박원일 교수

We report metalorganic vapor-phase epitaxial growth and structural and photoluminescent characteristics of ZnO nanorods. The nanorods were grown on Al2O3(00⋅1) substrates at 400 °C without employing any metal catalysts usually needed in other methods. Electron microscopy revealed that nanorods with uniform distributions in their diameters, lengths, and densities were grown vertically from the substrates. The mean diameter of the nanorods is as narrow as 25 nm. In addition, x-ray diffraction meas

Electroluminescent (EL) devices (see Figure) have been fabricated using n‐ZnO nanorod arrays grown on p‐GaN epilayers. Simple heteroepitaxial growth yields vertically aligned ZnO nanorods with an abrupt interface on GaN. The p–n heterojunction EL device shows a high current density and strong electroluminescence even at a reverse‐bias voltage of 3 V.

Catalyst‐free metal–organic chemical vapor deposition (MOCVD) is used to prepare ZnO nanoneedles, grown vertically on Si substrates. Electron microscopy reveals that the nanoneedles are sharp, have uniform diameters, lengths, and densities, and high crystallinity. The photoluminescence spectrum displays a strong emission peak at 3.29 eV with a very weak deep‐level emission, indicating that the nanoneedles are of high optical quality.

We report on the photoluminescent characteristics of ZnO single crystal nanorods grown by catalyst-free metalorganic vapor phase epitaxy. From photoluminescence (PL) spectra of the nanorods at 10 K, several PL peaks were observed at 3.376, 3.364, 3.360, and 3.359 eV. The PL peak at 3.376 eV is attributed to a free exciton peak while the other peaks are ascribed to neutral donor bound exciton peaks. The observation of the free exciton peak at 10 K indicates that ZnO nanorods prepared by the catal

High-quality Zn1−xMgxO(0.00⩽x⩽0.49) thin films were epitaxially grown at 500–650 °C on Al2O3(00⋅1) substrates using metalorganic vapor-phase epitaxy. By increasing the Mg content in the films up to 49 at. %, the c-axis constant of the films decreased from 5.21 to 5.14 Å and no significant phase separation was observed as determined by x-ray diffraction measurements. Furthermore, the near-band-edge emission peak position showed blueshifts of 100, 440, and 685 meV at Mg content levels of 9, 29, an

We report on fabrication and electrical characteristics of high-mobility field-effect transistors (FETs) using ZnO nanorods. For FET fabrications, single-crystal ZnO nanorods were prepared using catalyst-free metalorganic vapor phase epitaxy. Although typical ZnO nanorod FETs exhibited good electrical characteristics, with a transconductance of ∼140nS and a mobility of 75cm2∕Vs, the device characteristics were significantly improved by coating a polyimide thin layer on the nanorod surface, exhib

We report on fabrication and electrical characteristics of ZnO nanorod Schottky diode arrays. High quality ZnO nanorods were grown for the fabrication of the Schottky diodes using noncatalytic metalorganic vapor phase epitaxy and Au was evaporated on the tips of the vertically well-aligned ZnO nanorods. I–V characteristics of both bare ZnO and Au/ZnO heterostructure nanorod arrays were measured using current-sensing atomic force microscopy. Although both nanorods exhibited nonlinear and asymmetr

Multiple quantum well nanorods have been fabricated via heteroepitaxial growth of ZnO and ZnMgO (see Figure and also cover). Simple yet accurate thickness control allows the realization of nanosized well structures in individual nanorods that are tunable through the effects of quantum confinement. This approach should be readily extendible to other heteroepitaxial semiconductor nanorods.

Logic devices, including OR, AND, NOT, and NOR gates, based on single-crystalline ZnO nanorods are demonstrated. In these devices, ZnO nanorods are employed as semiconducting channels. They control metal/oxide semiconductor junction characteristics, to yield either good ohmic or Schottky contacts, ensuring fabrication of high-performance Schottky diodes and metal-semiconductor field-effect transistors.

We report the nanocluster-catalyzed growth of ultralong and highly uniform single-crystalline silicon nanowires (SiNWs) with millimeter-scale lengths and aspect ratios up to approximately 100,000. The average SiNW growth rate using disilane (Si 2H 6) at 400 degrees C was 31 microm/min, while the growth rate determined for silane (SiH 4) reactant under similar growth conditions was 130 times lower. Transmission electron microscopy studies of millimeter-long SiNWs with diameters of 20-80 nm show t

We report ZnO nanorod−graphene hybrid architectures (ZnO−G HAs) composed of regular arrays of ZnO nanorods formed on few-layer graphene films transferred to transparent and/or flexible substrates. The ZnO−G HAs exhibited a high current flow reaching ∼1.1 mA at an applied bias of 1 V and good optical transmittance in the range of 70−80%, comparable to those of a graphene layer. In addition, cathodoluminescence images and photoluminescence spectra of the ZnO−G HAs showed distinct light emission in

We report a type of device that combines vertical arrays of one-dimensional (1D) pillar-superlattice (PSL) structures with 2D graphene sheets to yield a class of light emitting diode (LED) with interesting mechanical, optical, and electrical characteristics. In this application, graphene sheets coated with very thin metal layers exhibit good mechanical and electrical properties and an ability to mount, in a freely suspended configuration, on the PSL arrays as a top window electrode. Optical char

We report a new facile route to synthesize the ZnO nanotubes by thermal annealing of solid nanorods in ambient NH 3 . The unique characteristic of this approach allows achievement of ultrathin nanotubes with well-organized hexagonal nanowalls and sealed layouts. On the basis of our experimental observations, we developed a nanotube formation mechanism illustrating the following: (i) energetically active nanorod surfaces could be readily passivated to form a few-atoms-thick Zn 3 N 2 layer and (ii

Abstract Despite many efforts to advance the understanding of nanowire mechanics, a precise characterization of the mechanical behavior and properties of nanowires is still far from standardization. The primary objective of this work is to suggest the most appropriate testing method for accurately determining the mechanical performance of silicon nanowires. To accomplish this goal, the mechanical properties of silicon nanowires with a radius between 15 and 70 nm (this may be the widest range eve