Novel encapsulated ITO/arc-ZnO:TiO 2 antireflective passivating layer for TCO conducting substrate prepared by simultaneous radio frequency-magnetron sputtering M.H. Abdullah a,⇑ , L.N. Ismail a , M.H. Mamat a , M.Z. Musa a , M. Rusop a,b a NANO-Electronic Centre, Faculty of Electrical Engineering, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia b NANO-SciTech Centre, Institute of Science, Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor, Malaysia article info Article history: Available online 14 February 2013 Keywords: Indium–tin oxide Nanocomposite Antireflection coating Encapsulated TiO 2 Compact layer Simultaneous radio frequency-magnetron sputtering abstract A thermally stable multilayered transparent conducting oxide utilizing nanocomposite ZnO:TiO 2 antire- flection thin film (arc-ZnO:TiO 2 ) on an indium–tin oxide (ITO) substrate has been prepared by radio fre- quency-magnetron sputtering. The effects of post-deposition annealing on the morphological, structural, optical and electrical properties were investigated with the aim to find the best conditions for the anti- reflection substrate. The X-ray diffraction behaviors of mixed type crystalline structures preferred at [2 2 2] and [1 0 1] between ITO and ZnO were observed, respectively. The grain size increased from 37.9 nm to 46.9 nm due to the aggregation of smaller grain during the annealing process. Average trans- mittances of approximately 82% were observed for all the samples in the range between 440 nm and 760 nm. A corresponding reduction in the reflectance of about 11% and 3% compared to bare ITO was achieved. The refractive index increased from 1.82 up to 2.0 due to the change in the packing density. For all ranges of annealing conditions, the arc-ZnO:TiO 2 layers conserved the low resistivity of ITO at 1.96  10 4 X. In other words, the oxygen consumed in the annealing process improved the crystallinity of the film without much change to the resistivity of the ITO-based substrate. The increment of the root mean square roughness from 2.12 nm to 3.21 nm evidenced by the atomic force microscopy analysis was supported by the increment of grain growth. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Indium–tin oxide (ITO) is the most widely used transparent conducting oxide (TCO) [1,2] for flat panel displays, primarily due to its high optical transmittance in the visible region, high electri- cal conductivity, surface uniformity and process compatibility. However, ITO is severely spoiled in an annealing process with tem- peratures higher than 400 °C. To avoid the decrease in carrier con- centration and the increase in sheet resistance, a compact layer of metal oxides, such as TiO 2 , ZnO, SnO 2 , (Al-doped TiO 2 ) ATO and Al-doped ZnO(AZO), is therefore sputtered on the ITO to obtain a multilayered conducting glass with thermally stable electrical properties. Moreover, the introduction of such a compact layer has been effectively proven to block the electron recombination via the indirect route [3–6]. Similarly, Noh et al. reported the NTO (Nb-doped TiO 2 )/AZO multilayer showed better photovoltaic performance due to the facilitated charge injection and the conserved high conductivity caused by the NTO overlayer [7]. Meanwhile, Kim et al. also reported the application of the compact TiO 2 (c-TiO 2 ) layer on the NTO to improve the transmittance for better efficiency of dye-sensitized solar cells (DSSC) [8]. Transmittance enhancement of the TiO 2 film is closely related to the improvement of its nanoparticle photocatalytic reaction. One way of improving the reaction is through the doping and/or coating of other materials onto the surface of the TiO 2 nanoparti- cles with metal ions and semiconductors [9,10]. In addition, the composite of two semiconductors provides a more efficient plat- form for charge separations, as well as extending the lifetime of the charge carriers, hence improving the interfacial charge transfer to adsorbed substrates [11,12]. Recently, Hernandez et al. reported that a compact ZnO layer on an FTO substrate decreased the recombination rate at the ITO-porous-ZnO interface, and at the same time maintained the transmittance at a specific wavelength region [13]. In the meantime, Liu et al. reported that the ZnO/Cu/ ZnO multilayer film used as TCO showed a low sheet resistance and high transmittance when the film thickness was ZnO (60 nm)/Cu (15 nm)/ZnO (60 nm) [14]. Chang et al. reported that the Ti-doped ZnO film used as TCO decreased the resistivity by 57% and slightly increased the average optical transmittance in the visible wavelength range (400–700 nm) [15]. Thus, we were motivated to develop a bi-functional ITO-based TCO substrate with 0167-9317/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.mee.2013.01.065 ⇑ Corresponding author. Tel.: +60 3 55431883; fax: +60 3 55443870. E-mail address: abuhanifahabllh@yahoo.com (M.H. Abdullah). Microelectronic Engineering 108 (2013) 138–144 Contents lists available at SciVerse ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee