The effects of the ageing on the characteristic parameters of polyaniline/p-type Si/Al structure M. Sag ˘lam a,* , M. Biber a , M. C ¸akar b , A. Tu ¨ru ¨t a a Department of Physics, Faculty of Science and Arts, Atatu ¨rk University, 25240 Erzurum, Turkey b Department of Chemistry, Faculty of Science and Arts, Su ¨tc ¸u ¨I ˙ mam University, K. Maras ¸, Turkey Received 28 January 2004; received in revised form 4 March 2004; accepted 4 March 2004 Available online 17 April 2004 Abstract A detailed study of the effects of the ageing on the characteristic parameters of polyaniline/p-type Si/Al structure has been presented. The polyaniline film has been formed on a p-type Si substrate by means of an anodization process. The polyaniline/p- Si/Al structure has demonstrated clearly rectifying behavior by the current–voltage (I–V) curves studied at room temperature. The current–voltage curves of the structure have been measured immediately, 15, 30, 60, 90 and 120 days after fabrication of the polyaniline/p-Si/Al structure. It has been seen that the characteristic parameters, such as barrier height (BH), ideality factor and series resistance of polyaniline/p-type Si/Al structure have slowly changed with increasing ageing time. The diode shows non- ideal I–V behavior with an ideality factor greater than unity that can be ascribed to the interfacial layer, the interface states and the series resistance. # 2004 Elsevier B.V. All rights reserved. 1. Introduction Conjugated polymers are a new class of material of great potential for fabrication of solid-state devices [1]. The electrical conductivity of these polymers can be changed from insulating to metallic by chemical or electrochemical doping and they can be used to pro- duce electronic devices, such as Schottky diodes, field effect transistors, light-emitting diodes, and photode- tectors, among others [1–7]. Owing to the technolo- gical importance of metal/semiconductor devices in the electronics industry contact properties of poly- mers, such as the polymer/inorganic semiconductors structures [8–10] and metal/semiconductor polymer contacts [11,12] have been extensively studied experi- mentally and theoretically [13]. In the field of organic semiconductor materials, polyaniline is one of the most studied polymers and the attractive and interest- ing conducting polymers for electrochemical devices because of its simple preparation technique, good chemical stability and excellent electrochemical prop- erties [9–14]. Its basic properties and application to electrochemical devices have been investigated [15–20]. Up to now, much effort has been devoted to the preparation and characterization of polymer/ inorganic semiconductor structures. However, there has been no report in the past on the changing with ageing time of characteristics parameters of polymer/ inorganic semiconductor structures. We report here our studies on such polyaniline/p-type Si/Al structure Applied Surface Science 230 (2004) 404–410 * Corresponding author. Tel.: þ90-442-231-4176; fax: þ90-442-236-0948. E-mail address: msaglam@atauni.edu.tr (M. Sag ˘lam). 0169-4332/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2004.03.003