Introduction Indium–tin–oxide (ITO) transparent conducting films have been widely applied in the field of anti-static electricity shielding coating, heat reflecting mirrors, solar cells, liquid crystal displays (LCDs) and organic light emitting devices (OLEDs) due to their unique combination of electrical and optical properties [1]. The problems due to gas inclusions in the ITO films become even more significant for vacuum mi- cro-electronic devices, because the operational life is directly related to the amount of residual gases pres- ent in the vacuum envelope [2, 3]. Thus, one needs to know the type of trapped gas and the process tempera- tures necessary to remove these gases from the films. Temperature programmed desorption (TPD) using a mass spectrometer is an excellent technique for ana- lyzing the minute amounts of gas species evolved from the film samples and for characterizing the bonding strength of the species with the surface of the solid. Our previous work [4, 5] found that the amount of the evolved water vapor from the crystalline ITO films is dependent on the deposition process such as spray CVD (chemical vapor deposition), sputtering, ion-plating, electron-beam heating vacuum evapora- tion or dip coating and the post-deposition annealing conditions such as temperature and time. The amount of evolved water vapor was related to the total surface area of the crystal grains; much amount of water evo- lution from porous films was ascribed to the surface of the open pores. The evolutions at the peak tempera- ture of approximately 373–393 K belonged to physi- cally adsorbed water. These, at temperatures higher than 473 K, were attributed to chemically adsorbed water or thermal decomposition of indium hydroxide formed on the surface of the crystal grains. Although polycrystalline films are used because of their high conductivity and transmittance, amorphous films have recently become increasingly important since they can be deposited at room temperature on heat-sensitive flexible organic substrates and organic light emitting layers [6–9]. Nishimura et al. [10] and Ando et al. [11] reported evolution of water vapor from partly-crystallized amorphous ITO films which was sputter-deposited in water vapor atmosphere in- troduced intentionally and discussed the crystalliza- tion process during the post-deposition annealing at various temperatures in atmospheric pressure of nitro- gen atmosphere for 1 h. The present study reports the evolution of water vapor as well as other gases from the fully amorphous ITO films sputter-deposited without intentional introduction of water vapor and discusses the crystallization process occurring simul- taneously during the heating process of a TPD mea- 1388–6150/$20.00 Akadémiai Kiadó, Budapest, Hungary © 2008 Akadémiai Kiadó, Budapest Springer, Dordrecht, The Netherlands Journal of Thermal Analysis and Calorimetry, Vol. 91 (2008) 1, 249–254 THERMALLY INDUCED CHANGES IN AMORPHOUS INDIUM-TIN-OXIDE THIN FILMS Gas evolution and crystallization M. H. Wang 1* , S. Tokiwa 2 , T. Nishide 2 , Y. Kasahara 1 , S. Seki 1 , T. Uchida 1 , M. Ohtsuka 1 , T. Kondo 1 and Y. Sawada 1 1 Center for Hyper Media Research, Graduate School of Engineering, Tokyo Polytechnic University, 1583 Iiyama, Atsugi Kanagawa 243-0297, Japan 2 College of Engineering, Nihon University, Tamura, Koriyama 963-8642, Japan Amorphous indium–tin–oxide (ITO) transparent conducting film (15 at% Sn; thickness, 150–190 nm) was deposited on silicon wa- fer at room temperature by RF magnetron sputtering for temperature programmed desorption (TPD) in vacuum. The thermal crys- tallization was accompanied by evolution of water vapor (the main gas), argon and carbon dioxide. The total amount of evolved wa- ter vapor (H 2 O [mol]/(In [mol]+Sn [mol])>0.2) was one or two orders of magnitude more than that from the nanocrystalline ITO films reported in our previous papers. The thermal change of amorphous ITO film was remarkably affected by the position of the substrate. An abrupt gas evolution was characteristic of the amorphous ITO films deposited on the position near the target center. The evolution temperature (548–563 K) was higher than the gas evolution temperature from the crystalline films. The far from cen- ter positioned films crystallized at higher temperature with relatively slower evolution of the gases. Keywords: amorphous ITO films, argon, carbon dioxide, TPD, water vapor * Author for correspondence: mhwang@nano.t-kougei.ac.jp