Effects of temperature, target/substrate distance, and background pressure on growth of ZnO nanorods by pulsed laser deposition.

The growth of ZnO nanorods on the c-plane of Al2O3 substrates by PLD was been investigated by controlling processing conditions such as growth temperature, distance between target and substrate, and background oxygen pressure. ZnO nanorods were observed from the growth temperature of 600 degrees C for the oxygen pressure of 30 mTorr and the target/substrate distance of 70 mm. The diameters of the ZnO nanorods at the temperature of 700 degrees C and the oxygen pressure of 30 mTorr were approximately 200, 70, and 40 nm for the distance of 45, 70, and 100 mm, respectively. ZnO films without nanorods were observed at the distance of 70 mm and the temperature of 700 degrees C when the oxygen pressure decreased to 1 mTorr. The kinetic energy of the ablated particles by the laser decreases during collisions with background oxygen molecules, resulting in conditions that favor the growth of ZnO nanorods.