Papers by Author: W.K. Choi

Abstract: The X-ray diffraction (XRD) pattern for the ZnO films grown on Si (100) substrates indicates that the grown ZnO films have a strong c-axis orientation. The pole figure indicates that ZnO thin films have columnars with the grains of the [0002] crystallographic axis perpendicular to the Si (100) substrate, indicative of the random rotational orientations along the c-axis. Selected area electron diffraction pattern (SADP) of the ZnO/Si (100) heterostructures shows that the ZnO preferential oriented film is formed on the Si substrate. A possible atomic arrangement of the crystal structure and the formation mechanism of the c-axis orientated ZnO thin films grown on p-Si substrates are discussed on the basis of the XRD, the pole figure, and SADP results.

Abstract: The results Co and Fe implanted ZnO thin films were studied before and after 200 MeV Ag ion irradiation. The as-implanted films shows the presence of nano sized Co and Fe clusters as seen through XRD patterns and exhibited high resistivity compared to un-implanted films. After Ag ion irradiation the Co and Fe clusters get dissolved in ZnO lattice and the films resistivity reduced to half of the as implanted values. The magnetic properties of Ag irradiated films were confirmed through magnetization hysteresis and Co implanted films exhibit higher magnetization compared to Fe implanted films.