Effect of Aspect Ratio (Length:Diameter) on a Single Polypyrrole Nanowire FET Device

• Published in: Journal of physical chemistry. C Vol. 114; no. 31; pp. 13375 - 13380
• Main Authors: Shirale, Dhammanand J, Bangar, Mangesh A, Chen, Wilfred, Myung, Nosang V, Mulchandani, Ashok
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 12.08.2010
• Subjects: C: Electron Transport, Optical and Electronic Devices, Hard Matter
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp104377e

The effect of different aspect ratios (length to diameter ratio, L:D) on single polypyrrole (Ppy) nanowire based field effect transistor (FET) sensors for real time pH monitoring was studied. Ppy nanowires with diameters of ∼60, ∼80, and ∼200 nm were synthesized by using electrochemical deposition inside anodized aluminum oxide (AAO) template and were assembled using AC dielectrophoretic alignment followed by maskless anchoring on a pair of gold electrodes separated with different gap lengths. Microfabricated gold electrode patterns with gap size between 1 and 4 μm were developed by means of MEMS technique (photolithography), and used in a field effect transistor geometry with a pair of microfabricated gold contact electrodes serving as a source and a drain, and a platinum (Pt) mesh (anchored in a microfluidic channel) as a gate electrode. When the effects of different aspect ratios of the nanowire were compared, higher sensitivity was recorded for a higher aspect ratio. The sensitivity was further improved by modulating the gate potential. These FET sensors based on a single polypyrrole nanowire exhibited excellent and tunable sensitivity toward pH variations.