Showing papers by "Jaehoon Park published in 2019"
TL;DR: In this article, a new method that enables the use of a Ru(II) dye without any anchoring groups (Ru(bpy)32+) was developed and investigated.
10 citations
TL;DR: In this article, the effect of the annealing time of copper oxide (CuO) on the morphological and chemical characteristics of films and the electrical properties of bottomgate/top-contact CuO thin-film transistors (TFTs) was investigated.
Abstract: In this study, we investigated the effect of the annealing time of copper oxide (CuO) on the morphological and chemical characteristics of films and the electrical properties of bottomgate/top-contact CuO thin-film transistors (TFTs). Thermogravimetric analysis showed that thermal annealing at 600 °C for 30 min and 3 h resulted in the formation of CuO films. The CuO films were analyzed by X-ray diffraction, X-ray photoemission spectroscopy, absorbance determination, and Raman spectroscopy. As the annealing time of the CuO film was increased, the composition of the films changed from Cu(OH)2 to CuO. Considering the overall TFT performance, the optimal annealing time in solution-processed CuO semiconductors was determined to be 3 h. These results suggest that the annealing time is crucial in modulating the chemical characteristics of solution-processed CuO thin films and the TFT performance.
10 citations
TL;DR: In this article, the effect of annealing temperature on the properties of indium oxide (In2O3) films was investigated from thermogravimetric analysis of the precursor solution.
Abstract: We investigate the effect of annealing temperature on the characteristics of solution-processed indium oxide (In2O3) films. From thermogravimetric analysis of the precursor solution, anneal...
10 citations
TL;DR: In this paper, the effect of Cu(II) on the photooxidation of arsenite to arsenate (As(V)) under UV-C (254 nm) irradiation and the role of CU(II), in the As(III) oxidation processes were mechanistically investigated.
Abstract: The effect of Cu(II) on the photooxidation of arsenite (As(III)) to arsenate (As(V)) under UV-C (254 nm) irradiation and the role of Cu(II) in the As(III) oxidation processes were mechanistically investigated. The presence of Cu(II) enhanced the oxidation of As(III), and the positive effect of Cu(II) increased with increasing Cu(II) concentration and pH. However, other metal ions, such as Al(III), Cr(III), Ni(II), and Mn(II), had little effect on the photooxidation kinetics of As(III). The UV absorption spectra of the As(III) and Cu(II) solutions indicated that not only As(III), but also Cu(II), can absorb 254 nm light. The absorption of 254 nm light by Cu(II) can induce electron transfer from Cu(II) to oxygen, which accelerates the production of hydroxyl radicals ( OH) as a primary oxidant for As(III) oxidation and generates Cu(III) as another primary oxidant. The photooxidation of As(III) in the absence of Cu(II) was limited under anoxic conditions, but was observed in the presence of Cu(II). This result suggests another role of Cu(II) as an alternative electron acceptor, which enhances the production of OH and Cu(III) by mediating electron transfer from As(III) (or Cu(II)) to oxygen. Therefore, both OH and Cu(III) are involved in the oxidation of As(III) to As(V) as primary oxidants in the presence of Cu(II). The photooxidation of As(III) with Cu(II) was not completely inhibited in the presence of excess tert-butyl alcohol (TBA, an OH scavenger), in contrast with the case without Cu(II). This result confirms the generation of Cu(III) and its involvement in the As(III) oxidation processes in the presence of Cu(II). The present results imply that Cu(II) can act as both a UV-C photosensitizer and an electron acceptor in photochemical water treatment processes under UV-C irradiation and significantly affect the kinetics of pollutant oxidation.
6 citations
TL;DR: The results will guide appropriate solvent selection and contribute to the improvement of flexible Fe-FET electrical properties and mechanical stability in the next generation of memory devices.
Abstract: Flexible organic ferroelectric field-effect transistors (Fe-FETs) have attracted attention for next-generation memory applications. A fundamental understanding of the electrical properties and mechanical stability of transistors is a prerequisite to realizing practical flexible electronics. Here, we demonstrate the solvent-dependent electrical characteristics and mechanical stability of flexible Fe-FETs. Poly(vinylidene fluoride-trifluoro-ethylene) (P(VDF-TrFE)) based Fe-FETs were fabricated by using dimethylformamide (DMF) and methyl ethyl ketone (MEK) solvents on a polyimide substrate. P(VDF-TrFE) from DMF formed a smoother surface than a surface from MEK; the surface property greatly affected the electrical properties and mechanical stability of the devices. Larger hysteresis and higher mobility were obtained from Fe-FET using DMF compared to those characteristics from using MEK. Furthermore, Fe-FET using DMF showed lower degradation of on-current and mobility under repetitive mechanical stress than an MEK-based Fe-FET, due to its excellent semiconductor-insulator interface. These results will guide appropriate solvent selection and contribute to the improvement of flexible Fe-FET electrical properties and mechanical stability in the next generation of memory devices.
