Papers by Author: Hyoun Woo Kim

Abstract: We have obtained one-dimensional (1D) nanomaterials of tin oxide (SnO2) on silicon nitride (Si3N4)-coated Si substrates by carrying out the thermal evaporation of solid Sn powders and varying the substrate temperature in an Ar/O2 ambient gas. We analyzed the samples with scanning electron microscopy, X-ray diffraction, transmission electron microscopy and photoluminescence (PL). Reactions at a lower substrate temperature gave rise to thinner 1D structures. The obtained 1D nanomaterials were single crystalline with a tetragonal rutile structure. We proposed a vapor-solid process as the growth mechanism for SnO2 nanorods. The PL spectrum exhibited visible light emission.

Abstract: We present a study of the photoresist (PR) etching and the low-k materials damage using a ferrite-core inductively coupled plasma (ICP) etcher, in order to develop an etching process for the low-k dielectric devices. We reveal that the N2/O2 flow ratio and bias power affected the PR etching rate. By Fourier transform infrared spectroscopy and HF dipping test, we investigated the effect of the gas flow ratio and bias power on the amount of etching damage to the low-k material.

Abstract: Indium oxide (In2O3) films were successfully grown on LiAlO2 substrates using the triethylindium (TEI) as a precursor in the presence of oxygen in the metalorganic chemical vapor deposition process. We have established the correlation between the substrate temperature and the structural properties. The grain structures were clearly shown on the surface of the films deposited at 350°C. The root mean square (RMS) surface roughness of the In2O3 films increased with increasing the substrate temperature. A photoluminescence measurement at room temperature exhibited a yellow-green emission band centered at 585 nm.

Abstract: We have fabricated the iron oxide nanowires directly from iron foils through the simple heating in N2 ambient. We have characterized the samples by means of scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray (EDX) spectroscopy, and selected area diffraction pattern. The EDX spectrum revealed that the nanowires contained elements of Fe and O. The iron oxide nanowires were crystalline with diameters in the range of 30-200 nm. We have discussed the possible growth mechanisms.

Abstract: This study reported the fabrication of tin oxide (SnO2) nanostructures on Co-coated Si substrates by the thermal heating of Sn powders. The microstructures and morphologies of the resultant nanostructures were studied by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and scanning electron microscopy (SEM). The product mainly comprised the tangled nanowires with average diameters in the range of 50-180 nm. The nanostructures were single-crystalline rutile structure of SnO2. The PL measurement with the Gaussian fitting exhibited visible light emission bands centered at 576 nm and 638 nm, respectively. We have discussed the possible growth mechanism of the nanostructures.

Abstract: This paper reports the fabrication of indium oxide (In2O3) films using a triethylindium and oxygen mixture. The deposition has been carried out on TiAlN substrates (200-350°C). We have established the correlation between the substrate temperature and the structural properties. The films deposited at 300-350°C were polycrystalline, whereas those deposited at 200°C was close to amorphous. XRD analysis and SEM images indicated that the films grown at 350°C had grained structures with the (222) preferred orientation. The room-temperature photoluminescence spectra of the In2O3 films exhibited a visible light emission.

Abstract: Influence of nitrogen and oxygen annealing atmospheres on the carrier concentration, carrier mobility, electrical resistivity and PL characteristics as well as the crystallinity of ZnO films deposited on sapphire substrates by atomic layer deposition (ALD) were compared. X-ray diffraction (XRD) and photoluminescence (PL) analyses, and Hall measurement were performed to investigate the crystallinity, optical properties and electrical properties of the ZnO thin films, respectively. The UV emission intensity for oxygen annealing is stronger than that for nitrogen annealing in the case of annealing at 600°C, but the difference decreases with the Increase of annealing temperature. The strongest UV emission is obtained by oxygen annealing at 800°C. However, from the viewpoint of electrical resistivity annealing at 1,000°C in either an oxygen or a nitrogen atmosphere is more desirable. Taking both the PL and electrical properties into consideration it may be concluded that optimum annealing condition for ZnO thin films grown on the sapphire substrate by ALD is an annealing temperature of 900°C and an annealing atmosphere of oxygen although the effects of annealing atmosphere on the optical and electrical properties are not so significant.

Abstract: Branched SnO2 nanowires were prepared by heating Sn powders. SEM images indicated that the single branched nanowires had diameters in the range 50-300 nm. XRD and SAED analysis revealed that the SnO2 nanowires were crystalline with tetragonal rutile structure. PL spectrum showed visible light emission.

Abstract: Indium oxide (In2O3) films was deposited on TiN substrates by the metal organic chemical vapor deposition technique using a triethylindium and oxygen mixture. The films deposited at 250-350°C were polycrystalline, while that deposited at 200°C was close to amorphous. XRD and SEM analyses indicated that the films grown at 350°C had grained structures with the (222) preferred orientation.

Abstract: We have prepared the gallium oxide (Ga2O3) films on sapphire substrates by a thermal evaporation of GaN powders. We have characterized the films by using the x-ray diffraction (XRD), scanning electron microscopy (SEM), and the photoluminescence (PL). SEM and XRD revealed that the deposits were Ga2O3 thin films with monoclinic structure. PL spectrum of Ga2O3 films under excitation at 325 nm showed a blue emission.