20 results on '"Sung-Hwan Choi"'
Search Results
2. Prediction of Fishman’s skeletal maturity indicators using artificial intelligence
- Author
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Harim Kim, Cheol-Soon Kim, Ji-Min Lee, Jae Joon Lee, Jiyeon Lee, Jung-Suk Kim, and Sung-Hwan Choi
- Subjects
Multidisciplinary - Abstract
The present study aimed to evaluate the performance of automated skeletal maturation assessment system for Fishman’s skeletal maturity indicators (SMI) for the use in dental fields. Skeletal maturity is particularly important in orthodontics for the determination of treatment timing and method. SMI is widely used for this purpose, as it is less time-consuming and practical in clinical use compared to other methods. Thus, the existing automated skeletal age assessment system based on Greulich and Pyle and Tanner-Whitehouse3 methods was further developed to include SMI using artificial intelligence. This hybrid SMI-modified system consists of three major steps: (1) automated detection of region of interest; (2) automated evaluation of skeletal maturity of each region; and (3) SMI stage mapping. The primary validation was carried out using a dataset of 2593 hand-wrist radiographs, and the SMI mapping algorithm was adjusted accordingly. The performance of the final system was evaluated on a test dataset of 711 hand-wrist radiographs from a different institution. The system achieved a prediction accuracy of 0.772 and mean absolute error and root mean square error of 0.27 and 0.604, respectively, indicating a clinically reliable performance. Thus, it can be used to improve clinical efficiency and reproducibility of SMI prediction.
- Published
- 2023
3. Stability of vertical dimension following total arch intrusion
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Dong-Ok Kang, Hyung-Seog Yu, Sung-Hwan Choi, Seong-Taek Kim, Hwi-Dong Jung, and Kee-Joon Lee
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General Dentistry - Abstract
Background The purpose of this study is to evaluate stability of vertical dimension following total arch intrusion using miniscrews by measuring the change during treatment and relapse amount after more than one year of retention. Methods Thirty patients (6 men, 24 women) were included in this study. Lateral cephalographs were taken with conventional radiography at the start of treatment (T0), after treatment (T1), and at least one year after treatment (T2). The evaluation was performed by measuring changes of selected parameters during treatment and the extent of relapse after more than one year. Results During total arch intrusion treatment (T1-T0), anterior and posterior teeth intruded significantly. The mean vertical distance between the maxillary posterior teeth and palatal plane was reduced by 2.30 mm (P P P P P Conclusions Anterior facial height significantly decreases after treatment. During retention period, relapse of AFH and maxillary anterior teeth observed. There was no correlation between initial amount of AFH, mandibular plane angle, or SNPog and posttreatment AFH relapse. However, there was a significant correlation between the amount of intrusion of anterior and posterior teeth achieved by the treatment and the extent of relapse.
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- 2023
4. Effect of bacterial resistant zwitterionic derivative incorporation on the physical properties of resin-modified glass ionomer luting cement
- Author
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Chengzan Wu, Min-Ji Kim, Utkarsh Mangal, Ji-Young Seo, Ji-Yeong Kim, Junho Kim, Ju-Young Park, Jae-Sung Kwon, and Sung-Hwan Choi
- Subjects
Multidisciplinary - Abstract
Biofilms induce microbial-mediated surface roughening and deterioration of cement. In this study, zwitterionic derivatives (ZD) of sulfobetaine methacrylate (SBMA) and 2-methacryloyloxyethyl phosphorylcholine, were added in concentrations of 0, 1, and 3% to three different types of commercially available resin-modified glass ionomer cement (RMGIC) (RMC-I: RelyX Luting 2, RMC-II: Nexus RMGI, and RMC-III: GC FujiCEM 2). The unmodified RMGICs served as the control group for comparison. The resistance of Streptococcus mutans to ZD-modified RMGIC was evaluated with a monoculture biofilm assay. The following physical properties of the ZD-modified RMGIC were assessed: wettability, film thickness, flexural strength, elastic modulus, shear bond strength, and failure mode. The ZD-modified RMGIC significantly inhibited biofilm formation, with at least a 30% reduction compared to the control group. The addition of ZD improved the wettability of RMGIC; however, only 3% of the SBMA group was statistically different (P P > 0.05). The experimental groups' flexural strength, elastic modulus, and shear bond strength showed an insignificant decrease from the control group; there was no statistical difference within the RMC-I (P > 0.05). The mode of failure differed slightly in each group, but all groups showed dominance in the adhesive and mixed failure. Thus, the addition of 1 wt.% ZD in RMGIC favorably enhanced the resistance to Streptococcus mutans without any tangible loss in flexural and shear bond strength.
