Homosexuality in the jurisprudence of the Supreme Court of India

Naik, Yeshwant Springer 2017 해외석사

(A) study on Ga doped metal oxide TFTs

Naik, Mude Narendra Kyung Hee University 2018 국내석사

The metal oxide semiconductor have been widely used for flat-panel display applications and sensor arrays over the past decade, because of their carrier mobility is high, transparency is higher, uniformity in large-area, and reasonable electrical stability. However, most of these oxide TFTs were integrated into conventional SiO2 dielectrics, which limit their applications in low power, portable electronics. Because the induced-field current is relative to the charge accumulated, a sensible technique to achieve low-current operation in TFTs. Gate insulator with high-k materials affords greater surface charge density at the interface of gate insulator and channel layer. The following thesis consists of fabrication of Ga doped TFTs with Ar /O2 plasma treatment with different time variation and also Y2O3 passivation on channel layer. In this chapter, we studied solution process oxide TFTs to complete reliable and high performance TFTs. This work divided into two parts. First, Ar/O2 plasma treatment on the surface of active layer was employed for the activation of metal bonding. The plasma breaks the oxygen bond with the metal surface from oxidation. Second, Y2O3 layer was deposited by spin coating on the top of Ga-In2O3 TFTs to solve the stability issue to protect the active layer.

Multi-color patterned photonic crystal structures for advanced security : Application of hidden cryptographic secrete message

Naik, Banavathi Tinku 서강대학교 대학원 2023 국내석사

Detecting of volatile organic compounds (VOCs) either in gas or liquid form has many methods in the current world. In-hale of indoor voc pollutants causes severe health hazards. So detecting the small concentration of voc in gas or liquid form is very eseential. For that choosing a very easy, quick method is necessary. Photonic crystals (PC) colorimetric sensors has upper hand in easy method detection inspired from the nature wildlife species include plants, butterfly, chameleon which has diverse colors. It has structural color and responds on external stimuli that leads to increase of lattice distance which can be visible to naked eye. Based on that phenomenon, to improve the sensitivity PC device composed of cured thin polymers can induce highly responsive upon chemical stimulus due to different polymers has different swelling properties. Colorimetric sensors have advantages over conventional sensors since it performs switchable colors with the changes in their interparrticle distance. Using the same principle, multi-color patterns on PC composed of different types of polymers exhibit different swelling effects upon solvent reaction. Based on that result, hidden codes were fabricated with thin polymers cured on a PC device and further can generate a secrete message. It is only possible to reveal the initial hidden patterns on the PC when it exposes to a specific solvent, which could enable to convey the secret message to the recipient from the sender.

Dynamic responses of submerged floating tunnels with mooring cables under waves, earthquakes, and moving loads

Naik, Muhammad 한양대학교 대학원 2019 국내박사

The increasing demand for transportation and development of innovative technology attract the researchers to investigate the economical floating structures such as submerged floating tunnels (SFTs). These tubular structures float at a specified depth and are supported by mooring cables. These structures are more economical alternatives for waterway crossings in comparison to long span cable-supported bridges, underground tunnels or immersed tunnels, especially for deep and wide crossings. The detailed objectives and scope of this thesis are as follows. The first objective is to develop an effective numerical method for the three-dimensional nonlinear analysis of mooring cables using catenary theory. In this method, the mooring line is divided into finite number of catenary elements. In addition to self-weight, each catenary element is subjected to drag force due to steady ocean currents. The proposed procedure was validated by comparing the results with those of the shooting optimization method and the finite element methods. Finally, a parametric study is conducted to study the effect of extensibility on the static response of mooring cables. The effects of fluid drag forces and cable extensibility on mooring cable tension, equilibrium configurations, and stressed lengths are illustrated for two- and three-dimensional mooring cable problems. From the numerical results, the method was found to be numerically stable, and it provided a more rational static response for mooring cables. The second objective is to evaluate the performance of mooring cable configurations of the submerged floating tunnel (SFT). The SFT responses were evaluated using three different mooring cable configurations under hydrodynamic loadings to determine the stability of the mooring configuration, and the most promising configuration was then used for further investigations. The third objective is to formulate and perform the three dimensional geometric nonlinear analysis of SFT under hydrodynamic, seismic and train loads. The nonlinear equations of motion of SFT were integrated by Newmark’s average acceleration method and Modified Newton-Raphson’s method was applied for equilibrium correction in each time step. Two numerical models for the application of seismic ground motions were designed. One of the model applies the ground motion as multi-support excitations and the second model applies uniformly along the tunnel, the first model was found to be more appropriate way of applying seismic excitations to SFT. The waves are dominant actions for SFT in comparison to seismic ground motions and cause extreme tunnel displacements that can cause the mooring cables to become slack. The dynamic responses of SFT under the high-speed train were evaluated. The SFT displacements, bending moments and cable top tension were significantly influenced by moving trains. The SFT experienced extreme vertical displacements and there was a large drop in the minimum cable top tensions. It was concluded that under the trainloads, the cable tensions will be reduced significantly and slackness can happen easily, which should be avoided for the stable SFT. The fourth objective is to investigate the responses of SFT under irregular waves. The irregular waves were modeled by JONSWAP spectrum. The average response of the 30 realizations of the time domain simulations was transformed to the frequency domain by Fast Fourier Transform (FFT). Some important conclusion were drawn from the numerical simulations.

