Electrochemical direct writing and erasing of silver nanostructures on phosphate glass using atomic force microscopy

This paper reports a liquid-free, mask-less electrochemical direct-write lithographic technique using an atomic force microscopy (AFM) probe for writing silver nanostructures in minutes on an optically transparent substrate. Under ambient conditions, silver is locally and controllably extracted to the surface of superionic (AgI)_0.25 (AgPO₃)_0.75 glass by bringing a conductive AFM probe tip in contact with it, biasing the probe with a negative voltage, and regulating the resulting current. The growth mechanism of the resulting nanostructure is explored by extracting silver with a stationary AFM tip on the surface of the silver. A moving tip was then used to produce continuous lines, solid films and discrete dots of silver by implementing continuous and pulsed current writing approaches. The line dimensions depend on writing speed and current flowing in the electrochemical circuit, while the size and spacing of the dots depend on the parameters (magnitude, duration and frequency) of the current pulses and the writing speed of the AFM tip. Line-widths in the ∼100 nm range are demonstrated. Our investigation also shows that a threshold potential must be overcome to be able to draw and reduce silver ions on the glass surface. When polarity between the electrodes is reversed, the patterned silver ionizes back into the glass, thus offering the capability to erase and rewrite Ag patterns on the glass surface.