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Field Emission Characteristics of Deffctive Diamond Films
Koh, Ken-Ha,Park, Kyung-Ho,Lee, Soon-Il The Korean Vacuum Society 1998 Applied Science and Convergence Technology Vol.7 No.1
The field emission characteristics of defective diamond films grown by microwave plasma enhanced chemical vapor deposition (MPECVD) have been studied. X-ray diffraction, the poor crystal quality and/or small grain sizes of the diamond phase and the inclusion of the non-diamond carbon phases in these films have been condirmed by raman spectroscopy, scanning electron microscopy, atomic force microscopy, and the reflectance measurements. The degrees of the film defectiveness and the emission characteristics were dependent on the methane concentration. Current-versus-voltage measurements have demonstrated that the defective diamond films have good electron emission characteristics. characteristics strongly suggests the defect-related electron-emission mechanism. The defective diamond films deposited on Si substrates show the field emission current density of 1$\mu\textrm{A}/\textrm{cm}^2$ and 1mA/$\textrm{cm}^2$ have been measured at electric fields as low as 4.5V/$\mu\textrm{m}$ and 7.6V/$\mu\textrm{m}$, respectively. We also observed the similar emission characteristics from the defective diamond film deposited on Cr/Si substrate and could decrease the deposition temperature to $600^{\circ}C$.
이순일,Ken Ha Koh,Nguyen Tuan Hong 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
We report fast growth of vertically-aligned carbon nanotubes (CNTs) via hot filament chemical vapor deposition (HFCVD). Mats of millimeter-long CNTs were produced in 10 minutes utilizing Fe/Al bimetal layers as catalysts. The growth rate was initially larger than 220 µm/min, but was substantially reduced after 10 minutes and became smaller than 50 µm/min after 15 minutes. A characteristic analysis showed that HFCVD-grown millimeter-long CNTs were clean with high oxidation stability and had an overall purity of better than 99.5 %.
In situ optical investigation of carbon nanotube growth in hot-filament chemical vapor deposition
Seungho Choi,Soonil Lee,Ken Ha Koh 한국물리학회 2006 Current Applied Physics Vol.6 No.1l
chemical vapor deposition (HFCVD) method using Fe catalysts pre-treated with argon plasma. The structural characteristics, such asthe thickness and surface roughness of CNT lms, deduced from the analysis of the optical reectivity while taking the scatteringdue to surface roughness into account were consistent with those estimated from ex situ SEM images. Moreover, the linear regressionanalysis of the temporal variation of reectivity revealed that an incubation period of. 50 s preceded the noticeable growth of CNTs,dropping rapidly, and that the active growth of CNTs up to tens of micrometer occurred in the short span of a few tens of seconds. Thus,in situ reectivity measurement can be used to investigate CNT growth, and may shed some light on the details of the CNT growth mech-anism in the HFCVD method.
Jinzhang Liu,안영환,박지용,Yong Sun Kim,Ken Ha Koh,이경문,이순일 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1
Vertically aligned ZnO nanorods have been grown on silicon substrates pre-coated with thin, less than 10 nm, textured ZnO seeding layers via a vapor-solid mechanism. The ZnO seeding layers, which were essential for vertical alignment of ZnO nanorods without using any metal catalyst, were prepared by decomposing zinc acetate. The structure and the luminescence properties of the ZnO nanorods synthesized onto ZnO seeding layers were investigated and their morphologies were compared with those of single-crystalline GaN substrates and silicon substrates covered with sputtered ZnO lms. Patterning of ZnO seed layers using photolithography allowed the fabrication of patterned ZnO-nanorod arrays.