Poisoning Attacks against Federated Learning in Load Forecasting of Smart Energy

QURESHI NAIK BAKHT SANIA 인천대학교 일반대학원 2021 국내석사

Big data and Cloud computing has made it possible to stimulate Machine learning. In past years ML has proved to be the most useful approach for answering questions in a wide range of fields. One of the examples is Load forecasting, which if estimated accurately and efficiently can help us in achieving the future load demand precisely but as the world is getting more and more concerned about its data, users feel insecure and hesitant in sharing their private data and hence the Privacy has become an important feature to be considered. To engage people more in cooperating with making the models advanced by using their private data Federated learning is introduced, which is a platform through which the users and the entities can train and improve the models without sharing their personal data or sensitive information. As FL is a new learning mechanism, it still has some challenges and limitations to be considered and solved. In our proposed work we are highlighting and studying the impact of the two major poisoning attacks i.e. Sign-Flipping attack and the Additive Noise attack in Federated Learning on the performance of Load forecasting. We also proposed and developed the algorithms for detecting these poisoning attacks in Load forecasting. Big data and Cloud computing has made it possible to stimulate Machine learning. In past years ML has proved to be the most useful approach for answering questions in a wide range of fields. One of the examples is Load forecasting, which if estimated accurately and efficiently can help us in achieving the future load demand precisely but as the world is getting more and more concerned about its data, users feel insecure and hesitant in sharing their private data and hence the Privacy has become an important feature to be considered. To engage people more in cooperating with making the models advanced by using their private data Federated learning is introduced, which is a platform through which the users and the entities can train and improve the models without sharing their personal data or sensitive information. As FL is a new learning mechanism, it still has some challenges and limitations to be considered and solved. In our proposed work we are highlighting and studying the impact of the two major poisoning attacks i.e. Sign-Flipping attack and the Additive Noise attack in Federated Learning on the performance of Load forecasting. We also proposed and developed the algorithms for detecting these poisoning attacks in Load forecasting. Big data and Cloud computing has made it possible to stimulate Machine learning. In past years ML has proved to be the most useful approach for answering questions in a wide range of fields. One of the examples is Load forecasting, which if estimated accurately and efficiently can help us in achieving the future load demand precisely but as the world is getting more and more concerned about its data, users feel insecure and hesitant in sharing their private data and hence the Privacy has become an important feature to be considered. To engage people more in cooperating with making the models advanced by using their private data Federated learning is introduced, which is a platform through which the users and the entities can train and improve the models without sharing their personal data or sensitive information. As FL is a new learning mechanism, it still has some challenges and limitations to be considered and solved. In our proposed work we are highlighting and studying the impact of the two major poisoning attacks i.e. Sign-Flipping attack and the Additive Noise attack in Federated Learning on the performance of Load forecasting. We also proposed and developed the algorithms for detecting these poisoning attacks in Load forecasting.

