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21. Optimization of the Fabrication Process for Phototransistors With IGZO/TiOx Bilayer Thin Films to Improve Electrical and Photoresponse Characteristics

Author

Lee, Jae-Yun, Tarsoly, Gergely, Lee, Sang-Bong, Lee, Jin-Hee, and Kim, Sung-Jin

Abstract

Metal oxides are among the most popular research targets in electronic materials for their high charge carrier mobility, transparency, and versatility. Recently, semiconductors based on multilayers of oxide thin films have attracted interest for applications, such as resistive memories or phototransistors. Here, a phototransistor was fabricated based on a bilayer of indium gallium zinc oxide (IGZO) and nonstochiometric, oxygen-deficient titanium oxide (TiOx) thin films formed via sputtering. The device fabrication was optimized by varying the temperature of the thermal annealing step to enhance the electrical performance and photoresponse characteristics. The IGZO/TiOx bilayer-based devices exhibited maximal performance when annealed at 350 °C with good mobility, low subthreshold swing, a turn-on voltage around 0 V, and high photoresponse through a wide range of gate bias. The dynamic photoresponse was evaluated under discrete light pulses. The device characteristics were measured after storage in an exicator for more than five months, and reasonable stability in photoresponse was observed.

Published
2024
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26. Distribution and Characteristics of Ammonia Concentration by Region in Korea.

Author

Song, In-Ho, Kim, Hyun-Woong, Park, Jong-Sung, Park, Seung-Myung, Lee, Jae-Yun, Nam, Eun-Jung, Lim, Yong-Jae, Park, Jung-Min, Yoo, Myung-Soo, Cho, Seog-Yeon, and Shin, Hye-Jung

Subjects
AMMONIA gas, SPRING, CITIES & towns, AGRICULTURE, ATMOSPHERIC ammonia, NITRATES
Abstract

In this study, the characteristics of ammonia and their effects on secondary particulate matter (PM) formation were analyzed by region in Korea in 2020. The NH3 concentration was high in GJ (11.4 ppb), a neighboring agricultural area, followed by DJ (9.0 ppb) and SE (8.6 ppb), which are located in urban areas. On the other hand, BI (2.6 ppb) and JI (4.5 ppb), which are background regions, demonstrated a lower concentration than other areas. Seasonally, ammonia was high in spring and summer, and it generally increased when human activities are active. Therefore, it is believed that the ammonia in the atmosphere not only changes depending on local emissions, but also based on temperature-dependent phase distribution characteristics. For SE and GJ, regions with relatively high ammonia concentrations, investigations into the effect of ammonia on secondary PM formation were conducted. In both regions, the ammonium-to-sulfate mole ratio tended to increase with increasing ammonia or PM2.5 concentration. It can be assumed that the PM2.5 concentration increases as nitrates are formed under the ammonia-sufficient condition. The adjusted gas ratio is generally greater than 4, indicating that there is a lot of free ammonia. Thus, it is estimated that a reduction in ammonia would not be effective to restrain nitrate formation. [ABSTRACT FROM AUTHOR]

Published
2024
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27. Optimized responsivity of a phototransistor using graphene oxide-doped solution-processed indium oxide active layer toward neuromorphic applications.

Author

Tarsoly, Gergely, Zhao, Han-Lin, Wang, Xiao-Lin, Lee, Jae-Yun, and Kim, Sung-Jin

Abstract

Recently, metal oxide semiconductors have attracted considerable interest in certain areas, such as displays. Applications of transparent metal oxide semiconductors in photosensors are also starting to develop owing to their high charge carrier concentration and mobility. By including a narrow bandgap material in the device, photoresponsivity can be improved, but it increases the number of fabrication steps. This paper suggests embedding an indium oxide thin film with graphene oxide (GO) photoactive particles in a single step from a mixed aqueous precursor solution by spin coating. The device performance was assessed as a function of the GO content. The device stability data showed that a higher GO content induced hole trapping under prolonged gate bias stress. Hole trapping at the In2O3/GO interface is important under illumination, where the trapping of the minor photogenerated carrier can improve the photocurrent via the photogating effect. The long-term trapping of holes in the n-type device also produces a persistent photocurrent, which makes the device respond to illumination like an artificial neuron. In addition to photodetection, the device applicability in binary logic circuits was also demonstrated via a load-type inverter. The phototransistor proposed in this study could achieve sensing, memory, and binary logic in the same device. [ABSTRACT FROM AUTHOR]

Published
2024
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42. Engineering a Solution-Processed In2O3 TFT With Improved Ambient Stability via MoO3 Doping

Author

Lee, Jae-Yun, Tarsoly, Gergely, Wang, Xiao-Lin, Zhao, Han-Lin, Heo, Kwan-Jun, and Kim, Sung-Jin

Abstract

The solution processing of metal–oxide–semiconductor devices is a less energy-intensive route for fabricating transparent, high-performance electronics for the display industry. On the other hand, the poor long-term stability of these solution-processed thin films limits their wide-scale adoption. One possible way of improving the stability of the devices is doping the semiconductor film with another metal oxide. This letter reports the fabrication of solution-processed indium oxide films with and without molybdenum (VI) oxide doping and the device characteristics immediately after fabrication and after 30 days of storage. The results showed that the transistor devices with a pristine indium oxide thin film exhibit a severe drop in the ON-current level and charge carrier mobility and a large change in the threshold voltage. When molybdenum ions were included in the thin film, significant improvement was achieved in the stability of the electronic performance characteristics of the device in terms of the charge carrier mobility and threshold voltage.

Published
2024
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47. Enhancement of Electrical Stability in Solution Processed In2O3 TFT by an Oxygen Plasma-Assisted Treatment

Author

Shan, Fei, Lee, Jae-Yun, Tarsoly, Gergely, Zhao, Han-Lin, Wang, Xiao-Lin, Anvar, Tukhtaev, Yoo, Suchang, and Kim, Sung-Jin

Abstract

Solution processing is a promising alternative to fabricate transparent metal oxide layers for display applications. One drawback is poor bias stability of the devices with as-deposited films. Here, we report on the postdeposition treatment of solution-processed indium oxide (In2O3) thin-film transistors (TFTs) performed by a helical-focused plasma source. The RF generator power of the plasma source is varied to optimize the treatment conditions. The electrical performance of the In2O3 TFTs showed improvement after treatment at lower and medium RF power, but when increased to 180 W, no transistor operation was observed. The best bias stability based on current deterioration and threshold voltage shift was observed when the RF power of the plasma generator was set to 60 W. The oxide films were further studied by measuring the optical absorbance, performing atomic force microscopy to analyze the surface roughness, and measuring the water contact angle to assess the hydrophilicity. A resistive load-type inverter was constructed by connecting optimized In2O3 TFTs with a resistor of 20 $\text{M}\Omega $ and the inversion characteristics were assessed.

Published
2023
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49. Parasphingorhabdus cellanae sp. nov., isolated from the gut of a Korean limpet, Cellana toreuma

Author

Yoo, Ji-Ho, primary, Han, Jeong Eun, additional, Lee, June-Young, additional, Jeong, Su-Won, additional, Jeong, Yun-Seok, additional, Lee, Jae-Yun, additional, Lee, So-Yeon, additional, Sung, Hojun, additional, Tak, Euon Jung, additional, Kim, Hyun Sik, additional, Kim, Pil Soo, additional, Choi, Jee-Won, additional, Kim, Do-Yeon, additional, Jeong, In Chul, additional, Gim, Do-Hun, additional, Kang, Seo Min, additional, and Bae, Jin-Woo, additional

Published
2022
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