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- 2023
5. Author Correction: Three-dimensional soft tissue landmark detection with marching cube algorithm
- Author
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Yoonjung Lee, Ji-Min Lee, Sun-Hyung Park, Yoon Jeong Choi, Sung-Hwan Choi, Jae Joon Hwang, and Hyung-Seog Yu
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Multidisciplinary - Published
- 2023
6. Three-dimensional soft tissue landmark detection with marching cube algorithm
- Author
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Yoonjung Lee, Ji-Min Lee, Sun-Hyung Park, Yoon Jeong Choi, Sung-Hwan Choi, Jae Joon Hwang, and Hyung-Seog Yu
- Subjects
Multidisciplinary - Abstract
Current method of analyzing three-dimensional soft tissue data, especially in the frontal view, is subjective and has poor reliability. To overcome this limitation, the present study aimed to introduce a new method of analyzing soft tissue data reconstructed by marching cube algorithm (Program S) and compare it with a commercially available program (Program A). Cone-beam computed tomography images of 42 patients were included. Two orthodontists digitized six landmarks (pronasale, columella, upper and lower lip, right and left cheek) twice using both programs in two-week intervals, and the reliability was compared. Furthermore, computer-calculated point (CC point) was developed to evaluate whether human error could be reduced. The results showed that the intra- and inter-examiner reliability of Program S (99.7–100% and 99.9–100%, respectively) were higher than that of Program A (64.0–99.9% and 76.1–99.9%, respectively). Moreover, the inter-examiner difference of coordinate values and distances for all six landmarks in Program S was lower than Program A. Lastly, CC point was provided as a consistent single point. Therefore, it was validated that this new methodology can increase the intra- and inter-examiner reliability of soft tissue landmark digitation and CC point can be used as a landmark to reduce human error.
- Published
- 2023
7. The success and effectiveness of miniscrew-assisted rapid palatal expansion are age- and sex-dependent
- Author
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Ji Yoon Jeon, Chooryung J. Chung, Kee Joon Lee, and Sung Hwan Choi
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Male ,Palatal Expansion Technique ,Sutures ,Palate ,business.industry ,Separation (statistics) ,Dentistry ,Age and sex ,Exact test ,Basal (phylogenetics) ,Suture (anatomy) ,Maxilla ,Mann–Whitney U test ,Humans ,Medicine ,Female ,Clinical significance ,business ,General Dentistry ,Retrospective Studies - Abstract
Objectives This study aimed to assess the success rate and the amount of suture separation after the miniscrew-assisted rapid palatal expansion (MARPE) procedure in relation to the chronological age and sex of the patients. Materials and methods The periapical radiographs of 215 subjects (95 male; 120 female; range, 6–60 years) who had undergone MARPE treatment were retrospectively analyzed. The success of suture separation was determined and, in suture-separated subjects, the amount of suture separation was evaluated by suture separation ratio calculated from the periapical radiograph obtained after active expansion. Association tests were performed using linear-by-linear association, the Jonckheere-Terpstra test, Fisher’s exact test, and the Mann–Whitney U test, and linear regression models were also developed. Results The success rate of suture separation was 61.05% in male, 94.17% in female, and 79.53% in both sexes. There was a statistically significant association between older age and suture nonseparation in male (p p = 0.221). In suture-separated subjects, there was a statistically significant trend toward a low amount of suture separation with older age subgroups in both sexes (p Conclusions Older patients treated with MARPE, particularly in male, may have a reduced likelihood of both success in suture separation and sufficient basal bone expansion. Clinical relevance This study demonstrates that clinicians should consider that the success rate of MARPE and the amount of suture separation may depend on chronological age and sex.
