Effects of surface porosity on tungsten trioxide(WO3) films' electrochromic performance

• Published in: Journal of electronic materials 2000-02, Vol.29 (2), p.183-187
• Main Authors: LEE, W. J, FANG, Y. K, HO, J.-J, HSIEH, W. T, TING, S. F, DAOYANG HUANG, HO, F. C
• Format: Article
• Language: English
• Subjects: Atomic force microscopes; Atomic force microscopy; Columns (structural); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Crystal structure; ELECTROCHROMISM; Exact sciences and technology; Magnetron sputtering; MATERIALS SCIENCE; Microscopes; Morphology; Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity); Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical density; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; POROSITY; ROUGHNESS; SAMPLE PREPARATION; SPUTTERING; Structure and morphology; thickness; Substrates; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; THIN FILMS; TUNGSTEN OXIDES; X-RAY DIFFRACTION
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-000-0139-8

In this paper, the correlation between the electrochromic performance and the surface morphology of the tungsten trioxide (WO3) thin films sputtered by dc reactive magnetron sputtering with widely varying target-substrate distances was investigated. It is found that the optical density change (ΔOD) of films is strongly affected by the target-substrate distance. The coloration efficiency (CE) at 633 nm was also found to be sensitive to the target-substrate distance, with 16 cm2/C of film sputtered at 6 cm and 50 cm2/C at 18 cm. X-ray diffraction showed that the crystal structure of films was amorphous. By using atomic force microscope to identify the surface porosity of the sputtered WO3 films, we found that the film at longer target-substrate distance was rough, porous, and having a cone-shaped columns morphology, thus offering a good electrochromic performance for opto-switching applications.