Universal model of bias-stress-induced instability in inkjet-printed carbon nanotube networks field-effect transistors

Jung, Haesun,Choi, Sungju,Jang, Jun Tae,Yoon, Jinsu,Lee, Juhee,Lee, Yongwoo,Rhee, Jihyun,Ahn, Geumho,Yu, Hye Ri,Kim, Dong Myong,Choi, Sung-Jin,Kim, Dae Hwan Elsevier 2018 Solid-state electronics Vol.140 No.-

<P><B>Abstract</B></P> <P>We propose a universal model for bias-stress (BS)-induced instability in the inkjet-printed carbon nanotube (CNT) networks used in field-effect transistors (FETs). By combining two experimental methods, i.e., a comparison between air and vacuum BS tests and interface trap extraction, BS instability is explained regardless of either the BS polarity or ambient condition, using a single platform constituted by four key factors: OH<SUP>−</SUP> adsorption/desorption followed by a change in carrier concentration, electron concentration in CNT channel corroborated with H<SUB>2</SUB>O/O<SUB>2</SUB> molecules in ambient, charge trapping/detrapping, and interface trap generation. Under negative BS (NBS), the negative threshold voltage shift (ΔV<SUB>T</SUB>) is dominated by OH<SUP>−</SUP> desorption, which is followed by hole trapping in the interface and/or gate insulator. Under positive BS (PBS), the positive ΔV<SUB>T</SUB> is dominated by OH<SUP>−</SUP> adsorption, which is followed by electron trapping in the interface and/or gate insulator. This instability is compensated by interface trap extraction; PBS instability is slightly more complicated than NBS instability. Furthermore, our model is verified using device simulation, which gives insights on how much each mechanism contributes to BS instability. Our result is potentially useful for the design of highly stable CNT-based flexible circuits in the Internet of Things wearable healthcare era.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We proposed a bias stress induced instability model for CNT FETs in air/vacuum. </LI> <LI> The V<SUB>T</SUB> shift is composed of ad/desorption of OH<SUP>−</SUP>, electron/hole trapping, and D<SUB>it.</SUB> </LI> <LI> We verified our model by using device simulation. </LI> <LI> We provides insight into how much each mechanism contributes to instability. </LI> <LI> Our model is useful for stable flexible circuit designs in wearable healthcare era. </LI> </UL> </P>

Hybrid complementary inverter based on carbon nanotube and IGZO thin-film transistors with controlled process conditions

Yoon, Jinsu,Jung, Haesun,Jang, Jun Tae,Lee, Jieun,Lee, Yongwoo,Lim, Meehyun,Kim, Dong Myong,Kim, Dae Hwan,Choi, Sung-Jin Elsevier 2018 Journal of Alloys and Compounds Vol.762 No.-

<P><B>Abstract</B></P> <P>Carbon nanotubes (CNTs) and indium-gallium-zinc oxide (IGZO) have emerged as important materials for p-type and n-type thin-film transistors (TFTs), respectively, due to their high mobility, flexibility, and low fabrication temperature. However, fabricating sophisticated macroelectronic circuits operating in complementary mode is challenging using only a single material, because implementing n-type CNT TFTs and p-type IGZO TFTs is difficult. Therefore, hybrid complementary circuits integrated with p-type CNT TFTs and n-type IGZO TFTs have been demonstrated to combine the strength of each TFT. However, limited efforts have been devoted to optimizing the circuit performance by tuning the process conditions under which the percolated CNT network channel and IGZO channel are formed. In particular, the densities of CNTs in the network channel and the amount of oxygen vacancies in the IGZO channel can be simply adjusted, which are important in determining the electrical properties of each TFT. In this work, we systematically investigated the device and circuit performance by varying such conditions; hence, we confirmed the design features of each TFT that can be optimized to enhance the hybrid complementary circuits.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A hybrid complementary inverter was fabricated using different n-type and p-type materials. </LI> <LI> The carbon nanotube was employed as a channel for the p-type transistor. </LI> <LI> The indium-gallium-zinc oxide was employed as a channel for the n-type transistor. </LI> <LI> The process conditions during formation of the channels were tuned and optimized. </LI> <LI> The performance of the inverter was optimized through controlling such conditions. </LI> </UL> </P>

과학기술 공동연구의 연결망 구조

김용학(Kim Yong Hak),윤정로(Yoon Jung Ro),조혜선(Cho Haesun),김영진(Kim Yung Jin) 한국사회학회 2007 韓國社會學 Vol.41 No.4

