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Unformatted text preview: 3400 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 54, NO. 12, DECEMBER 2007 Design Considerations of Silicon Nanowire Biosensors Pradeep R. Nair, Student Member, IEEE , and Muhammad A. Alam, Fellow, IEEE Abstract Biosensors based on silicon nanowires (Si-NWs) promise highly sensitive dynamic label-free electrical detection of biomolecules. Despite the tremendous potential and promising experimental results, the fundamental mechanism of electrical sensing of biomolecules and the design considerations of NW sensors remain poorly understood. In this paper, we discuss the prospects and challenges of biomolecule detection using Si-NW biosensors as a function of device parameters, fluidic environment, charge polarity of biomolecules, etc., and refer to experimental re- sults in literature to support the nonintuitive predictions wherever possible. Our results indicate that the design of Si nanobiosensor is nontrivial and as such, only careful optimization supported by numerical simulation would ensure optimal sensor performance. Index Terms Biosensors, DNA, PoissonBoltzmann (PB), protein detection, random dopant fluctuations, sensitivity. I. INTRODUCTION E LECTRONIC, rather than chemical, detection of biomole- cules is one of the widely researched topics in nanotech- nology. Systems based on nanosensor arrays, which can provide fast, low-cost, and high-throughput analysis of biological processes, promise to revolutionize many areas in medicine and biochemistry, ranging from the detection and diagnosis of diseases to the discovery of new drug delivery systems. Since the early 1970s, microelectronic sensors based on thin film transistors and ion-sensitive field-effect transistors (ISFETs) have been explored as a low-cost alternative to traditional chemical sensors with potential for on-chip integration [1]. However, lack of good solid-state electrodes, parasitic sensi- tivity to temperature and light, time-dependent instability of sensor parameters, etc., have hindered their development as a disruptive biosensor technology [2]. Instead, over the years, the chemical sensors have adopted fluorescent labeling and parallel optical detection techniques for fast detection of biomolecules at relatively low concentrations (e.g., DNA microarray [3]). Although these fluorescence-based sensors are now widely used, they still require expensive and time-consuming pre- processing and postprocessing for sample preparation and data Manuscript received February 8, 2007; revised August 21, 2007. This work was supported in part by the National Science Foundation (NSF), by the National Institutes of Health, and by the NSF Network for Computational Nanotechnology. The review of this paper was arranged by Editor C. Nguyen....
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