Article
Multidisciplinary Sciences
Sungjae Hong, Chang-Ui Hong, Sol Lee, Myeongjin Jang, Chorom Jang, Yangjin Lee, Livia Janice Widiapradja, Sam Park, Kwanpyo Kim, Young-Woo Son, Jong-Gwan Yook, Seongil Im
Summary: Graphene has been widely used as an insertion layer in vertically stacked devices due to its excellent electrical tunabilities. However, its implications at ultrahigh frequencies have been rarely explored. In this study, diode operation of vertical Pt/n-MoSe2/graphene/Au assemblies at a cutoff frequency of about 200 GHz was demonstrated. The electric charge modulation by the inserted graphene becomes essentially frozen above a few GHz frequencies, transforming the Ohmic graphene/MoSe2 junction into a pinning-free Schottky junction. The diodes with graphene insertion exhibit much lower total capacitance and an order of magnitude higher cutoff frequency compared to devices without graphene, highlighting the significance of graphene at high frequencies.
Review
Materials Science, Multidisciplinary
Ruo-Si Chen, Guanglong Ding, Ye Zhou, Su-Ting Han
Summary: This review summarizes the recent progress on how to circumvent Fermi-level pinning (FLP) between 2D TMDs semiconductors and metals, including introducing related concepts, discussing factors contributing to FLP, and strategies of Fermi-level depinning. The summary and outlook provides a guideline for suppressing FLP in the process of fabricating high-performance 2D TMD devices.
JOURNAL OF MATERIALS CHEMISTRY C
(2021)
Article
Chemistry, Multidisciplinary
Po-Hsun Ho, Yu-Ying Yang, Sui-An Chou, Ren-Hao Cheng, Po-Heng Pao, Chao-Ching Cheng, Iuliana Radu, Chao-Hsin Chien
Summary: In this study, chloroauric acid was used as a strong p-dopant for high-performance WSe2 monolayer transistors. By designing a suitable doping spacer length, a normally off, high-performance underlap top-gate device can be achieved without the need for additional gating in the contact and spacer regions.
Article
Engineering, Electrical & Electronic
Federica Catania, Niloofar Saeedzadeh Khaanghah, Dianne Corsino, Hugo de Souza Oliveira, Alejandro Carrasco-Pena, Koichi Ishida, Tilo Meister, Frank Ellinger, Giuseppe Cantarella, Niko Muenzenrieder
Summary: This study explores the performance tuning of flexible IGZO thin-film transistors (TFTs) using a double-gate configuration. It is found that bottom-gate biasing is effective for efficient switching, while top-gate biasing allows for control of performance. The tunability of fT and f(MAX) is observed in devices with different channel lengths, with better control observed in longer TFTs. Furthermore, the tunability of performance is also reported even when the double-gate TFTs are exposed to tensile strain.
IEEE TRANSACTIONS ON ELECTRON DEVICES
(2023)
Article
Nanoscience & Nanotechnology
Po-Cheng Tsai, Coung-Ru Yan, Shoou-Jinn Chang, Shu-Wei Chang, Shih-Yen Lin
Summary: We fabricated top-gate transistors on MoS2 with different layer thicknesses in the source and drain regions using atomic layer etching. The transistor exhibited high and low levels of drain current under forward and reverse gate bias, respectively, at zero gate voltage due to the presence of ALE. The hysteresis loop on the transfer curve indicated the existence of two distinct charge states within a certain range of gate bias, and a long retention time of the charge was observed.
Article
Chemistry, Physical
Yuhang Guan, Yuqing Zhang, Jinxiong Li, Jiye Li, Yuhan Zhang, Zhenhui Wang, Yuancan Ding, Mansun Chan, Xinwei Wang, Lei Lu, Shengdong Zhang
Summary: In recent years, high-k gate dielectrics have received increasing attention in amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) due to the need for stronger gate controllability. This study developed an ultra-thin top-gate insulator of atomic-layer-deposited (ALD) HfOx for amorphous indium-gallium-zinc oxide (a-IGZO) TFTs. However, the reliability of the 4-nm HfOx-gated a-IGZO transistor is poor due to interface defects caused by the interface reaction between HfOx and a-IGZO during the ALD process. To improve stability, the a-IGZO channel is pre-treated with strong oxidizing plasma. However, further reducing HfOx thickness increases gate leakage current.
APPLIED SURFACE SCIENCE
(2023)
Article
Nanoscience & Nanotechnology
Ji-Min Park, Hyunkyu Lee, Gun Oh Lee, Seong Cheol Jang, Yun Hee Chang, Hyunmin Hong, Kwun-Bum Chung, Kyung Jin Lee, Dae Hwan Kim, Hyun-Suk Kim
Summary: In this study, metal capped Zn-Ba-Sn-O transistors with top-gate structures were proposed to enhance mobility, which can be applied in various fields such as high-resolution, large-area, and flexible displays.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Multidisciplinary
Tien Dat Ngo, Tuyen Huynh, Inyong Moon, Takashi Taniguchi, Kenji Watanabe, Min Sup Choi, Won Jong Yoo
Summary: This study presents a novel approach to overcome the challenges faced by 2D materials in CMOS technology, specifically in the production of high-performance p-type field effect transistors (p-FETs). By fabricating lateral p+-p-p+ junction WSe2 FETs with self-aligned TG stacks and utilizing selective oxygen plasma-doping, the researchers achieve exceptional electrostatic controllability and low power consumption in PMOS inverters.
Article
Chemistry, Multidisciplinary
Jae-Keun Kim, Kyungjune Cho, Juntae Jang, Kyeong-Yoon Baek, Jehyun Kim, Junseok Seo, Minwoo Song, Jiwon Shin, Jaeyoung Kim, Stuart S. P. Parkin, Jung-Hoon Lee, Keehoon Kang, Takhee Lee
Summary: Doping in transition metal dichalcogenides (TMDCs) can affect charge transport properties, especially the Coulomb scattering induced by dopant counterions on the surface of TMDCs. The amount of charge transfer is related to doping density and the contribution of each dopant ion towards Coulomb scattering.
ADVANCED MATERIALS
(2021)
Article
Chemistry, Multidisciplinary
Dongryul Lee, Yongha Choi, Junghun Kim, Jihyun Kim
Summary: In this study, we demonstrate a self-aligned fabrication process for ultrathin tungsten diselenide field-effect transistors with low contact resistance and high on/off current ratio. This approach involves self-terminated p-doping and layer-by-layer chemical etching to thin the WSe2 channel without damaging the selectively doped source/drain regions.
Article
Chemistry, Multidisciplinary
Taro Sasaki, Keiji Ueno, Takashi Taniguchi, Kenji Watanabe, Tomonori Nishimura, Kosuke Nagashio
Summary: Two-dimensional heterostructures have been extensively studied as NVM devices, but their operation mechanisms are not fully understood. Detailed operation mechanisms have been elucidated by exploiting FG voltage measurements, revealing three current-limiting paths controlling tunneling behavior between the channel and FG, and emphasizing the importance of the access region in achieving 2D channel/FG tunneling.
Article
Nanoscience & Nanotechnology
Yifu Guo, Mingqun Yang, Junyang Deng, Chenming Ding, Chunhui Duan, Mengmeng Li, Ling Li, Ming Liu
Summary: By fine-tuning the supramolecular assembly of two thiazole flanked naphthalene diimide-based conjugated polymers, well-defined fibrillar morphology monolayers with approximately 2.5 nm thickness were successfully grown. The resulted monolayer FETs demonstrated high electron mobility up to 0.25 cm(2) V-1 s(-1), setting a new record for n-type polymer monolayer FETs. Additionally, the first demonstration of polymer monolayer complementary integrated circuits was achieved, with a record-high inverter gain of 113, which is identical to the best polymer thin-film inverters.
ADVANCED ELECTRONIC MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Cong Peng, Huixue Huang, Meng Xu, Longlong Chen, Xifeng Li, Jianhua Zhang
Summary: This paper proposes a facile modifying technique for self-aligned top-gate In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) by controlling the process parameter of the passivation layer at relatively low temperatures. The modified IGZO TFTs show stable electrical performance.
