Article
Chemistry, Multidisciplinary
Yu Shan, Jiawei Wang, Zean Guo, Dongyang Liu, Ying Zhao, Nianduan Lu, Ling Li
Summary: Molecular doping is an effective method to improve the electrical-transport performances in organic field-effect transistors (OFETs). In this study, robust transconductance enhancements are achieved in OFETs through surface molecular doping using van der Waals epitaxially growing crystalline single crystals.
ADVANCED MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Songang Peng, Zhi Jin, Dayong Zhang, Jingyuan Shi, Jiebin Niu, Chaoyi Zhu, Yanhui Zhang, Guanghui Yu
Summary: The drain current of GFET is not inversely proportional to the channel length, which is abnormal and mainly caused by the modification of channel resistance induced by metal contact doping. As the channel length decreases, the field-effect mobility of GFET tends to saturate.
ADVANCED ENGINEERING MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Zihong Shen, Zunxian Yang, Yuanqing Zhou, Yuliang Ye, Bingqing Ye, Qiaocan Huang, Wenbo Wu, Hongyi Hong, Zeqian Hong, Zongyi Meng, Zhiwei Zeng, Songwei Ye, Zhiming Cheng, Qianting Lan, Jiaxiang Wang, Ye Chen, Hui Zhang, Tailiang Guo, Yun Ye, Zhenzhen Weng, Yongyi Chen
Summary: Artificial photonic synapses, with their high sensitivity and low power consumption, have been developed as new sensors for the IoT and ANNs. This study successfully fabricates photonic synaptic transistors using ternary organic array films, which exhibit both short-term and long-term plasticity. The low power consumption and wireless optical communication capabilities make these synapses highly valuable for next-generation human-computer interaction sensors.
JOURNAL OF MATERIALS CHEMISTRY C
(2023)
Article
Optics
Min Gyu Kwon, Cihyun Kim, Kyoung Eun Chang, Tae Jin Yoo, So-Young Kim, Hyeon Jun Hwang, Sanghan Lee, Byoung Hun Lee
Summary: In this paper, we improved the performance of a near-infrared graphene/germanium heterojunction photodetector by doping graphene with p-type chemical, which lowered the Fermi level and increased the Schottky barrier. The responsivity and detectivity were significantly improved, making it valuable for the development of graphene/semiconductor based photodetectors and near-infrared sensors.
Article
Chemistry, Physical
Xiaoqiao Ma, Bin He, Jinrui Guo, Jiale Han, Wenqi Gao, Jiaqing Wang, Yue Han, Hong Fang, Weiming Lu
Summary: In this study, a transistor composed of graphene and PZT was fabricated, and it was found that applying voltage to PZT can result in hysteresis in the graphene transport curve, thus tuning the conductivity of graphene. This provides a new strategy for designing electronic devices based on 2D materials.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Physics, Multidisciplinary
Maoyun Di, Lin Fu, Yuan Zhou, Hongzhe Pan, Yongjie Xu, Youwei Du, Nujiang Tang
Summary: The mechanism of strong ferromagnetism in nitrogen-doped graphene is closely related to the nitrogen concentration and geometric configuration of nitrogen complexes, which can drive the experimental optimization of ferromagnetism in NG.
NEW JOURNAL OF PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Haiyang Xu, Pingping Li, Zihui Chen, Bing Yang, Bin Wei, Chaoying Fu, Xingwei Ding, Jianhua Zhang
Summary: High stability of metal oxide thin film transistors (TFTs) is crucial for high-resolution displays and sensors. In this study, tantalum cation (Ta5+) doping is used to enhance the stability of zinc-tin-oxide (ZnSnO) TFTs. The results demonstrate that 1 mol% Ta5+-doped TaZnSnO TFTs exhibit excellent stability, with reduced oxygen vacancy defects and threshold voltage shifts compared to undoped devices. Additionally, Ta5+ doping in TaInZnSnO TFTs leads to improved performance and stability, making it a promising strategy for enhancing the stability of ZnSnO-based TFTs.
