Papers by Author: Yun Hua Huang

Abstract: The electrical properties of single ZnO nanowire were researched in the chamber of a scanning electron microscope under high-vacuum conditions using nanomanipulator and measurement system. The result shows that ZnO nanowire resistivity was about 1.4 Ω•cm with Ohmic contact. The local change of electron density induced by Shottky contacts or Ohmic contact with tip and semiconductor/metal materials significantly affects the current transport through the nanowire. Single ZnO nanowire was configured as field effect transistors (FET) and based on metal tantalum (Ta) as electrodes show a pronounced n-type gate modulation with an electron concentration of ~1.0×1019 cm−3 and an electron mobility of ~52 cm2 /V s at a bias voltage of 1 V.

Abstract: The plasma-induced emission properties of ZnO nanorod and carbon nanotube (CNT) arrays were investigated under the pulse electric field. The formation of plasma on the array surface was found and high intensity electron beams were obtained from the two kinds of arrays. The plasma-induced emission properties of the ZnO nanorod and CNT arrays have big differences. Under the same electric field, the CNT arrays have higher emission current than the ZnO nanorod arrays. With the emission currents changing, the electron emissions of the ZnO nanorod arrays always are very uniform; but that of the CNT arrays are non-uniform. The plasma expansion velocity of the ZnO nanorod arrays is lower than that of the CNT arrays. Accordingly, the emission stability of the ZnO nanorod arrays is better than that of the CNT arrays.

Abstract: Three-dimensional (3D) ZnO nanorod networks were synthesized through the direct evaporation of metal zinc with high purity via a chymical evaporation deposition (CVD) method in Ar and O2 at 910 °C without any catalyst. The nanorod networks of as-synthesized ZnO were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD). The branches within one network show very regular orientation relationships: either perpendicular or parallel to each other. The nanorods follow a growth direction [0001]. Photoluminescence (PL) spectroscopy were measured at room temperature and showed the different PL features of other nanostructures. Two typical emission peaks at -401 nm and at 452-495 nm were observed. Specially, the emission peak at 452-495 nm includes four subordinate peaks.

Abstract: Mn-doped ZnO nanowires were successfully synthesized on silicon substrate by chemical vapor deposition method with Au catalyst. The X-ray diffraction (XRD) pattern indicates that the Mn-doped ZnO nanowires are hexagonal wurtzite structure and no second phase. The X-ray spectroscopy (EDX) and X-ray photoelectron spectrum (XPS) spectra exhibited the Mn ions were induced into the ZnO nanowires. Photoluminescence (PL) spectra were excited by 325 nm Xe lamp laser. Three peaks are observed in Mn-doped ZnO nanowires, two ultraviolet (UV) emissions at 370 nm and 386 nm, a visible emission at 405 nm. The emission at 405 nm is first found in Mn-doped ZnO nanowires that attributed to the electron transition from bottom of the conduction band to zinc vacancy defect energy level. The existence of Mn element changes the optical property of the ZnO nanowires.

Abstract: In-doped ZnO nanodisks were successfully fabricated by thermal evaporation Zn, In2O3 and graphite powder mixture without catalyst. Morphology, structures and components of ZnO nanodisks were investigated by SEM, HRTEM, EDS and X-Ray diffraction. ZnO nanodisks have perfect hexagonal shape, with 1~3μm size and 40~100 nm in thickness. The nanodisks are single-crystalline ZnO with wurtzite structure and In content of nanodisks reaches 2.2%. The growth along [0001] is suppressed leading to the formation of ZnO nanodisks. Room temperature photoluminescence spectra of the nanodisks shows that the UV emission peak blueshifts and becomes broader after doping.

Abstract: The microstructure of a microalloying non-quenching and tempering steel developed recently was analyzed through OM, SEM and TEM, in order to find the strengthening and toughening mechanisms of the steel. All of the dislocations and subgrain boundaries in the grains, the martensite in the martensite-austenite islands of the grainy bainite structure, the dispersed phases in the grains and at the grain boundaries, and the grain size were observed and studied in our experiments. The results indicate that the strengthening results from phase transition, dislocation, subgrain structure, dispersion phase and fined grain, and the toughness relates with the ferrite matrix consisting of the grainy bainite and the grain size of the steel. The mechanisms between the hot-rolled-and-cooled and the tempered steel are slightly different.