Direct patterning of dense cerium oxide thin film by developed ink-jet deposition method at moderate temperatures R. Gallage ⁎, A. Matsuo, T. Fujiwara, T. Watanabe, N. Matsushita, M. Yoshimura Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama, Japan abstract article info Article history: Received 15 January 2008 Received in revised form 5 December 2008 Accepted 10 December 2008 Available online 24 December 2008 Keywords: Ink-jet Cerium Oxide Thin films Patterning Solution deposition Direct fabrication of ceria film and patterns were conducted by an ink-jet deposition method where a precursor solution was jetted towards a heated substrate (≤300 °C) according to the required pattern without any post heat treatments. X-ray diffraction and Raman spectroscopic analyses revealed that the formed phases were crystallized CeO 2 without any impurity phases and consisted of nanosized crystallites of b 10 nm. The thicknesses were several hundred nanometers and the width of the patterns was about 350 μm. The film was dense and showed a high optical transparency in the visible region(N 90%). Scanning electron microscopic analysis revealed that thin film patterns were free of cracks and all the films showed good adherence to the substrate. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Modern industry has produced many kinds of electronic devices using thin film technologies, in which constituent thin films are deposited by a vacuum deposition process or a solution deposition process and then cut into the desired pattern using a photolitho- graphic process. Since the photolithographic technology is excellent for fabricating submicron-sized devices, and its application is still expanding. However, it has inherent shortcomings, such as a multi- step complex production process that is insufficient in its use of energy and materials and it is also a time consuming process. Moreover, the subsequent photolithographic process removes the greater part of the film (sometimes exceeding 90%) and the supplemental materials in the photolithography process, such as the photoresist, are also inefficiently used. In addition during the vacuum deposition process, where high energetic species like ions, atoms, clusters, molecules, etc., are involved, the yield of the materials from the source to the deposited materials is low (b 10%). To avoid these inherent shortcomings of the vacuum and/or gaseous processings, that have been used for fabricating high performance products, liquid processes should be developed [1,2]. The liquid processings (solution deposition processes) of ceramic films are believed to have several merits; (1) possibility to use higher concentration of precursor content than gaseous precursor, (2) homogeneous composition of precursor in a solution as well as in the gas phase, (3) potential to coat larger areas at comparatively low cost, and (4) lower energy for production than gaseous and/or vacuum processes [3,4]. Therefore, the processes, based on a liquid phase (solution deposition) instead of a gas phase and on direct patterning rather than a multi-step photolithograph, etc., provide more benefits for the fabrication of a ceramic film/pattern over conventional methods. Ink-jet printing is the one of the fabrication methods of ceramic films/patterns that minimizes material waste and has fewer processing steps. This has widely been used for the fabrication of ceramic films, patterns and even for three-dimensional (3D) structures using an ink, which is mostly a suspension of ceramic nanoparticles (previously synthesized) in an organic solvent (colloidal fluid) [5–10]. During the ink-jet printing, these particles in the suspension are arranged into the required shape on the substrate, but there is no driving force to consolidate these particles and/or to fix the particles to the substrate except for their surface energy, thus a heat treatment at high temperature is needed for sintering [5,11]. However, heat treatment at high temperatures can cause grain growth that affects the final properties of the film (e.g., electro-optical properties). Furthermore, contamination of the film due to the series of reactions occurs between the printed ceramic particles and chemical species of the substrate at high temperature is also possible in this method [12–14]. In order to minimize these drawbacks in the ink-jet printing methods, we have introduced a method called “ink-jet deposition” in which an aqueous “precursor solution” is used instead of colloidal ink and then ink-jetted onto the “heated” substrate according to the required patterns using a modified commercial ink-jet printer [15]. Post-firing [16,17] and post treatments like masking, etching, etc., are not required in this method, as crystalline films/patterns can be Thin Solid Films 517 (2009) 4515–4519 ⁎ Corresponding author. E-mail address: rgallage@gmail.com (R. Gallage). 0040-6090/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2008.12.029 Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf