Graphene is a two-dimensional (2-D) material which has attracted significant research interest for its unique properties such as tremendous thermal and electrical conductivity, elasticity, transparency, and atomically thin structure. Due to these remarkable merits, studies on graphene for varied applications have become active from few years ago. Over the past few decades, the researchers have studied on gas sensors over diverse materials. However, researches on gas sensors based on graphene are still in the beginning stage. Furthermore, the irreversible response of graphene-based sensors to target gases is one of the critical problems to be overcome for real applications. In this work, we report the reliable operation of highly sensitive graphene chemiresistors using self-heating effect. Since graphene is a 2-D material, both active sensing area and electrodes composed of graphene could be easily defined by simple lithography processes. To prevent heat losses to substrate, graphene oxide bumps and metal oxide nanoposts were used to suspend graphene activation layer. The graphene oxide bumps were built up by drop-casting method and the nanoposts were fabricated by e-beam evaporator. As the chemiresistors consist of suspended structures, they can very efficiently preserve the heat even under low voltage. For the optimal self-heating and consequent high performance of gas sensing, various chemiresistors with different patterns have been fabricated and the responses of the chemiresistors to various gases such as C2H5OH, CH3COCH3, CO, H2, and NO2 have been measured with varying input bias voltages without external heating. Our results show that suspended and self-heated graphene chemiresistors have high and reversible responses to the various gases, which cannot be achieved in conventional graphene sensors. High response and heater-less operation of the suspended graphene chemiresistors suggest the bright future of the graphene-based chemiresistors for use in a wide variety of applications.

Suspended graphene structures on graphene oxide bumps and metal oxide nanoposts with superior chemoresistive properties

248th National Meeting (2014)

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