Sang-Hun Jeong

Photoluminescence dependence of ZnO films grown on Si(100) by radio-frequency magnetron sputtering on the growth ambient

We report the effects of the growth ambient on photoluminescence (PL) emission properties of ZnO films grown on Si (100) by rf magnetron sputtering. Upon increasing the O2/Ar+O2 ratio in the growing ambient, the visible emission in the room-temperature PL spectra was drastically suppressed without sacrificing the band-edge emission intensity in the ultraviolet region. This tendency is estimated to be due to the reduction of the oxygen vacancies and zinc interstitials in the film induced by the improvement of the film stoichiometry with respect to high oxygen content, indicating that the visible emission in ZnO originates from oxygen vacancy or zinc interstitial related defects. The violet emission peaked at about 401 nm (3.09 eV) was observed in the low-temperature PL spectra of the ZnO films grown under oxygen-rich conditions. This emission band was assigned to the electron transition from the bottom of the conduction band to the Zn vacancy level, positioned approximately 3.06 eV below the conduction ban...

Effects of growth conditions on the emission properties of ZnO films prepared on Si(100) by rf magnetron sputtering

ZnO films were prepared on Si(100) substrates using rf magnetron sputtering and the correlations between the growth conditions and the resultant film properties were discussed. The intensity of the visible emission related with intrinsic defects in ZnO film was dramatically suppressed by increasing the O2/Ar+O2 ratio in the growing ambient, which provides further evidence that the visible luminescence of ZnO originates from the oxygen vacancy or Zn interstitial related defects. It was also certain that the exciton related emission of ZnO is strongly dependent on the size of the micro-crystallites forming the film, showing the noticeable increase of the emission intensity with increasing grain size.

Growth and characterization of single crystalline Ga-doped ZnO films using rf magnetron sputtering

In this article it is shown that high quality single crystalline Ga-doped ZnO (GZO) films could be achieved on ac-plane sapphire using conventional rf magnetron sputtering. High-resolution x-ray diffractometry, transmission electron microscopy (TEM), and scanning electron microscopy investigations clearly confirmed that the GZO films with low Ga doping levels up to 1wt% were of high quality single crystal, which is featured by the (0002) rocking curve as narrow as 0.14°, symmetric six poles in pole figure, sharply defined spot pattern in the TEM diffraction diagram of the interfacial region, and the flat surface. It was also estimated from the Hall measurements and photoluminescence spectroscopy that these single crystalline GZO films possessed good optical and electrical characteristics including the narrow band-width and higher intensity of exciton-related emission peak, Hall mobility as large as 66 cm2 V−1 s−1, and the resistivity as low as 1.69 × 10− 3 Ω cm.

Magnetron sputtering growth and characterization of high quality single crystal ZnO thin films on sapphire substrates

ZnO films were grown on sapphire substrates by rf magnetron sputtering and their structural and optical properties were characterized in detail. It was observed that high quality single crystal ZnO films are obtained when grown at high temperature (>600 °C) and low plasma power in oxygen-rich ambient. Films grown at 800 °C and 75 W in pure O2 showed sharp and intense photoluminescence (PL) and high resolution x-ray diffraction (XRD) peaks, with full-width-at-half-maximum values of 155 meV (room temperature PL), 23 meV (12 K PL) and 280 arcsec (XRD), which is comparable with previously reported values from ZnO films grown by more sophisticated techniques such as metal-organic chemical vapour deposition.

Growth and characterization of high quality homoepitaxial ZnO films by RF magnetron sputtering

Zinc oxide (ZnO) films were grown on bulk ZnO substrates by the RF magnetron sputtering system. High resolution x-ray diffraction and photoluminescence spectra of the homoepitaxial films showed sharp and intense peaks with full-width at half-maximum values of 10?65 arcsec ((0?0?0?2) peak) and 106?116 meV (band edge emission), respectively, representing crystalline qualities better than or comparable with ZnO films grown by molecular beam epitaxy. It was also observed that ZnO films grown on Zn-face substrates showed a higher quality than those on O-face wafers. Doping of the films with about 1 wt% Ga resulted in n-type materials with about 1.5 ? 1018 cm3 free electron density.

Comparative proteomic analysis for the insoluble fractions of colorectal cancer patients

We used label-free quantitative proteomics with the insoluble fractions from colorectal cancer (CRC) patients to gain further insight into the utility of profiling altered protein expression as a potential biomarker for cancer. The insoluble fractions were prepared from paired tumor/normal biopsies from 13 patients diagnosed with CRC (stages I to IV). Fifty-six proteins identified in data pooled from the 13 cases were differentially expressed between the tumor and adjacent normal tissue. The connections between these proteins are involved in reciprocal networks related to tumorigenesis, cancer incidence based on genetic disorder, and skeletal and muscular disorders. To assess their potential utility as biomarkers, the relative expression levels of the proteins were validated using personal proteomics and a heat map to compare five individual CRC samples with five normal tissue samples. Further validation of a panel of proteins (KRT5, JUP, TUBB, and COL6A1) using western blotting confirmed the differential expression. These proteins gave specific network information for CRC, and yielded a panel of novel markers and potential targets for treatment. It is anticipated that the experimental approach described here will increase our understanding of the membrane environment in CRC, which may provide direction for making diagnoses and prognoses through molecular biomarker targeting.

