Nae-Man Park

Electronics and Telecommunications Research Institute, Sŏul, Seoul, South Korea

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Publications (66)117.25 Total impact

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    ABSTRACT: In this study, we investigated Ti-doped ITO films formed through ionized physical vapor deposition (IPVD) using inductively coupled plasma (ICP). Ti-doped ITO thin films showed an enhanced mobility with ICP power; owing to the improved crystallinity, and the sheet resistance of the Ti-doped ITO (30 nm) largely decreased from 295.1 to 134.5 ohm/sq, even during at room temperature. Therefore, IPVD technology offers a useful tool for transparent electrodes with a large area window-unified touch-screen panel.
    No preview · Article · Oct 2015 · Journal of Nanoscience and Nanotechnology
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    Nae-Man Park · Dae-hyung Cho · Kyu-Seok Lee

    Full-text · Article · Sep 2015 · Etri Journal
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    ABSTRACT: Indium-tin oxide (ITO) films were successfully grown at low temperatures by ionized physical vapor deposition (IPVD) method, equipped with an internal-type inductively coupled plasma reactor (ICP-reactor). Radio-frequency antenna for ICP was made by Cu tube for the flow of cooling water, which was shielded by a quartz tube for excluding Cu-contamination from re-sputtering near the plasma field. Due to the high plasma density of IPVD, in-situ crystallization during the deposition of ITO film occurred even at the low temperatures, which lowering the sheet resistance. Therefore, IPVD could be used as an effective tool for low temperature processing devices such as plastic cover-unified touch sensors.
    No preview · Article · Feb 2015 · Surface and Coatings Technology
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    ABSTRACT: We have investigated the electrical properties of indium tin oxide (ITO) thin films deposited on chemically strengthened glass (CSG) substrate by room-temperature ionized physical vapor deposition (IPVD). The ITO thin film on the CSG substrate shows a higher sheet resistance after high-temperature anneal process (>200 °C) possibly due to the out-diffusion of potassium ions (K+) from the CSG. We have improved the electrical properties of the ITO thin film by inserting Nb2O5/SiO2 buffer layers between the ITO layer and the CSG substrate. As a result, a protected and index-matched 30-nm-thick ITO thin film with sheet resistance less than 120 Ω/sq and optical transmittance higher than 90% (at 550 nm) has been achieved.
    No preview · Article · Jul 2014 · Japanese Journal of Applied Physics
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    Full-text · Dataset · Jun 2014
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    Nae-Man Park · Chel-Jong Choi
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    ABSTRACT: A new method for growing silicon nanowires is presented. They were grown in an aqueous solution at a temperature of 85 °C under atmospheric pressure by using sodium methylsiliconate as a water-soluble silicon precursor. The structure, morphology, and composition of the as-grown nanowires were characterized by scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectrometry. It was also confirmed by X-ray powder diffraction and Raman spectroscopy that the silicon nanowire has a hexagonal structure. It was possible to grow the crystalline silicon nanowires at low temperature under atmospheric pressure because potassium iodide, which was used as a gold etchant, sufficiently increased the surface energy and reactivity of gold as a metal catalyst for the reaction of the Si precursor even at low temperature.
    Preview · Article · Jun 2014 · Nano Research
  • Jeha Kim · Ho-Sub Lee · Nae-Man Park
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    ABSTRACT: Using a reactive co-sputtering from Cu0.6Ga0.4 and Cu0.4In0.6 alloy targets, we prepared CuIn1-xGaxSe2 (CIGS) thin films on Mo/soda-lime glass (SLG) in association with a thermal cracker for elemental atomic Se radicals. The film growth was performed at 500 degrees C for 90 min. To achieve the composition ratio of CIGS absorber layer, Cu0.6Ga0.4 target was set at RF power of 50 W, 60 W, 70 W, and 80 W while keeping at 100 W for Cu0.4In0.6 alloy target. Post-annealing was done for all the CIGS films at 550 degrees C for 30 min. The composition ratio of [Cu]/[In + Ga] and [Ga]/[In + Ga] was increased with RF power but showed no change after post-annealing. X-ray diffraction analysis revealed all the samples has grown dominantly in the [112] crystal orientation. We found the Cu2-xSe and (InGa)(2-x)Se-3 defect phase both at the surface and in the bulk, and developed with post-annealing. From the devices fabricated in the structure of grid/ITO/i-ZnO/CdS/CIGS/Mo/soda-lime glass (SLG), the external quantum efficiency (EQE) was observed to improve in the wavelength, lambda >= 550 nm in the samples treated with annealing. In the current-voltage (J-V) measurements, the solar cell showed the best performance of FF = 54.1%, V-oc = 0.48 V, J(sc) = 33.1 mA/cm(2) and eta = 8.5% in the sample with [Cu]/[In + Ga] = 0.84 that improved largely from eta = 4.6% for the solar cell with an as-grown CIGS films.
    No preview · Article · Feb 2014 · Current Applied Physics
  • Jeha Kim · Nae-Man Park
