• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.742-748
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• 2005

Transparent conductive indium-tin oxide (ITO) films are widely used as transparent electrodes for flat panel displays. Many of the ITO films for practical use have been prepared by magnetron sputtering, chemical vapor deposition, electron beam evaporation, etc. An oxide target composed of 10 wt% $SnO_2$ and 90 wt% $In_2O_3$ has been deposited onto polycyclic olefin polymer (POP) substrate by electron beam evaporation. POP has a higher glass transition temperature ($Tg=330^{\circ}C$) than other conventional polymers. In this study, the effects of substrate temperature and the $O_2$ introduction flow rate were investigated in terms of physical, electrical and optical properties of deposited ITO films. We investigated the effects of processing variables such as substrate temperature and the oxygen introduction flow rate. The best electrical and optical properties of deposited ITO films obtained from this study were electrical resistivity value of ${\rho}=1.78{\times}10^{-3}{\Omega}{\cdot}cm$ and optical transmittance of about 85% at 8 sccm (Standard Cubic Centimeter per Minute) $O_2$ introduction flow rate, $5{\AA}/sec$ deposition rate, $1000{\AA}$ deposited ITO thickness and $200^{\circ}C$ substrate temperature.

• Journal of the Korean Vacuum Society
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• v.16 no.2
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• pp.105-109
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• 2007

In this paper, we fabricated TCO (transparent conductive oxide) electrode on flexible substrate in order to study effects of electrical and optical properties according to Al-doped ZnO(AZO) film thickness. The thickness of film was from 100 nm to 500 nm and was controlled by changing deposition time. We used High Resolution X-ray Diffractometer (HR-XRD) to analyze crystal structure and UV-visible spectrophotometer to measure property of optical transmittance, respectively. The surface images are obtained by using ESEM (Environment Scanning Electron Microscopy). In this experiment, all the AZO films deposited on flexible substrate show high transmittance over 90% and especially in the films with 400 nm and 500 nm thickness, the resistivity ($4.5{\times}10^{-3}\;{\Omega}-cm$) and optical bandgap energy (3.61 eV) are superior to the other films.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.235.2-235.2
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• 2015

The front transparent conductive oxide (TCO) films must exhibit good transparency, low resistivity and excellent light scattering properties for high efficiency amorphous silicon (a-Si) thin film solar cells. The light trapping phenomenon is limited due to non-uniform and low aspect ratio of the textured glass [1]. We present the low cost electrochemically deposited uniform zinc oxide (ZnO) nanorods with various aspect ratios for a-Si thin film solar cells. Since the major drawback of the electrochemically deposited ZnO nanorods was the high sheet resistance and low transmittance that was overcome by depositing the RF magnetron sputtered AZO films as a seed layer with various thicknesses [2]. The length and diameters of the ZnO nanorods was controlled by varying the deposition conditions. The length of ZnO nanorods were varied from 400 nm to $2{\mu}m$ while diameter was kept higher than 200 nm to obtain different aspect ratios. The uniform ZnO nanorods showed higher haze ratio as compared to the commercially available FTO films. We also observed that the scattering in the longer wavelength region was favored for the high aspect ratio of ZnO nanorods and much higher aspect ratios degraded the light scattering phenomenon. Therefore, we proposed our low cost and uniform ZnO nanorods for the high efficiency of thin film solar cells.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.95-95
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• 2014

An OLED(Organic Light-Emitting Diode) device based on the emissive electroluminescent layer a film of organic materials. OLED is used for many electronic devices such as TV, mobile phones, handheld games consoles. ULVAC's mass production systems are indispensable to the manufacturing of OLED device. ULVAC is a manufacturer and worldwide supplier of equipment and vacuum systems for the OLED, LCD, Semiconductor, Electronics, Optical device and related high technology industries. The SMD Series are single-substrate sputtering systems for deposition of films such as metal films and TCO (Transparent Conductive Oxide) films. ULVAC has delivered a large number of these systems not only Organic Evaporating systems but also LTPS CVD systems. The most important technology of thin-film encapsulation (TFE) is preventing moisture($H_2O$) and oxygen permeation into flexible OLED devices. As a polymer substrate does not offer the same barrier performance as glass substrate, the TFE should be developed on both the bottom and top side of the device layers for sufficient lifetimes. This report provides a review of promising thin-film barrier technologies as well as the WVTR(Water Vapor Transmission Rate) properties. Multilayer thin-film deposition technology of organic and inorganic layer is very effective method for increasing barrier performance of OLED device. Gases and water in the organic evaporating system is having a strong influence as impurities to OLED device. CRYO pump is one of the very useful vacuum components to reduce above impurities. There for CRYO pump is faster than conventional TMP exhaust velocity of gases and water. So, we suggest new method to make a good vacuum condition which is CRYO Trap addition on OLED evaporator. Alignment accuracy is one of the key technologies to perform high resolution OLED device. In order to reduce vibration characteristic of CRYO pump, ULVAC has developed low vibration CRYO pumps to achieve high resolution alignment performance between Metal mask and substrate. This report also includes ULVAC's approach for these issues.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.236.1-236.1
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• 2015