Synthesis and Structure-Activity Relationship Studies of HIF-1α Inhibitors, Chemical Probes for HIF-1α and P-glycoprotein Inhibitors

Ravi Naik 동국대학교 2014 국내박사

Tumor hypoxia has been recognized as a common feature of solid tumor and a negative prognostic factor for response to treatment and survival of cancer patients. Hypoxia inducible factor (HIF)-1 is a key transcription factor that functions as a mast regulator in the response of growing tumor to hypoxia. In normoxia, the subunit HIF-1α becomes hydroxylated at several proline residues and this leads to ubiquitination and proteasomal degradation. Under hypoxic conditions, stabilized HIF-1α dimerizes with HIF-1β. The HIF-1 heterodimer binds to hypoxia response elements (HRE) in gene promoters along with coactivators and induces the expression of target genes involved in angiogenesis, metabolic reprogramming, cell proliferation, and drug resistance to apoptosis. Therefore, HIF-1α is considered as an important target for the development of novel cancer therapeutics. At present, a number of HIF-1α inhibitors including natural products are reported as anticancer drugs. However, most of presently available inhibitors are in early stage of drug development. Thus, in an attempt to develop novel small molecule inhibitors targeting HIF-1α pathway in solid tumor, we conducted phenotype-based structure-activity relationship (SAR) study to develop novel series of small molecule HIF-1α inhibitors. Our group previously identified an aryloxyacetylamino benzoic acid analogue, LW6, which potently inhibited HIF-1α accumulation by degrading HIF-1α without affecting the HIF-1α mRNA levels during hypoxia. LW6 has been used in various studies as an HIF-1α inhibitor. To identify more potent and efficient HIF-1α inhibitors, we performed structural modifications of LW6 that include replacement of the oxyacetylamide linker portion with a more conformationally constrained oxyacrylic amide linker. Accordingly, we synthesized a series of (E)-phenoxyacrylic amide derivatives and evaluated as HIF-1α inhibitors using HRE dependent Luc assay. Among the synthesized analogues, a compound with morpholinoethyl containing ester was found to be the most potent inhibitor against HIF-1α under hypoxic conditions in HCT116 cells. Its effect on HIF-1α pathway was demonstrated by suppression of hypoxia-induced HIF-1α accumulation and target gene expression in dose dependent manner. Of note, chemical biology approaches using multifunctional chemical probes are useful for identification of direct target of HIF-1α inhibitors, such as LW6. Photoaffinity labeling, click conjugation, and biotinylation, are very useful tools for detecting target proteins of biologically active molecules. On the basis of this technique, we designed and synthesized a series of LW6-derived chemical probes by installing a clickable tag and a photoactivatable moiety. We observed the mitochondrial localization of LW6 and identified malate dehydrogenase 2(MDH2) as a target protein. The intracellular localization of LW6 was visualized through click chemistry with probe containing an acetylene group, in colon cancer HCT116 cells. Labile trifluromethyl diazirine photoreactive group was introduced into the phenyl ring of LW6 analogue were used for photoafiinity labeling, which bound to MDH2 in the mitochondrial TCA cycle. Chemical probes installed with biotin derivatives were also synthesized to confirm the direct target by pull-down assay. Significantly, the structure-activity relationship of this series in HRE dependent Luc assay was consistent with that in MDH2 enzyme assay, suggesting that MDH2 is the direct target protein of LW6 and chemical biology techniques are the most reliable for target identification in drug discovery. Furthermore, one of major problems in chemotherapy is multidrug resistance (MDR) against anticancer drugs. ATP-binding cassette (ABC) transporters, such as ABCB1 (P-gp), ABCC1-7 (multidrug resistant related protein 1-7, MRP1-7) and ABCG2 (breast cancer resistance