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    ABSTRACT: Using reactive sputtering, we fabricated stoichiometric CuIn1−x Gax Se2 (CIGS) thin films. Both Cu0.6Ga0.4 (CuGa) and Cu0.4In0.6 (CuIn) alloy targets were simultaneously sputtered under the delivery of elemental Se produced from a thermal cracker. By changing the sputtering rates of the CuGa and the CuIn, we were able to obtain the composition ratios of Cu/(Ga+In) and Ga/(Ga+In) in the range of 0.71–0.95 and 0.10–0.30, respectively. Both the grain size and the surface roughness of the CIGS film increased as the Cu/(Ga+In) ratio increased. In the X-ray diffraction analysis on CIGS films of 0.9 m, preferential growth with a [112] orientation was found, and reflections from the (211), (220)/(204), (301), (312)/(116), (400)/(008), and (332)/(316) planes were observed. The CIGS films showed the existence of Cu2−x Se phases in the Cu-rich samples and ordered defect compound (ODC) phases in the Cu-poor films, as confirmed in the Raman measurements. A best device performance of η = 8.1%, Voc = 0.442 V, Jsc = 34.3 mA/cm2, and FF = 53.4% was obtained from a cell fabricated with a CIGS layer (t = 0.9 µm) with the Cu/(Ga+In) ratio = 0.71 and the Ga/(Ga+In) ratio = 0.10.
    No preview · Article · Jan 2014 · Journal- Korean Physical Society
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    ABSTRACT: Index-matched indium tin oxide (ITO) electrodes for capacitive touch screen panels have been fabricated to improve optical transmittance and reduce the difference of reflectance (deltaR) between the etched and un-etched regions. 8.5 nm Nb2O5 and 49 nm SiO2 thin films were deposited by magnetron sputtering as index-matching layers between an ITO electrode and a glass substrate. In case of 30 nm ITO electrode, a 4.3% improvement in the optical transmittance and a deltaR of less than 1% were achieved, along with a low sheet resistance of 90 omega/.
    No preview · Article · Nov 2013 · Journal of Nanoscience and Nanotechnology
  • Jeha Kim · Ho-Sub Lee · Nae-Man Park
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    ABSTRACT: The reactive co-sputtering was developed as a new way of preparing high quality CuInGaSe2(CIGS) films from two sets of targets; Cu0.6Ga 0.4 and Cu0.4In0.6 alloy and Cu and (In0.7Ga0.3)2Se3 compound targets. During sputtering, Cu, In, Ga metallic elements as well as the compound materials were reacted to form CIGS simultaneously in highly reactive elemental Se atmosphere generated by a thermal cracker. CIGS layer had been grown on Mo/soda-lime glass(SLG) at 500°C. For both sets of targets, we controlled the composition of CIGS thin film by changing the RF power for target components. All the films showed a preferential (112) orientation as observed from X-ray diffraction analysis. The composition ratios of CIGS were easily set to 0.71-0.95, 0.10-0.30 for [Cu]/[III] and [Ga]/[III], respectively. The grain size and the surface roughness of a CIGS film increased as the [Cu]/[III] ratios increased. The solar cells were fabricated using a standard base line process in the device structure of grid/ITO/i-ZnO/CdS/CIGS/Mo/ SLG. The best performance was obtained the performance of Voc = 0.45 V, Jsc =35.6, FF = 0.535, η = 8.6% with a 0.9 μm-CIGS solar cell from alloy targets while Voc = 0.54 V, Jsc =30.8, FF = 0.509, η = 8.5% with a 0.8 μm-CIGS solar cell from Cu and (In0.7Ga0.3)2Se3.
    No preview · Conference Paper · Sep 2013
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    ABSTRACT: A transparent non-volatile memory device was fabricated using silicon quantum dots in silicon nitride film as a gate insulator. A silicon quantum dots were grown in-situ in the film by plasma-enhanced chemical vapor deposition. The silicon quantum dot film had a high optical transmittance of over 95% at 550 nm with a thickness of 50 nm. A large hysteresis curve was observed in a current-voltage measurement. When we increased the voltage sweep range, electrons were charged into the silicon quantum dots because of the electrical n-type channel in an oxide thin film transistor.
    No preview · Article · Jul 2013 · Electronic Materials Letters
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    ABSTRACT: We studied the electrical and optical properties of lightly aluminum-doped zinc oxide (L-AZO) films, which were deposited on soda-lime glass substrates by radio frequency (RF) magnetron sputtering using a 0.2 wt.% aluminum-doped zinc oxide target and a 0.3 wt.% hydrogen-mixed argon (Ar/0.3% H-2) gas. The L-AZO films were characterized in terms of structural, optical, and electrical properties by X-ray diffraction, ultraviolet-visible spectrophotometry, photoluminescence and Hall measurements at room temperature. The Al contents of the L-AZO film were analyzed with secondary ion mass spectroscopy. As the Ar/0.3%H-2 gas flow was increased up to 200 sccm, the transmittance and conductivity of the film simultaneously improved as a function of the increasing flow rate without additional thermal or gas treatment. The 40 nm-thick L-AZO film, which was deposited by an Ar/0.3% H-2 gas flow of 200 sccm at a substrate temperature of 100 degrees C, had a carrier concentration of 1.0 x 10(20)/cm(3), resistivity of 5.5 x 10(-3) Omega-cm, and an average transmittance of 93% in the wavelength range from 300 nm to 2000 nm.
    Full-text · Article · Jul 2013 · Thin Solid Films

