Optimisation of GaAs nanocrystals synthesis by laser ablation in water

Laser ablation of a gallium arsenide (GaAs) wafer immersed in distilled water was carried out using the fundamental wavelength of a high frequency Nd:YAG laser with 240 ns pulse duration. Rate of nanoparticles generation through laser ablation for various amounts of laser pulse energies (0.4–0.94 mJ) and repetition rates (400–2000 Hz) were studied and a maximum ablation rate of 19.6 µgr/s was obtained. Formation of the pure GaAs nanocrystals (NCs) is confirmed using TEM micrograph and X-ray diffraction analysis. Band-gap energy of generated GaAs NCs is calculated by Tauc method to be between 2.48 and 2.60 eV which is larger than the band-gap energy of bulk GaAs. The band-gap energy of NCs is increased by increasing the energy of laser pulses and is decreased by increasing the pulse repetition rate.