Suspended graphene arrays for gas sensing applications

Suspended graphene (SUS-G) has long been hailed as a potential 'true graphene' as its conductive properties are much closer to those of theoretical graphene. However, substantial issues with yield during any device fabrication process have severely limited its use to date. We report the successful fabrication of a fully operational prototype of a miniature 9 mm2 suspended graphene array sensor chip, incorporating 64 graphene sensor devices, each comprising of 180 SUS-G membranes with ever reported 56% fully intact graphene membranes for sensitive and selective gas sensing applications. While a bare sensor chip can operate as a sensitive gas sensor for a variety of gasses such as ammonia, nitrogen dioxide and carbon monoxide, down to ppm/ppb concentrations, a tetrafluorohydroquinone functionalized sensor acquires specificity to formaldehyde gas molecules with limited cross-sensitivity for ethanol, toluene and humidity. Unlike an equivalent device with fully supported functionalized graphene sensor, a functionalized SUS-G sensor can be furthermore reset to its baseline by using UV assisted desorption instead of substrate heating. The low power UV irradiation does not show severe damage to the SUS-G structures and loss of functional probes for the formaldehyde gas - a previously unreported feature. A resettable and selective formaldehyde gas sensor array with mass manufacturability, low power consumption and overall dimensions down to 1 mm2, would represent a significant technological step forward in the development of an electronic nose, for the simultaneous detection of multiple-target gases, with potential for integration in portable electronic devices and the internet of things.