Smart Gas Sensor and Noise Properties of Single ZnO Nanowire

A new zinc oxide nanowire (NW) gas sensor based on the commercially available 0.35 mu m complementary metal-oxide-semiconductor (CMOS) process is developed. The smart gas sensor consists of a gas-sensing resistor and an interface circuit for resistance measurement. The single ZnO NW synthesized by the vapor-liquid-solid (VLS) process is utilized as the gas-sensing resistor. The interface circuit for the resistance measurement of the single ZnO NW is composed of a ring oscillator circuit, in which the oscillation period is optimized with regards to the ZnO NW resistance and external capacitance to. accurately detect the resistance of the ZnO NW after exposure to the gas. Because the low-frequency noise contains information about the charge, fluctuations which are important for determining the gas-sensing reliability, the low-frequency noise of the single ZhO NW at various agate voltages, source-drain voltages and resistances is systematically characterized and compared with those of CMOS field-effect transistors (FETs) and network carbon nanotubes (CNTs) resistor. (C) 2009 The Japan Society of Applied Physics