Nanotribology and Nanofabrication of MoO ₃ Structures by Atomic Force Microscopy

Atomic force microscopy was used to characterize the sliding of molybdenum oxide (MoO 3 ) nanocrystals on single-crystal molybdenum disulfide (MoS 2 ) surfaces. Highly anisotropic friction was observed whereby MoO 3 nanocrystals moved only along specific directions of the MoS 2 surface lattice. The energy per unit area to move the MoO 3 nanocrystals along their preferred sliding direction was an order of magnitude less than required to slide macroscopic MoS 2 -bearing contacts. This extreme friction anisotropy was exploited to fabricate multicomponent MoO 3 nanostructures. These reversibly interlocking structures could serve as the basis for devices such as mechanical logic gates.