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탁영준,구경희,이금화,남기우 한국산업융합학회 2022 한국산업융합학회 논문집 Vol.25 No.3
In this study, austenitic 316L stainless steel was rolled at three different temperatures (100℃, -50℃, -196℃) at five rolling degree (0, 16, 33, 50, 66 and 80%). The rolled specimen was examined for micro structure, and the volume fraction and mechanical properties were evaluated. In particular, the rolling specimen detected the elastic wave generated in tensile and investigated the relationship between the rolling degree and the dominant frequency. As the rolling degree increased, austenite decreased and martensite increased. The volume fraction of martensite more increased at lower temperatures, but increased rapidly at the rolling degree of 50% of all rolling temperature. Tensile strength increased rapidly with the increase of the rolling degree, and was larger at lower temperatures. The elongation decreased sharply to the rolling degree of 33%, but decreased gently thereafter. The dominant frequency highly appeared as the volume fraction of martensite increased, but the dominant frequency was higher at the low temperature rolling temperature. A similar trend was also observed in the relationship between tensile strength and dominant frequency.
탁영준,박성표,정태수,이희수,김원기,박정우,김현재 한국정보디스플레이학회 2016 Journal of information display Vol.17 No.2
Activation using the simultaneous UV-thermal (U-T) treatment of sputter-processed InGaZnO (IGZO) thin-film transistors (TFTs) is suggested. This treatment was performed to lower the activation temperature from 300°C (thermal activation alone) to 150°C as well as to improve the electrical characteristics and stability. Despite the low temperature, the U-T-treated devices showed superior electrical characteristics and stability compared to the devices that were only thermally activated (300°C): the mobility improved from 5.19±1.8 to 16.20±1.5 cm2/Vs, the on-off ratio increased from (5.58±3.21)×108 to (2.50±2.23)×109, and the threshold voltage shift (under positive bias stress for 1000 s) decreased from 7.1 to 2.2 V. These improvements are attributed to the following two contributions: (1) generation of reactive oxygen radical at a low temperature and (2) decomposition-rearrangement of the metal oxide (MO) bonds in the IGZO active layer. Contributions (1) and (2) effectively increased the MO bonds and decreased the defect-site-related oxygen vacancies.
역변태 온도 및 시간이 다른 STS316L의 기계적 및 탄성파 특성
도재윤,탁영준,신기항,남기우 한국산업융합학회 2022 한국산업융합학회 논문집 Vol.25 No.6
In this study, the mechanical properties of 80% cold-rolled austenitic 316L stainless steel were evaluated using specimens subjected to reverse transformation at 500–750℃ for 20 minutes and reverse transformation at 700℃ for 2–60 minutes. Also, for the elastic wave obtained from the tensile test, the dominant frequency according to the reverse transformation condition was investigated by time-frequency analysis. The SEM image of the 80% cold-rolled material was transformed into martensite and showed line and cross shapes. The TEM image showed that line shapes were shown at the grain, and grain boundary of martensite. The higher the heat treatment temperature and the longer time, the larger the grain. Tensile strength decreased as the heat treatment temperature and time increased, but elongation increased. Hardness was proportional to tensile strength. This is because the grain with different directions showed the same direction due to reverse transformation. The dominant frequency was decreased and then increased as the temperature and time increased. This is because the direction of the grain is different at a low temperature and the same direction is shown at a high temperature.
김원기,탁영준,김현재 한국정보디스플레이학회 2018 Journal of information display Vol.19 No.1
A novel organic material named ‘collodion’ was suggested as a gate insulator for amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs). To find the optimized condition of the collodion gate insulator (CGI), the following three parameters of collodion solution were controlled: (1) the concentration of collodion solution; (2) the number of stacked layers; and (3) the spin-coating speed. The single-layered diluted CGI (collodion:ethanol=1:1) that was fabricated with a 3 krpm spin-coating speed exhibited an acceptable dielectric strength (J < 10−10 A/cm2 in the range of 1.1 MV/cm) and a high-dielectric constant (∼6.57) for the gate insulator layer. As a result, a-IGZO TFTs with CGI showed high-field effect mobility (∼17.11 cm2/Vs).
서브제로 온도 및 시간이 다른 STS316L의 탄성파 특성
이금화,구경희,탁영준,권영국,신기항,남기우,Lee, Gum-Hwa,Gu, Kyoung-Hee,Tak, Young-Joon,Kwon, Yung-Kug,Shin, Ki-Hang,Nam, Ki-Woo 한국산업융합학회 2022 한국산업융합학회 논문집 Vol.25 No.5
In this study, STS316L rolled at five rolling degrees were treated with two types of subzero temperatures for 10, 30, and 60 minutes, respectively, and the dominant frequencies of elastic waves was investigated. The dominant frequency was higher as the subzero temperature was lower and the subzero treatment time was longer at each rolling degree. On the other hand, the dominant frequency was higher as the elongation decreased. In the time-frequency analysis for subzero temperature and time of the specimen with a rolling degree of 33%, the dominant frequency was higher at a subzero temperature of -196℃ than -50℃ regardless of subzero treatment time.
Low-temperature activation under 150°C for amorphous IGZO TFTs using voltage bias
이희수,장기수,탁영준,정태수,박정우,김원기,정주성,정찬배,김현재 한국정보디스플레이학회 2017 Journal of information display Vol.18 No.3
Proposed herein is a new technique of activation for the backplane of low-temperature amorphous indium gallium zinc oxide thin-film transistors (a-IGZO TFTs) by applying a bias voltage to gate, source, and drain electrodes and simultaneously annealing them at 150°C. This ‘voltage bias activation’ can be an effective method of reducing the backplane processing temperature from 300°C to 150°C. Compared with the reference a-IGZO TFTs fabricated at 300°C, the a-IGZO TFTs fabricated through voltage bias activation showed sufficient switching characteristics: 10.39 cm2/Vs field effect mobility, 0.41 V/decade subthreshold swing, and 3.65×107 on/off ratio. These results were analyzed thermodynamically using infrared micro-thermography. In the case of the positive gate voltage bias condition, the maximum temperature of the a-IGZO channel increased to 48°C, and this additional annealing effect and activation energy lowering compensated for the insufficient thermal energy of annealing at a low temperature (150°C). With this approach, a-IGZO TFTs were successfully fabricated at a low temperature.