5 citations
Abstract: The electronic device industry has recently focused its attention towards the development of organic memory devices. This research highlights the development of organic memory devices by ut...
2 citations
12 Jun 2019
TL;DR: This paper analyzes the impact of the slotframe length on the end-to-end delay performance in IEEE 802.15.4 TSCH network and the results can be used as the guideline that determines the appropriate slot frame length for various industrial applications.
Abstract: IEEE 802.15.4 Time Slotted Channel Hopping (TSCH) is designed to provide high reliability and predictable time delay for industrial applications that require strict preconditions. IEEE 802.15.4 TSCH operates on the slotframe structure consisting of multiple slotOffsets and channelOffsets. However, the IEEE 802.15.4-2015 standard does not specify how to determine the slotframe length. Thus, the inappropriate slotframe length can cause a long end-to-end delay in industrial applications. Therefore, in this paper, we analyze the impact of the slotframe length on the end-to-end delay performance in IEEE 802.15.4 TSCH network. The results of the analysis can be used as the guideline that determines the appropriate slotframe length for various industrial applications.
2 citations
TL;DR: In this paper, the authors demonstrate a dimethyl ketone treatment to produce a hydrophobic surface of cross-linked poly(4-vinylphenol) (c-PVP) insulators for pentacene thin-film transistors.
Abstract: We demonstrate a dimethyl ketone treatment to produce a hydrophobic surface of cross-linked poly(4-vinylphenol) (c-PVP) insulators for pentacene thin-film transistors (TFTs). Through water contact angle measurements, the dimethyl ketone treatment is proven to significantly increase the surface hydrophobicity of c-PVP films. The results of X-ray diffraction analyses indicate that the dimethyl ketone-treated c-PVP insulator contributes to enhancing the crystallinity of pentacene films and reducing the density of lamellar grains and bulk phase crystallites in pentacene films. In addition, the growth of lamellar grains is elucidated by examining the initial growths of the pentacene films on the c-PVP films with different surface energies. Consequently, the enhancement in the performance of pentacene TFTs is achieved by incorporating the dimethyl ketone-treated c-PVP films as gate insulators.
2 citations
TL;DR: The results suggest that the electrical stability of solution-processed In₂O₃ TFTs is significantly affected by the electron-trapping phenomenon at crystal grain boundaries in the In‽O⁽ semiconductor and the electrostatic interactions between electrons and polar water molecules.
Abstract: We investigated the electrical stability of bottom-gate/top-contact-structured indium oxide (In₂O₃) thin-film transistors (TFTs) in atmospheric air and under vacuum. The solution-processed In₂O₃ film exhibits a nanocrystalline morphology with grain boundaries. The fabricated In₂O₃ TFTs operate in an n-type enhancement mode. Over repeated TFT operation under vacuum, the TFTs exhibit a slight increase in the field-effect mobility, possibly due to multiple instances of the "trapping and release" behavior of electrons at grain boundaries. On the other hand, a decrease in the fieldeffect mobility and an increase in the hysteresis are observed as the measurement continues in atmospheric air. These results suggest that the electrical stability of solution-processed In₂O₃ TFTs is significantly affected by the electron-trapping phenomenon at crystal grain boundaries in the In₂O₃ semiconductor and the electrostatic interactions between electrons and polar water molecules.
2 citations
TL;DR: The electrical properties of solution-processed 6,13-bis(triisopropylsilylethynyl)pentacene thin-film transistors were investigated under various light irradiation wavelengths as mentioned in this paper.
Abstract: The electrical properties of solution-processed 6,13-bis(triisopropylsilylethynyl)pentacene thin-film transistors were investigated under various light irradiation wavelengths. Irradiated l...
1 citations
TL;DR: In this paper, the authors investigated the annealing temperature and exposure period dependence of electrical characteristics of bottom-gate/top-contact solution-processed organic thin-film transistors (TFTs) fabricated by TFTs.
Abstract: We investigated the annealing temperature and exposure period dependence of electrical characteristics of bottom-gate/top-contact solution-processed organic thin-film transistors (TFTs) fabricated ...