Highly sensitive NO2 sensors by pulsed laser deposition on graphene

Abstract: Graphene as a single-atomic-layer material is fully exposed to environment and has therefore a great potential for creating of sensitive gas sensors. However, in order to realize this potential for different polluting gases, graphene has to be functionalized - adsorption centers of different type and with high affinity to target gases have to be created at its surface. In this present work, modification of graphene by small amounts of laser ablated materials is introduced for this purpose as a versatile and precise tool. The approach was demonstrated with two very different materials chosen for pulsed laser deposition (PLD), a metal (Ag) and a dielectric oxide (ZrO2). It was shown that the gas response and its recovery rate can be significantly enhanced by choosing the PLD target material and deposition conditions. The response to NO2 gas in air was amplified up to 40 times in case of PLD-modified graphene in comparison with pristine graphene and reached 7-8% at 40 ppb of NO2 and 20-30% at 1 ppm of N2. These results were obtained after PLD in gas environment (5 x 10-2 mbar oxygen or nitrogen) and atomic areal densities of deposited materials of were about 10 15 cm-2. The ultimate level of NO2 detection in air, as extrapolated from the experimental data obtained at room temperature under mild UV-excitation, was below 1 ppb.