Influence of post-annealing temperature on the properties exhibited by ITO, IZO and GZO thin films G. Gonçalves ⁎ , E. Elangovan, P. Barquinha, L. Pereira, R. Martins, E. Fortunato Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa and CEMOP, Campus da Caparica, 2829-516 Caparica, Portugal Available online 1 April 2007 Abstract In this work we present a study on the effect of annealing temperatures on the structural, morphological, electrical and optical characteristics of gallium doped zinc oxide (GZO), indium zinc oxide (IZO) and indium-tin-oxide (ITO) films. GZO and IZO films were deposited at room temperature by r.f. magnetron sputtering, whereas the ITO films were commercial ones purchased from Balzers. All films were annealed at temperatures of 250 and 500 °C in open air for 1 h. The GZO and ITO films were polycrystalline. The amorphous structure of as-deposited IZO films becomes crystalline on high temperature annealing (500 °C). The sheet resistivity increased with increase in annealing temperature. GZO films showed an increase of 6 orders of magnitude. The optical transmittance and band gap of as-deposited films varied with annealing. The highest transmittance (over 95 %) and maximum band gap (3.93 eV) have been obtained for ITO films. © 2007 Elsevier B.V. All rights reserved. Keywords: Transparent conductive oxides; Annealing treatments; Electrical and optical properties 1. Introduction Transparent conductive oxide (TCO) films such as indium tin oxide (ITO), gallium doped zinc oxide (GZO) and zinc doped indium oxide (IZO) have been studied for several applications such as solar cells [1], thin film transistors (TFTs) [2] and organic light emitting diodes (OLEDs) [3,4] due to their high transmittance and good electrical conductivity. Zinc based TCOs work out the problems of cost and demand [5–7]. Otherwise indium based TCOs showed better electro-optical properties [8–11] but also a higher cost. Several deposition techniques have been used for these materials, namely sputtering, spray pyrolysis, metal organic chemical vapor deposition, laser deposition and sol–gel deposition [4]. In this paper, we report on the electrical, structural, morphological and optical properties of ITO, GZO and IZO thin films prepared by r.f. magnetron sputtering at room temperature (GZO and IZO films) as a function of the annealing temperature on air atmosphere. 2. Experimental GZO films were deposited onto glass substrates by radio frequency (13.56 MHz) magnetron sputtering, using a ceramic oxide target (ZnO:Ga 2 O 3 ; 95:5 wt.%) from Super Conductor Materials, Inc. (99.995%). Prior to deposition, the sputtering chamber was pumped down to 10 - 4 Pa. The deposition was carried out at room temperature at a pressure of 1.4 × 10 - 1 Pa in an argon atmosphere. The distance between the substrate and the target was 10 cm and the r.f. power density was 9 W/cm 2 . ITO thin films were obtained from Balzers for comparison purposes. For IZO films, a ceramic oxide target of In 2 O 3 :ZnO (89.3:10.7 wt.%) from Super Conductor Materials, Inc. (99.99%) was used; films were deposited at room temperature in the presence of a mixture of argon (20 sccm) and oxygen (0.4 sccm) at a deposition pressure of 1.2 × 10 - 1 Pa; r.f. power density was 5 W/cm 2 and the target– substrate distance was 10 cm. The samples were annealed (Thermolyne tubular furnace; Model: 21100) at temperatures of 250 and 500 °C for 1 h in an open air atmosphere with heating and cooling rates of 3 and 2 °C/min, respectively. The structural characterization was done using X-ray diffraction measurements with Cu-K α radiation (Rigaku DMAX III-C series). The surface morphology was analyzed using a Field Emission Scanning Thin Solid Films 515 (2007) 8562 – 8566 www.elsevier.com/locate/tsf ⁎ Corresponding author. E-mail address: gpg@fct.unl.pt (G. Gonçalves). 0040-6090/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2007.03.126