Magnetron sputtering growth and characterization of high quality single crystal Ga-doped n-ZnO thin films

Ga-doped n-type ZnO (ZnO:Ga) films were grown on sapphire substrates by rf magnetron sputtering and their structural, electrical and optical properties were characterized in detail. It was observed that high quality single crystal ZnO:Ga films are obtained, containing up to 1 wt% of Ga. The ZnO:Ga (1 wt%) films grown at 700 ?C in pure O2 showed sharp and intense photoluminescence (PL) and high resolution x-ray diffraction (XRD) peaks, with full-width-at-half-maximum values of 150 meV (room temperature PL), 24 meV (12 K PL) and 380 arcsec (XRD), which is slightly better than or comparable with corresponding values from the previously reported ZnO:Ga films. Electrical properties of ZnO:Ga films significantly improved after the rapid thermal processing, resulting in 2.6 ? 1019 cm?3 free electron density and 47 cm2 V?1 s?1 mobility after annealing at 900 ?C in the case of 1 wt% film. The intensity of the PL peaks was also enhanced by the heat treatment.

Realization of As-doped p-type ZnO thin films using sputter deposition

Arsenic-doped p-type ZnO (p-ZnO:As) thin films were deposited by the magnetron sputtering technique. High-resolution low-temperature photoluminescence (PL) spectra of the films revealed emissions at 3.35 eV and 3.32 eV, representing the neutral-acceptor-bound exciton transition and the free electron to acceptor level transition. Electroluminescence spectra of the p–n diodes fabricated from the p-ZnO:As/n-GaN heterostructure showed UV emission at about 380 nm and yellowish visible lights centered at 600–650 nm, which resembled the PL spectrum of the ZnO:As layer. The p-type ZnO films with 1at% As grown at 500°C showed a hole concentration of 5 × 1012–7 × 1013 cm−3 after the deposition and 4 × 1014–1 × 1016 cm−3 after annealing at 600 °C in oxygen atmosphere. High-resolution x-ray photoelectron spectroscopy indicated that most of the As dopants occupy Zn sites within the ZnO:As films.

Characterization and preparation of SiO2 and SiOF films using an RF PECVD technique from TEOS/O2 and TEOS/O2/CF4 precursors

Preparation of high quality SiO2 and SiOF films has been attempted from tetraethoxysilane (TEOS)/O2 and TEOS/O2/CF4 precursors by modifying deposition variables. The deposited films were fully characterized by various analytical tools, such as FT-IR, UV-VIS-NIR spectrophotometry, XPS, ex situ ellipsometry and SEM. From the characterization of SiO2 films, it was demonstrated that the TEOS/O2 flow ratio is a critical parameter that controls the film quality and, when the TEOS/O2 flow ratio is low enough to prevent the physical adsorption of TEOS on the film surface during growth, good quality SiO2 films can be deposited at a high growth rate, even at low temperatures of 100°C. It is also noted that the addition of CF4 ranging from 0 to 70 sccm to the TEOS/O2 mixture can induce a lowering of the refractive index by replacing the highly polarizable Si–OH and OH bonds with less polarizable Si–F bonds and result in the formation of an SiOF film having good optical and structural characteristics without disadvantages such as a porous structure and hygroscopicity.

In‐depth analysis of cysteine oxidation by the RBC proteome: Advantage of peroxiredoxin II knockout mice

Peroxiredoxin II (Prdx II, a typical 2‐Cys Prdx) has been originally isolated from erythrocytes, and its structure and peroxidase activity have been adequately studied. Mice lacking Prdx II proteins had heinz bodies in their peripheral blood, and morphologically abnormal cells were detected in the dense red blood cell (RBC) fractions, which contained markedly higher levels of reactive oxygen species (ROS). In this study, a labeling experiment with the thiol‐modifying reagent biotinylated iodoacetamide (BIAM) in Prdx II−/− mice revealed that a variety of RBC proteins were highly oxidized. To identify oxidation‐sensitive proteins in Prdx II−/− mice, we performed RBC comparative proteome analysis in membrane and cytosolic fractions by nano‐UPLC‐MSE shotgun proteomics. We found oxidation‐sensitive 54 proteins from 61 peptides containing cysteine oxidation, and analyzed comparative expression pattern in healthy RBCs of Prdx II+/+ mice, healthy RBCs of Prdx II−/− mice, and abnormal RBCs of Prdx II−/− mice. These proteins belonged to cellular functions related with RBC lifespan maintain, such as cytoskeleton, stress‐induced proteins, metabolic enzymes, signal transduction, and transporters. Furthermore, protein networks among identified oxidation‐sensitive proteins were analyzed to associate with various diseases. Consequently, we expected that RBC proteome might provide clues to understand redox‐imbalanced diseases.