Optical analysis of room temperature magnetron sputtered ITO films by reflectometry and spectroscopic ellipsometry
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Jagadeesh Kumar Semiconductor Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
Péter Petrik Department of Photonics, Research Centre for Natural Sciences, Institute for Technical Physics and Materials Science, H-1121 Budapest, Hungary; and Department of Nanotechnology, University of Pannonia, H-8200 Veszprém, Hungary
Aryasomayajula Subrahmanyam Semiconductor Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036, India
István Bársony Research Centre for Natural Sciences, Institute for Technical Physics and Materials Science, H-1121 Budapest, Hungary; and Department of Nanotechnology, University of Pannonia, H-8200 Veszprém, Hungary (Received 2 March 2014; accepted 26 June 2014)
Indium-tin-oxide (ITO) thin films were prepared by reactive magnetron sputtering; their optical constants and thickness were determined by spectral reflectometry (SR) in the wavelength range from 400 nm to 800 nm and spectroscopic ellipsometry (SE) in the wavelength range from 191 nm to 1690 nm. A comparative evaluation of the measured data from SR and SE has been made using the same single layer optical model based on the Cauchy dispersion relation. The introduction of a surface roughness layer into the optical model considerably improved the fit quality during evaluation of SE data. Vertical inhomogeneity of the ITO thin films was assessed using a multilayer optical model describing porosity gradient and the three-layer optical model suggested by Jung [Y.S. Jung, Thin Solid Films 467, 36 (2004)] from the SE data. I. INTRODUCTION
Thin films of tin doped indium oxide (ITO) have been subjected to intensive investigation by several workers, mainly because of the varied and versatile applications of these thin films.1–27 These ITO thin films are quite complex and the properties are very sensitive to oxygen vacancies. The physical properties, in specific, the optical and electrical properties, of these thin films depend upon: (i) the thickness, (ii) the technique of preparation, and (iii) the growth parameters even in the same technique. With the advent of applications6,28–33 demanding the preparation (manufacture) of these ITO films at relatively low temperature or preferably at room temperature (300 K) (mainly for the touch panel displays on plastics and top electrode for solar cells and electrochromic devices on flexible plastic substrates), our laboratory has reported the physical properties (including photocatalytic properties) of ITO thin films (as a function of thickness) prepared at room temperature (300 K) by reactive DC magnetron sputtering technique.27 a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2014.173 1528
J. Mater. Res., Vol. 29, No. 14, Jul 28, 2014
http://journals.cambridge.org
Downloaded: 16 Aug 2014
The aim of the present communication is mainly (i) to report the optical constants of room temperature (300 K) magnetron sputtered ITO thin films and (ii) to compare the optical constants of these ITO thin films
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