The surface morphology of front transparent conductive oxide (TCO) films is very important to achieve high current density in amorphous silicon (a-Si) thin film solar cells since it can scatter the light in a better way. In this study, we present the low cost hydrothermal deposited uniform zinc oxide (ZnO) nano-flower structure with various aspect ratios for a-Si thin film solar cells. The ZnO nano-flower structures with various aspect ratios were grown on the RF magnetron sputtered AZO films. The diameters and length of the ZnO nano-flowers was controlled by varying the annealing time. The length of ZnO nano-flowers were varied from 400 nm to $2{\mu}m$ while diameter was kept higher than 200 nm to obtain different aspect ratios. The ZnO nano-flowers with higher surface area as compared to conventional ZnO nano structure are preferred for the better light scattering. The conductivity and crystallinity of ZnO nano-flowers can be enhanced by annealing in hydrogen atmosphere at 350 oC. The vertical aligned ZnO nano-flowers showed higher haze ratio as compared to the commercially available FTO films. We also observed that the scattering in the longer wavelength region was favored for the high aspect ratio of ZnO nano-flowers. Therefore, we proposed low cost and vertically aligned ZnO nano-flowers for the high performance of thin film solar cells.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.12
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• pp.961-965
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• 2010

In this study, we investigated the optical, electrical, and structural properties of the IGZO($In_2O_3:Ga_2O_3:ZnO$=1:9:90 wt.%) thin films prepared by RF-magnetron sputtering system under various substrate temperatures. All of the IGZO thin films shows an average transmittance of over the 80% in visible range. Most of all, deposited IGZO thin film at $100^{\circ}C$ substrate temperature have ZnO (002) of main growth peak and 17.02 nm of increased grains. And also IGZO thin film have low resistivity($1.35{\times}10^{-3}\;\Omega{\cdot}cm$), high carrier concentration($6.62{\times}10^{20} cm^{-3}$) and mobility($80.1 cm^2$/Vsec). IGZO thin film have 2.08 mV at surface potential of electric force microscopy(EFM). We suggest that pre-annealing at $100^{\circ}C$ can be applied for improving optical, electrical and structural properties.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.39-46
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• 2024

In this study, GTZO(Ga-Ti-Zn-O) thin films were deposited at various working pressures (1~7mTorr) by RF magnetron sputtering to examine the structural, electrical, and optical properties. All GTZO thin films exhibited c-axis preferential growth regardless of working pressure, the GTZO thin film deposited at 1mTorr showed the most excellent crystallinity having 0.38˚ of FWHM. The average transmittance in the visible light region (400~800nm) showed 80% or more regardless of the working pressure. We could observed the Burstein-Moss effect that carrier concentration decrease with the increase of working pressure and thus the energy band gap is narrowed. Figure of merits of GTZO thin film deposited at 1mTorr showed the highest value of 9.08 × 103 Ω-1·cm-1, in this case resistivity and average transmittance in the visible light region were 5.12 × 10-4 Ω·cm and 80.64%, respectively.

• Korean Chemical Engineering Research
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• v.51 no.6
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• pp.766-773
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• 2013

A transparent film was fabricated based on bacterial cellulose (BC), BC has excellent physical strength and stability at high temperature and it is an environmental friendly flexible material. In order to improve the conductivity, silver nanowire (AgNW) and/or graphene were introduced to the BC membrane. The aspect ratio of the AgNW synthesized in this study was 214, with a length of $15{\mu}m$ and width of 70 nm. The higher aspect ratio improved the conductivity by reducing the contact resistance. The thermal and electrical properties of 7 types of films prepared were investigated. Each film was fabricated with rectangular shape ($2mm{\times}2mm{\times}50{\mu}m$). The films were scored with a net shape by a knife, and filled with AgNW and graphene to bestow conductivity. The film filled with AgNW showed favorable electrical characteristics with a thickness of $350{\mu}m$, electron concentration of $1.53{\times}10^{19}$, electron mobility of $6.63{\times}10^5$, and resistivity of 0.28. The film filled with graphene had a thickness of $360{\mu}m$, electron concentration of $7.74{\times}10^{17}$, electron mobility of 0.17, and resistivity of 4.78. The transmittances at 550 nm were 98.1% and 80.9%, respectively. All the films were able to light LEDs bulbs although their brightness differed. A thermal stability test of the BC and PET films at $150{\pm}5^{\circ}C$ showed that the BC film was more stable, whereas the PET film was quickly banded. From these results, it was confirmed that there it is possible to fabricate new transparent conductivity films based on BC.

• Carbon letters
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• v.15 no.2
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• pp.77-88
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• 2014

Double walled carbon nanotubes (DWCNTs) are considered an ideal model for studying the coupling interactions between different concentric shells in multi-walled CNTs. Due to their intrinsic coaxial structures they are mechanically, thermally, and structurally more stable than single walled CNTs. Geometrically, owing to the buffer-like function of the outer tubes in DWCNTs, the inner tubes exhibit exciting transport and optical properties that lend them promise in the fabrication of field-effect transistors, stable field emitters, and lithium ion batteries. In addition, by utilizing the outer tube chemistry, DWCNTs can be useful for anchoring semiconducting quantum dots and also as effective multifunctional fillers in producing tough, conductive transparent polymer films. The inner tubes meanwhile preserve their excitonic transitions. This article reviews the synthesis of DWCNTs, their electronic structure, transport, and mechanical properties, and their potential uses.

• Journal of Electrical Engineering and Technology
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• v.4 no.1
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• pp.93-97
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• 2009

The nanoporous $F:SnO_2$ materials have been prepared through the controlled hydrolysis of fluoro(2-methylbutan-2-oxy)di(pentan-2,4-dionato)tin followed by thermal treatment at $400-550^{\circ}C$. The main IR features include resonances at 660, 620 and 540 cm-1. From the TG-DTG result, three main mass losses of 6.5, 13.3 and 3.8 at 81, 289 and $490^{\circ}C$ are observed between 50 and $650^{\circ}C$ yielding a final residue of 76.0%. The size of Sn $O_2$ nanoparticles rose from 5 nm to 10-12 nm as the temperature of thermal treatment is increased from 400 to $550^{\circ}C$.