Laser Synthesis of ZnO Nanostructures
Shiva Gadag and Mool Gupta
Solid state sintering of ZnO powder particles is possible by using µs pulses of a light emitting diode laser induced acoustic ablation shockwave when undertaken in water. Solid state sintering of ZnO was possible with a 300 µS pulse width and an 805 nm wavelength diode laser. The overall growth of 300 nm and uni-dimensional growth of 500 nm along the  C-axis of hexagonal ZnO structures are confirmed by SEM and AFM nanoscope studies of solid-state shock wave sintering of ZnO by 300 µs pulses of the diode laser. On the other hand, solid state sintering of spin coated ZnO nanoparticles (24–71 nm initial size) by a 10 ns pulsed Nd:YAG laser ablation in air generates massive growth of 5 micrometre bulbs resembling the growth of cactus plants. However, at a higher laser fluence ‘vapour-liquid-solid’ phase condensation by rapid cooling results in an evolution of nanostructures – tetrapods, nanospheres, nanorods, nanowire and their interconnections. Optically transparent but electrically conductive nano wire interconnections synthesised by the liquid phase laser induced “shockwave sintering” by Q-switched nanosecond pulses by a Nd:YAG laser are of immense importance to integrated microelectronics as also of optoelectronics applications.