  • No preview · Conference Paper · May 2013
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    ABSTRACT: Silicon nanocrystals (Si-NCs) were grown in situ in carbide-based film using a plasma-enhanced chemical vapor deposition method. High-resolution transmission electron microscopy indicates that these nanocrystallites were embedded in an amorphous silicon carbide-based matrix. Electron diffraction pattern analyses revealed that the crystallites have a hexagonal-wurtzite silicon phase structure. The peak position of the photoluminescence can be controlled within a wavelength of 500 to 650 nm by adjusting the flow rate of the silane gas. We suggest that this phenomenon is attributed to the quantum confinement effect of hexagonal Si-NCs in silicon carbide-based film with a change in the sizes and emission states of the NCs.
    Full-text · Article · Nov 2012 · Nanoscale Research Letters
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    Nae-Man Park · Ho Sub Lee · Jeha Kim
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    ABSTRACT: (CIGS) thin films are grown on Mo/soda lime glass using a reactive sputtering process in which a Se cracker is used to deliver reactive Se molecules. The Cu and targets are simultaneously sputtered under the delivery of reactive Se. The effects of Se flux on film composition are investigated. The Cu/(In+Ga) composition ratio increases as the Se flux increases at a plasma power of less than 30 W for the Cu target. The (112) crystal orientation becomes dominant, and crystal grain size is larger with Se flux. The power conversion efficiency of a solar cell fabricated using an 800-nm CIGS film is 8.5%.
    Preview · Article · Oct 2012 · Etri Journal
  • Ho-Sub Lee · Nae-Man Park · Kyu-Seok Lee · Jeha Kim · Ho-Jung Chang
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    ABSTRACT: Cu(In1−x Gax )Se2 (CIGS) thin-film solar cells have been fabricated using the CIGS compound prepared with a two-step selenization process at 400 °C followed by successive thermal annealing at 550 °C. The compositions of the Cu-In-Ga precursors were controlled by changing the thickness ratio of the Cu-In and the Cu-Ga films. After the selenization, the thickness of the CIGS film was approximately three times that of the precursor layer. X-ray diffraction peaks showed that the CIGS had the chalcopyrite structure with a preferential orientation in the (112) direction. The composition analysis using X-ray fluorescence revealed that the Cu/[III] and the Ga/[III] ratios of CIGS changed in ranges of 0.66 ∼ 0.80 and 0.11 ∼ 0.20, respectively, with variations in the precursor thickness. We obtained a power conversion efficiency of 3.91% from the fabricated CIGS solar cell.
    No preview · Article · May 2012 · Journal- Korean Physical Society
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    ABSTRACT: We have studied the influence of growth temperature (TG) in the deposition of an indium tin oxide (ITO) transparent conducting oxide layer on Cu(In,Ga)Se2 (CIGS) thin-film solar cells. The ITO films were deposited on i-ZnO/glass and i-ZnO/CdS/CIGS/Mo/glass substrates using radio-frequency magnetron sputtering at various TG up to 350°C. Both the resistivity of ITO and the interface quality of CdS/CIGS strongly depend on TG. For a TG≤200°C, a reduction in the series resistance enhanced the solar cell performance, while the p–n interface of the device was found to become deteriorated severely at TG>200°C. CIGS solar cells with ITO deposited at TG=200°C showed the best performance in terms of efficiency.