Article
Nanoscience & Nanotechnology
Bo He, Gang He, Qingqing Hu, Shanshan Jiang, Qian Gao, Elvira Fortunato, Rodrigo Martins
Summary: Nanofiber channel transistors with high electron mobility and operational stability can be achieved by selectively doping Zn element into electrospun In2O3 NFs. Optimized parameters have demonstrated the significant advance of this electrospinning technique toward practical applications for high performance and large-scale electronics.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Chemistry, Physical
Pingjian Li, Kesai Xu, Yu Zhou, Yuanfu Chen, Wanli Zhang, Zegao Wang, Xuesong Li
Summary: Theoretical calculations suggest that sulfur doping can modulate the electrical properties of graphene, with sulfur-hydrogen structures being more effective at n-type doping than thiophene-like sulfur-carbon structures. The synthesized monolayer sulfur-doped graphene film exhibits n-type behavior in air, with a high electron concentration and mobility, surpassing previous reports. This study not only demonstrates the potential applications of sulfur-doped graphene films, but also enhances our understanding of the impact of sulfur structures on their properties.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Nanoscience & Nanotechnology
Sivasakthya Mohan, Dmitry Kireev, Shanmukh Kutagulla, Nicholas Ignacio, Yuqian Gu, Hugo Celio, Xun Zhan, Deji Akinwande, Kenneth M. Liechti
Summary: This study explores the direct growth of metal-catalyst-free graphene on sapphire substrates at conventional metal CVD temperatures. Annealing the substrate prior to growth improves the quality of graphene, resulting in uniformly bilayer graphene. The interaction strength between graphene and sapphire is higher, suggesting potential electronic applications.
ACS APPLIED NANO MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Dingyi Lu, Fanming Huang, Caifang Gao, Jianming Yang, Jing Guo, Yuanyuan Hu, Qinye Bao, Yong-Young Noh, Junhao Chu, Wenwu Li
Summary: A new doping system using an organic salt p-dopant is reported to significantly improve the device performance of organic field-effect transistors (OFETs). The optimized doping ratios increase the hole mobility and reduce the threshold voltage, while also reducing contact resistance and activation energy. The study also explores the impact of doping ratios on trap density.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Review
Materials Science, Multidisciplinary
Md Tanvir Uddin Malik, Aditya Sarker, S. M. Sultan Mahmud Rahat, Sanzeeda Baig Shuchi
Summary: The rapid development of graphene-based supercapacitors has reached a point where there is a need for devices with definite adaptability, which will be a fundamental benefit in innovative electronic devices. Graphene, with its unique properties such as wide surface area and high conductivity, is considered a potential candidate for usage as a building material for superconductors. Different materials are being tested to ensure suitable properties, and researchers are comparing processes to determine the most suitable way to achieve the best electrochemical performance.
MATERIALS TODAY COMMUNICATIONS
(2021)
Article
Nanoscience & Nanotechnology
Longlong Zeng, Linquan Zhang, Yunfeng Liang, Chunhong Zeng, Zeyu Qiu, Haofeng Lin, Ruijiang Hong
Summary: In this study, a novel low-temperature fabrication strategy of CIGS solar cells using the bismuth (Bi)-doping method is reported, and its growth-promoting mechanism is studied. Bi doping significantly improves grain growth and enhances the efficiency of solar cells. The formation of Cu-Bi-Se compounds promotes the crystallization of CIGS absorbers and enhances carrier transport. Bi doping also increases the open circuit voltage of the solar cells.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Nanoscience & Nanotechnology
A. Gumprich, J. Liedtke, S. Beck, I Chirca, T. Potocnik, J. A. Alexander-Webber, S. Hofmann, S. Tappertzhofen
Summary: The fabrication and characterization of steep slope transistor devices based on low-dimensional materials require precise control over electrostatic doping profiles. In this study, we present a versatile graphene heterostructure platform with three buried individually addressable gate electrodes. The platform facilitates analysis of electrostatic doping of low-dimensional materials for novel low-power transistor devices.
Article
Chemistry, Multidisciplinary
Sung Hyeon Jung, Ji Sook Yang, Young Been Kim, Nishad G. Deshpande, Dong Su Kim, Ji Hoon Choi, Hee Won Suh, Hak Hyeon Lee, Hyung Koun Cho
Summary: A strategically designed electrodeposition method is proposed for the coating of p-type copper(i) oxide (Cu2O) channels for oxide thin film transistors. The vertically aligned grain boundaries in the electrodeposited Sb doped Cu2O (Sb:Cu2O) offer superior electrical performances for vertical transistors. The Cu2O vertical field effect transistors exhibit extraordinary transistor performances and power efficient logic inverter circuits with unprecedented performances.
MATERIALS HORIZONS
(2022)
Article
Engineering, Electrical & Electronic
Gyusoup Lee, Jungyeop Oh, Eui Joong Shin, Seongho Kim, Youngkeun Park, Min Ju Kim, Sung-Yool Choi, Byung Jin Cho
Summary: We propose a single device neuron called SD L-FeFET that simulates neuronal dynamics for both excitatory and inhibitory connections while reducing standby power. The spiking neural network (SNN) using SD L-FeFET achieves a pattern recognition accuracy of 92.5% for MNIST handwriting digits and 91.7% for face recognition, comparable to state-of-the-art SNN simulations with conventional complex cell designs.
