Formation and size control of tungsten nano particles produced by Nd:YAG laser irradiation

Abstract
Nanometer-size particles (nanoparticles) of tungsten (W) were synthesized by the laser irradiation of a substrate under low He gas pressure using a Q-switch Nd:YAG laser and measured with the TEM and a low-pressure differential mobility analyzer (LP-DMA). Two particle formation mechanisms were shown for the pressure dependency of the nanoparticles size distribution. The smaller size nanoparticles were mainly formed by an evaporation mechanism and the large crystalline nanoparticles were made by a kind of a splash induced by laser incidence. The two nanoparticle formation mechanisms were not observed clearly when using normal pulse Nd:YAG laser.