Synthetic Metals 161 (2011) 51–55 Contents lists available at ScienceDirect Synthetic Metals journal homepage: www.elsevier.com/locate/synmet Threshold voltage control of 2,3 benzanthracene organic thin-ﬁlm transistor by visible light for integration of transistors into electronic circuits Fahrettin Yakuphanoglu a,b,∗ , W. Aslam Farooq b a Department of Metallurgical and Materials Engineering, Fırat University, Elazı˘ g, Turkey b Department of Physics, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia article info Article history: Received 8 September 2010 Received in revised form 17 October 2010 Accepted 23 October 2010 Available online 26 November 2010 Keywords: Organic thin ﬁlm transistor 2,3 Benzanthracene Photovoltaic effect abstract The organic ﬁeld-effect transistor having 2,3 benzanthracene as active layer grown on SiO 2 dielectric layer was fabricated. AFM results indicate that 2,3 benzanthracene thin ﬁlm is formed from homogeneous small crystal grains with an average diameter about 200 nm. The electrical parameters such as mobility, threshold voltage, I on /I off ratio and SS value were determined. The obtained I on /I off and S values increase with visible light illumination due to more photogenerated charges. The mobility and threshold values were changed by visible light illumination. The organic thin ﬁlm transistor exhibits a photovoltaic effect in turn-on state. The control of the threshold voltage of 2,3 benzanthracene-based organic thin ﬁlm transistor was achieved by visible light illumination. The change in the threshold voltage is enough for the electronic technology applications of organic thin ﬁlm transistors. © 2010 Elsevier B.V. All rights reserved. 1. Introduction In recent years, there is a great interest in organic thin-ﬁlm transistors (OTFTs) as an alternative to conventional silicon-based transistors because of their various applications including low cost and large-area electronic devices [1–5]. OTFTs can potentially be developed into light-weight, ﬂexible, and low-cost electronic devices [6]. The thin ﬁlm transistors based on p-type organic semiconductors have showed the high-performance and high hole mobilities—of the order of 1 cm 2 /V s [7–9]. p-Type organic semi- conductors, pentacene, rubrene, anthracene, or thiophene organic semiconductors have been extensively used in OTFT applica- tions [8–13,1,14–16] and furthermore, high performance OTFTs can be improved by use of derivatives of pentacene, rubrene, anthracene, or thiophene. On the other hand, organic photo- transistors (OPT) which are type of optical transducer in which light detection and signal ampliﬁcation are one of three ter- minal optoelectronic devices in which light can be used as an external stimulus to create photogenerated carriers in addition to the carriers induced by the gate voltage [17,20,18,19,21]. Organic phototransistors (OPTs) are considered to be one of the feasible applications of OTFTs because of their large absorption properties in ultraviolet (UV) and visible light and the excellent ∗ Corresponding author at: Fırat University, Department of Physics, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia. Tel.: +90 424 237 0000/3621; fax: +90 424 23300 62. E-mail addresses: fyhanoglu@ﬁrat.edu.tr, fyakuphanoglu.v@ksu.edu.sa (F. Yakuphanoglu). photo current generation efﬁciency of organic semiconductors [22–25]. In this work, the ﬁeld-effect transistor having 2,3 benzan- thracene as active layer was grown at room temperature by thermal evaporation deposition. For the ﬁrst time, the electrical and visible light photosensing properties of the 2,3 benzanthracene transistor will be presented. The photocurrent mechanisms of the transistor are also discussed. 2. Experimental details The SiO 2 (200 nm) was grown on p-Si wafer at 1000 ◦ C for 2.5 h and it was used as a dielectric layer. The 2-3 benzanthracene was used as active layer purchased from Aldrich with >99% purity. For fabrication of 2-3 benzanthracene OTFT, the following process was followed. Firstly, the 2-3 benzanthracene thin ﬁlm with 300 nm thickness as an active layer was evaporated on SiO 2 layer by using a Vaksis PVD Handy thermal evaporation system. The thickness of the 2-3 benzanthracene thin ﬁlm was measured by an AFM and was found to be 300 nm. Then, Au source/drain top electrodes onto this ﬁlm were deposited by thermal evap- oration method using a tungsten basket. These electrodes with 100 nm thickness were made through the shadow mask. The channel in 2-3 benzanthracene-OTFT was deﬁned with width (W) 2500 m and length (L) 100 m. The schematic structure of the 2-3 benzanthracene-OTFT is shown in Fig. 1. The surface morphology of 2-3 benzanthracene thin ﬁlm was investigated by atomic force microscope (AFM, Park System, XE100) using noncontact mode. The transistor characteristics of the 2-3 benzanthracene-OTFT were measured by using a KEITHLEY 0379-6779/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.synthmet.2010.10.033