Gas sensing of colloidal polyaniline in a chemoresistor consisting of nanometer electrodes

• Published in: Microelectronic engineering 2011-09, Vol.88 (9), p.3035-3042
• Main Authors: Park, S.Y., Bae, M.S., Jeon, I.D., Lee, J.J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemoresistor; Colloid Pani; Colloids; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Diffusion in solids; Electric potential; Electro migration; Electrodes; Electromigration; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronics; Exact sciences and technology; Gaps; Gas sensor; General equipment and techniques; Hopping mechanism; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Lithography; Metal particles; Microelectronic fabrication (materials and surfaces technology); Nanometer electrode; Networking structure; Nonlinearity; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sensors; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Surface double layers, schottky barriers, and work functions; Transport properties of condensed matter (nonelectronic)
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2011.05.003

The high conductivity of colloid-conducting polymers is explained by the networking structures and the hopping mechanisms of the metallic particles [1,2,4]. To observe how the metallic region and the networking structures differ in sensing NH 3 gas, E-beam lithography and electromigration were used to make chemoresistors with nanometer-gap electrodes. Colloid Pani was coated on a nanometer gap as a reaction matrix for the gas. The I– V curves were measured in a vacuum and the NH 3 gas was nonlinear. In sensors with a gap of less than 10 nm, there was a two- or threefold increase in the conductivity, and the work function decreased from 600 meV in a vacuum to 250 meV in NH 3 gas. In contrast, the conductivity of sensors with gaps of 200 and 500 nm decreased to 1/1000 in the NH 3 gas environment. The decrease of the conductivity can be explained by electron–hole annihilation, which appears to occur on the surface of the secondary particles. With comb-type electrodes, the operating voltage can be decreased by three orders of magnitude. In electrodes with 200 and 500 nm gaps, the I– V has a step-type response to NH 3 gas.