• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.525-532
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• 2017

The development of an inkjet-based manufacturing machine for the production of next-generation displays using organic and quantum-dot light emitting diodes at a low cost has been conducted. To employ inkjet printing in production lines of displays, the development of a high-speed inkjet-monitoring device to verify the reliable droplet jetting status from multiple nozzles is required. In this study, an inkjet monitoring device using a rotatable mirror with rotary and linear ultrasonic motors is developed in place of a conventional, linear reciprocating, motion-based inkjet monitoring device. Its performance is also demonstrated. The measurements of circular patterns with diameters of $10{\mu}m$, $30{\mu}m$, and $50{\mu}m$ are performed with the accuracies of $0.5{\pm}1.0{\mu}m$, $-1.2{\pm}0.3{\mu}m$, and $0.2{\pm}0.5{\mu}m$, respectively, within 17 sec. By optimizing the control program, the takt time can be reduced to as short as 8.6 sec.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.199-199
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• 2011

Recently, Thin film transistors (TFTs) with amorphous oxide semiconductors (AOSs) can offer an important aspect for next generation displays with high mobility. Several oxide semiconductor such as ZnO, $SnO_2$ and InGaZnO have been extensively researched. Especially, as a well-known binary metal oxide, tin oxide ($SnO_2$), usually acts as n-type semiconductor with a wide band gap of 3.6eV. Over the past several decades intensive research activities have been conducted on $SnO_2$ in the bulk, thin film and nanostructure forms due to its interesting electrical properties making it a promising material for applications in solar cells, flat panel displays, and light emitting devices. But, its application to the active channel of TFTs have been limited due to the difficulties in controlling the electron density and n-type of operation with depletion mode. In this study, we fabricated staggered bottom-gate structure $SnO_2$-TFTs and patterned channel layer used a shadow mask. Then we compare to the performance intrinsic $SnO_2$-TFTs and doping hafnium $SnO_2$-TFTs. As a result, we suggest that can be control the defect formation of $SnO_2$-TFTs by doping hafnium. The hafnium element into the $SnO_2$ thin-films maybe acts to control the carrier concentration by suppressing carrier generation via oxygen vacancy formation. Furthermore, it can be also control the mobility. And bias stability of $SnO_2$-TFTs is improvement using doping hafnium. Enhancement of device stability was attributed to the reduced defect in channel layer or interface. In order to verify this effect, we employed to measure activation energy that can be explained by the thermal activation process of the subthreshold drain current.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.450-450
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• 2012

In recent days, advances in ZnO-based oxide semiconductor materials have accelerated the development of thin-film transistors (TFTs), which are the building blocks for active matrix flat-panel displays including liquid crystal displays (LCD) and organic light-emitting diodes (OLED). In particular, the development of high-mobility ZnO-based channel materials has been proven invaluable; thus, there have been many reports of high-performance TFTs with oxide semiconductor channels such as ZnO, InZnO (IZO), ZnSnO (ZTO), and InGaZnO (IGZO). The reliability of oxide TFTs can be improved by examining more stable oxide channel materials. In the present study, we investigated the effects of an ALD-deposited water vapor permeation barrier on the stability of ZnO and HfZnO (HZO) thin film transistors. The device without the water vapor barrier films showed a large turn-on voltage shift under negative bias temperature stress. On the other hand, the suitably protected device with the lowest water vapor transmission rate showed a dramatically improved device performance. As the value of the water vapor transmission rate of the barrier films was decreased, the turn-on voltage instability reduced. The results suggest that water vapor related traps are strongly related to the instability of ZnO and HfZnO TFTs and that a proper combination of water vapor permeation barriers plays an important role in suppressing the device instability.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.110.1-110.1
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• 2012

Recently, advances in ZnO based oxide semiconductor materials have accelerated the development of thin-film transistors (TFTs), which are the building blocks for active matrix flat-panel displays including liquid crystal displays (LCD) and organic light-emitting diodes (OLED). However, the electrical performances of oxide semiconductors are significantly affected by interactions with the ambient atmosphere. Jeong et al. reported that the channel of the IGZO-TFT is very sensitive to water vapor adsorption. Thus, water vapor passivation layers are necessary for long-term current stability in the operation of the oxide-based TFTs. In the present work, $Al_2O_3$ and $TiO_2$ thin films were deposited on poly ether sulfon (PES) and $SnO_x$-based TFTs by electron cyclotron resonance atomic layer deposition (ECR-ALD). And enhancing the WVTR (water vapor transmission rate) characteristics, barrier layer structure was modified to $Al_2O_3/TiO_2$ layered structure. For example, $Al_2O_3$, $TiO_2$ single layer, $Al_2O_3/TiO_2$ double layer and $Al_2O_3/TiO_2/Al_2O_3/TiO_2$ multilayer were studied for enhancement of water vapor barrier properties. After thin film water vapor barrier deposited on PES substrate and $SnO_x$-based TFT, thin film permeation characteristics were three orders of magnitude smaller than that without water vapor barrier layer of PES substrate, stability of $SnO_x$-based TFT devices were significantly improved. Therefore, the results indicate that $Al_2O_3/TiO_2$ water vapor barrier layers are highly proper for use as a passivation layer in $SnO_x$-based TFT devices.

