• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.169-169
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• 2010

As display industry requires various applications for future display technology, which can guarantees high level of flexibility and transparency on display panel, oxide semiconductor materials are regarded as one of the best candidates. $InGaZnO_4$(IGZO) has gathered much attention as a post-transition metal oxide used in active layer in thin-film transistor. Due to its high mobility fabricated at low temperature fabrication process, which is proper for application to display backplanes and use in flexible and/or transparent electronics. Electrical performance of amorphous oxide semiconductors depends on the resistance of the interface between source/drain metal contact and active layer. It is also affected by sheet resistance on IGZO thin film. Controlling contact/sheet resistance has been a hot issue for improving electrical properties of AOS(Amorphous oxide semiconductor). To overcome this problem, post-annealing has been introduced. In other words, through post-annealing process, saturation mobility, on/off ratio, drain current of the device all increase. In this research, we studied on the relation between device's resistance and post-annealing temperature. So far as many post-annealing effects have been reported, this research especially analyzed the change of electrical properties by increasing post-annealing temperature. We fabricated 6 main samples. After a-IGZO deposition, Samples were post-annealed in 5 different temperatures; as-deposited, $100^{\circ}C$, $200^{\circ}C$, $300^{\circ}C$, $400^{\circ}C$ and $500^{\circ}C$. Metal deposition was done on these samples by using Mo through E-beam evaporation. For analysis, three analysis methods were used; IV-characteristics by probe station, surface roughness by AFM, metal oxidation by FE-SEM. Experimental results say that contact resistance increased because of the metal oxidation on metal contact and rough surface of a-IGZO layer. we can suggest some of the possible solutions to overcome resistance effect for the improvement of TFT electrical performances.

• Korean Journal of Optics and Photonics
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• v.34 no.4
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• pp.157-169
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• 2023

Augmented reality (AR) using a head mounted display (HMD) is used in various fields such as military, medicine, manufacturing, gaming, and education. In this paper, we discuss the design and fabrication of the AR optical system, which is most essential for HMD. The AR optical system for HMD requires a wide transparent area in which the augmented image of the display and the real world can be viewed at the same time. To this end, an AR optical system was designed and manufactured by dividing it into three parts according to each characteristic. Also, the refractive index of the ultra-violet (UV) adhesive layer required to make the three optical systems into one complete AR optical system was considered from the design stage to minimize the optical path shift phenomenon when the input light source passes through the UV adhesive layer. In addition, when designing the AR optical system, two aspheric surfaces were used to compensate for off-axis aberration and to be suitable for mass production. Finally, for HMD mass production, an aspheric AR optical system with a thickness of 11 mm, a diagonal field of view of 40°, and a weight of 11.3 g was designed and manufactured.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.291-294
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• 2015

Recently, ZnO based oxide TFTs used in the flexible and transparent display devices are widely studied. To apply to OLED display switching devices, electrical performance and stability are important issues. In this study, to improve these electrical properties, we fabricated TFTs having Al doped Zinc Oxide (AZO) layer inserted between the gate insulator and ZnO layer. The AZO and ZnO layers are deposited by Atomic layer deposition (ALD) method. I-V transfer characteristics and stability of the suggested devices are investigated under the positive gate bias condition while the channel defects are also analyzed by the photoluminescence spectrum. The TFTs with AZO layer show lower threshold voltage ($V_{th}$) and superior sub-threshold slop. In the case of $V_{th}$ shift after positive gate bias stress, the stability is also better than that of ZnO channel TFTs. This improvement is thought to be caused by the reduced defect density in AZO/ZnO stack devices, which can be confirmed by the photoluminescence spectrum analysis results where the defect related deep level emission of AZO is lower than that of ZnO layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.358-358
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• 2012

The application of BZO (Boron-doped Zinc Oxide) films use as the TCO(Transparent Conductive Oxide) material for display and solar cell industries, where the conductivity of the BZO films plays a critical role for improvement of cell performance. Thin BZO films are deposited on glass substrates by using RF sputter system. Then charging flow rates of O2 gas from zero to 10 sccm, thereby controlling the impurity concentration of BZO. BZO deposited on soda lime glass and RF power was 300 W, frequency was 13.56 MHz, and working pressure was $5.0{\times}10-6$ Torr. The Substrate and glass between distance 200 mm. We measured resistivity, conductivity, mobility by hall measurement system. Optical properties measured by photo voltaic device analysis system. We measured surface build according to oxygen flow rate from XPS (X-ray Photoelectron Spectroscopy) system. The profile of the energy distribution of the electrons emitted from BZO films by the Auger neutralization is measured and rescaled so that Auger self-convolution arises, revealing the detail structure of the valence band. It may be observed coefficient ${\gamma}$ of the secondary electron emission from BZO by using ${\gamma}$-FIB (Gamma-Focused Ion Beam) system. We observed the change in electrical conductivity by correlation of the valence band structure. Therefore one of the key issues in BZO films may be the valence band that detail structure dominates performance of solar cell devices. Demonstrating the secondary electron emission by the Auger neutralization of ions is useful for the determination of the characteristics of BZO films for solar cell and display developments.