protein, BCRP), are a family of proteins that mediate MDR via ATP-dependent drug efflux pumps. P-gp is the first found human ABC transporter and considered to be clinically significant drug target. Intensive efforts have been directed on developing P-gp modulators to overcome MDR. Many inhibitors of MDR transporters have been identified and some are undergoing clinical trials, but clinically useful drugs have yet to make it to market. Our efforts are focused on development of effective MDR reversal agents via inhibition of P-gp that result in an increased intracellular accumulation of anticancer drugs. In order to synthesize less toxic and more potent inhibitors of P-gp, screening process was proceeded from natural products and chemical library. Herein we described synthesis and biological evaluation of novel classes of adamantyl derivatives as P-gp inhibitors. The core structure modification of adamantyl based compounds was carried out and MDR reversal activities of the synthesized derivatives were assessed in P-gp overexpressed human cancer cell lines. These results indicated that some derivatives were potential MDR reversal agents and are promising for further development. 종양 저산소증(Tumor hypoxia)은 주로 고형암에서 발견되며 환자의 나쁜 예후와 관련하여 낮은 감수성(susceptibility)과 생존율(rate of survival)을 보인다. HIF-1(Hypoxia Inducible Factor-1)은 저산소증(hypoxia)에서 유도되는 중요한 전사인자로써 암세포의 성장과 관련한다. 산소 존재 하에서 HIF-1α 서브 유니트(subunit)의 여러 프롤린 잔기들은 수산화 되고 이 잔기들은 유비퀴틴화(ubiquitination)와 단백질 분해를 초래한다. 저산소증에서 HIF-1α는 HIF-1β와 다이머(dimerization)를 구성한다. HIF-1 헤테로 다이머(heterodimer)는 공활성제 (coactivatior)와 함께 프로모터 유전자의 저산소 반응 요소(Hypoxia Response Elements, HRE)와 결합하여 혈관 형성, 대사적 재프로그래밍, 세포 확산, 아포토시스의 약제 내성 등의 유전자 발현을 유도한다. 그러므로 HIF-1α는 신규한 항암제 개발에 주요한 타깃으로 여겨진다. 현재까지 항암제로써 다수의 저분자 및 천연물 HIF-1α 저해제가 보고되어 있지만 개발 가능성이 있는 약물들 대부분이 임상 초기 단계에서 연구되고 있다. 따라서, 신규한 저분자 HIF-1α 저해제를 개발하기 위해 페노 타입(phenotype-based)을 기반으로 한 구조-활성 상관관계 (structure-activity relationship, SAR) 연구를 수행하였다. 지난 연구에서 저산소증에서 HIF-1α mRNA 수준에 영향을 주지 않으면서 HIF-1α를 분해해 축적을 저해하는 아릴옥소아세틸아미노 벤조익 액시드 유도체인 LW6를 규명하였다. LW6는 여러 연구에서 HIF-1α 저해제로 사용되고 있다. 더 높은 효과와 활성이 있는 HIF-1α 저해제를 발견하기 위하여, 본 연구에서는 LW6의 옥시아세틸아미드 링커 부분을 옥시아크릴릭 아미드 링커 부분으로 더 견고한 구조적 변형을 수행하였다. 이에 따라서, (E)-페녹시아크릴릭 아미드 유도체 시리즈를 합성하였고 HRE 의존적 Luc 어세이(HRE dependent Luc assay)를 통하여 HIF-1α 저해제의 활성을 확인하였다. 그 중에서 모르폴리노에틸기를 포함한 에스테르 화합물이 저산소 HCT116 cell 조건 하에서 가장 좋은 활성을 보였으며, HIF-1α 축적을 저해하는 활성을 용량 의존적으로 나타내었다. 흥미롭게도, 다기능적인 화학적 탐침(multifunctional chemical probe)을 이용한 화학 생물적 접근은 LW6 같은 HIF-1α 저해제의 타깃을 규명하는데 유용하다. 광 친화성 레이블링, 클릭 컨쥬게이션, 바이오티닐레이션은 생물학적으로 활성이 있는 분자의 타깃 단백질을 감지하는데 유용하게 쓰인다. 이 기술을 바탕으로, 본 연구에서는 LW6에 화학적 탐침을 이용한 유도체들을 고안하고 합성하였다. 또한 LW6가 세포 내 미토콘드리아에 위치함(mitochondrial localization)을 관찰하였고 타깃 단백질로서 말레이트 디하이드로지네이즈 2(MDH2)를 규명하였다. 결장암 HCT116 cells (colon cancer HCT116 cells) 내 LW6의 로컬라이제이션은 아세틸렌 그룹을 포함한 탐침인 클릭 반응응 통해 가시화 하였다. 반응성이 큰 트라이플루오르메틸 다이아지린 광활성 그룹(labile trifluoromethyl diazirine photoreactive group)은 LW6의 페닐 고리에 도입하여 미토콘드리아의 TCA 사이클(mitochondrial TCA cycle)에서 MDH2와 결합하는데 이용하였다. 바이오틴 유도체 또한 새로 합성하여 풀-다운 어세이(pull-down assay)를 통해 타깃 단백질과의 결합을 재확인하는데 활용하였다. 특히, HRE 의존적 Luc 어세이 및 MDH2 어세이를 활용한 구조-활성 상관관계 연구를 통해 LW6의 타깃 단백질이 MDH2라는 것을 일관되게 나타낸 것으로 미루어 보아 화학 생물학적 기술은 신약 개발에서 타깃을 규명하는데 매우 유용하다고 판단 된다. 한편, 화학요법의 주요 문제 중 하나는 항암제에 대한 다중 약물 내성 (multidrug resistance, MDR)이다. ABCB1 (P-gp), ABCC1-7 (multidrug resistant related protein 1-7, MRP1-7), ABCG2(breast cancer resistance protein, BCRP)와 같은 ATP-binding cassette (ABC) transporter 단백질을 통하여 MDR은 ATP 의존적 약물 유출 펌프작용을 나타낸다. P-gp는 임상적으로 중요하게 여겨지는 타깃으로 처음으로 발견된 인간 ABC transporter이다. 또한 P-gp의 조절게 개발에 집중하여 MDR을 극복하고자 한다. 다양한 ABC transporter 저해제가 개발되었으며, 그 중 몇몇의 저해제는 임상 실험 단계를 진행하고 있으나 아직 약물로써 사용되는 사례는 없다. 본 연구에서는 P-gp의 활성을 저해함으로써 효과적인 MDR 가역제(reversal agent)를 개발함으로써 세포 내 항암제의 축적 증가 효과를 높이고자 하였다. 독성이 적고 활성이 높은 P-gp 저해제를 합성하기 위해, 스크리닝 기법을 이용하여 천연물과 화홥물 라이브러리를 검색하였다. 이러한 연구를 바탕으로 신규한 P-gp 저해제로써 아다맨틸 유도체(adamantyl derivatives)를 합성하고 생물학적 활성을 측정하였다. P-gp가 과발현된 인간 암 cell line에서 MDR reversal activity를 나타내는 신규한 화합물들을 아다맨틸 구조의 변형 등을 통하여 발굴하였다. 본 연구는 MDR 가역제로써 높은 잠재성과 개발 가능성을 제안하고 있다.

