Nanometer-scale deposition of metal plating using a nanopipette probe in liquid condition

We describe a novel technique of a local metal plating using an atomic force microscope (AFM) with a nanopipette probe in liquid condition. A glass nanopipette, filled with CuSO₄ electrolyte solution, was used as the AFM probe. An electrode wire inside the electrolyte-filled nanopipette and the conductive surface of a Au-sputtered glass slide were employed as the anode and the cathode, respectively. To avoid drying of the nanopipette solution and clogging of the probe-edge aperture, the edge of the nanopipette was immersed in the same electrolyte solution in a liquid cell placed on the Au substrate. As for controlling the distance between the probe edge and the surface in the liquid, the nanopipette probe glued on a tuning fork quartz crystal resonator was vertically oscillated to use a method of frequency modulation in tapping-mode. By utilizing the probe-surface distance control during the deposition, nanometer-scale Cu dots were successfully deposited on the Au surfaces without diffusion of the deposition even in the liquid condition. This technique of local deposition in a liquid would be applicable for various fields such as the fabrication of micro/nanometer-scale devices and the arrangement of biological samples.