Hyun Ruh

Field emission from well-aligned zinc oxide nanowires grown at low temperature

Field electron emission from vertically well-aligned zinc oxide (ZnO) nanowires, which were grown by the vapor deposition method at a low temperature of 550 °C, was investigated. The high-purity ZnO nanowires showed a single crystalline wurtzite structure. The turn-on voltage for the ZnO nanowires was found to be about 6.0 V/μm at current density of 0.1 μA/cm2. The emission current density from the ZnO nanowires reached 1 mA/cm2 at a bias field of 11.0 V/μm, which could give sufficient brightness as a field emitter in a flat panel display. Therefore, the well-aligned ZnO nanowires grown at such low temperature can promise the application of a glass-sealed flat panel display in a near future.

Low temperature growth and photoluminescence of well-aligned zinc oxide nanowires

Abstract Well-aligned single-crystalline zinc oxide (ZnO) nanowires with high density were successfully synthesized on nickel monoxide (NiO) catalyzed alumina substrate through a simple metal–vapor deposition method at an extremely low temperature (450 °C). The single-crystalline ZnO nanowires had a hexagonal wurzite structure and diameters of about 55 nm, and lengths up to 2.6 μm. The photoluminescence spectra under excitation 325 nm showed a ultra-violet (UV) emission at 3.26 eV and a green emission at 2.44 eV. The UV emission and green emission bands were attributed to near band-edge transition and radial combination of a singly ionized oxygen vacancy with a photo-induced hole, respectively.

Catalytic synthesis and photoluminescence of gallium nitride nanowires

Abstract Single crystalline wurzite GaN nanowires were successfully synthesized on the NiO catalyzed alumina substrate through a simple thermal chemical vapor deposition method. The mixture of Ga and GaN powder was used as the source material of Ga for synthesizing GaN nanowires. The diameter of nanowires ranged 50–60 nm and the length was about hundreds of micrometers. The nanowires were single crystal with hexagonal wurzite structure. The peaks of Raman spectra of GaN nanowires appeared broadened and asymmetric compared with those of bulk GaN. PL spectra under excitation at 325 nm showed a strong emission at 3.315 eV from near band-edge transition and a broad weak emission at 2.695 eV related to deep level defects.

Characterization of ternary boron carbon nitride films synthesized by RF magnetron sputtering

Boron carbon nitride (BCxNy) films were deposited on silicon wafers by RF magnetron sputtering of boron and graphite targets. BCN films with different compositions were obtained by varying the sputtering power of the graphite target (60, 180, 240 W). Chemical bonding states, composition and structure of the films were investigated by FTIR, XPS and AES analysis. The BCN films synthesized in this work were found to be BCN hybridized amorphous material, whose microstructure was examined with TEM observation. Mechanical properties of BCN films were compared to find the effect of the carbon sputtering power and resultant compositional changes on this ternary system. A BCN film with hardness of 15 GPa was synthesized at the high power of carbon source. With a higher sputtering power of carbon, hardness, elastic modulus and friction coefficients of a BCN film were increased due to the increase of strong BC, CC and CN bonds in the amorphous BCN film.

Synthesis of high-purity GaP nanowires using a vapor deposition method

Abstract High-purity gallium phosphide (GaP) nanowires were successfully synthesized on the nickel monoxide (NiO) or the cobalt monoxide (CoO) catalyzed alumina substrate by a simple vapor deposition method. To synthesize the high-purity GaP nanowires, the mixture source of gallium (Ga) and GaP powder was directly vaporized in the range of 850–1000 °C for 60 min under argon ambient. The diameter of GaP nanowires was about 38–105 nm and the length was up to several hundreds of micrometers. The GaP nanowires have a single-crystalline zinc blend structure and reveal the core-shell structure, which consists of the GaP core and the GaPO4/Ga2O3 outer layers. We demonstrate that the mixture of Ga/GaP is an ideal source for the high-yield GaP nanowires.

Effects of a Ni alloying element on Al?Ni metallization

The effect of the Ni content (2?18 at.% Ni) in Al thin films on their resistivity, hillock formation and Al3Ni compound formation was investigated. The as-deposited Al?Ni-alloy films showed high elastic strains which increased with increasing Ni content. In addition, the annealing of the supersaturated Al?Ni-alloy thin films yielded two phases: Al3Ni and Al with strong (2?2?0) and (1?1?1) textures, respectively, suggesting that the nucleation of (2?2?0) Al3Ni is closely associated with (1?1?1) Al. The resistivity of the as-annealed Al?Ni-alloy films varied as functions of the volume fraction and grain size of the two phases, which were determined by the Ni content and annealing temperature, respectively. The hillock formation was effectively suppressed when a small amount of Ni was added to the Al alloy. The results showed that a Ni content of less than approximately 4.5 at.% produced hillock-free Al-alloy thin films with a low resistivity of less than 6.0 ?? cm upon annealing at 350 ?C.

Amorphous Phase Formation of Titanium Silicide on The 4° off-Axis and on-Axis Si(100) Substrates

Two different Si(100) substrates, the 4°off-axis and the on-axis Si(100), were prepared. Ti thin films were deposited in an e-beam evaporation system and the amorphous layers of Ti-silicide were formed at different annealing temperatures. The Si(100) substrates before Ti film deposition were examined with AFM to verify the atomic scale roughness of the initial Si substrates. The amorphous layer was observed by HRTEM and TEM. And the chemical analysis and phase identification were examined by AES and XRD. The Si(100) substrate after HF clean shows the atomic scale microroughness such as atomic steps and pits on the Si surface. The on-axis Si(100) substrate exhibits much rougher surface morphologies than those of the off-axis Si(100). These differences of atomic scale roughnesses of Si substrates result in the difference of the thicknesses of amorphous Ti-silicide layers. The amorphous layer thicknesses on the on-axis exhibit thicker than those of the off-axis Si(100) and these differences inamorphous layer thicknesses became decreased as annealing temperatures increased. These indicate that the role of the atomic scale roughness on the amorphous layer thickness is much significant at low temperatures. In this study, the correlation between the atomic scale roughness and the amorphous layer thickness is discussed in terms of the atomic steps and pits based on the observation with using analysis tools such as AFM, TEM and HRTEM.