Ji-Yong Yang

Quantum confinement effect in ZnO thin films grown by pulsed laser deposition

High quality crystalline nanostructured ZnO thin films were fabricated by pulsed laser deposition on (0001) sapphire substrates. The films were investigated by x-ray diffraction, scanning electron microscopy, and optical absorption spectroscopy. The exciton peak energy from absorption spectra was used to determine the band gap energy Eg, which was found to increase systematically with the decrease in the mean grain size and ranged from 3.388to3.647eV. This is consistent with the quantum confinement model and, up until now, not observed in a convincing manner in the ZnO thin films.

Grain size dependence of electrical and optical properties in Nb-doped anatase TiO2

Anatase thin films of pure TiO2 and 6% niobium doped TiO2 (Nb:TiO2) were fabricated on LaAlO3(100) by pulsed laser deposition. The electrical properties of Nb:TiO2 films are grain-size dependent, i.e., the larger grain size, the higher conductivity, and mobility. For all TiO2 and for Nb:TiO2 with small mean grain size (d 15 nm), particularly, a blueshift in Nb:TiO2 is governed by the Burstein–Moss effect.

d carrier induced intrinsic room temperature ferromagnetism in Nb:TiO2 film

High crystalline anatase TiO2 and Nb:TiO2 thin films were fabricated on LaAlO3 (100) substrates by pulsed laser deposition. Room temperature ferromagnetism was obtained in Nb:TiO2 but absent in pure TiO2. The Kondo effect and anomalous Hall effect observed in metallic Nb:TiO2 strongly confirmed the existence of exchange interaction between intrinsic local magnetic moments and carriers. High energy resolution x-ray photoelectron spectroscopy studies of the Nb:TiO2 thin film revealed clear signals of Ti3+ and Nb4+ ions, which had one unpaired d electron responsible for the local magnetic moments. This result consisted quite well with the spin polarized first principle calculation.

Scanning tunneling microscopy/spectroscopy studies of resistive switching in Nb-doped SrTiO3

Scanning tunneling microscopy and spectroscopy (STM/S) was utilized to study the resistive switching (RS) effect in Nb-doped SrTiO3 (STON). It was found that the RS effect could be realized on the STON surface by applying an appropriate bias on the STM tip, and the RS block could be controlled at nanometer scale. The electrode contact effect on the RS process could be excluded according to the STM method. More importantly, the investigation of scanning tunneling spectroscopy combined with the measurement of x-ray photoelectron spectroscopy demonstrated that the oxygen migration should be the dominant mechanism for the variation of electronic structure during the RS process, which can explain the origin of RS in this oxide. These results can be helpful for both the understanding of RS and its applications.

Scanning tunnelling microscope studies of angstrom-scale Co3O4 nanowires

We report the bottom-up assembly of an atomic-scale building block, which consists of four Co(3+) cations, two Co(2+) cations, and eight O(2-) anions, for generating one-dimensional Co(3)O(4) nanostructures with diameters ranging from 0.5 to 3 nm. Controlled experiments were carried out and the growth mechanism of the Co(3)O(4) nanowires was investigated. The effects of a single cation defect on the epitaxial growth of the one-dimensional nanostructures were investigated. We proposed a self-rectifying growth mechanism on the basis of direct experimental observations. This mechanism will help us to understand synthesized crystals usually exhibiting homogeneous composition and uniform morphology, though the existence of defects is inevitable in the growth process.

Enhanced intervalley scattering of twisted bilayer graphene by periodic AB stacked atoms

The electronic properties of twisted bilayer graphene on SiC substrate were studied via a combination of transport measurements and scanning tunneling microscopy. We report the observation of enhanced intervalley scattering from one Dirac cone to the other, which contributes to weak localization of the twisted bilayer graphene by increasing the interlayer coupling strength. Our experiment and analysis demonstrate that the enhanced intervalley scattering is closely related to the periodic

Inhibited single-electron transfer by electronic band gap of two-dimensional Au quantum dot superlattice

AB

Evidence for surface states in a single 3 nm diameter Co3O4 nanowire

stacked atoms (the

Size-dependent magnetic moments in ultrafine diamagnetic systems

A

Effect of exchange-type zero-bias anomaly on single-electron tunneling of Au nanoparticles

atom of layer 1 and the