External-field-controlled laser wet etching of polycrystalline Al₂O₃TiC

Laser-induced etching of polycrystalline Al₂O₃TiC material by tightly focused CW Ar ion laser has been investigated in both H₃PO₄ and KOH solutions with influence of an external electric field. It is found that a weak external electric field will change the ions distribution in chemical solutions and cause obvious change in etching behavior. The laser etching in a H₃PO₄ solution can be enhanced by both positive and negative biases of the substrate. While etching in a KOH solution, a positive bias can enhance the etching reaction, whereas a negative bias can suppress the etching process. It is also found that the external electric field can always enhance the mass transfer between reaction products and fresh etchant in a H₃PO₄ solution. It is revealed that the supply of H⁺ ions contributes to the etching process in a H₃PO₄ solution, while the supply of OH^- ions contributes to the etching process in a KOH solution. The electric field can be used to control the etching process to achieve fast tuning and higher accuracy.