(A) Study on solution processed amorphous metal oxide and their applications to thin-film transistors

Ravindra Naik, Bukke 경희대학교 대학원 2016 국내석사

(A) Study on High Efficiency and Long Lifetime InP-based Quantum Dot Light-Emitting Diodes

MUDE NAGARJUNA NAIK 경희대학교 대학원 2023 국내박사

This study focus on the improvement of high efficiency and long-lifetime InP-based quantum dot light-emitting diodes (QLEDs). Generally, zinc oxide (ZnO) is commonly used as an electron transport layer (ETL) in QLEDs due to its superior properties compared to other metal-oxide ETLs. However, the efficiency and device lifetime of QLEDs shows poor performances due to charge imbalance because of its high mobility and well-matched energy level of ZnO with QD emissive layer (EML). To overcome such issues we have developed different techniques to modulate the charge injection and electronic structure behavior of ZnO. This research work is divided into five different parts and emphasis on improvement of InP-based QLED device performance. In the first part, we studied about the magnesium (Mg) doped ZnO NPs as ETL in inverted QLED and applied self-aging technique. The maximum external quantum efficiency (EQE) of inverted red InP-QLED is improved from 4.4% to 10.2%. This study specifies that a decrease in electron injection is due to raise in conduction band minimum (CBM) after aging times. During the aging periods of QLED device, the oxygen vacancies of ZnMgO NPs is reduced, which causes the conductivity of ZnMgO NPs to decrease. As a result, the exciton quenching is suppressed at the ZnMgO NPs/QD interface and charge balance is enhanced. In second part, we employed optimized sol-gel ZnMgO ETL and a high mobility hole transport layer (HTL) with deep HOMO level in inverted red InP-based QLEDs. To decrease the ZnMgO NPs ETL mobility, a sol−gel ZnMgO ETL with a 17% doping of Mg, at low annealing temperature (180 °C), and self-aging method is used on ITO. Good charge balance condition and suppression of non-radiative losses in QLEDs are achieved by high mobility HTL (DBTA) and an optimized Zn0.83Mg0.17O sol-gel ETL with self-aging technique. The QLED shown a maximum EQE of 21.8% with a half-lifetime (LT50) of 1095 hours at 1000 cd/m2. We also examined, with and without UV-ozone treatment effect on ITO and attained a maximum EQE of 20.2%. In the third part, we studied about the BPPB small molecule doped ZnO as hybrid interlayer in inverted red InP-QLEDs. The ZnO:BPPB (15 wt%) device showed a maximum EQE of 16.7% with a half-lifetime (LT50) of 595 hours. Using a 15 nm hybrid interlayer, the exciton quenching of QD at the interface is suppressed and also reduced the electron injection of ZnO to match the charge balance. In the fourth part, used a novel stable inorganic zinc sulfide (ZnS) ETL material, which has a relatively higher CBM and lower electron mobility compared to ZnO. Analysis shows that by using ZnO/ZnS cascaded ETL, the electron injection is reduced resulting in an improvement of charge balance in the QD layer, and also the exciton quenching is suppressed and preserves the emission properties of QDs. The optimized device with ZnO/ZnS cascaded ETL shows a maximum EQE of 10.8%, maximum current efficiency (CE) of 37.5 cd/A, and a long lifetime (LT50) of 1000 hours at 1000 cd/m2 in inverted green InP-QLED device. We also studied QD:HTL doping approach in inverted red QLED device, achieved a maximum EQE of 11.5% with a long operational lifetime (LT50) of 3800 hours at 1000 cd/m2. In final part, we studied about (nickel) Ni doping in ZnO as an alternative ETLs. Using Ni-doping in ZnO, the CBM and conductivity can be modulated, which helps in enhancement of charge balance in the QLEDs. The optimized devices with NiZnO-3% ETL shows a maximum EQE of 5.0% with a long operational lifetime. Furthermore, using ZnS as interlayer, the device demonstrated a maximum EQE of 10.6 %, which are 2.1-fold higher than NiZnO-3% ETL devices. The device also exhibited a long operational lifetime (LT50) of 2600 hours at 1000 cd/m2.