- Published
- 2021
8. Similarity index for intuitive assessment of three-dimensional facial asymmetry
- Author
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Sung Hwan Choi, Sun Mi Kwon, Chung Ju Hwang, Jae Joon Hwang, Kee Joon Lee, Bong-Hae Cho, and Yun Hoa Jung
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Adult ,Male ,0301 basic medicine ,Adolescent ,Cephalometry ,medicine.medical_treatment ,media_common.quotation_subject ,Orthognathic surgery ,lcsh:Medicine ,Mandible ,Asymmetry ,Article ,Young Adult ,03 medical and health sciences ,Imaging, Three-Dimensional ,0302 clinical medicine ,Similarity (network science) ,medicine ,Humans ,lcsh:Science ,media_common ,Mathematics ,Orthodontics ,Multidisciplinary ,Orthognathic Surgical Procedures ,lcsh:R ,Soft tissue ,Translational research ,medicine.disease ,Sagittal plane ,Malocclusion, Angle Class III ,Treatment Outcome ,030104 developmental biology ,medicine.anatomical_structure ,Facial Asymmetry ,Outcomes research ,Face ,Female ,lcsh:Q ,Malocclusion ,030217 neurology & neurosurgery ,Facial symmetry - Abstract
Evaluation of facial asymmetry generally involves landmark-based analyses that cannot intuitively assess differences in three-dimensional (3D) stereoscopic structures between deviation and non-deviation sides. This study tested a newly developed similarity index that uses a mirroring technique to intuitively evaluate 3D mandibular asymmetry, and characterised the resulting lower facial soft tissue asymmetry. The similarity index was used to evaluate asymmetry before and after surgery in 46 adult patients (27 men, 19 women; age, 22 ± 4.8 years) with skeletal Class III malocclusion and facial asymmetry who underwent conventional bimaxillary orthognathic surgery. Relative to the midsagittal plane used as the reference plane, the non-overlapping volume of the mandible significantly decreased, and the similarity index significantly increased after surgery. Similarity indexes of the mandible and lower facial soft tissue were strongly negatively correlated with non-overlapping volumes of each measurement. Differences in bilateral hemi-mandibular and hemi-lower facial soft tissue surface and volume measurements before surgery were significantly negatively correlated with similarity indexes of the mandible before and after surgery. This newly developed similarity index and non-overlapping volume using a mirroring technique can easily and intuitively evaluate overall 3D morphological discrepancies, especially 3D mandibular asymmetry, before and after surgery in skeletal Class III patients with facial asymmetry.
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- 2019
9. Novel anti-biofouling light-curable fluoride varnish containing 2-methacryloyloxyethyl phosphorylcholine to prevent enamel demineralization
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Sungil Jang, Sung Hwan Choi, Chung Ju Hwang, Jae-Sung Kwon, Ji-Young Kim, Jeong Hyun Ryu, Kwang Mahn Kim, Myung-Jin Lee, and Dohyun Kim
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0301 basic medicine ,Phosphorylcholine ,Science ,Bacterial Adhesion ,Article ,Streptococcus mutans ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,immune system diseases ,medicine ,Actinomyces ,Animals ,Fluorides, Topical ,Bovine serum albumin ,Dental Enamel ,Tooth Demineralization ,Multidisciplinary ,biology ,Fluoride varnish ,biology.organism_classification ,Tooth enamel ,Cariostatic Agents ,Anti-Bacterial Agents ,Demineralization ,Streptococcus sanguinis ,030104 developmental biology ,medicine.anatomical_structure ,chemistry ,Actinomyces naeslundii ,biology.protein ,Methacrylates ,Medicine ,Cattle ,Fluoride ,030217 neurology & neurosurgery ,Nuclear chemistry - Abstract
We evaluated the efficacy of light-curable fluoride varnish (LCFV) that contains 2-methacryloyloxyethyl phosphorylcholine (MPC) in terms of anti-biofouling properties and prevention of tooth enamel demineralization. MPC was mixed with and incorporated into LCFV at 0 (control), 1.5, 3.0, 5.0, 10.0, 20.0, and 40.0 weight percentage (wt%). Addition of high wt% of MPC resulted in increased film thickness and decreased the degree of conversion, indicating loss of the advantageous properties of LCFV. Addition of 1.5, 3, or 5 wt% MPC significantly reduced the amount of bovine serum albumin adsorbed from a solution and proteins adsorbed from brain heart infusion medium compared to the control (P Streptococcus mutans cells adhered on the surface of LCFV with 1.5, 3, or 5 wt% MPC (P Actinomyces naeslundii and Streptococcus sanguinis adherence to LCFV with 3 wt% MPC. Finally, bacterial adhesion, surface microhardness loss, and the depth of demineralization were substantially lower on bovine tooth enamel surface coated with LCFV containing 3 wt% of MPC than in the control treatment (0 wt% MPC). Therefore, this novel LCFV containing a low concentration of MPC (e.g., 3 wt%) would be effective in anti-biofouling while maintaining the important advantageous features of light-curable fluoride in preventing demineralization.
