Preparation And Optical Properties Of ZnO Films Grown By Pulsed Laser Deposition

Zinc Oxide (ZnO) is a semiconductor with a wide direct band gap of 3.37eV at room temperature and high exciton binding energy of 60 meV. ZnO films have many realized and potential applications such as surface acoustic wave devices, ultraviolet photodetectors, piezoelectric devices, varistors, etc. ZnO thin films have excellent transparent conductivity, piezoelectricity, photoelectricity, gas sensitivity and press sensitivity. In my thesis, an advanced film preparation technique was used for the ZnO thin film preparation on the Si(100) substrates, the preparation parameters' effect on the films was also discussed.The crystallinity of the films was analyzed by the X ray Diffraction. The spectrum show that all the films have the C-axis orient and the (002) peak's FHWM decreases as the substrate temperature and the O₂ pressure riseThe surface topography of the films were observed by AFM and SEM, from the images, it can be found that all the films grew perpendicular to the substrates, and dimension of the surface grain distributes uniformly. The film grown at substrate temperature 600℃show the trend of transforming into ZnO nanorod array.The room temperature photoluminescence spectra of the ZnO samples show a strong UV emission as well as a deep energy level emission. But the Mg doped ZnO films show intense UV emission. The feeble deep energy level emission tells us the ZnO films doped moderately have less defects.From the measured result of spectroscopic ellipsometry, we know that the refractive index (n) and the extinction coefficient (k) are reduced with the rise of the substrate temperature and the increase of wavelength.