Effects of Deposition Pressure and Target-Substrate Distance on Growth of ZnO by Femtosecond Pulsed Laser Deposition

Undoped Zinc oxide (ZnO) was successfully deposited on silicon (100) substrate by femtosecond pulsed laser deposition. A mode-locked femtosecond laser operating at 790 nm wavelength, 100 fs pulse duration and 80 MHz repetition rate was used as an excitation source. The depositions were carried out at vacuum pressures of 10-10 mbar and oxygen background gas pressures of 10 -10 mbar. Energy dispersive spectroscopy of samples grown without oxygen background gas shows higher zinc composition on deposited material as compared to oxygen that leads to off stoichiometric ZnO films. Scanning electron microscopy (SEM) images shows that increasing oxygen gas pressure increased the particle size of the deposited ZnO. The material deposited at 2x10 mbar oxygen pressure revealed clustering of nanorods forming a flower-like structure that has an average length of 2700 nm and an average diameter of 450 nm. The X-ray diffraction spectra show c-axis orientation of the deposited ZnO with (002) and (110) reflection.