Etching of Sapphire in Supercritical Water at Ultrahigh Temperatures and Pressures under the Conditions of Pulsed Laser Thermoplasmonics

The method of thermoplasmonic laser-induced backside wet etching (TPLIBWE) is applied for effective and well-controlled microstructuring of sapphire. The method is based on the generation of highly absorbing silver nanoparticles in the course of the pulsed-periodic laser irradiation. The silver nanoparticles are formed as a result of the reduction of a water-dissolved precursor, AgNO3. The process of sapphire etching occurs via the formation of supercritical water at ultrahigh temperatures and pressures (which significantly exceed the critical values for water) and the formation of silver nanoparticles at the sapphire/water interface as a result of the absorption of laser radiation. The mechanism of TPLIBWE is considered and the etching rate, which reaches ~100 nm/pulse, is determined. The formation of aluminum nanoparticles, which indicates a deep destruction of Al2O3 as a result of TPLIBWE, is observed.