• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.10
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• pp.805-810
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• 2012

Transparent conducting oxides (TCOs) have wide range of application areas in transparent electrode for display devices, Transparent coating for solar energy heat mirrors, and electromagnetic wave shield. $SnO_2$ is intrinsically an n-type semiconductor due to oxygen deficiencies and has a high energy-band gap more than 3.5 eV. It is known as a transparent conducting oxide because of its low resistivity of $10^{-3}{\Omega}{\cdot}cm$ and high transmittance over 90% in visible region. In this study, co-doping effects of Al and Y on the properties of $SnO_2$ were investigated. The addition of Y in $SnO_2$ was tried to create oxygen vacancies that increase the diffusivity of oxygen ions for the densification of $SnO_2$. The addition of Al was expected to increase the electron concentration. Once, we observed solubility limit of $SnO_2$ single-doped with Al and Y. $\{(x/2)Al_2O_3+(x/2)Y_2O_3\}-SnO_2$ was used for the source of Al and Y to prevent the evaporation of $Al_2O_3$ and for the charge compensation. And we observed the valence changes of aluminium oxide because generally reported of valence changes of aluminium oxide in Tin - Aluminium binary system. The electrical properties, solubility limit, densification and microstructure of $SnO_2$ co-doped with Al and Y will be discussed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.225-229
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• 2011

In this study, capacitive type pressure sensors based on low temperature co-fired ceramics (LTCC) technology for environmental monitoring were demonstrated. The LTCC is one of promising technology than is based one since it has many advantages (e.g., low cost production, high manufacturing yields and easy realizing 3D structure etc.) for sensor application. Especially, it has good mechanical and chemical properties for robust environmental application. The 3D LTCC diaphragm with thickness of 400 ${\mu}m$ were fabricated by laminating 4 green sheets using commercial powder (NEG, MLS 22C). To evaluate the sensing properties of the different cavity areas, two types of diaphragm which had different cavity areas with 25, 49 $mm^2$ respectively, were fabricated. To realize capacitive type pressure sensor, the Au top electrode was fabricated using thermal evaporator and the bottome electrode was compressed using aluminium foil. The sensing properties of the fabricated sensors showed linear characteristic under different pressure (0~30 psi) using pressure measurement system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.10
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• pp.901-906
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• 2006

The transparent conductive oxide(TCO) has been used in necessity as front electrode for increasing efficiency of LED. In our paper, aluminium-doped zinc oxide films(AZO), which has transparent conducting were prepared with RF magnetron sputtering system on glass substrate(corning 1737) and annealed at $400^{\circ}C$ for 2 hr in vacuum ambient and $600^{\circ}C$ for 2hr with $O_2$ ambient respectively. The smooth AZO films were etched in diluted HCL(0.5 %) to examine the surface properties, which in ambient post-annealing process. We confirmed that the electric, structural and optical properties of textured AZO thin films, which implemented using the methods of XRD, FWHM, AFM and Hall measurement. The properties of textured AZO thin films especially depended on the ambient post-annealing process. We presumed that the change of transmittances as R G B LED and the ambient post-annealing process will be increasing the efficiency of LED.

• Progress in Medical Physics
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• v.9 no.1
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• pp.29-35
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• 1998

There has been necessity of an air free ionization chamber using the gold-crystal-aluminium plates, henceforth called the crystal chamber. The crystal chamber formed of parallel plates is very small in size and has more response for absorbed dose of therapeutic radiation beams. The gold plate on the crystal facing the photon and electron beam acts as an intensifier of signals and crystal plate as an ionization medium respectively. Both the copper guard ring and the aluminum collecting electrode are connected to an electrometer. Using high energy photon (6, 15 MV) and electron (9, 12, 15, 18 MeV) beams, the responses of the crystal chamber are evaluated against a PTW Farmer-type chamber at a field size of 10${\times}$10cm$^2$ and 100 cm SSD. The responses of crystal chamber for therapeutic radiation electron and photon beams are greater in magnitude by several order than Farmer. The crystal chamber has good linearity without correction factor C$\_$t,p/ with respect to the signals, a reading reproduction with good accuracy and precision less than 0.5%, and has other useful functions in measuring radiation beams.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1262-1263
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• 2008

Recently film-typed dye sensitized solar cell(DSC) attracts much attention with increasing applications for its flexibility and transparency. The ZnO:Al thin film, which serves mainly as transparent conducting electrode, Aluminium-doped zinc oxide(ZnO:Al) thin film has emerged as one of the most promising transparent conducting films since it is inexpensive, mechanically stable, and highly resistant to deoxidation. In this paper ZnO:Al thin film was deposited on the polyethylene terephthalate(PET) substrate by the capacitively coupled r. f. magnetron sputtering method. The effects of gas pressure and r. f. discharge power on the morphological, electrical and optical properties of ZnO:Al thin film were studied. Especially the variation in substrate thickness after sputtering and surface morphology of the substrate were investigated and clarified. The results showed that the film deposited on the PET substrate at r. f. discharge power of 180 W showed the minimum resistivity of about $1.5{\times}10^{-3}{\Omega}-cm$ and a transmittance of about 93%.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.129.2-129.2
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• 2013