    Full-text · Article · Jan 2012 · Thin Solid Films
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    ABSTRACT: In the current study, chemical bath deposition (CBD) was used to grow CdS thin films on a Cu(In,Ga)Se2 (CIGS) absorption layer, in order to examine the effects of CdS deposition conditions on the properties of CIGS solar cell devices. The dip time leading up to the start of CdS synthesis is thought to be an important process variable determining the concentration of Cd ions diffused into the CIGS as well as the condition of the CIGS surface. Accordingly, the behavior of the CIGS solar cell efficiency variation was observed while different dip times were applied, at 4, 15 and 30 minutes, respectively. When the dip time was extended, the series resistance (Rs) of the device fell by a substantial margin, leading to improved photoelectric conversion efficiency and enhanced uniformity in device properties. This can be attributed to the effect of CIGS surface cleaning by the NH4OH contained in the reaction solution.
    Full-text · Article · Nov 2011 · Molecular Crystals and Liquid Crystals
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    ABSTRACT: Cd2SnO4(CTO) thin film was made using RF magnetron sputtering and a single (CTO) target. Among various deposition variables, the effect of changes in plasma power on the electrical and optical properties of the film was investigated. It was observed, as plasma power grows, specific resistivity of the thin film increases while transmittance considerably decreases. It was found that such a phenomenon occurred because of the density of the thin film reduced by increased deposition speed. Another noteworthy result obtained through the X-ray photoelectron spectroscopy analysis is that Sn has metallic bond in the case of the thin film deposited under high power. It seems that existence of such metal was another cause of the reduced transmittance of the thin film.
    No preview · Article · Nov 2011 · Molecular Crystals and Liquid Crystals
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    ABSTRACT: Electrical properties of the Silicon quantum dots (Si-QD) light-emitting diodes (LEDs), in its dependence on the nitrogen source used in the silicon nitride (SiNx) matrix growth, have been studied. Si-QDs are formed in-situ during the SiNx film growth, and no post-annealing process for crystallization was applied. To confirm the electrical properties of the Si-QD devices, we manufacture the Si-QD LED. Both p-type and p+-type Si substrate were tested in role of hole tunneling in the LED performance. The high-resolution transmission electron microscopy (HRTEM) analyses and the current--voltage (I--V) measurement show that the Si-QDs embedded in the SiNx grown with ammonia (NH3) are located at the interface between the SiNx film and the Si substrate. This is related to the observed increase in the forward current by considering a decrease in the hole tunneling barrier width between the Si substrate and the Si-QDs.
    Full-text · Article · Apr 2011 · Japanese Journal of Applied Physics

Publication Stats

1k Citations
117.25 Total Impact Points

Institutions

  • 2002-2013
    • Electronics and Telecommunications Research Institute
      • • Components and Materials Research Laboratory
      • • Department of Intelligent Convergence Technology Research
      • • Department of Future Technology Research
      Sŏul, Seoul, South Korea
  • 2004-2005
    • Gwangju Institute of Science and Technology
      • School of Materials Science and Engineering
      Gwangju, Gwangju, South Korea