• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.577-582
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• 2013

AZO (aluminum-doped zinc oxide) is one of the best candidate materials to replace ITO (indium tin oxide) for TCOs (transparent conductive oxides) used in flat panel displays, organic light-emitting diodes (OLEDs), and organic solar cells (OSCs). In the present study, to apply an AZO thin film to the transparent electrode of an organic solar cell, a low-temperature selective atomic layer deposition (ALD) process was adopted to deposit an AZO thin film on a flexible poly-ethylene-naphthalate (PEN) substrate. The reactive gases for the ALD process were di-ethyl-zinc (DEZ) and tri-methyl-aluminum (TMA) as precursors and H2O as an oxidant. The structural, electrical, and optical characteristics of the AZO thin film were evaluated. From the measured results of the electrical and optical characteristics of the AZO thin films deposited on the PEN substrates by ALD, it was shown that the AZO thin film appeared to be comparable to a commercially used ITO thin film, which confirmed the feasibility of AZO as a TCO for flexible organic solar cells in the near future.

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.215-218
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• 2013

Vanadium dioxide ($VO_2$) is an attractive material for smart window applications where the transmittance of light can be automatically modulated from a transparent state to an opaque state at the critical temperature of ${\sim}68^{\circ}C$. Meanwhile, F : $SnO_2$ (F-doped $SnO_2$, FTO) glass is a transparent conductive oxide material that is widely used in solar-energy-related applications because of its excellent optical and electrical properties. Relatively high transmittance and low emissivity have been obtained for FTO-coated glasses. Tunable transmittance corresponding to ambient temperature and low emissivity can be expected from $VO_2$ films deposited onto FTO glasses. In this study, FTO glasses were applied for the deposition of $VO_2$ thin films by pulsed DC magnetron sputtering. $VO_2$ thin films were also deposited on a Pyrex substrate for comparison. To decrease the phase transition temperature of $VO_2$, tungsten-doped $VO_2$ films were also deposited onto FTO glasses. The visible transmittance of $VO_2$/FTO was higher than that of $VO_2$/pyrex due to the increased crystallinity of the $VO_2$ thin film deposited on FTO and decreased interface reflection. Although the solar transmittance modulation of $VO_2$/FTO was lower than that of $VO_2$/pyrex, room temperature solar transmittance of $VO_2$/FTO was lower than that of $VO_2$/pyrex, which is advantageous for reflecting solar heat energy in summer.

• Korean Journal of Materials Research
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• v.24 no.10
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• pp.543-549
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• 2014

A zinc oxide (ZnO) hybrid structure was successfully fabricated on a glass substrate by metal organic chemical vapor deposition (MOCVD). In-situ growth of a multi-dimensional ZnO hybrid structure was achieved by adjusting the growth temperature to determine the morphologies of either film or nanorods without any catalysts such as Au, Cu, Co, or Sn. The ZnO hybrid structure was composed of one-dimensional (1D) nanorods grown continuously on the two-dimensional (2D) ZnO film. The ZnO film of 2D mode was grown at a relatively low temperature, whereas the ZnO nanorods of 1D mode were grown at a higher temperature. The change of the morphologies of these materials led to improvements of the electrical and optical properties. The ZnO hybrid structure was characterized using various analytical tools. Scanning electron microscopy (SEM) was used to determine the surface morphology of the nanorods, which had grown well on the thin film. The structural characteristics of the polycrystalline ZnO hybrid grown on amorphous glass substrate were investigated by X-ray diffraction (XRD). Hall-effect measurement and a four-point probe were used to characterize the electrical properties. The hybrid structure was shown to be very effective at improving the electrical and the optical properties, decreasing the sheet resistance and the reflectance, and increasing the transmittance via refractive index (RI) engineering. The ZnO hybrid structure grown by MOCVD is very promising for opto-electronic devices as Photoconductive UV Detectors, anti-reflection coatings (ARC), and transparent conductive oxides (TCO).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.201-202
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• 2009

ZnO:Al transparent conductive films for solar cells were deposited on the glass substrates at room temperature by facing target sputtering (FTS) method. The sputtering targets were 100 mm diameter disks of 2w.t..%. AZO and Zn metal. ZnO:Al thin films were deposited as a function film thickness. A base pressure was $2{\times}10^{-6}$torr, and a working pressure was 1mTorr. The properties of thin films on the structural, electrical and optical properties of the deposited films were investigated using a four-point probe (Chang-min), an X-ray diffraction (Rigaku), a Hall Effect measurement (Ecopia), an UV/VIS spectrometer (HP) and a $\alpha$-step (Tencor). The lowest resistivity of film was $5.67{\times}10^{-4}[{\Omega}-cm]$ at 500nm. The average transmittance of over 80% was seen in the visible range.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.302-305
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• 1995

ITO(indium tin oxide) that is both conductive in electricity and transparent to the visible ray is called transparent conducting thin film. Nowaday, according to the development of flat panel display such as LCD(Liquid Crystal display, EL(electolumine- scence display), PDP(plasma display panel), ECD(electrocromic display), the higher quality in the low temperature process has been asked to reduce the production cost and to have a good uniformity on a large substrate. In this study, we prepared indium tin oxide(ITO) by a cylindrical DC magnetron sputtering with Indium-tin (9:1) alloy target instead of indium-tin oxide target. To reduce the defact in ITO, the effect on ITO by varing the magnetic field intensity and the applied voltage ares studied. the resistivity of the film deposited in oxygen partial pressure of 5% and substrate temperature of 140$^{\circ}C$. is 1.6${\times}$10$\^$-1/$\Omega$$.$cm with 85% optical transmission in viaible ray.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.48-49
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• 2006