(A) Study on Solution Processed P-Channel Thin Film Transistors

MUDE NARENDRA NAIK 경희대학교 대학원 2022 국내박사

We introduced changing the concentration of a solution0processed copper0tin sulfide (CTS) thin film0in a thin-film0transistor (TFT). The optical and0electrical properties of CTS thin film0were subjected to a systematic investigation. With a hole0mobility of 9.81 cm2V-1s-1, hall0measurement showed p-type0conduction0of CTS film. The CTS thin films were successfully integrated into the TFT, resulting in high0mobility of 2.43 cm2V-1s-1, low0subthreshold0swing of 664 mV/dec., threshold voltage VTH of -0.53 V, and hysteresis0voltage of 2.31 V. Furthermore, 0with a threshold0voltage shift (VTH) of 0.54 V at a low working voltage, the CTS TFT exhibits good stability under negative bias stress (i.e., -5 V). In air, the CTS TFT's drain current drops by 10% in two days, showing the requirement for a0passivation layer0to avoid moisture0absorption. The high-performance p-channel CTS TFTs at a low operating voltage and their incorporation in the creation of low0power consumption0electronic0devices are suggested by these findings. The development0of p-type0metal-oxide0semiconductors (MOS) is gaining traction for use in next-generation0optoelectronic devices, display backplanes, and complementary0MOS circuits with low power consumption. Using UV/O3 exposure, we demonstrate the outstanding performance0of solution0processed p0channel copper0tin0sulfide0gallium oxide (CTSGO) thin-film transistors (TFTs). The p-type0conduction of CTSGO with a Hall 0mobility of06.02 ± 0.50 cm2V-1s-1 was validated by Hall Effect measurements. At a low working voltage of -5V, the p-channel CTSGO TFT with UV/O3 treatment had a field0effect0mobility (FE) of 1.75 ± 0.15 cm2V-1s-1 and an on/off current ratio (ION/IOFF) of 104. The good0p-type0CTSGO material, 0smooth surface morphology, and less interfacial0traps between0the semiconductor and Al2O3 gate insulator are responsible for the considerable improvement in device performance. As a result, the p-channel0CTSGO TFT 0can be used in CMOS MOS TFTs for next0generation0display circuits. The p-type semiconducting materials are essential building blocks for high0performance complementary metal-oxide0semiconductor (CMOS) thin-film transistor (TFT) circuits. The performances of n-channel TFTs with wide band gap, transparent semiconductor such as oxide should be greatly improved. Here, 0we report0the development of the transparent0and high0performance of p-channel0copper-iodide-tin (CuISn) TFTs. Sn alloy in CuI exhibits remarkable changes in structural and physical properties, which are studied by scanning electron0microscopy (SEM), high-resolution0transmission electron microscopy (HR-TEM), and X-ray0photoelectron0spectroscopy (XPS), and Hall effect measurements. It is confirmed that 25% Sn-alloyed CuI (CuISn) has p-type0conductivity with a0carrier concentration of 2.13×1017 cm-3 and Hall mobility of 63.85 cm2V-1s-1. The TFT made with 25% CuISn exhibited the high field-effect mobility (µFE) of 45.49 cm2V-1s-1, which is 10-fold higher than that of the pristine CuI TFT. The CuISn TFT on0polyimide (PI) substrate exhibits0the µFE of 42.50 cm2V-1s-1 and0ON/OFF current ratio of ~107. In addition, the CuISn TFT showed excellent0stability with the threshold voltage shift (ΔVTH) of 0.61 V under negative gate bias stress.

