Papers by Author: Hyeong Tag Jeon

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: Co thin films were deposited by remote plasma atomic layer deposition (ALD) method using dicobalt hexacarbonyl t-butylacetylene (C12H10O6(Co)2) or cyclopentadienyl cobalt dicarbonyl (CpCo(CO)2) as the Co precursor. The impurity contents were minimized when the Co films deposited by remote plasma ALD with H2 plasma within the process pressure range of 0.1~2 Torr at plasma power of 300W. Co-Cp bond in CpCo(CO)2 precursor was easily broken under H2 remote plasma atmosphere. The carbon content of Co films were examined with Auger electron spectroscopy (AES) and Rutherford backscattering spectroscopy (RBS) to be ~21 at.% with C12H10O6(Co)2, and ~7 at.% with CpCo(CO)2. The surface morphologies of Co films were measured with atomic force microscope (AFM) and root mean square (RMS) values of Co films using C12H10O6(Co)2 and CpCo(CO)2 were 1.73
and 1.51
, respectively.

Abstract: The ferroelectric properties of UV irradiated and non-irradiated SBT thin films using photosensitive starting precursors were investigated. The observation of surface microstructure showed that UV irradiation and increase in anneal temperature induced the grain growth of SBT. The measured remnant polarization values of UV irradiated and non-irradiated SBT films after anneal at 700oC were 5.8 and 4.7 )C/cm2 and after anneal at 750oC, the values were 10.8 and 9.3 )C/cm2, respectively.

Abstract: The organic-inorganic field effect transistors (OIFETs) with ZnS active layer were fabricated on the ITO/glass substrate using cross-linked PVP (poly-4-vinylphenol) as a gate insulator. ZnS semiconductor films were prepared by the atomic layer deposition method. In the case of cross-linked PVP film, the leakage current and capacitance were about 1× 10-8 A and 12 nF/cm2, showing good gate insulation property. The carrier concentration and mobility of ZnS film deposited on SiO2/Si wafer was found to be -9.4×1015 cm-3 and 49.0 cm2/ V·sec, respectively. For the OIFET devices with ITO/PVP/ZnS/Ti:Au structure, the carrier mobility was about 1.9 cm2/V·sec. From the AFM images, lower mobility in the OIFET device compared with ZnS film on SiO2/Si substrate may be attributed to a rough surface morphology of ZnS film.

Abstract: ZnS thin films were grown by Atomic Layer Deposition (ALD) method with Diethyl- Zinc (DEZ) and hydrogen sulfide (H2S) for the application of a channel layer of OITFT (Organic-Inorganic Thin-Film Transistor). ZnS has many advantages such as high channel mobility, high deposition rate, transparency at room temperature due to the broad band gap (bandgap of ZnS : 3.7 eV), nontoxic characteristic, low resistivity, and less sensitive about oxidation than ZnO. The deposition rate of the ZnS films in our system was about 1.6 Å/cycle. ZnS film was characterized by AES, XRD, Hall-effect measurement.

Abstract: ZrO₂/Al₂O₃ bilayer structure was investigated as one of potential replacements for SiO₂ gate dielectric. Al₂O₃ and ZrO₂ films were also examined and showed stoichiometric characteristics with negligible chlorine and carbon impurities. Al₂O₃ film exhibited an amorphous structure without interlayer formation while ZrO₂ film showed a randomly oriented polycrystalline structure with amorphous phase of interlayer. ZrO₂/Al₂O₃bilayer film exhibited no interfacial layer between Si substrate and Al₂O₃ layers. The flat band voltage and hysteresis of ZrO₂/Al₂O₃bilayer film were 0.8 V and 150 mV, respectively, with fully reversible hysteresis. The measured leakage current of ZrO₂/Al₂O₃bilayer film was 1.2E-6 A/cm2 with EOT value of 1.4 nm. ZrO2/Al2O3 bilayer film showed significantly enhanced gate oxide properties compared to those of the individual Al₂O₃ and ZrO₂ films.