Article
Computer Science, Information Systems
Abdelkader Abderrahmane, Changlim Woo, Pil-Ju Ko
Summary: In this study, a novel nanoelectronic device based on a black-phosphorus-gated WSe2/SnSe2 van der Waals tunnel field-effect transistor (TFET) was fabricated and characterized. The TFET device exhibited p-type behavior and negative differential resistance (NDR), with low optoelectronic performance but promoting the integration of black phosphorus into low-energy-consumption 2D van der Waals TFETs.
Article
Nanoscience & Nanotechnology
Wanyu Zeng, Zengchong Peng, Dong Lin, Anna A. Guliakova, Qun Zhang, Guodong Zhu
Summary: This study reports a dual-mode proximity sensor based on an oxide thin-film transistor(TFT) that utilizes a tungsten carrier suppresser to develop semiconducting materials and devices. The sensor performs well in flat panel display applications and can also sense the proximity and angle of approach of charged objects.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Chemistry, Multidisciplinary
Samarth Vadia, Johannes Scherzer, Kenji Watanabe, Takashi Taniguchi, Alexander Hoegele
Summary: Chirality is a fundamental asymmetry phenomenon observed in chiral optical elements that exhibit asymmetric response to circularly polarized light. Recent developments include nanoplasmonic systems with broken-mirror symmetry and circular dichroism through polarization-contrasting optical absorption. Excitons in atomically thin semiconductors offer an alternative route to circular dichroism through spin-valley polarized excitons. This study demonstrates the transfer of polarization-contrasting optical transitions from excitons in monolayer WSe2 to proximal plasmonic nanodisks through coherent coupling, resulting in magneto-induced circular dichroism. This research highlights the potential of exciton-plasmon interfaces for applications in information processing, nonlinear optics, and sensing.
Article
Physics, Applied
Tetta Suzuki, Yuichi Yamazaki, Takashi Taniguchi, Kenji Watanabe, Yusuke Nishiya, Yu-ichiro Matsushita, Kazuya Harii, Yuta Masuyama, Yasuto Hijikata, Takeshi Ohshima
Summary: In this study, two thermal treatment methods were used to successfully generate negatively charged boron vacancies (V (B) (-)) in hexagonal boron nitride with superior spin properties. Both methods improved the signal-to-noise ratio of the optically detected magnetic resonance signal by a factor of 4. Furthermore, the crystal distortion reflected by the zero-field splitting parameter E significantly reduced after irradiation above 650 degrees C. These findings indicate that thermal treatment is an effective method for a V (B) (-) based quantum sensor.
APPLIED PHYSICS EXPRESS
(2023)
Article
Chemistry, Physical
Donggyu Kim, Trang Thu Tran, Takashi Taniguchi, Kenji Watanabe, Jeongyong Kim, Joon I. Jang
Summary: Monolayer transition metal dichalcogenides (TMDs) have been extensively studied for their optoelectronic properties and applications. However, their light-emitting capability is severely limited by Auger-type exciton-exciton annihilation (EEA) even at moderate exciton densities. Previous studies using oversimplified models underestimated the Auger coefficient. In this work, we accurately determined the Auger coefficient of monolayer WS2 as a function of temperature by considering laser pulse width and spatially inhomogeneous exciton distribution. Our results provide guidance for enhancing the luminescence quantum yield of TMDs.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Sanghyeok Park, Dongha Kim, Yun-Seok Choi, Arthur Baucour, Donghyeong Kim, Sangho Yoon, Kenji Watanabe, Takashi Taniguchi, Jonghwa Shin, Jonghwan Kim, Min-Kyo Seo
Summary: Researchers developed a meta-mirror platform to customize the radiative decay rate and polarization correlation of excitons in TMDCs. By altering the optical layout, the radiative decay rate could be reduced by two orders of magnitude and a statistical correlation between emission intensity and spectral line width was observed. This platform shows great potential for tailoring the two-dimensional distributions of lifetime, density, diffusion, and polarization of TMDC excitons in advanced opto-excitonic applications.
