Solution-processed high-k thin films as a resistive switching for ReRAM applications

장기현,오세만,안호명,조원주 한국물리학회 2014 Current Applied Physics Vol.14 No.3

Resistive switching characteristics of solution-processed high-k thin films (HfOx and TaOx) were investigated for ReRAM applications. The thickness of solution-processed high-k thin films can be easily controlled by simple spin coating. We optimized the critical thickness of solution-processed HfOx and TaOx thin films, for reliable ReRAM operations. A similar bipolar resistive switching behavior was observed from both solution-processed and sputter-processed HfOx films. Furthermore, it was found that the solution-processed HfOx and TaOx films have a uniform resistive switching characteristic. The dominant conduction of these solution-processed films is described by Ohmic conduction in the lowresistance state. On the other hand, Ohmic conduction at low voltage and PooleeFrenkel emission at high voltage dominate in the high-resistance state. It was verified that the solution-processed HfOx and TaOx films have superior endurance and retention characteristics. Therefore, ReRAM devices based on solution-processed high-k materials are expected to be a promising candidate, for usage of resistive memory in glass substrate or flexible substrate based electronic devices.

Solution-processed high-k thin films as a resistive switching for ReRAM applications

Jang, K.H.,Oh, S.M.,An, H.M.,Cho, W.J. Elsevier 2014 Current Applied Physics Vol.14 No.3

Resistive switching characteristics of solution-processed high-k thin films (HfO<SUB>x</SUB> and TaO<SUB>x</SUB>) were investigated for ReRAM applications. The thickness of solution-processed high-k thin films can be easily controlled by simple spin coating. We optimized the critical thickness of solution-processed HfO<SUB>x</SUB> and TaO<SUB>x</SUB> thin films, for reliable ReRAM operations. A similar bipolar resistive switching behavior was observed from both solution-processed and sputter-processed HfO<SUB>x</SUB> films. Furthermore, it was found that the solution-processed HfO<SUB>x</SUB> and TaO<SUB>x</SUB> films have a uniform resistive switching characteristic. The dominant conduction of these solution-processed films is described by Ohmic conduction in the low-resistance state. On the other hand, Ohmic conduction at low voltage and Poole-Frenkel emission at high voltage dominate in the high-resistance state. It was verified that the solution-processed HfO<SUB>x</SUB> and TaO<SUB>x</SUB> films have superior endurance and retention characteristics. Therefore, ReRAM devices based on solution-processed high-k materials are expected to be a promising candidate, for usage of resistive memory in glass substrate or flexible substrate based electronic devices.

최적화된 전자 수송층을 활용한 완전한 용액공정 기반 녹색 유기발광다이오드

한주원,김용현,Han, Joo Won,Kim, Yong Hyun 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.7

Solution-processed organic light-emitting diodes (OLEDs) have the advantages of low cost, fast fabrication, and large-area devices. However, most studies on solution-processed OLEDs have mainly focused on solution-processable hole transporting materials or emissive materials. Here, we report fully solution-processed green OLEDs including hole/electron transport layers and emissive layers. The electrical and optical properties of OLEDs based on solution-processed TPBi (2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) as the electron transport layer were investigated with respect to the spin speed and the number of layers. The performance of OLEDs with solution-processed TPBi exhibits a power efficiency of 9.4 lm/W. We believe that the solution-processed electron transport layers can contribute to the development of efficient fully solution-processed multilayered OLEDs.

2LD-1 Rational Design of Molecular Precursor and Processing Method for High Performance and Low Temperature Solution-Processed Oxide Electronics

김명길,박성규,김충익 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

Solution processed metal oxide electronics could potentially meet the requirements of commercial large area electronics, such as high-throughput fabrication processes and a choice of materials with appropriate electrical performance characteristics, including conductor, semiconductor and insulator. However, this area still faces several challenges, such as low performance, high annealing temperatures, and the inability to fine-tune intrinsic properties. An intensive study of interface optimization, novel fabrication concepts, and new materials development can addresses critical issues in solution processed metal oxide semiconductor electronics. The new precursor designing principle, processing concepts and hybrid interface afford the development of high performance electronic materials (conductor, semiconductor, insulator), low processing temperature (T_process ~ 60 ℃) and device stabilzation against Cu ion and gas diffusion.