과학적 지식을 생산하는 공동연구 연결망은 과학자들의 의사소통 및 지식확산의 중요한 기제가 되고, 연결망의 구조적 특성은 연구성과에도 영향을 미칠 가능성이 있기에 중요한 연구의 대상이 되어왔다. 본 연구는 한국 과학자들 사이의 공동연구 연결망이 서구와 마찬가지로 ‘좁은 세상’의 특징을 지니며 전공 분야별로 연결망 구조에 차이가 있는지, 그리고 좁은 세상 연결망에서의 과학자 위치가 그의 연구 생산성과 어떤 관련이 있는지를 분석한다. 본 연구는 과학자들의 공동연구자 수가 대부분의 좁은 세상의 연결망에서처럼 멱함수 형태로 분포되어 있으며, 경로거리는 무작위 연결망에서의 그것과 비슷하고, 군집계수는 높게 나타나는 ‘좁은 세상’의 구조를 보인다는 점을 발견했다. 연결망의 구조적 특징은 연구 분야별로 다르게 나타난다. 대표적인 예로서 BT 분야는 포괄적이고, IT 분야는 분절적이라는 사실을 발견했다. 또 공동연구 연결망에서 징검다리 역할을 하거나 연결망의 중심에 놓인 연구자들의 연구 생산성이 높다는 사실도 발견했다. 다양한 전공분야에서 생산되는 새로운 지식과 정보를 접하는 데 유리한 구조적 위치에 놓인 과학자의 연구생산성이 나타난 것이다. Research on the network structure of scientific knowledge production has become a main concern, since it enables us to discern the structure of communication and knowledge diffusion among scientists. This study examines if the scientific collaboration network in Korea reveals the characteristics of the "small world" as in the Western scientific community and identifies the structural differences across he subfield of scientific research. We also attempt to identify the effect of network locations on scientific performance. We found that the collaboration network among Korean scientists can be characterized as a small world network, where the degree distribution fits the power aw, the path distances are close to the random network, and the clustering coefficient s much higher than that expected in the random network. There are structural differences across research fields; for instance, the network in Bio Technology area s inclusive, whereas the network in Information Technology is segmented. We also found that researchers who are the bridges or who are at the center of the network ire more productive. This confirms that the position in the collaboration network s associated with scientific productivity.

Ultrasound diagnosis and treatment of intractable anterior chest pain from golf - A case report –

Park Jihye,Kim Su Jin,Kim Hyunho,Jung Haesun,신화용 대한마취통증의학회 2023 Anesthesia and pain medicine Vol.18 No.1

Background: Pleurisy is an inflammation of the parietal pleura and is characterized by pleuritic pain. The most common cause of pleurisy is infection; other causes include rheumatoid arthritis, malignancy, rib fractures, or trauma. Possible causes of chest pain associated with golf include costochondritis, stress fractures of the ribs, intercostal muscle strain, or, rarely, Tietze’s syndrome and slipping rib syndrome.Case: A 64-year-old female presented with intractable chest pain that began 4 months prior while playing golf. No specific cause was found after various examinations. There was persistent pain despite medical treatment. Ultrasonography (US) was performed over the painful areas, which revealed focal pleural effusions. A mixture of ropivacaine and triamcinolone was injected into the focal pleural effusions using US guidance, which dramatically relieved her pain.Conclusions: This case demonstrates that US can be used as a diagnostic and therapeutic modality for intractable chest pain with an undetected pathology.

Effectiveness of virtual reality immersion on procedure-related pain and anxiety in outpatient pain clinic: an exploratory randomized controlled trial

( Young Joo ),( Eun-kyung Kim ),( Hyun-gul Song ),( Haesun Jung ),( Hanssl Park ),( Jee Youn Moon ) 대한통증학회 2021 The Korean Journal of Pain Vol.34 No.3

Background: The study investigated virtual reality (VR) immersion in alleviating procedure-related pain in patients with chronic pain undergoing fluoroscopy-guided minimally-invasive intervention in a prone position at an outpatient clinic. Methods: In this prospective randomized controlled study, 38 patients undergoing lumbar sympathetic ganglion block were randomized into either the VR or the control group. In the VR group, procedure-related pain was controlled via infiltration of local anesthetics while watching a 30-minute VR hypnotic program. In the control group, the skin infiltration alone was used, with the VR device switched off. The primary endpoint was an 11-point score on the numerical rating scale, indicating procedure-related pain. Patients’ satisfaction with pain control, anxiety levels, the need for additional local anesthetics during the procedure, hemodynamic stability, and any adverse events were assessed. Results: Procedure-related pain was significantly lower in the VR group (3.7 ± 1.4) than in the control group (5.5 ± 1.7; P = 0.002). Post-procedural anxiety was lower in the VR group than in the control group (P = 0.025), with a significant reduction from pre-procedural anxiety (P < 0.001). Although patients’ satisfaction did not differ significantly (P = 0.158) between the groups, a higher number of patients required additional local anesthetics in the control group (n = 13) than in the VR group (n = 4; P = 0.001). No severe adverse events occurred in either group during the study. Conclusions: VR immersion can be safely used as a novel adjunct to reduce procedural pain and anxiety during fluoroscopic pain intervention.

