Effects of graphene defects on gas sensing properties towards NO₂ detection

Abstract

The crystal structure of graphene flakes is expected to significantly affect their sensing properties. Here we report an experimental investigation on the crystalline structure of graphene aimed at exploring the effects on the gas sensing properties. The morphology of graphene, prepared via Chemical Vapor Deposition (CVD), Liquid Phase Exfoliation (LPE) and Mechanical Exfoliation (ME), is inspected through Raman spectroscopy, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). CVD and LPE-graphene structures are found to be more defective with respect to ME-graphene. The defects are due to the jagged morphology of the films rather than originating from intrinsic disorder. The flatness of ME-graphene flakes, instead, explains the absence of defects. Chemiresistors based on the three different graphene preparation methods are subsequently exposed to NO in the concentration range 0.1-1.5 ppm (parts per million). The device performance is demonstrated to be strongly and unambiguously affected by the material structure: the less defective the material is, the higher the response rate is. In terms of signal variation, at 1.5 ppm, for instance, ME-graphene shows the highest value (5%) among the three materials. This study, comparing simultaneously graphene and sensors prepared via different routes, provides the first experimental evidence of the role played by the graphene level of defectiveness in the interaction with analytes. Moreover, these findings can pave the path for tailoring the sensor behavior as a function of graphene morphology.

Wafer-scale transfer-free process of multi-layered graphene grown by chemical vapor deposition

“…The average thickness of about 10 nm [51] could indicate the nature of the material more similar to the ultra-thin graphite. However, the presence of multi-layered structures is confirmed by the Raman spectra, as reported in previous report [46].…”

“…The average ratio I(D)/I(G) indicates the presence of some defects in the material [43,46,47,49,50]. In this letter, we mostly showed the power of the transfer-free process.…”

“…The growth and target substrate are the same, thus avoiding any transfer from the two substrates, reducing the possibility to degrade the film and enabling the direct integration of graphene-based devices at large scale [42]. This outcome represents a remarkable step forward compared to the method we reported in our previous works [43][44][45][46]. In those papers, we dealt with areas of patterned MLG of hundreds μm 2 which we fabricated using several steps in the lithographic process.…”

Research Progress of Gas Sensor Based on Graphene and Its Derivatives: A Review

“…In 2017, F. Ricciardella et al from Delft University of Technology contrasted the response of mechanical peel graphene (ME-Gr), CVD prepared graphene (CVD-Gr), and liquid peeling graphene (LPE-Gr) toward NO 2 [74], as shown in Figure 11. LPE-Gr (green line) showed no obvious recovery.…”

Mass measurement of graphene using quartz crystal microbalances

“…The remarkable electronic [1,2], thermal [3][4][5] and mechanical [6][7][8] properties of graphene have opened the door for many new electronic devices [9][10][11][12] and sensors [13][14][15][16][17][18][19][20]. Fabrication of these devices on wafer-scale often requires transfer of sheets of single-layer graphene grown by chemical vapor deposition, using a support polymer [21][22][23][24][25][26].…”