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- 2019
10. Comparative study of hydrodynamic characteristics with respect to direction of installation of gas-liquid ejector system
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Sung Hwan Choi, Ho Seong Ji, and Kyung Chun Kim
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Flow visualization ,Engineering ,Engineering drawing ,business.industry ,Water flow ,Mechanical Engineering ,Airflow ,Injector ,Mechanics ,Local Void ,law.invention ,Physics::Fluid Dynamics ,Mechanics of Materials ,law ,Homogeneity (physics) ,Air entrainment ,business ,Porosity ,Physics::Atmospheric and Oceanic Physics - Abstract
The gas-liquid two-phase ejector is a device without moving parts, in which a liquid is used to drive a gas of a low-pressure source. In this study, the effect of the direction of installation on hydrodynamic characteristics was examined using the same air/water ejector loop. The entrained air flow rates and local void fraction profiles were also measured at various water flow rates for three types of installation: horizontal, vertical-upward, and vertical-downward, and were compared. From the study, the vertical-downward installation was found to be the best in terms of air entrainment ratio and homogeneity of bubbles.
- Published
- 2015
11. Rock preference of planulae of jellyfish Aurelia aurita (Linnaeus 1758) for settlement in the laboratory
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Changhoon Han, Won-Gyu Park, Sung-Hwan Choi, and Won Duk Yoon
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Basalt ,Gabbro ,biology ,Schist ,Geochemistry ,Mineralogy ,Oceanography ,biology.organism_classification ,Conglomerate ,Rhyolite ,Substrate (aquarium) ,Aurelia aurita ,Geology ,Gneiss - Abstract
Planulae of Aurelia aurita were exposed to 11 types of rocks (basalt, gabbro, granite, rhyolite, sandstone, limestone, conglomerate, gneiss, quartzite, marble and schist) to examine their attachment preference among rock material and position. Numbers of attached polyps was the highest on marble and the least on limestone. Their preference with regard to settling position was the same among the rocks, showing the highest density of polyps on the underside (88.5%) compared to upper (23.6%) and perpendicular sides (10.3%) of rock. The results showed that while position preference is more important than rock property, higher numbers of polyps were observed in rocks with a medium surface hardness.
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- 2014
12. High-temperature oxidation behaviors of Fe-Cr-Al bulk and powder-sintered materials
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Young-Min Kong, Byoung-Kee Kim, Sung-Hwan Choi, Song-Yi Kim, Jung-Yeul Yun, and Kee-Ahn Lee
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Materials science ,Metallurgy ,Alloy ,technology, industry, and agriculture ,Metals and Alloys ,Oxide ,Electron microprobe ,engineering.material ,Condensed Matter Physics ,Microstructure ,Isothermal process ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,Materials Chemistry ,engineering ,Thermal analysis ,Oxidation resistance ,Internal diffusion - Abstract
In this study, cast bulk specimens and powder sintered specimens were produced from a Fe-22% Cr-5.8% Al alloy, which has been drawing industrial attention for its outstanding high-thermal and oxidation resistance as well as for its applicability as a filter and support material. The high-temperature oxidation behaviors of the specimens were compared and analyzed. Two types of specimens were subjected to 24-hour isothermal oxidation (temperatures of 900 °C, 1000 °C, and 1100 °C and a gas atmosphere of 79% N2+21% O2) to understand their high-temperature oxidation properties. The oxidized specimens were examined via X-ray, SEM, FE-SEM, and EPMA for microstructure and oxide analyses. The results of the oxidation tests showed that both bulk and powder-sintered specimens gained weight as temperature increased, with the powder sintered specimens gaining far more weight than the bulk specimens. As the temperature increased, the bulk specimens showed sequential formation of Al2O3, Cr2O3, and Fe3O4 oxide layers. The stable Al2O3 on the surface of the bulk specimens was found to play a role in arresting the rapid growth of oxide layers. In the powder-sintered specimens, however, the internal diffusion of O2 easily took place along the powder interfaces. As a result, far more oxidation occurred in the powder-sintered specimens than in the bulk specimens. Cracks and disintegration of the oxide layers were also found to have occurred as the temperature increased. The high-temperature oxidation mechanisms of bulk and powder-sintered materials in relation to temperature increase are further discussed.