Effect of oxygen content of the LaAlO₃ layer on the synaptic behavior of Pt/LaAlO₃/Nb-doped SrTiO₃ memristors for neuromorphic applications

Jang, Jun Tae,Ko, Daehyun,Ahn, Geumho,Yu, Hye Ri,Jung, Haesun,Kim, Yeon Soo,Yoon, Chansoo,Lee, Sangik,Park, Bae Ho,Choi, Sung-Jin,Kim, Dong Myong,Kim, Dae Hwan Elsevier 2018 Solid-state electronics Vol.140 No.-

<P><B>Abstract</B></P> <P>We report the effect of the oxygen content of the LaAlO<SUB>3</SUB> layer on the synaptic behavior in the Pt/LaAlO<SUB>3</SUB>/Nb-doped SrTiO<SUB>3</SUB> memristor for neuromorphic applications. As the oxygen-content decreases, the current becomes larger and the spike time-dependent plasticity (STDP) becomes less sensitive to the time difference between pre- and post-synaptic spike voltage. In addition, the conduction mechanism, which was found to be a combination of thermionic and Poole-Frenkel emissions, and the effect of oxygen content are explained in association with the oxygen vacancy in the LaAlO<SUB>3</SUB> layer. The trade-off between large current and efficient STDP can be controlled by the oxygen content. Furthermore, the results of extracting the synaptic strength-based model parameters indicate that the Pt/LaAlO<SUB>3</SUB>/Nb-doped SrTiO<SUB>3</SUB> shows the efficient STDP characteristics in comparison to previously reported memristor materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Spike time-dependent plasticity (STDP) in the Pt/LaAlO<SUB>3</SUB>/Nb-doped SrTiO<SUB>3</SUB> memristor. </LI> <LI> The effect of oxygen content in the LaAlO<SUB>3</SUB> layer on synaptic behavior. </LI> <LI> The trade-off between large current and efficient STDP controlled by oxygen content. </LI> </UL> </P>

Isolation and characterization of cultured chicken oviduct epithelial cells and in vitro validation of constructed ovalbumin promoter in these cells

Yang, Hyeon,Lee, Bo Ram,Lee, Hwi-Cheul,Jung, Sun Keun,Kim, Ji-Youn,No, Jingu,Shanmugam, Sureshkumar,Jo, Yong Jin,Lee, Haesun,Hwang, Seongsoo,Byun, Sung June Asian Australasian Association of Animal Productio 2021 Animal Bioscience Vol.34 No.8

Objective: Transgenic hens hold a great promise to produce various valuable proteins. Through virus transduction into stage X embryo, the transgene expression under the control of constructed chicken ovalbumin promoters has been successfully achieved. However, a validation system that can evaluate differently developed ovalbumin promoters in in vitro, remains to be developed. Methods: In the present study, chicken oviduct epithelial cells (cOECs) were isolated from oviduct tissue and shortly cultured with keratinocyte complete medium supplemented with chicken serum. The isolated cells were characterized with immunofluorescence, western blot, and flow cytometry using oviduct-specific marker. Chicken mutated ovalbumin promoter (Mut-4.4-kb-pOV) was validated in these cells using luciferase reporter analysis. Results: The isolated cOECs revealed that the oviduct-specific marker, ovalbumin protein, was clearly detected by immunofluorescence, western blot, and flow cytometry analysis revealed that approximately 79.40% of the cells contained this protein. Also, luciferase reporter analysis showed that the constructed Mut-4.4-kb-pOV exhibited 7.1-fold (p<0.001) higher activity in the cOECs. Conclusion: Collectively, these results demonstrate the efficient isolation and characterization of cOECs and validate the activity of the constructed ovalbumin promoter in the cultured cOECs. The in vitro validation of the recombinant promoter activity in cOECs can facilitate the production of efficient transgenic chickens for potential use as bioreactors.