IEEE ELECTRON DEVICE LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Joon Pyo Kim, Seong Kwang Kim, Seohak Park, Song-hyeon Kuk, Taeyoon Kim, Bong Ho Kim, Seong-Hun Ahn, Yong-Hoon Cho, YeonJoo Jeong, Sung-Yool Choi, Sanghyeon Kim
Summary: The advent of big data has created a need for power-efficient computing beyond the capabilities of the Von Neumann architecture. Inspired by the human brain, neuromorphic computing has the potential to greatly reduce power consumption through matrix multiplication, but current synaptic devices often suffer from limited linearity and symmetry without the use of incremental step pulse programming (ISPP). In this study, we successfully demonstrated a charge-trap flash (CTF)-based synaptic transistor using a trap-level engineered Al2O3/Ta2O5/Al2O3 gate stack for efficient neuromorphic computing. By precisely controlling the conductance with a precision of more than 6 bits, we achieved highly linear and symmetric modulation of conductance using short and low-voltage pulses, resulting in low power consumption and high reliability. Additionally, we achieved high learning accuracy in training 60,000 MNIST images.
Article
Chemistry, Multidisciplinary
Cheolmin Park, Seung Hun Han, Hyeok Jun Jin, Woonggi Hong, Sung-Yool Choi
Summary: In order to solve the image deterioration caused by the pixel miniaturization in high-resolution CMOS image sensor technology, a photodiode with an enhanced mechanism based on a distinctive device structure is needed. This study introduced a photodiode consisting of gold nanoparticles/monolayer graphene/n-type trilayer MoS2/p-type Si bulk, which achieved ultrafast rising/falling times due to the narrow depletion width resulting from the 2D/3D heterojunction. To compensate for the expected low absorbance, plasmonic gold nanoparticles on monolayer graphene were introduced, resulting in broadband enhanced EQE.
Article
Chemistry, Multidisciplinary
Jungyeop Oh, Sungkyu Kim, Changhyeon Lee, Jun-Hwe Cha, Sang Yoon Yang, Sung Gap Im, Cheolmin Park, Byung Chul Jang, Sung-Yool Choi
Summary: With advances in artificial intelligent services, brain-inspired neuromorphic systems with synaptic devices are recently attracting significant interest to solve the von Neumann bottleneck. However, deep neural networks suffer from huge power consumption and vanishing gradient problem. This research proposes a memristor-based compact and energy-efficient neuron device to implement the ReLU activation function, successfully resolving the vanishing gradient problem and achieving high-density and energy-efficient hardware neuromorphic systems.
ADVANCED MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Yonghee Jeong, Hyunjin Kim, Jungyeop Oh, Sung-Yool Choi, Hamin Park
Summary: This study comprehensively investigates the bias temperature instability of a-IGZO thin-film transistors (TFTs) by analyzing the behavior of transfer characteristics under repeated bias stress and recovery at different temperatures. The results reveal that the correlation between transfer characteristics and stress time depends on temperature, exhibiting opposite trends. This can be explained by the competition between trapped electron and oxygen vacancy mechanisms, with the predominant mechanism determined by temperature.
JOURNAL OF ELECTRONIC MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Wonbae Ahn, Han Beom Jeong, Jungyeop Oh, Woonggi Hong, Jun-Hwe Cha, Hu Young Jeong, Sung-Yool Choi
Summary: This study proposes a copper migration-controlled electrochemical metallization (ECM) memristor using two-dimensional materials, MoS2 and Al2O3, as the switching medium. The device exhibits low switching voltage, uniform switching, and a wide switching range, with excellent retention characteristics in the long-term reliable neuromorphic system. The contribution of the Al2O3 layer to the retention characteristic is investigated through filament morphology observation and copper migration component analysis.
Article
Engineering, Electrical & Electronic
Juwon Kim, Hyunjin Kim, Jungyeop Oh, Sung-Yool Choi, Hamin Park
Summary: The threshold voltage of a-IGZO TFTs can shift under certain stress conditions, and the direction of the shift depends on the illumination condition. The shift is mainly influenced by ionized oxygen vacancies and trapped electrons.
SOLID-STATE ELECTRONICS
(2023)
Article
Materials Science, Multidisciplinary
Injun Lee, Cheolmin Park, Tae Soo Kim, Minsoo Kang, Hyeongyeol Oh, Jinhyeong Jang, Jungjae Park, Jong Min Yuk, Hohjai Lee, Chan Beum Park, Sung-Yool Choi, Kibum Kang, Wonryung Lee, Byeong-Soo Bae
Summary: Upconversion nanoparticles (UCNPs) are encapsulated with a siloxane polymer (UCNP@SiOx) through a sol-gel process, enabling water stability and photo-patternability. The UCNP@SiOx demonstrates no significant decrease in upconversion photoluminescence (PL) intensities and PL decay time after immersion in water, and is found to be non-toxic. Integration of UCNP@SiOx with MoS2 phototransistors results in enhanced responsivity and specific detectivity, as well as excellent mechanical durability. This work introduces a facile synthesis method for water-stable and photo-patternable siloxane-encapsulated UCNPs and a strategy for fabricating high-performance flexible NIR phototransistors through wavelength conversion.
