ИСТИНА

Micro- and nanostructures are becoming increasingly important for technology and basic science. One of the methods for the formation of micro- and nanostructures is the local deposition of 3D microstructures of high aspect ratio using an end-face of a wire as the microanode. The microanode moves at a constant velocity with respect to the cathode surface to create structures. A simplified analytical solution of the problem of the formation of micro-structure (microcolumn) during the local electrodeposition of metal with moving disk microanode is presented. The calculated results enable one to determine the voltage, which ensures a constant interelectrode distance during the deposit growth, by the prescribed initial interelectrode distance and to estimate the height of microcolumn at any time. A mathematical model and a scheme of numerical simulation of the formation of 3D microstructures by maskless local electrochemical deposition of metal using a moving anode are developed [1, 2]. The numerical solution of the mathematical problem is performed using the finite element method on the irregular grid, which is deformed and adaptively remeshed during modeling of the deposit growth. Evolution of deposit surface at various exchange current densities, transfer coefficients, interelectrode distances and various dependences of current efficiency on the current density is calculated. It is shown that the kinetic parameters of electrochemical reaction and the interelectrode distance have a pronounced effect on the shape and dimensions of the formed microstructures. At low exchange current densities, nearly cylindrical deposits form. With an increase in the exchange current density, the role of the edge effect near the outer boundary of the disk anode increases and the distribution of the current density in the radial direction becomes nonmonotonic. As a result, the shape of the deposit changes from cylindrical to tubular. The wall thickness of tubular deposit decreases with increasing exchange current density. It is found that a decrease of the current efficiency with increasing current density (for example, due to the hydrogen evolution) reduces the edge effect and promotes the formation of cylindrical deposits. The edge effect limits the value of the deposit aspect ratio. To raise the aspect ratio of the deposit, it is necessary to reduce the initial interelectrode distance. The results of modeling allow one to determine the relationships between the parameters of electrodeposition and the shape and dimensions of formed microstructures. These data can be used to predict the results of local electrodeposition of metal and to optimize the operation conditions.