Nanofriction characteristics of h-BN with electric field induced electrostatic interaction

The nanofriction properties of hexagonal boron nitride (h-BN) are vital for its application as a substrate for graphene devices and solid lubricants in micro- and nano-electromechanical devices. In this work, the nanofriction characteristics of h-BN on Si/SiO₂ substrates with a bias voltage are explored using a conductive atomic force microscopy (AFM) tip sliding on the h-BN surface under different substrate bias voltages. The results show that the nanofriction on h-BN increases with an increase in the applied bias difference (V_t-s) between the conductive tip and the substrate. The nanofriction under negative V_t-s is larger than that under positive V_t-s. The variation in nanofriction is relevant to the electrostatic interaction caused by the charging effect. The electrostatic force between opposite charges localized on the conductive tip and at the SiO₂/Si interface increases with an increase in V_t-s. Owing to the characteristics of p-type silicon, a positive V_t-s will first cause depletion of majority carriers, which results in a difference of nanofriction under positive and negative V_t-s. Our findings provide an approach for manipulating the nanofriction of 2D insulating material surfaces through an applied electric field, and are helpful for designing a substrate for graphene devices.