- Published
- 2011
13. Effect of pore size on the high temperature oxidation of Ni-Fe-Cr-Al porous metal
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Byoung-Kee Kim, Kee-Ahn Lee, Jung-Yeul Yun, Sung-Hwan Choi, Song-Yi Kim, and Young-Min Kong
- Subjects
Materials science ,Metallurgy ,Metals and Alloys ,Oxide ,Condensed Matter Physics ,Isothermal process ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Mechanics of Materials ,Specific surface area ,Materials Chemistry ,Thermal analysis ,Porous medium ,Porosity ,Layer (electronics) ,BET theory - Abstract
This study investigated the effect of the pore size of Ni-22.4%Fe-22%Cr-6%Al porous metal on its hightemperature oxidation. Two types of open porous metals with pore sizes of 800 μm and 580 μm were used. A 24-hour isothermal oxidation test was conducted at three different temperatures of 900 °C, 1000 °C, and 1100 °C under a 79% N2 + 21% O2 atmosphere. The results of the BET analysis revealed that the specific surface area increased as the pore size decreased from 800 μm to 580 μm. The high-temperature oxidation results showed that porous metals exhibited far lower levels of oxidation resistance compared with bulk metals, and that the oxidation resistance of porous metals decreased with a decreasing pore size. According to the microstructural observations of the oxide layers, the 900 °C and 1000 °C oxidation layer contained Ni, Cr, and Al oxides mainly on the strut. The 800 μm porous metal strut exhibited similar oxidation behavior at 1100 °C to that found at lower temperatures. In contrast, the 580 μm porous metal strut was found to consist of Ni and Fe oxides in the upper layer and Ni, Cr, and Al oxides in the lower layer, representing a low oxidation resistance. For powders affixed to the strut inside the porous metal, a different oxide-forming behavior from that of the strut was observed. In addition, the Ni-Fe-Cr-Al porous metal high-temperature oxidation microscopic mechanism is also discussed.
- Published
- 2011
14. Microinjection molded disposable microfluidic lab-on-a-chip for efficient detection of agglutination
- Author
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Sung Hwan Choi, Tai Hun Kwon, and Dong Sung Kim
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Materials science ,business.industry ,Microfluidics ,Micromixer ,Nanotechnology ,Molding (process) ,Lab-on-a-chip ,Cyclic olefin copolymer ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,Agglutination (biology) ,chemistry ,Hardware and Architecture ,law ,Direct agglutination test ,Optoelectronics ,Electrical and Electronic Engineering ,Photolithography ,business - Abstract
Previous diagnosing methods based on agglutination have a limitation in view of emergency and point-of-care diagnoses due to the requirement of large scale equipments and much agglutination time. In this paper, we propose a low cost microfluidic lab-on-a-chip for more efficient detection of agglutination. In the present lab-on-a-chip, two inlet microwells, flow guiding microchannels, chaotic micromixer and reaction microwell are fully integrated. Mold inserts for the lab-on-a-chip were manufactured by UV photolithography and nickel electroplating process. The complete lab-on-a-chip was realized by the microinjection molding of cyclic olefin copolymer and the subsequent thermal bonding. The improved serpentine laminating micromixer, developed by our group, integrated in the lab-on-a-chip showed the high-level of chaotic mixing, thereby enabling us to get a reliable mixing of sample and reagent. The performance of the fabricated lab-on-a-chip was demonstrated by agglutination experiments with simulated bloods of 10 μl and simulated sera of 10 μl. The results of agglutination inside the reaction microwell were clearly read by means of the level of light transmission. The present microfluidic lab-on-a-chip could be widely applied to various clinical diagnostics based on agglutination tests.