Solution Processable Hybrid Hole Transport Layers for Organic Solar cells with Highly Enhanced Open-Circuit Voltage and Fill Factor

이형석,한용운,문두경 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0

Organic solar cells (OSCs) have been studied because of their low cost and simple manufacture process. However, OSCs have some disadvantages such as unbalanced carrier mobility, low stability resulted from energy level mismatch between electrode and active layer. To solve these issues, many researchers replaced MoO3 to various HTLs materials. Through solution process, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is commonly used as HTLs by its high conductivity and solution processable properties. However, devices introduced PEDOT:PSS still attain lower power conversion efficiency (PCE) and stability than MoO3 deposited devices. Solution processable hybrid HTLs can be modified properties of carrier mobility and energy levels. In this study, we fabricated inverted structured OSCs with hybrid HTLs via solution process. As a result, the stability and performance of OSCs with solution processable hybrid HTLs were enhanced.

Dieletric Engineering via Humidity Control for Solution-processed High Performance Oxide Semiconductor Thin-film Transistors

김연상 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.1

Solution-processed oxide semiconductors thin film transistors (OS TFTs) with continuous, large scale, and low cost processibility have potential for next-generation display technology. Especially, studies on various precursors for high quality OS thin films in a low-temperature process have been focused for an OS film on a flexible substrate. Among them, OS TFTs fabricated with a metal aqua complex have attracted much attention because they have low temperature processibility as well as high field-effect mobility. However, despite of remarkable results, important factors to optimize their performance with a fidelity have not been achieved. Here, we demonstrate the importance of humidity control to enhance the electrical performance of OS TFTs. Through humidity control during the spin-coting process and annealing process, we successfully demonstrate solution-processed InOx/SiO₂ TFTs with a good fidelity of ~ 5% standard deviation, showing high average field-effect mobility.

Effective Atmospheric-Pressure Plasma Treatment toward High-Performance Solution-Processed Oxide Thin-Film Transistors

Park, Jintaek,Huh, Jae-Eun,Lee, Sung-Eun,Lee, Junhee,Lee, Won Hyung,Lim, Keon-Hee,Kim, Youn Sang American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.36

<P>Solution-processed oxide semiconductors (OSs) have attracted much attention because they can simply, quickly, and cheaply produce transparent channels on flexible substrates. However, despite such advantages, in the fabrication process of OS thin-film transistors (TFTs) using the solution process, it is a fatal problem that there are hardly any ways to simply and effectively control important TFT parameters, including the turn-on voltage (<I>V</I><SUB>on</SUB>) and on/off current ratio. For the practical application of solution-processed OS TFT, approaches to simply and effectively control the parameters are urgently required. Here, we newly propose an atmospheric-pressure plasma (APP) treatment that can simply and effectively control the electrical properties in solution-processed InO<I><SUB>x</SUB></I> TFTs. Through exposure of APP, we successfully realized the changes in important TFT parameters of solution-processed InO<I><SUB>x</SUB></I> TFT, <I>V</I><SUB>on</SUB> from −11.4 to −1.9 V and the on/off current ratio from ∼10<SUP>3</SUP> to ∼10<SUP>6</SUP>, which still keep up the high field-effect mobility (>20 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>). On the basis of various analyses such as X-ray-based analysis and UV-visible spectroscopy, we identified that the APP treatment can effectively control oxygen vacancy and carrier concentration in solution-processed OS.</P> [FIG OMISSION]</BR>

Impact of Interface Mixing on the Performance of Solution Processed Organic Light Emitting DiodesImpedance and Ultraviolet Photoelectron Spectroscopy Study

Ahn, Dong A,Lee, Seungjun,Chung, Jaegwan,Park, Yongsup,Suh, Min Chul American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.27

