Electric field induced patterning in Cr film under ambient conditions: A chemical reaction based perspective

Electric field-induced "etching" of Cr film is a tip-based patterning technique that is used to create micro- and nano-sized trenches in the film under ambient conditions. The experimental data obtained in this study reveals that the etching of Cr occurs via the formation of water-soluble CrO3, which spontaneously forms at the cathode tip when a large electric field is applied using a pointed tip in the presence of humid air. By varying experimental conditions, such as vacuum level, gaseous environment, temperature, and humidity, the kinetics of the electric field induced chemical reaction at the cathode was studied. Subsequently, the obtained insights were incorporated into a model to explain the mechanism of the phenomenon. Water vapor in the air surrounding the tip acts as a limiting reactant in the electrochemical oxidation of Cr to CrO3. Insights obtained from this study open new avenues for technological improvements in the patterning technique using this chemical method.