Young Soo No

Growth mechanisms of thin-film columnar structures in zinc oxide on p-type silicon substrates

X-ray diffraction analysis reveals that the crystallinity of (0001)-oriented columnar grains in ZnO thin films grown on p-Si (100) substrates is enhanced with increasing growth temperature, and transmission electron microscopy confirms that the columnar structures become more stable at higher growth temperature. The morphological evolution of the columnar structure in ZnO thin films is described on the basis of experimental measurements.

Effects of thermal treatment on the formation of the columnar structures in ZnO thin films grown on p-Si (100) substrates

X-ray diffraction patterns showed that crystallinity of the annealed ZnO films was improved by thermal annealing. Transmission electron microscopy images showed that columnar structures were preferentially formed in ZnO thin films due to thermal annealing, and electron energy loss spectroscopy images showed that annealing caused O2 atoms to diffuse out from the upper region in the ZnO thin film. The effects of thermal treatment on the formation of the columnar structures in ZnO thin films grown on Si (100) substrates are described on the basis of the experimental results.

Correlation between the atomic structures and the misorientation angles of [0001]-tilt grain boundaries at triple junctions in ZnO thin films grown on Si substrates

The correlation between the atomic structures and the misorientation angles of [0001]-tilt grain boundaries at triple junctions in ZnO thin films grown on Si substrates was investigated by using high-resolution transmission electron microscopy (HRTEM) measurements. The HRTEM images showed three symmetric grain boundaries and one asymmetric grain boundary around the triple junction in the ZnO film. The correlation between the atomic structures and the misorientation angles of the grain boundaries at triple junctions in ZnO films is described on the basis of the HRTEM results.

Transformation mechanisms from metallic Zn nanocrystals to insulating ZnSiO3 nanocrystals in a SiO2 matrix due to thermal treatment

Transmission electron microscopy (TEM), high-resolution TEM, and x-ray energy dispersive spectroscopy results showed that Zn metallic nanocrystals and ZnSiO3 insulating nanocrytals embedded in a SiO2 matrix were created from the ZnO thin films deposited on n-Si (001) substrates due to rapid thermal annealing. The formed Zn metallic nanocrystals were transformed into monoclinic ZnSiO3 insulating nanocrystals with increasing number of Zn atoms resulting from an increase in the annealing time up to 10 min. The transformation mechanisms from metallic Zn nanocrystals to insulating ZnSiO3 nanocrystals in a SiO2 matrix due to rapid thermal annealing are described on the basis of the experimental results.

Formation mechanisms of metallic Zn nanodots by using ZnO thin films deposited on n-Si substrates

High-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy results showed that metallic Zn nanodots (NDs) were fabricated through transformation of ZnO thin films by deposition of SiOx on ZnO/n-Si (100) heterostructures. The Zn NDs with various sizes and densities were formed due to the occurrence of the mass diffusion of atoms along the grain boundaries in the ZnO thin films. The fabrication mechanisms of metallic Zn NDs through transformation of ZnO thin films deposited on n-Si substrates are described on the basis of the experimental results.

Evolution mechanisms of the surface morphology of grains in ZnO thin films grown on p-InP substrates due to thermal annealing

Transmission electron microscopy (TEM), high-resolution TEM, and atomic force microscopy images showed that the columnar structure and the surface morphology of grains in ZnO thin films grown on p-InP substrates were changed due to thermal treatment. The surface morphology variation of the ZnO thin films was attributed to the curvature modification of the subpopulations consisting of ZnO grains. While the top surface of the ZnO grains became parallel with the {0001} planes due to thermal treatment, the curvature of the subpopulations in the ZnO grains became rough. Evolution mechanisms of the surface morphology of ZnO thin films are described.

Atomic arrangement variations of [0001]-tilt grain boundaries in ZnO thin films grown on p-Si substrates due to thermal treatment

The plane-view high-resolution transmission electron microscopy (HRTEM) images in ZnO thin films grown on p-Si substrates showed that (101¯0) asymmetric grain boundaries with a periodic array of strain contrast features existed in a sparse columnar structure for as-grown ZnO thin films and that (112¯0) asymmetric grain boundaries and (8513¯0) symmetric grain boundaries existed in a dense columnar structure for annealed ZnO thin films. The atomic arrangement variations of [0001]-tilt grain boundaries in ZnO thin films grown on Si substrates due to thermal treatment are described on the basis of the HRTEM results.

Effect of Potassium Chloride Concentration on the Structural and Optical Properties of ZnO Nanorods Grown on Glass Substrates Coated with Indium Tin Oxide Film

ZnO nanorods were grown on glass substrates coated with an indium tin oxide film by electrochemical deposition. X-ray photoelectron spectroscopy spectra of the ZnO samples included Zn 2p3/2, Zn 2p1/2, and O 1s peaks, indicative of the formation of ZnO nanorods. Scanning electron microscopy images showed that the density of the ZnO nanorods decreased with increasing potassium chloride (KCl) concentration. No spurious phase was observed in X-ray diffraction patterns, regardless of the KCl concentration. A strong UV peak between 382 and 385 nm in the PL spectra was related to the near band-edge emissions of ZnO nanorods.

Effect of Indium–Tin-Oxide Schottky Contact on the Resistance Switching of NiO Film

The effect of electrode materials on resistance switching was evaluated on the Pt/NiO/electrode (EL) structures where the EL contacts were Pt, Al, and indium–tin-oxide (ITO). It was confirmed that ohmic Pt contact needs to induce the effective electric field for resistance switching across the NiO film. For the Pt/NiO/Al structure, the barrier height of the Al Schottky contact was measured as 0.66 eV and no resistance switching was observed owing to a large voltage drop at the rectifying interface induced by the reduction of NiO resulting from the formation of Al oxide. In the ITO (EL)/NiO/Pt structure, the barrier height of the Schottky contact between ITO and NiO was about 0.52 eV and it did not show any resistance switching, either. Through the depth-profile study by X-ray photoelectron spectroscopy, chemical reactions at the interface ITO/NiO was identified to be not too much evolved compared with that of NiO/Al, which might due to be abundant oxygen on the ITO surface. Such Schottky barrier heights 0.52–0.66 eV were considered too high to induce a sufficient electric field in the NiO film causing the resistance switching.

The creation of sub-10 nm In(PO3)(3) nanocrystals in an insulating matrix, and underlying formation mechanisms

Sub-10 nm In(PO(3))(3) nanocrystals (NCs) were created in an insulating matrix by rapid thermal annealing to form nanocomposite structures. On annealing at a temperature of 400 degrees C, P(2)O(5) NCs were formed by substituting P for Zn atoms in ZnO films via the kickout diffusion mechanism based on the fixed oxygen sublattice. On annealing at a higher temperature of 600 degrees C, however, In(PO(3))(3) NCs were nucleated by diffusion of In atoms from the substrate into the sites of P(2)O(5) NCs that coalesced by moving atoms to neighboring grains in the strain relaxed region. The formation mechanisms of sub-10 nm In(PO(3))(3) NCs in an insulating matrix due to rapid thermal annealing are described on the basis of the experimental results.