(A) Study on Metal-Oxide Based High-k Dielectrics and Semiconductors for Thin-film Transistors

BUKKE RAVINDRA NAIK 경희대학교 대학원 2022 국내박사

The performance of metal-oxide thin-film0transistors (TFTs) plays a vital0role in the applications of next-generation displays. 0Metal-oxide TFTs have been0widely used0for display applications0and sensor arrays0over the past decade0due to their high0mobility (~10 cm2V-1s-1), excellent0large-area uniformity, and0good electrical0stability. However, oxide TFTs such as a-IGZO TFTs generally exhibit relatively low field-effect0mobility (FE) of ~ 10 cm2V-1s-1, which are relatively low mobility for applying high PPI AMOLED backplane applications. Therefore, high mobility, stable under bias stress, is required to develop oxide semiconductor materials and devices. Both the vacuum and solution processes can be used to fabricate the TFT. The solution process, such as0spin coating, inkjet0printing, spray pyrolysis, etc., has advantages in manufacturing cost and maintenance compared to its counterpart. However, solution-processed oxide TFTs' high mobility with excellant stability (bias stress and long term) is a critical issue to be solved. High mobility and excellent stability of amorphous oxide-based hysteresis-free n-channel and p-channel TFT are prerequisites for the high performance of complementary metal-oxide semiconductors (CMOS). To improve these parameters, a high-quality interface0between a semiconductor layer and gate insulator is necessary. This thesis has developed the high-k gate insulator and the semiconductor materials via a novel precursor solution synthesis route i.e., purification of metal oxide precursors (high-k dielectrics and the semiconductors). The high-quality film (i.e., gate insulator and channel layer) is required for superior TFT performance. The impurities0in the precursor solutions make the film with poor0quality, which a higher annealing temperature could improve, but a high temperature is0not suitable for flexible0substrates. To address the issues mentioned above, the0preparation methods0of MOs precursor solution0with high purity0were reported; for example, chemical combustion, purification, and thermally purification solution (TPS) process0could lead to0chemical reactions0together with0pre-hydrolysis by0thermal energy in0the MO-based precursor0solution. These0chemical reactions can0improve the MO0film quality. Likewise, 0the chemical additives0(such as solvents,0stabilizers, and0dopants) and0simple precursor0modification routes0(for example, TPS,0gels) are0used to0obtain better semiconducting0materials, which provides0a good quality (i.e., continuous0as well as0crack free) thin film0at low temperatures. Integration of good quality film in the TFT could provide higher mobility. However, high mobility along with bias stability is one of the major issues to be considered. The issue, as mentioned above, is motivated to perform this work. Therefore, developing high-quality gate insulators and n-/p-type MO semiconductor layers becomes essential for high-performance, low-power electronics for next-generation display applications.