• Polymer(Korea)
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• v.29 no.2
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• pp.204-210
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• 2005

We describe a colorless, transparent polyimide films for plastic display substrate which should have heat resistance, roll-to-roll processability and low CTE (coefficient of thermal expansion) property. Colorless polyimides were synthesized from 3,3',4,4'-oxydiphthalic anhydride (ODPA) 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and diamines such as sulfonyldianiline, aminophenoxybenzene (TPE-p, TPE-q, TPE-r) and bis[4-(3-aminophen oxy)phenyl] sulfone (m-BAPS). Their optical properties were measured by UV spectrophotometer, colormeter and hazemeter. We prepared polyimide/organophilic layered silicate nanocomposite to improve dimension stability. These colorless polyimide films showed UV transmittance by the level upper $89\%$, at 440 nm and excellent optical property having the value under yellow index (YI)=7. In addition, polyimide nanocomposite films also showed an improvement of CTE value as decreased according to the amount of layered silicate contents.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.260-264
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• 2007

We have studied stability in organic light-emitting diode depending on buffer layer and cathode. A transparent electrode of indium-tin-oxide(ITO) was used as an anode. An electron injection energy barrier into organic material is different depending on a work function of cathodes. Theoretically, the energy barriers for the electron injection are 1.2 eV, -0.1 eV, and 0.0 eV for Al, LiAl, and LiF/Al at 300 K, respectively. We considered the cases that holes are injected to organic light-emitting diode. The hole injection energy barrier is about 0.7 eV between ITO and TPD without buffer layer. For hole-injection buffer layers of CuPc and PEDOT:PSS, the hole injection energy barriers are 0.4 eV and 0.5 eV, respectively. When the buffer layer of CuPc and PEDOT:PSS is existed, we observed the effects of hole injection energy barrier, and a reduction of operating-voltage. However, in case of PVK buffer layer, the hole injection energy barrier becomes high(1.0 eV). Even though the operating voltage becomes high, the efficiency is improved. A device structure for optimal lifetime condition is ITO/PEDOT:PSS/TPD/$Alq_3$/LiAl at an initial luminance of $300cd/m^2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.4
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• pp.344-349
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• 2005

The optical and electrical characteristics of plasma display panel(PDP) using the vacuum in-line sealing technology compared with the conventional sealing process in this research. This PDP consisted of MgO protecting layer by e-beam evaporation and battier rib, transparent dielectric layer, dielectric layer, and electrodes by screen printer and then sealed off on Ne-Xe(4 ％) 400 Torr and 430。C. The brightness and luminous efficiency were good as the base vacuum level was higher, and it was to check the advantage of high vacuum level sealing, one of the strong points of the vacuum in-line sealing process. However, the brightness and luminous efficiency was dropped sharply because of a crack on MgO protecting layer by the difference of the expansion and contraction stress on high temperature in the vacuum states between MgO and substrate. Fortunately, the crack was prevented by MgO was deposited on higher temperature than 300。C. Finally, the PDP, was fabricated by the vacuum in-line sealing process, resulted the lower brightness than processing only the thermal annealing treatment in the vacuum chamber, but the luminous efficiency was increased by the reducing power consumption with the decreasing luminous current. The vacuum in-line sealing technology was not to need the additional thermal annealing process and could reduce the fabrication process and bring the excellent optical and electrical properties without the crack of MgO protecting layer than the conventional sealing process.

• Journal of Information Display
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• v.11 no.2
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• pp.49-51
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• 2010

Nanoimprint lithography (NIL) using ultraviolet (UV) rays is a technique in which unconventional lithographic patterns are formed on a substrate by curing a suitable liquid resist in contact with a transparent patterned mold, then releasing the freshly patterned material. Here, various solutions are introduced to achieve sufficient overlay accuracy and to overcome the technical challenges in resist patterning via UV imprinting. Moreover, resist patterning of all the layers in TFT and of the BM layer in CF was carried out using UV imprinting lithography to come up with a 12.1-inch TFT-LCD panel with a resolution of $1280{\times}800$ lines (125 ppi).

• Journal of the Semiconductor & Display Technology
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• v.7 no.4
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• pp.7-11
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• 2008

ITO (Indium Tin Oxide) thin films have been extensively studied for OLED devices because they have high transparent properties in the visible wavelength and a low electrical resistivity. These ITO films are deposited by rf-magnetron sputtering under different ambient gases (Ar, Ar+$O_2$ and Ar+$H_2$) at $300^{\circ}C$. In order to investigate the influences of the oxygen and hydrogen, the flow rate of oxygen and hydrogen in argon has been changed from 0.5sccm to 5sccm and from 0.01sccm to 0.25sccm respectively. The resistivity of ITO film increased with increasing flow rate of $O_2$ under Ar+$O_2$ while it is nearly constant under Ar+$H_2$. And the peak of ITO films obtained (222) and (400) orientations and the average transmittance was over 80% in the visible range. The OLED device fabricated with different ITO substrates made by configuration of ITO/$\alpha$-NPD/Alq3/LiF/Al to elucidate the performance of ITO substrate for OLED device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.1
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• pp.1-5
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• 2016

The ultimate aims of display market is transparent or flexible. Researches have been carried out for various applications. It has been possible to reduced the process steps and get good electrical properties for semiconductors with large optical bandgaps. Oxide semiconductors have been established as one of the leading and promising technology for next generation display panels. In this paper, alternative treatment processes have been tried for oxide semiconductors of thin film transistors to increase the electrical properties of the thin film transistors and to investigate the mechanisms. There exist a various oxide semiconductors. Here, we focused on InGaZnO, ZnO and InSnZnO which are commercialized or researched actively.