Article
Multidisciplinary Sciences
Wenyu Zhao, Shaoxin Wang, Sudi Chen, Zuocheng Zhang, Kenji Watanabe, Takashi Taniguchi, Alex Zettl, Feng Wang
Summary: Thermally excited electrons and holes form a quantum-critical Dirac fluid in ultraclean graphene. The electrodynamic responses of this fluid are described by a universal hydrodynamic theory. Researchers observed the presence of a hydrodynamic plasmon and energy wave in ultraclean graphene using on-chip terahertz spectroscopy technique. These findings open up new opportunities to explore collective hydrodynamic excitations in graphene systems.
Article
Nanoscience & Nanotechnology
Gan Liu, Tianyu Qiu, Kuanyu He, Yizhou Liu, Dongjing Lin, Zhen Ma, Zhentao Huang, Wenna Tang, Jie Xu, Kenji Watanabe, Takashi Taniguchi, Libo Gao, Jinsheng Wen, Jun-Ming Liu, Binghai Yan, Xiaoxiang Xi
Summary: In this study, electrical switching of ferro-rotational domain states in the charge-density-wave phases of nanometre-thick 1T-TaS2 crystals is demonstrated. Despite the lack of coupling between the electric field and the ferroic order due to symmetry mismatch, the electric field drives domain wall propagation, resulting in reversible, durable, and non-volatile isothermal state switching.
NATURE NANOTECHNOLOGY
(2023)
Article
Multidisciplinary Sciences
Zachary J. Krebs, Wyatt A. Behn, Songci Li, Keenan J. Smith, Kenji Watanabe, Takashi Taniguchi, Alex Levchenko, Victor W. Brar
Summary: In this study, we used scanning tunneling potentiometry to investigate the nanometer-scale flow of electron fluids in graphene. We observed a transition from ballistic to viscous flow regime as the temperature and channel widths increased.
Article
Multidisciplinary Sciences
Xin Huang, Yangyu Guo, Yunhui Wu, Satoru Masubuchi, Kenji Watanabe, Takashi Taniguchi, Zhongwei Zhang, Sebastian Volz, Tomoki Machida, Masahiro Nomura
Summary: This study experimentally confirms the existence of phonon Poiseuille flow in graphitic systems, providing important insights into phonon hydrodynamics and advances in heat manipulation applications.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Applied
Clarisse Fournier, Sebastien Roux, Kenji Watanabe, Takashi Taniguchi, Stephanie Buil, Julien Barjon, Jean-Pierre Hermier, Aymeric Delteil
Summary: Recently discovered quantum emitters in 2D materials have the potential to revolutionize integrated photonic devices for quantum information. In order to utilize these emitters effectively, it is crucial to achieve indistinguishable emitted photons. This study investigates two-photon interference in hexagonal boron nitride and finds that the emitted photons exhibit a partial indistinguishability of 0.44 +/- 0.11 in a 3-ns time window, with a corrected value of 0.56 +/- 0.11 accounting for imperfect emitter purity. The dephasing time of the emitter is estimated to be approximately 1.5 ns, half the limit set by spontaneous emission, and a visibility greater than 90% could be achieved with current 2D-material photonics and the Purcell effect.
PHYSICAL REVIEW APPLIED
(2023)
Article
Nanoscience & Nanotechnology
Sayantan Ghosh, Muhammad Bilal Khan, Phanish Chava, Kenji Watanabe, Takashi Taniguchi, Slawomir Prucnal, Rene Huebner, Thomas Mikolajick, Artur Erbe, Yordan M. Georgiev
Summary: This work introduces the concept of a mixed-dimensional reconfigurable field effect transistor (RFET) by combining a one-dimensional silicon nanowire with a two-dimensional hexagonal boron nitride (hBN) gate dielectric. The hBN encapsulation improves the device's electrical parameters, reducing hysteresis and increasing the on-off ratio. RFETs have great potential in reducing device count and power consumption, and the concept of mixed-dimensional RFET could further enhance their functionality.