- Published
- 2008
15. Effect of Dynamic Bias Stress (AC) In Short-Channel (L=1.5μm) p-Type polycrystalline Silicon (poly-Si) Thin Film Transistors (TFTs) on the glass substrate
- Author
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Yeon-Gon Mo, Sung-Hwan Choi, and Min-Koo Han
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Materials science ,business.industry ,Substrate (electronics) ,engineering.material ,Threshold voltage ,Stress (mechanics) ,Polycrystalline silicon ,Thin-film transistor ,engineering ,Optoelectronics ,Thin film ,business ,DC bias ,Communication channel - Abstract
We have investigated the stability of short channel (1.5μm) p-Type polycrystalline silicon (poly-Si) Thin Film Transistors (TFTs) on the glass substrate under AC bias stress. The variation of threshold voltage in short channel poly-Si TFT was considerably higher than that of long channel poly-Si TFT. Threshold voltage of the short channel TFT was considerably moved to the positive direction during AC bias stress, whereas the threshold voltage of a long channel was rarely moved. The variation of threshold voltage in the short channel p-type TFT under AC bias stess was more compared to that under DC bias stress. The threshold voltage of short channel (L=1.5μm) poly-Si TFT was increased about -7.44V from -0.305V to -7.745V when VGS = 5 (base value) ~ -15V (peak value), VDS = -15V was applied for 3,000 seconds. This positive shift of threshold voltage and significantly degraded s-swing value in the short channel TFT under dynamic stress (AC) may be due to the increase of the stress-induced trap state density at gate insulator / channel interface region.
- Published
- 2011
16. Investigation of Amorphous IGZO TFT Employing Ti/Cu Source/Drain and SiNx Passivation
- Author
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Jang Yeon Kwon, Sung-Hwan Choi, Young-Wook Lee, Jeong-Soo Lee, and Min-Koo Han
- Subjects
Negative shift ,chemistry.chemical_compound ,Materials science ,Passivation ,chemistry ,business.industry ,Thin-film transistor ,Oxide ,Optoelectronics ,business ,Volume concentration ,Amorphous solid - Abstract
We successfully fabricated a-IGZO TFTs employing a Ti/Cu source/drain (S/D) and SiNx passivation in order to reduce the line-resistance, as compared to most oxide TFTs that use Mo (or TCO) and SiO2 for their S/D and passivation, respectively. Although passivated with SiNx, the TFT exhibits good transfer characteristics without a negative shift. However, the TFT employing a Mo S/D exhibited conductor-like characteristics when passivated with SiNx. Our investigation suggests that the IGZO oxygen vacancies found in the Ti/Cu S/D are controlled, resulting in low concentrations, and so prevent the SiNx-passivated TFT from having a negative shift.
- Published
- 2011
17. High Haze and Low Resistive MgO/AZO Bi-layer Transparent Conducting Oxide for Thin Film Solar Cells
- Author
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Heon Min Lee, Sung-Hwan Choi, Dong-Won Kang, Seung Yoon Lee, Min-Koo Han, and Jong Seok Woo
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Materials science ,business.industry ,Oxide ,Analytical chemistry ,law.invention ,Full width at half maximum ,chemistry.chemical_compound ,Crystallinity ,chemistry ,Sputtering ,law ,Solar cell ,Transmittance ,Optoelectronics ,Quantum efficiency ,Texture (crystalline) ,business - Abstract
We have propsed MgO/AZO bi-layer transparent conducting oxide (TCO) for thin film solar cells. From XRD analysis, it was observed that the full width at half maximum of AZO decreased when it was grown on MgO precursor. The Hall mobility of MgO/AZO bi-layer was 17.5cm2/Vs, whereas that of AZO was 20.8cm2/Vs. These indicated that the crystallinity of AZO decreased by employing MgO precursor. However, the haze (=total diffusive transmittance/total transmittance) characteristics of highly crystalline AZO was significantly improved by MgO precursor. The average haze in the visible region increased from 14.3 to 48.2%, and that in the NIR region increased from 6.3 to 18.9%. The reflectance of microcrystalline silicon solar cell was decreased and external quantum efficiency was significantly improved by applying MgO/AZO bi-layer TCO. The efficiency of microcrystalline silicon solar cell with MgO/AZO bi-layer front TCO was 6.66%, whereas the efficiency of one with AZO single TCO was 5.19%.