The electron trap parameter extraction-based investigation of the relationship between charge trapping and activation energy in IGZO TFTs under positive bias temperature stress

Rhee, Jihyun,Choi, Sungju,Kang, Hara,Kim, Jae-Young,Ko, Daehyun,Ahn, Geumho,Jung, Haesun,Choi, Sung-Jin,Myong Kim, Dong,Kim, Dae Hwan Elsevier 2018 Solid-State Electronics Vol.140 No.-

<P><B>Abstract</B></P> <P>Experimental extraction of the electron trap parameters which are associated with charge trapping into gate insulators under the positive bias temperature stress (PBTS) is proposed and demonstrated for the first time in amorphous indium-gallium-zinc-oxide thin-film transistors. This was done by combining the PBTS/recovery time-evolution of the experimentally decomposed threshold voltage shift (ΔV<SUB>T</SUB>) and the technology computer-aided design (TCAD)-based charge trapping simulation. The extracted parameters were the trap density (N<SUB>OT</SUB>) = 2.6×10<SUP>18</SUP> cm<SUP>−3</SUP>, the trap energy level (ΔE<SUB>T</SUB>) = 0.6 eV, and the capture cross section (σ<SUB>0</SUB>) = 3 × 10<SUP>−19</SUP> cm<SUP>2</SUP>.</P> <P>Furthermore, based on the established TCAD framework, the relationship between the electron trap parameters and the activation energy (E<SUB>a</SUB>) is comprehensively investigated. It is found that E<SUB>a</SUB> increases with an increase in σ<SUB>0</SUB>, whereas E<SUB>a</SUB> is independent of N<SUB>OT</SUB>. In addition, as ΔE<SUB>T</SUB> increases, E<SUB>a</SUB> decreases in the electron trapping-dominant regime (low ΔE<SUB>T</SUB>) and increases again in the Poole–Frenkel (PF) emission/hopping-dominant regime (high ΔE<SUB>T</SUB>). Moreover, our results suggest that the cross-over ΔE<SUB>T</SUB> point originates from the complicated temperature-dependent competition between the capture rate and the emission rate. The PBTS bias dependence of the relationship between E<SUB>a</SUB> and ΔE<SUB>T</SUB> suggests that the electric field dependence of the PF emission-based electron hopping is stronger than that of the thermionic field emission-based electron trapping.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The use of ΔV<SUB>T</SUB> de-embedded from the measured PBTS ΔV<SUB>T</SUB> which is associated only with the charge trapping into gate insulator. </LI> <LI> Detailed and clear procedure of extracting the gate insulator electron trap parameters in IGZO thin-film transistors. </LI> <LI> Analysis of the relationship between activation energy and electron trap parameters. </LI> <LI> Useful in the joint-optimization of gate insulator and active films in highly stable IGZO thin-film transistors. </LI> </UL> </P>

Effects of structure and oxygen flow rate on the photo-response of amorphous IGZO-based photodetector devices

Jang, Jun Tae,Ko, Daehyun,Choi, Sungju,Kang, Hara,Kim, Jae-Young,Yu, Hye Ri,Ahn, Geumho,Jung, Haesun,Rhee, Jihyun,Lee, Heesung,Choi, Sung-Jin,Kim, Dong Myong,Kim, Dae Hwan Elsevier 2018 Solid-state electronics Vol.140 No.-

<P><B>Abstract</B></P> <P>In this study, we investigated how the structure and oxygen flow rate (OFR) during the sputter-deposition affects the photo-responses of amorphous indium-gallium-zinc-oxide (a-IGZO)-based photodetector devices. As the result of comparing three types of device structures with one another, which are a global Schottky diode, local Schottky diode, and thin-film transistor (TFT), the IGZO TFT with the gate pulse technique suppressing the persistent photoconductivity (PPC) is the most promising photodetector in terms of a high photo-sensitivity and uniform sensing characteristic. In order to analyze the IGZO TFT-based photodetectors more quantitatively, the time-evolution of sub-gap density-of-states (DOS) was directly observed under photo-illumination and consecutively during the PPC-compensating period with applying the gate pulse. It shows that the increased ionized oxygen vacancy (V<SUB>O</SUB> <SUP>2+</SUP>) defects under photo-illumination was fully recovered by the positive gate pulse and even overcompensated by additional electron trapping. Based on experimentally extracted sub-gap DOS, the origin on PPC was successfully decomposed into the hole trapping and the V<SUB>O</SUB> ionization. Although the V<SUB>O</SUB> ionization is enhanced in lower OFR (O-poor) device, the PPC becomes more severe in high OFR (O-rich) device because the hole trapping dominates the PPC in IGZO TFT under photo-illumination rather than the V<SUB>O</SUB> ionization and more abundant holes are trapped into gate insulator and/or interface in O-rich TFTs. Similarly, the electron trapping during the PPC-compensating period with applying the positive gate pulse becomes more prominent in O-rich TFTs. It is attributed to more hole/electron traps in the gate insulator and/or interface, which is associated with oxygen interstitials, or originates from the ion bombardment-related lower quality gate oxide in O-rich devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effect of structure and oxygen flow rate on photo-response in IGZO-based photodetector. </LI> <LI> Decomposition of persistent photoconductivity based on extracted sub-gap DOS. </LI> <LI> Quantitative analysis of photo-response including the PPC-eliminating technique. </LI> </UL> </P>