The Illumination Intensity and Applied Bias Voltage on Dielectric Properties of Au/Polyvinyl Alcohol (Co, Zn-Doped)/n-Si Schottky Barrier Diodes Habibe Uslu, 1 S emsettin Altındal, 1 Tuncay Tunc ¸, 2 _ Ibrahim Uslu, 3 Tofig S. Mammadov 1,4 1 Department of Physics, Faculty of Science and Arts, Gazi University, Ankara, Turkey 2 Science Education Department, Faculty of Education, Aksaray University, Aksaray, Turkey 3 Department of Chemistry Education, Selc ¸uk University, Konya, Turkey 4 Department of Nano Technology, National Academy of Science, Institute of Physics, Baku, Azerbaijan Received 16 April 2010; accepted 2 August 2010 DOI 10.1002/app.33131 Published online 13 October 2010 in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: The Au/polyvinyl alcohol (PVA) (Co, Zn- doped)/n-Si Schottky barrier diodes (SBDs) were exposed to various illumination intensities. Illumination effect on the dielectric properties has been investigated by using capaci- tance–voltage (C–V) and conductance–voltage (G/x–V) char- acteristics at 1 MHz and room temperature. The values of dielectric constant (e 0 ), dielectric loss (e 00 ), loss tangent (tand), electric modulus (M 0 and M 00 ), and AC electrical conductiv- ity (r AC ) were found strongly intensity dependent on both the illumination levels and applied bias voltage especially in depletion and accumulation regions. Such bias and illumina- tion dependency of these parameters can be explained on the basis of Maxwell–Wagner interfacial polarization and restructuring and reordering of charges at interface states. In addition, the e 0 –V plots also show an intersection feature at  2.8 V and such behavior of the e 0 –V plots appears as an abnormality compared with the conventional behavior of an ideal SBD. The obtained results revealed that illumination intensity enhances the conductivity of Au/PVA(Co, Zn- doped)/n-Si SBD. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: 322–328, 2011 Key words: PVA; illumination effect; voltage dependent; dielectric properties; AC electrical conductivity INTRODUCTION Polyvinyl alcohol (PVA) is the most interesting ma- terial in view of its large scale electronic application and optoelectronic application. A metal such as cobalt (Co), nickel (Ni), and zinc (Zn) doped PVA films causes improvement of the polymer behavior and often even brings about a progress in perform- ance. Recently, illumination intensity has become one of the most common process producing modifi- cations in their morphological structures, electronic, optoelectronic, and dielectric properties. 1–6 The exis- tence of interfacial layer like insulator or organic materials makes them rather sensitive to illumina- tion intensity. The performance of Schottky barrier diodes (SBDs) and solar cells is drastically influ- enced by the quality of interfacial layer between the metal and semiconductor surface. In general, consid- ering the performance of these devices, there are several effects that cause deviations of the ideal behavior, and, therefore, they must be taken into account. These include the effects of interfacial layer, interface states (N ss ), and the barrier homogeneity at metal/semiconductor (M/S) interface, series resist- ance (R s ) of device, and fabrication process. Photo- diode based on metal-semiconductor SBDs can be fabricated by using different organic semiconduc- tors. When these devices, with an organic interfacial layer, are illuminated, electron-hole pairs are pro- duced so that these devices show photovoltaic fea- ture. Organic materials have a wide application in the thin film electronics because of their low cost production, low molecular weight, and their being produced easily compared with conventional inor- ganic based technologies. They can be produced in large quantities by simple methods like spin coating, which lowers the production cost. 7 There are many reports about conjugated conduct- ing polymers on the area of electronic and optoelec- tronic. Among the various conducting polymers, polyvinyl alcohol, polyaniline, poly (alkylthiophene), polypyrrole, polyophene, and poly (3-hexylthio- phene) became an attractive research topic to chem- ists, physicists, and electrical engineers alike because of their potential applications and interesting prop- erties. 5,8–11 In addition, there are many reports in the literature on PVA based electronic devices and their electric, optic, and dielectric properties as a function of frequency and temperature. 1–16 However, there are few studies on the electrical and dielectric prop- erties and AC electrical conductivity (r AC ) under Correspondence to: H. Uslu (h.uslu@gazi.edu.tr). Journal of Applied Polymer Science, Vol. 120, 322–328 (2011) V C 2010 Wiley Periodicals, Inc.