<P>We investigated interfacial mixing of solution-processed organic light-emitting devices (OLEDs) using impedance spectroscopy (IS) and ultraviolet photoelectron spectroscopy (UPS) and its impact on device performance. We focused on interfacial mixing between a solution processed cross-linkable hole transport layer (XM) and an emitting layer (EML), formed either by solution processing or vacuum evaporation. The results of IS and UPS clearly indicated that extensive interfacial mixing was unavoidable, even after the XM was cross-linked to make it insoluble and rinsed to remove residual soluble species, if the subsequent EML was solution processed. In addition, we also demonstrated that interfacial mixing indeed increased hole current density in corresponding hole only device (HOD). In fact, the hole injection efficiency could be an order of magnitude better when the EML was solution processed rather than vacuum evaporated. We investigated such behavior to find the desirable process condition of solution-processed OLEDs.</P>

Solution-processed lanthanum-doped Al₂O₃ gate dielectrics for high-mobility metal-oxide thin-film transistors

Kim, Jaeyoung,Choi, Seungbeom,Jo, Jeong-Wan,Park, Sung Kyu,Kim, Yong-Hoon Elsevier 2018 THIN SOLID FILMS - Vol.660 No.-

<P><B>Abstract</B></P> <P>Solution-processed oxide gate dielectrics play an important in thin-film transistors (TFTs), determining their operation voltage, device performance and power consumption. Up to now, various solution-processed oxide gate dielectrics such as aluminum oxide (Al<SUB>2</SUB>O<SUB>3</SUB>) have been surveyed, however, they generally exhibit relatively high leakage current, low dielectric constant, and hysteresis which are unfavorable for stable device operation. Here, we demonstrate solution-processed lanthanum (La)-doped Al<SUB>2</SUB>O<SUB>3</SUB> (LAO) gate dielectrics which exhibit low leakage current density, high dielectric constant, and relatively small frequency-dependent capacitance variation. In order to find the optimal doping concentration of lanthanum in Al<SUB>2</SUB>O<SUB>3</SUB> film, various electrical, morphological, and spectroscopic analyses were carried out. We found that the addition of lanthanum in Al<SUB>2</SUB>O<SUB>3</SUB> film effectively reduced the defective metal hydroxide bonding states within the film and significantly enhanced its dielectric characteristics. At an optimal doping concentration of lanthanum (20 at.%), gate dielectrics showing leakage current density, dielectric constant, and breakdown field of ~10<SUP>−8</SUP> A/cm<SUP>2</SUP> (at 2 MV/cm), 10.5, and >5 MV/cm were obtained. Using the LAO film as a gate dielectric, solution-processed indium-zinc-oxide TFTs having a field-effect mobility of 11.9 cm<SUP>2</SUP>/V-s, subthreshold slope of 0.38 V/dec, and on/off ratio of 10<SUP>4</SUP>–10<SUP>5</SUP> were demonstrated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lanthanum-doped Al<SUB>2</SUB>O<SUB>3</SUB> gate dielectrics were fabricated by using a solution process. </LI> <LI> The lanthanum doping enhanced the dielectric properties of Al<SUB>2</SUB>O<SUB>3</SUB> films. </LI> <LI> Solution-processed indium-zinc-oxide thin-film transistors were demonstrated. </LI> </UL> </P>

Cost-based feasibility study and sensitivity analysis of a new draw solution assisted reverse osmosis (DSARO) process for seawater desalination

Park, K.,Kim, D.Y.,Yang, D.R. Elsevier Scientific Pub. Co 2017 Desalination Vol. No.

In this study, a newly devised seawater desalination process, namely, the draw solution assisted reverse osmosis (DSARO) process, is proposed. A mathematical model for the DSARO process was developed and energy consumption and economic evaluation models were constructed to assess the feasibility of the DSARO process compared to the conventional reverse osmosis (RO) process. This work presents a characterization of important variables and the research on the effects of these variables. Compared to the conventional RO process, the DSARO process could have a 10% lower specific water production cost. The operating pressures required to reach 40% of overall recovery were approximately 35bar in the 1st RO process, and 30bar in the 2nd RO process. Due to its operating pressure being lower than the conventional RO process, the capital and membrane replacement costs could be reduced. The required conditions in the 1st RO membrane to drive the DSARO process were that the membrane structure parameter must be lower than 0.13mm, and the maximum operating pressure should be higher than 35bar. Even though these conditions are not available commercially at present, they could be attained based on the best available membrane technology in the literature.