ACS APPLIED MATERIALS & INTERFACES
(2023)
Article
Physics, Applied
S. Nakaharai, T. Arakawa, A. Zulkefli, T. Iwasaki, K. Watanabe, T. Taniguchi, Y. Wakayama
Summary: As an application of cryo-CMOS technology for future quantum computing, this study explores low-frequency noise reduction in a two-dimensional system with a molybdenum disulfide channel sandwiched by hexagonal boron nitride layers. The passivation effect of boron nitride layers significantly reduces low-frequency noise, compared to directly placing the molybdenum disulfide channel on a silicon dioxide substrate and silicon devices. This indicates that the clean interface and protected surface contribute to the strong reduction in noise, making 2D materials suitable for cryo-CMOS technology.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Fan Wu, Marco Gibertini, Kenji Watanabe, Takashi Taniguchi, Ignacio Gutierrez-Lezama, Nicolas Ubrig, Alberto F. Morpurgo
Summary: Transistors made from the 2D antiferromagnetic semiconductor CrPS4 display significant magnetoconductance due to changes in magnetic state induced by an external magnetic field. Through analysis of the transistor behavior with temperature and magnetic field, we identify the microscopic mechanism linking conductance and magnetic state, specifically the carrier mobility and threshold voltage. Near the Neel temperature T-N, the magnetoconductance is caused by an increase in mobility due to the magnetic field reducing spin fluctuation-induced disorder, while at much lower temperatures (T << T-N), the threshold voltage changes, leading to an increase in the density of accumulated electrons with increasing magnetic field at a fixed gate voltage. These phenomena are explained by the predicted shift in the conduction band edge using ab initio calculations. Our findings demonstrate the dependence of CrPS4's band structure on its magnetic state and reveal a previously unidentified mechanism for magnetoconductance.
Article
Chemistry, Physical
Ruiheng Su, Manabendra Kuiri, Kenji Watanabe, Takashi Taniguchi, Joshua Folk
Summary: Identifying the essential components of superconductivity in graphene-based systems remains a critical problem in two-dimensional materials research. This field is connected to the mysteries that underpin investigations of unconventional superconductivity in condensed-matter physics. Here we report the discovery of superconductivity in twisted double bilayer graphene (TDBG) in proximity to WSe2, showing the correlation between a high density of states and the emergence of superconductivity in TDBG while revealing a possible role for isospin fluctuations in the pairing.
Article
Chemistry, Multidisciplinary
Alessandra Canetta, Sergio Gonzalez-Munoz, Viet-Hung Nguyen, Khushboo Agarwal, Pauline de Crombrugghe de Picquendaele, Yuanzhuo Hong, Sambit Mohapatra, Kenji Watanabe, Takashi Taniguchi, Bernard Nysten, Benoit Hackens, Rebeca Ribeiro-Palau, Jean-Christophe Charlier, Oleg Victor Kolosov, Jean Spiece, Pascal Gehring
Summary: Using Ultrasonic Force Microscopy (UFM), researchers have quantified the variation of out-of-plane Young's modulus in minimally twisted double bilayer graphene (TDBG). They found a softening of the Young's modulus by 7% and 17% along single and double domain walls, respectively. This study highlights the tunability of nanomechanical properties in engineered twisted materials and opens new possibilities for future applications of designer 2D nanomechanical systems.
Article
Physics, Multidisciplinary
Ayan Ghosh, Souvik Chakraborty, Unmesh Ghorai, Arup Kumar Paul, K. Watanabe, T. Taniguchi, Rajdeep Sensarma, Anindya Das
Summary: Researchers have discovered a compensated semimetallic phase at the charge neutrality point of twisted double bilayer graphene. This phase exhibits electronic correlation and is accompanied by a two orders of magnitude enhancement of thermopower and large magnetoresistance at low magnetic fields. Additionally, the resistance displays an unusual sublinear temperature dependence at low temperatures.
COMMUNICATIONS PHYSICS
(2023)