Tribological properties of two dimensional (2D) atomic layers are quite different from the three-dimensional (3D) continuum materials, due to the unique mechanical responses of 2D layers. Friction in 2D layered materials is highly dependent on thickness, substrate, chemical composition, and microstructure such as ripple. It has been found that friction of 2D layered materials increases when the thickness decreases. It was also found that friction in 2D materials is drastically increased after chemical modification, such as fluorination, oxidation and hydrogenation.<br/>In this study, we show the nanotrological properties of graphene oxide (GO) investigated with friction force microscopy in ultrahigh vacuum. By using the combination of friction force microscopy and conductive atomic force microscopy, we investigated the subdomain structures of single-layer GO. Friction and conductance mapping showed that a single-layer GO flake has subdomains several tens to a few hundreds of nanometers in lateral size. The GO subdomains exhibited low friction (high conductance) in the sp2-rich phase and high friction (low conductance) in the sp3-rich phase. The friction of GO and reduced graphene oxide (rGO) were studied as changing the number of layers. We show that friction on GO does not exhibit the thickness dependence, while that on rGO shows the clear thickness dependence. We provide the relevant theoretical interpretation to explain the influence of thickness and chemical reduction of GO on the nanoscale friction.

Effect of thickness and chemical reduction of graphene oxide on nanoscale friction

253rd National Meeting (2017)

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