127 Mater. Res. Soc. Symp. Proc. Vol. 1439 © 2012 Materials Research Society DOI: 10.1557/opl.2012.1152 ABSTRACT Highly sensitive electrolyte-insulator-semiconductor (EIS) sensors were realized by the integration of Si nanowires (NWs), which were fabricated by using a simple and economic electroless wet etching technique. EIS sensors with NWs longer than 1 μm were observed to have considerably increased capacitance and high pH sensitivity. The pH sensitivity of the EIS sensor with 3.8 μm long NWs was 60.2 mV/pH, which is higher than the theoretical Nernstian of 59 mV/pH. The EIS sensors with NWs exhibited slightly worse pH hysteresis and drift properties than that of the conventional planar type EIS sensor. The increases in pH sensitivity, hysteresis and drift are attributable to the extended surface area of the EIS sensors enabled by the NWs. INTRODUCTION EIS sensor can detect a small variation in the concentration change of ions at the gate by measuring the capacitance change of its system [1]. It has been attracting interests owing to its bio-chemical sensing capability, fast response, and simple and miniaturized structures. EIS sensors, however, were not widely used because they have shortcomings, such as sensing limit lower than the the Nernstian (59 mV/pH), small capacitance, and low reliability. Diverse materials and structures, such as high-k dielectric materials and porous Si have been applied to EIS sensors in order to improve sensing capability and reliability of the sensors [2, 3]. Similar to the porous Si EIS sensors, Si NWs were employed to increase the surface area of EIS sensors. There are ample number of publications on NW based sensors, however, the integration of electroless wet-etched Si NWs into EIS sensors was demonstrated for the first time in this work. The electroless wet etch technique allows us to fabricate uniform Si NWs in a large substrate without using expensive tools and a number of hazardous chemicals. A slight disadvantage of the NW EIS sensors is that it needs relatively more careful handling because NWs are not mechanically robust. However, the extended gate structrure of an EIS sensor can address this issue [4]. In the present work, sensing capabilities such as pH sensitivity and reliability as well as structural characterization of NW integrated EIS sensors were discussed. EXPERIMENTAL DETAILS NW integrated EIS sensors were fabricated in p-type (100) Si substrates. Si nanowires Silicon Nanowire Integrated Electrolyte-Insulator-Semiconductor Sensor with an Above-Nernstian Sensitivity for Bio-Sensing Applications Jin Yong Oh 1 , Hyun-June Jang 2 , Won-Ju Cho 2 , Nezih Pala 3 , M. Saif Islam 1 1 Department of Electrical and Computer Engineering, University of California, Davis, CA 95616 2 Department of Electronic Materials Engineering, Kwangwoon University, Seoul, Korea 3 Electrical & Computer Engineering, Florida International University, Miami, FL 33174