Highly conductive and transparent films of Ga-doped ZnO have been prepared by pulsed laser deposition using a ZnO target with 3 wt% ${Ga_2}{O_3}$ dopant. Films with the resistivity as low as $3.3{\times}10^{-4}{\Omega}cm$ and the transmittance above 80 % at the wavelength of 400 to 800 nm can be fabricated on glass substrate at room temperature. It is shown that a stable resistivity for the use in oxidation ambient at high temperature can be obtained for the films. Heat treatments were performed to examine the thermal stability of ZnO and GZO films at ptemperature range from $100^{\circ}C$ to $400^{\circ}C$ in $O_2$ ambient for 30 minutes. The resistivity of ZnO film annealed at $400^{\circ}C$ increased by two orders of magnitude, in case of GZO film was relatively stable up to at $400^{\circ}C$. For practical applications at high temperatures the thermal stability of resistivity of GZO thin films might become an advantage for transparent electrodes.

• Journal of the Semiconductor & Display Technology
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• v.13 no.2
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• pp.13-16
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• 2014

We prepared the ITO/Ag multilayer thin films on soda-lime glass substrate by the Facing Target Sputtering System (FTS) at room temperature. To confirm the effect of Ag layer in ITO/Ag multilayer thin films, we have prepared various range of Ag layer in its thickness and investigated prior to the setting of ITO/Ag multilayer thin films. The thickness of Ag layer was controlled by the sputtering deposition time. Properties of as-prepared samples were investigated by using a four-point probe, UV-Visual spectrometer with a spectral visual range (400 - 800 nm) and X-ray diffractometer (XRD). As a result, the transmittance of as-prepared samples turned out to be very low in the visible range due to light-scattering on the surface of thin film as the thickness of Ag layer got increased. However, reduction of phenomenon of light-reflection in visual range was observed around 20nm of Ag thickness. We prepared the ITO/Ag multilayer thin film with a resistivity of about $8{\times}10^{-5}[{\Omega}-cm]$ and a transmittance of more than 80 % at 550 nm.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.2
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• pp.13-21
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• 1999

Flip chip assembly directly on organic boards offers miniaturization of package size as well as reduction in interconnection distances resulting in a high performance and cost-competitive Packaging method. This paper describes the investigation of alternative low cost flip-chip mounting processes using electroless Ni/Au bump and anisotropic conductive adhesives/films as an interconnection material on organic boards such as FR-4. As bumps for flip chip, electroless Ni/Au plating was performed and characterized in mechanical and metallurgical point of view. Effect of annealing on Ni bump characteristics informed that the formation of crystalline nickel with $Ni_3$P precipitation above $300^{\circ}C$ causes an increase of hardness and an increase of the intrinsic stress resulting in a reliability limitation. As an interconnection material, modified ACFs composed of nickel conductive fillers for electrical conductor and non-conductive inorganic fillers for modification of film properties such as coefficient of thermal expansion(CTE) and tensile strength were formulated for improved electrical and mechanical properties of ACF interconnection. The thermal fatigue life of ACA/F flip chip on organic board limited by the thermal expansion mismatch between the chip and the board could be increased by a modified ACA/F. Three ACF materials with different CTE values were prepared and bonded between Si chip and FR-4 board for the thermal strain measurement using moire interferometry. The thermal strain of ACF interconnection layer induced by temperature excursion of $80^{\circ}C$ was decreased with decreasing CTEs of ACF materials.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.4
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• pp.59-65
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• 2001

Epoxy/$BaTiO_3$composite capacitor films with excellent stability at room temperature, uniform thickness, and electrical properties over a large area ware successfully fabricated. The composite capacitor films with good film formation capability and easy process ability were made from epoxy resin developed for ACF as a matrix and two kinds of $BaTiO_3$powders as fillers to increase the dielectric constant of the composite film. The crystal structure of the powders and its effects on dielectric constant of the films were investigated by X-ray diffraction (XRD). And the optimum amount of dispersant, phosphate ester, was determined by viscosity measurement of suspension. DSC and dielectric property tests were conducted to decide the right curing temperature and the optimum amount of the curing agent. As a result, the capacitors of 7 $\mu \textrm{m}$ thick film with 10 nF/$\textrm{cm}^2$ and low leakage current were successfully demonstrated.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.336.2-336.2
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• 2014

Indium Tin Oxide (ITO) thin films are used as the Transparent Conducting Oxide (TCO), such as flat panel display, transparent electrodes, solar cell, touch screen, and various optical devices. ZnO has attracted attention as alternative materials to ITO film due to its resource availability, low cost, and good transmittance at the visible region. Recently, very thin film deposition is important. In order to minimize the damage caused by bending. However, ZnO thin film such as Ga-doped ZnO(GZO) has poor sheet resistance characteristics. To solve this problem, By adding the conductive metal on films can decrease the sheet resistance and increase the mobility of the films. In this study, We analyzed the electrical and optical characteristics of GZO/Ag/GZO (GAG) films by change in Ag and GZO thickness.