Electron injection enhancement at OLED (organic light-emitting diodes) cathode side has mostly been achieved by insertion of a low work function layer between metal electrode and emissive layer. We investigated the interfacial chemical reactions and electronic structures of alkaline-earth metal (Ca, Ba)/Alq3 [tris(8-hydroxyquinolinato)aluminium] and Ca/BaF2/Alq3 using in-situ X-ray & ultraviolet photoelectron spectroscopy. The alkaline-earth metal deposited on Alq3 generates two energetically separated gap states in sequential manner. This phenomenon is explained by step-by-step charge transfer from alkali-earth metal to the lowest unoccupied molecular orbital (LUMO) states of Alq3, forming new occupied states below Fermi level. The BaF2 interlayer initially prevents from direct contact between Alq3 and reactive Ca metal, but it is dissociated into Ba and CaF2. However, as the Ca thickness increases, the Ca penetrates the interlayer to directly participate in the reaction with underlying Alq3. The influence of the multiple gap state formation by the interfacial chemical reaction on the OLED performance will be discussed.

• 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.

• Journal of Industrial Convergence
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• v.20 no.12
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• pp.79-85
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• 2022

Recently, a smartphone manufactured on a flexible substrate has been released as an electronic device, and research on a stretchable electronic device is in progress. In this paper, a silicon-based stretchable material is made and used as a substrate to implement and evaluate an optical sensor device using oxide semiconductor. To this end, a substrate that stretches well at room temperature was made using a silicone-based solution rubber, and the elongation of 350% of the material was confirmed, and optical properties such as reflectivity, transmittance, and absorbance were measured. Next, since the surface of these materials is hydrophobic, oxygen-based plasma surface treatment was performed to clean the surface and change the surface to hydrophilicity. After depositing an AZO-based oxide film with vacuum equipment, an Ag electrode was formed using a cotton swab or a metal mast to complete the photosensor. The optoelectronic device analyzed the change in current according to the voltage when light was irradiated and when it was not, and the photocurrent caused by light was observed. In addition, the effect of the optical sensor according to the folding was additionally tested using a bending machine. In the future, we plan to intensively study folding (bending) and stretching optical devices by forming stretchable semiconductor materials and electrodes on stretchable substrates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.277-278
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• 2009

We have studied an angular dependence of emission pattern of top-emssion organic light-emitting diodes (TEOLED). Device structure is Al(100nm)/TPD(40nm)/$Alq_3$(60nm)/LiF(0.5nm)/Al(2nm)/Ag(30nm). N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) and tris-(8-hydroxyquinoline) aluminium ($Alq_3$)were used as a hole transport layer and emission layer, respectively. Organic layers and cathode were thermally evaporated at $2\times10^{-5}$torr. The evaporation rate of the organic material was maintained to be $1.5\sim2.0{\AA}/s$, and that of metal layer to be $0.5\sim5{\AA}/s$. A transmittance of a cathode electrode(Al/Ag) in visible region is about 25~30%. In order to measure view-angle dependent intensity, electroluminenscence spectra of the device at each angle were integrated. Angle dependent emission spectra of the device do not show blue shift. Emission intensity of the device that the going straight characteristic is stronger the bottom-emission organic light-emitting diodes is shown.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1260-1261
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• 2008

Aluminium doped zinc oxide (ZnO:Al) thin film has emerged as one of the most promising transparent conducting electrode in flat panel displays(FPD) and in photovoltaic devices since it is inexpensive, mechanically stable, and highly resistant to deoxidation. In this paper ZnO:Al thin film was deposited on the polyethylene terephthalate(PET) substrate by the capacitively coupled r.f. magnetron sputtering method. Wide ranges of bias voltage, -30V${\sim}$45V, was applied to the growing films as an additional energy instead of substrate heating, and the effect of positive and negative bias on the film structure and electrical properties of ZnO:Al films was studied and discussed. The results showed that a bias applied to the substrate during sputtering contributed to the improvement of electrical properties of the film by attracting ions and electrons in the plasma to bombard the growing films. These bombardments provided additional energy to the growing ZnO film on the substrate, resulting in significant variations in film structure and electrical properties. The film deposited on the PET substrate at r. f. discharge power of 200 W showed the minimum resistivity of about $2.4{\times}10^{-3}{\Omega}-cm$ and a transmittance of about 87%.