Key words: sapphire, laser backside wet etching, microstructuring, thermoplasmonic, supercritical water, ultrahigh pressures and temperatures
For effective and well-controlled microstructuring of sapphire, the method of thermoplasmonic laser-induced backside wet etching (TPLIBWE) was applied. The method is based on the generation of highly absorbing silver nanoparticles generated in the course of the pulsed-periodic laser irradiation, which are formed as a result of laser destruction of AgNO3, a silver precursor dissolved in water. The process of sapphire etching is carried out by supercritical water at ultrahigh temperatures and pressures substantially exceeding the critical values for water and formed at the sapphire/water interface as a result of the absorption of laser pulses by silver nanoparticles. The mechanism of TPLIBWE is considered, the etching rates reaching ∼100 nm/pulse are determined. The formation of aluminum nanoparticles is revealed, which indicates the deep destruction of Al2O3 as a result of TPLIBWE.