Nanoobjects microscopy
Peculiarities of electrochemical reactions in an aqueous nano-cell formed in the contact of AFM probe with graphene/graphene oxide
Lytvyn P.M., Efremov A.A., Prokopenko I.V.
V. Lashkaryov Institute of Semiconductor Physic, NAS of Ukraine. Prospect Nauky, 41, Kyiv-03028, Ukraine. 
E-mail: plyt@isp.kiev.ua

 The transition from a synthesis of graphene-based and graphene-like materials to the formation of operation-ready nanostructures for device applications is a prospective and actual R&D problem. The nanolithography with a scanning probe is the very method that has the greatest potential for laboratory prototyping in 2D electronics. It allows to perform the transition from macroscopic electrochemistry to nano-electrochemistry and to the direct mask-less formation of structural elements such as oxide or conductor tracks and nano-trenches. The problem of synthesis and modification of graphene has its own specific nuances caused by the uncertainty in the reaction mechanisms in ultra-small volumes of liquids at high values of the Laplace pressure in meniscus or capillary, in strong electrostatic fields, under the complicated control of the liquid phase purity and others.
	
Fig.1. AFM image of locally modified surface. Insert shows the model of electrochemical capillary. 	
We analyzed some features of physical processes and electrochemical reactions inside the aqueous nano-capillary, formed in the contact of metallized tip of a scanning microscope with a surface of carbon material under application of electric field. Several variants of the numerical model for the description of mass transfer and electrochemical reactions in a nano-sized capillary under the tip of atomic force microscope have been developed. Dependencies of the modification depth of sp3/sp2 carbon films and rate of graphene oxide reducing on the mode of electrochemical treatments were obtained. Intensity of the heat dissipation in nano-capillaries under an electrochemical surface scratching was analyzed. The value and role of electrostatic forces in the stabilization of geometrical parameters of generated electrochemical nano-reactor near the AFM tip was evaluated. Calculations and numerical estimations are compared with the available experimental data.