ADVANCED OPTICAL MATERIALS
(2023)
Article
Nanoscience & Nanotechnology
Cheolmin Park, Gi Woong Shim, Woonggi Hong, Sung-Yool Choi
Summary: In this study, large-area hierarchical transition metal dichalcogenide (TMD) nanostructures were grown vertically on a substrate, showing potential for electrochemical applications due to their high density of edge states. A singular point promoting vertical growth was identified through optical dark-field data and micro-Raman spectroscopy, attributed to the layer-dependent dielectric constant of MoS2. Furthermore, a method for expanding the vertically grown MoS2 region on a substrate was discussed using analytical methods based on hydromechanics.
ACS APPLIED NANO MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Dong-Ha Kim, Jun-Hwe Cha, Sanggyu Chong, Su-Ho Cho, Hamin Shin, Jaewan Ahn, Dogyeong Jeon, Jihan Kim, Sung-Yool Choi, Il-Doo Kim
Summary: This paper reports an ultrafast flash-thermal shock (FTS)-induced annealing technique for the preparation of single-atom-stabilized N-doped graphene in an ambient-air environment. The method offers advantages such as high throughput, large area, and vacuum-free manufacturing of single-atom catalysts. Experimental results demonstrate that the single-atom-stabilized N-doped graphene produced by this method exhibits excellent chemiresistive gas sensing capabilities and electrocatalytic activities.
Article
Chemistry, Multidisciplinary
Jun-Hwe Cha, Su-Ho Cho, Dong-Ha Kim, Dogyeong Jeon, Seohak Park, Ji-Won Jung, Il-Doo Kim, Sung-Yool Choi
Summary: High-entropy alloys (HEAs) have unique physicochemical properties compared to unary nanoparticles (NPs). Conventional alloying guidelines limit the possible combinations of alloying elements, but recent research has shown that carbon thermal shocks (CTS) and a high-entropy environment play a critical role in HEA synthesis. This study proposes a photo-thermal approach using carbon nanofibers to successfully synthesize HEA NPs with up to nine elements, demonstrating high activity and stability in water splitting reactions.
ADVANCED MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Inseong Lee, Mingu Kang, Seohak Park, Cheolmin Park, Hyeonji Lee, Sanggeun Bae, Hyeongjin Lim, Sungkyu Kim, Woonggi Hong, Sung-Yool Choi
Summary: This study proposes a method to heal donor defect states in monolayer MoS2 using oxygen plasma, with an aluminum oxide (Al2O3) barrier layer that protects the MoS2 channel from damage. The successful healing of donor defect states in MoS2 by oxygen atoms, even in the presence of an Al2O3 barrier layer, has been confirmed. The proposed method enhances the channel properties of MoS2.
Article
Nanoscience & Nanotechnology
Hyeok Jun Jin, Cheolmin Park, Hyo Hoon Byun, Seo Hak Park, Sung-Yool Choi
Summary: A multicolor imaging system using a two-dimensional van der Waals MoTe2/MoS2 heterostructure has been developed, achieving high responsivity within ultra-broadband for high-resolution photodetection. The system is capable of detecting and identifying target objects at visible-to-infrared wavelengths, with fast photoresponse time and unique cutoff wavelengths.
Article
Chemistry, Multidisciplinary
Cheolmin Park, Woonggi Hong, Sung-Yool Choi
Summary: By using thermal process, the high defect concentration in a large area (2 x 2 cm(2)) few-layer MoS2 (2.3 nm thick) was uniformly repaired. The defect concentration of the healed sample decreased by 3.8 times, and both the PL intensity and field-effect mobility over the entire area increased by more than two times.
ADVANCED MATERIALS INTERFACES
(2023)
Article
Chemistry, Multidisciplinary
Jungyeop Oh, Sang Yoon Yang, Sungkyu Kim, Changhyeon Lee, Jun-Hwe Cha, Byung Chul Jang, Sung Gap Im, Sung-Yool Choi
Summary: This study proposes a novel method to enhance the stability and controllability of conductive filaments by introducing imidazole groups that boost the nucleation of Cu nanoclusters in the ultrathin polymer switching layer through the initiated chemical vapor deposition (iCVD) process. It is confirmed that conductive filaments based on nanoclusters with specific gaps are generated in the copolymer medium using this method. Furthermore, by modulating the tunneling gaps, an ultra-wide conductance range of analog tunable conductive filaments is achieved from several hundreds of nS to a few mS with a sub-1 V driving voltage. This approach paves the way for the extension of state availability in synaptic devices to overcome the tunability-stability dilemma, which is essential for the synaptic elements in neuromorphic systems.
MATERIALS HORIZONS
(2023)
