = {285-296},
  month = {08/1996},
  doi = {10.1016/0927-0248(95)00147-6},
  language = {eng},
}