The two-dimensional nature of graphene leads to an extremely high surface-to-volume ratio, which promises ultrahigh sensitivity of graphene-based sensors. The ultimate thinness and high Young’s modulus of graphene may be utilized in membrane-based devices with very high resonant frequencies for mass sensing applications. In combination with an impressive stretchability, this may further lead to applications as piezoresistive graphene membrane-based sensors. While the fundamental properties of graphene apparently make it an ideal candidate for such applications, in reality one has to deal with a number of parasitic effects that can influence and falsify the response of a graphene sensor. This talk aims to carefully balance the discussion about the merits and disadvantages of graphene-based sensors based on experimental data. 

This presentation will discuss a laser annealing technique for the fabrication of large-area graphene-based transparent thin film conductors. The graphene ink was produced by a liquid phase exfoliation (LPE) method through exfoliating graphite powders in dimethylformamide (DMF), stabilizing the obtained graphene flakes with polymers, and finally exchanging DMF by terpineol to increase graphene concentration, adjust ink  viscosity, and reduce solvent toxicity. The ink was deposited on substrates by drop casting and then annealed to remove stabilizing polymers. Subsequently, a laser beam was scanned across the film. While the drop casted films are highly resistive, the laser treatment results in sheet resistances on the order of 30kΩ/sq. Meanwhile, the transmittance of the films increases from 60% to more than 85% (at λ = 550 nm). Furthermore, Raman data indicate that by laser annealing the films, both the FWHM of the Raman G band and the integrated intensity ratio of the D band to the G band decrease significantly. This confirms that the laser treatment reduces structural disorder within the graphene flakes. AFM and SEM images show topography changes in the films after laser treatment, which have a significantly more homogenous and smooth surface on the order of 10 nm roughness. The method also improves the resistivity and transparency of inkjet printed graphene films. The final part of the presentation will be dedicated to laser annealing of 2D materials other than graphene.

The two-dimensional nature of graphene leads to an extremely high surface-to-volume ratio, which promises ultrahigh sensitivity of graphene-based sensors. The ultimate thinness and high Young’s modulus of graphene may be utilized in membrane-based devices with very high resonant frequencies for mass sensing applications. In combination with an impressive stretchability, this may further lead to applications as piezoresistive graphene membrane-based sensors. While the fundamental properties of graphene apparently make it an ideal candidate for such applications, in reality one has to deal with a number of parasitic effects that can influence and falsify the response of a graphene sensor. This talk aims to carefully balance the discussion about the merits and disadvantages of graphene-based sensors based on experimental data. 

This presentation will discuss a laser annealing technique for the fabrication of large-area graphene-based transparent thin film conductors. The graphene ink was produced by a liquid phase exfoliation (LPE) method through exfoliating graphite powders in dimethylformamide (DMF), stabilizing the obtained graphene flakes with polymers, and finally exchanging DMF by terpineol to increase graphene concentration, adjust ink  viscosity, and reduce solvent toxicity. The ink was deposited on substrates by drop casting and then annealed to remove stabilizing polymers. Subsequently, a laser beam was scanned across the film. While the drop casted films are highly resistive, the laser treatment results in sheet resistances on the order of 30kΩ/sq. Meanwhile, the transmittance of the films increases from 60% to more than 85% (at λ = 550 nm). Furthermore, Raman data indicate that by laser annealing the films, both the FWHM of the Raman G band and the integrated intensity ratio of the D band to the G band decrease significantly. This confirms that the laser treatment reduces structural disorder within the graphene flakes. AFM and SEM images show topography changes in the films after laser treatment, which have a significantly more homogenous and smooth surface on the order of 10 nm roughness. The method also improves the resistivity and transparency of inkjet printed graphene films. The final part of the presentation will be dedicated to laser annealing of 2D materials other than graphene.