- Published
- 2011
18. Effects of Hydrogen Plasma Treatment on Hysteresis Phenomenon and Electrical Properties for Solid Phase Crystallized Silicon Thin Film Transistors
- Author
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Sang-Geun Park, Changyeon Kim, Min-Koo Han, and Sung-Hwan Choi
- Subjects
Materials science ,Thin-film transistor ,business.industry ,Plasma-enhanced chemical vapor deposition ,Phase (matter) ,Field effect ,Optoelectronics ,Grain boundary ,Plasma ,Thin film ,business ,Threshold voltage - Abstract
We have investigated the effects of hydrogen plasma treatment on the hysteresis phenomenon and electrical properties of solid phase crystallized silicon thin film transistors (SPC-Si TFTs) employing alternating magnetic field crystallization (AMFC). We employed H2 plasma treatment on the SPC-Si active layer before SiO2 gate insulator deposition. By increasng the power and time duration of H2 plasma treatment, it was observed that hysteresis phenomenon of SPC-Si TFT was suppressed and electrical properties such as threshold voltage, field effect mobility was improved considerably. This is due to role of hydrogen atom by passivating the defects and grain boundary trap states in SPC-Si film. However, relatively high power and long hydrogen plasma treatment (100W, 5 minutes) could degrade the electrical characteristics of the device. SPC-Si TFT for 100W power of PECVD and 3 minutes with the H2 plasma treatment exhibit the significant improvement of electrical characterics (VTH = - 3.85V, μFE = 21.16cm2/Vs), and a smaller hysteresis phenomenon (∆VTH = -0.30V) which is suitable for high quality AMOLED Display.
- Published
- 2009
19. The Effect of Electrical Stress on the New Top Gate N-type Depletion Mode Polycrystalline Thin Film Transistors Fabricated by Alternating Magnetic Field Enhanced Rapid Thermal Annealing
- Author
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Min-Koo Han, Won-Kyu Lee, Joon-hoo Choi, Sang-Myeon Han, Sang-Geun Park, and Sung-Hwan Choi
- Subjects
Amorphous silicon ,Materials science ,Excimer laser ,business.industry ,medicine.medical_treatment ,Low-temperature polycrystalline silicon ,Transistor ,engineering.material ,law.invention ,Threshold voltage ,chemistry.chemical_compound ,Polycrystalline silicon ,chemistry ,law ,Thin-film transistor ,medicine ,engineering ,Optoelectronics ,Thin film ,business - Abstract
We have fabricated the new top gate depletion mode n-type alternating magnetic field enhanced rapid thermal annealing (AMFERTA) polycrystalline silicon (poly-Si) thin film transistors (TFTs), which show the excellent electrical characteristics and superior stability compared with hydrogenated amorphous silicon (a-Si:H) TFTs and excimer laser crystallized (ELC) low temperature polycrystalline silicon (LTPS) TFTs. The fabricated AMFERTA poly-Si TFTs were not degraded under hot-carrier stress, and highly biased vertical field stress. The considerably large threshold voltage shift (ΔVTH) and trap state density reducing were occurred when the gate bias and drain bias were both large enough. The dominant mechanism of instability in the fabricated depletion mode AMFERTA poly-Si TFTs may be due to carrier induced donor-like defects reduction within the channel layer, especially near the drain junction.
- Published
- 2008
20. Hysteresis Phenomenon in Sequential Lateral Solidification poly-Si Thin Film Transistor at low temperature (213K)
- Author
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Min-Koo Han, Sung-Hwan Choi, Sang-Geun Park, Won-Kyu Lee, and Tae-Jun Ha
- Subjects
Materials science ,business.industry ,Electron ,Substrate (electronics) ,engineering.material ,Hysteresis ,Polycrystalline silicon ,AMOLED ,Thin-film transistor ,engineering ,Optoelectronics ,Thin film ,business ,Voltage - Abstract
We have investigated temperature dependence on the hysteresis phenomenon of SLS poly-Si TFT on a glass substrate, extremely at low temperature (213K). The p-type sequential lataral solidification (SLS) polycrystalline Silicon (poly-Si) TFT was fabricated on glass substrate. As the temperature was reduced, it was observed that hysteresis phenomenon was increased, whereas the hysteresis was suppressed at high temperature. This could be explained by a difference of initially electron and hole trapped charges into gate insulator is much larger in low temperature than in high temperature. And we have verified that drain current was changed with a different previous gate starting voltage even at same bias condition by experimental results due to the hysteresis phenomenon of SLS poly-Si TFT. Hysteresis of SLS poly-Si TFT should be improved for a pixel element of high quality AMOLED display.
- Published
- 2008
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