• The Journal of the Convergence on Culture Technology
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• v.7 no.1
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• pp.662-667
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• 2021

Vibrotactile feedback is a major function of the latest touch displays, which greatly improves the user's operability and immersion when interacting with the interface on the screen. In this study, we propose a vibrotactile actuator suitable for mounting on the back side of a mid- to large-sized display because it can generate a strong vibration output by applying an electrostatic force-based mechanism and can be manufactured in a thin flat panel type. The proposed actuator was developed in a structure capable of amplifying the vibration force by alternating up and down with electrostatic force by the upper and lower electrodes that are spaced apart from the electrically grounded mass suspended from a radial leaf spring. As a result of the performance evaluation, the developed bar-type module with two built-in actuators showed excellent vibration output of up to 3.3 g at 170 Hz, confirming the possibility of providing haptic feedback in medium and large touch displays.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.49-54
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• 2021

The display industry is transitioning from traditional rigid products such as flat panel displays to flexible or wearable ones designed to be folded or rolled. Accordingly, colorless and optically transparent polyimide (CPI) films are one of the prime candidates to substitute traditional cover glass as a passivation layer to accommodate product flexibility. However, CPI films subjected to repetitive pure bending loads inevitably entail an accumulation of residual strain that can eventually cause wrinkles or delamination in the underlying component after a certain number of static and cyclic loading. The purpose of this study is to establish an experimental method to systematically evaluate the bending residual strain of CPI films. Films were monotonically and cyclically wrapped on mandrels of various diameters to ensure a constant strain in each. After unwrapping the wound CPI film, the residual radius of curvature remaining on the film was measured and converted into residual strain. The critical radius of curvature at which residual strain does not remain was about 5 mm, and the residual strain decreased in proportion to the log time. It is expected that flexible displays can be reliably designed using the data between the applied bending strain and the residual strain.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.362-362
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• 2012

Graphene-based materials have been gaining the unprecedented academic and industrial applications, due to the unique charge transport as a new kind of 2-dimensional materials. The applications incorporate electronic devices, nonvolatile memories, batteries, chemical sensors, etc. based on the electrical, mechanical, structural, optical, and chemical features newly reported. The current work employs thermal chemical vapor deposition involving H2 and CH4, in order to synthesize the 2-dimensional graphene materials. The qualitative/quantitative characterizations of the synthesized graphene materials are evaluated using Raman spectroscopy and Hall Measurements, In particular, the effect of processing variables is systematically investigated on the formation of graphene materials through statistical design of experiments. The optimized graphene materials will be attempted towards the potential applications to flat-panel displays.

• Journal of Magnetics
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• v.21 no.3
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• pp.348-355
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• 2016

Precision motion stages used in the manufacturing process of flat-panel displays have inevitably low settling performance due to their huge mass and bulky structures. In order to improve the settling performance, several methods of frame vibration compensation have been developed so far. These methods are used to cancel the vibration by imposing a counter force or modifying the resonance mode of the frame of the stage. To compensate the frame vibration, high force actuators are required. In this paper, a mighty voice coil actuator is proposed to generate the counter force against the frame vibration. The proposed voice coil actuator has an axis-symmetric rectangular structure to achieve a large force with simple and low cost fabrication. Also, the voice coil actuator allows radial clearance up to ${\pm}4mm$. Using an optimized design process and a magnetic circuit model, the power consumption is minimized while the required force is obtained. With a power of 322 W, the VCA has been designed to have a maximum force of 574 N with a force constant of 164 N/A. Experimental results verified the force constant of the fabricated voice coil actuator is well matched with the designed value.

• Journal of Sensor Science and Technology
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• v.11 no.6
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• pp.371-377
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• 2002

$Y_2O_3:Eu^{3+}$ and Li-doped $Y_2O_3:Eu^{3+}$ thin films have been grown on sapphire substrates using a pulsed laser deposition technique. The thin film phosphors were deposited at a substrate temperature of $600^{\circ}C$ under the oxygen pressure of 100, 200 and 300 mTorr. The films grown under different deposition conditions have been characterized using microstructural and luminescent measurements. The crystallinity and photoluminescence (PL) of the films are highly dependent on the oxygen pressure. The PL brightness data obtained from $Y_2O_3:Eu^{3+}$ films grown under optimized conditions have indicated that sapphire is one of the most promising substrate for the growth of high quality $Y_2O_3:Eu^{3+}$ thin film red phosphor. In particular, the incorporation of $Li^{+}$ ions into $Y_2O_3$ lattice could induce a remarkable increase of PL. The highest emission intensity was observed with LiF-doped $Y_{1.84}Li_{0.08}Eu_{0.08}O_3(Y_2O_3LiEu)$, whose brightness was increased by a factor of 2.7 in comparison with that of $Y_2O_3:Eu^{3+}$ films. This phosphor may promise for application to the flat panel displays.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.36-36
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• 2008

Organic light-emitting device (OLED) have become very attractive due to their potential application in flat panel displays. One important problem to be solved for practical application of full-color OLED is development of three primary color (Red, Green and Blue) emitting molecule with high luminous operation. Particularly, the development of organic materials for blue electroluminescence (EL) lags significantly behind that for the other two primary colors. For this reason, Flu-Si was synthesized and characterized by means of high-resolution mass spectro metry and elemental analyses. Flu-Si has the more wide optical band gap (Eg = 3.86) than reference material (Cz-Si, Eg = 3.52 eV). We measured the photophysical and electrochemical properties of Flu-Si. The HOMO-LUMO levels were estimated by the oxidation potential and the onset of the UV-Vis absorption spectra. The EL properties were studied by the device fabricated as a blue light emitting material with FIrpic.