Photoluminescence of chemical bath deposited ZnO:Al films trea rapid thermal annealing S.T. Shishiyanu a, * , O.I. Lupan a , E.V. Monaico a , V.V. Ursaki b , T.S. Shishiyanu a , I.M. Tiginyanu a,b a Department of Microelectronics and Semiconductor Devices, Technical University of Moldova, MD-2004, Chisinau, Moldova b Institute of Applied Physics, Academy of Sciences of Moldova, MD-2028, Chisinau, Moldova Received 5 May 2004; accepted in revised form 1 April 2005 Available online 10 May 2005 Abstract Aluminum-doped zinc oxide (ZnO:Al) films fabricated by chemical bath deposition are characterized using scanning elec and photoluminescence (PL) spectroscopy. The impactof rapid thermal annealing (RTA) upon the morphology and luminescence characteristics of ZnO:Al layers is studied in an annealing temperature interval up to 650 -C. The as deposited films consis microcrystalline grains surrounded by a material of poor quality. RTA attemperatures around 650 -C proves to increase the grain size, enhance the ultraviolet PL with simultaneous suppression of the visible luminescence, and activate the Al donor impurities. D 2005 Elsevier B.V. All rights reserved. PACS: 81.15.Lm; 81.40.Tv; 78.66.Hf; 78.55.Et; 68.37.Hk Keywords: Zinc oxide; Rapid thermal annealing; Luminescence; Surface morphology 1. Introduction Aluminum-doped zinc oxide (ZnO:Al) films are promis- ing for various applications including gas sensors [1], solar cells [2], optical waveguide and exciton related devices [3], transparent conductors in thin-film transistors [4]. The defect chemistry of ZnO:Al films is the key factor defining the application. The properties of such films prove to be strongly dependent on the fabrication method, co-doping speciesand conditions of postgrowth treatment. A wide variety of synthetic methods has been used to fabricate high quality ZnO:Althin films, someof which are radio- frequency thermal plasmaevaporation [5], pulsed laser deposition [6], chemical vapor deposition [7], metalorganic chemical vapor deposition and sputtering [8]. Over the past years,themethod ofchemical bath deposition became widely used for the fabrication of ZnO:Al thin films due to its simplicity of preparation, satisfactory stability, low cost equipment and low deposition temperatures. Annealing is the most important and widely used proces for removing the defects and improving the properties of t oxide films. Rapid thermal annealing (RTA) was proposed as an alternative thermal processing solution. The lamp- based RTA systems provide short cycle time and flexibility compared to batch-type furnaces. Strong demand in thermal load reduction and cycle time reduction made RTA a very popular processing method in recent years [9,10]. In this paper, we report the fabrication ZnO:Al thin films from an aqueoussolutionat low temperatures. Undoped films were also grown for compar- ison purpose. The impact of the RTA on the morphology and luminescence properties of ZnO:Al films is studied. 2. Experimental details The ZnO:Al films weredeposited on Corning glass (Vycor 7913) substrate by chemical bath deposition using 0040-6090/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2005.04.004 * Corresponding author. Tel.: +37322497007; fax: +37322497007. E-mail addresses: sergeteo7@yahoo.co.uk, sergeteo@mail.utm.md (S.T.Shishiyanu). Thin Solid Films 488 (2005) 15 – 19 www.elsevier.com/locate/tsf