Effect of air on oxygen p‐doped graphene on SiO₂

Abstract

Stability in ambient air or in vacuum‐controlled atmosphere of molecular oxygen‐induced p‐type doping of graphene monolayer on SiO2 substrate on Si is investigated by micro‐Raman spectroscopy and atomic force microscopy (AFM). The Raman 2D and G bands spectral positions and amplitude ratio are affected by the permanence in air atmosphere in a time scale of months whereas the vacuum safely maintains the doping effects determined through Raman bands. No morphological effects are induced by the doping and post‐doping treatments. A reactivity of ambient molecular gas with stably trapped oxygen is suggested to induce the doping modification.

Graphene‐SiO2 Interaction from Composites to Doping

“…Overall the effectiveness of doping by oxygen for the sample Gr/SiO 2 /Si has been proven by the previous experiments and this effect has been disentangled from the strain effect. Nevertheless, by maintaining a doped sample in ambient atmosphere for a prolonged time it is observed that some changes in the Raman spectra occur . As shown in Figure , it is found, in particular, that maintaining a sample in room atmosphere for 1 month after being treated in oxygen a red shift of the G and 2D bands peak position occurs and their intensity ratio I 2 D /I G starting from about 1, after treatment, has the tendency to go back to the native value larger than 2 suggesting that some effects have occurred to change the doping.…”

“…As reported in refs. , these effects can also give rise to a complete recovery of the native sample features after a prolonged time of exposure to air and it has been suggested that the role of water in removing the doping is critical. Furthermore, the evolution of the sample during the loss of doping is featured by two trends with very different time‐scales, very similar (in opposite direction) to the already shown doping occurrence of Figure c.…”

“…To go deeper in these effects a specific experiment in water vapor ambient has been carried out. In particular, a Gr/SiO 2 /Si doped by O 2 has been exposed in a Parr reactor to water vapor at the partial pressure of 2 bar and at the temperature of 150 °C . This treatment was able to fully recover the features of the untreated sample evidencing the dedoping properties of water vapor.…”

“…Top: Schematic trapping of oxygen molecules in the interlayer between Gr and substrate. Adapted with permission . Copyright 2016, Wiley.…”

“…The microscope is equipped with a closed‐loop scanner (X,Y,Z maximum scan ranges: 35, 35, 3 µm, respectively) and each image was obtained with a pixel resolution comparable to the tip size. The second is a Veeco DI3100 atomic force microscope using a Nanoscope V controller and TESPA Silicon probes with 8 nm nominal curvature radius for tapping mode measurements …”