Article
Engineering, Electrical & Electronic
Jiaxuan Wen, V. R. Saran Kumar Chaganti, Steven J. Koester
Summary: This study demonstrates back-gated, multifinger graphene RF varactors with a de-embedded quality factor frequency product, Qx f, above 300 GHz. The effects of different design parameters on tuning ratio and quality factor at 77 K and room temperature are explored at frequencies between 1 MHz and 18 GHz. Small signal equivalent circuit modeling is performed to further explain the impact of design parameters on RF performance. These results hold promise for future integration of graphene varactors in high-speed analog applications.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Electrochemistry
Qingxiao Zhou, Li Wang, Weiwei Ju, Dongtao Su, Juncheng Zhu, Yongliang Yong, Shilin Wu
Summary: The charge storage capacity, quantum capacitance, and atomic structures of transition-metal doped graphene-like/graphene heterostructures were studied using density functional theory (DFT). The impact of transition-metal (TM) doping on the capacitance capacity of different types of heterostructures was also examined. The findings showed that doping was more effective than vacancy defects in enhancing the quantum capacitance of heterostructures. The Sc-doped WSe2/graphene exhibited the highest quantum capacitance (838.24 mu F/cm2), making it a promising material for supercapacitors.
ELECTROCHIMICA ACTA
(2023)
Article
Chemistry, Physical
Fanhao Tang, Dongxu He, Hao Jiang, Rongshuo Wang, Zheling Li, Weidong Xue, Rui Zhao
Summary: In this study, a top-down strategy was presented to directly fabricate GO/graphite foam from graphite paper. The synergistic effect with GO and graphite greatly enhanced the electrochemical performance of the electrode.
Article
Chemistry, Multidisciplinary
Chuyao Tong, Rebekka Garreis, Angelika Knothe, Marius Eich, Agnese Sacchi, Kenji Watanabe, Takashi Taniguchi, Vladimir Fal'ko, Thomas Ihn, Klaus Ensslin, Annika Kurzmann
Summary: Quantum states in graphene have two-fold degeneracy in spins and valleys, which can be utilized for qubit preparations. In bilayer graphene quantum dots, the valley g-factor can be tuned by gate voltage adjustments, resulting in larger g-factor with larger electronic dot sizes. Bipolar operation on the versatile device allows for the observation of transitions from electron dots to hole dots. Addition of gates can extend the system to host tunable double dots.
Article
Chemistry, Physical
L. Flores-Larrea, J. A. Rivera-Mayorga, Y. K. Kshetri, V. Rodriguez-Gonzalez, C. R. Garcia, S. W. Lee, J. Oliva
Summary: Textile supercapacitors were fabricated with cotton-fabric+graphene electrodes, incorporating NiO:Yb microparticles to enhance capacitance and energy density. Devices with YbNi MPs showed superior performance in terms of capacitance and energy density, with optical, Raman, and XPS spectra confirming the presence of YbNi MPs as redox centers for charge storage. Impedance measurements demonstrated reduced electrical resistance at the electrode/electrolyte interface in YbNi-containing SCs, facilitating ion diffusion/transport.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Materials Science, Multidisciplinary
Sara Beikzadeh, Alireza Akbarinejad, John Taylor, Simon Swift, Denis Simonov, Jacqueline Ross, Janesha Perera, Paul A. Kilmartin, Jadranka Travas-Sejdic
Summary: The capacitance-based antibacterial and antiviral properties of graphene-based materials were investigated in this study. Laser-induced graphene (LIG) electrodes with tunable capacitances were produced using a CO2 laser. The charged LIG electrodes showed high antibacterial and antiviral performance against various bacteria and viruses. The novel concept of capacitance-based antibacterial and antiviral surfaces is promising in applications where sustainable and rechargeable active surfaces are required.
APPLIED MATERIALS TODAY
(2023)
Article
Chemistry, Physical
Kareem M. Gameel, Mohamed K. Elshazly, Ahmed Huzayyin, Francis Dawson
Summary: We present a computational model based on density functional theory (DFT) calculations to calculate the interfacial capacitance of low-dimensional materials in contact with a bulk substrate. The model incorporates key electrostatic and quantum mechanical components and introduces a material-agnostic formalism based on classical electromagnetic theory. Case studies on monolayer and bilayer graphene adsorbed on a silica substrate show that the predicted electrostatic capacitance of the interfaces is field-independent and aligns well with experimental measurements, offering a better understanding of the electrochemical behavior of nanoscopic interfaces.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Engineering, Electrical & Electronic
Hanul Kim, Jihoon Kim, Inayat Uddin, Nhat Anh Nguyen Phan, Dongmok Whang, Gil -Ho Kim
Summary: Two-dimensional semiconductor heterostructures have great research potential for electronic and optoelectronic applications due to their scalable thickness, pristine heterostructure interface, and ultrafast carrier transport. We present a dual-channel field-effect transistor based on n-type WS2 and p-type WSe2 layered heterostructure, using multilayered graphene as electrodes to enable electron-dominated ambipolar electrical transport. WS2 exhibits a mobility of 20 cm2 V-1 s(-1) and an on/off ratio of 105, while WSe2 exhibits a mobility of 5 cm2 V-1 s(-1) and an on/off ratio of 104. Moreover, our results show negative Schottky barrier heights between the dual-channel heterostructure and multilayered graphene. This proposed design simplifies the fabrication of devices with integrated heterostructures, especially for complementary metal-oxide semiconductor inverter applications.
ACS APPLIED ELECTRONIC MATERIALS
(2023)
Article
Engineering, Electrical & Electronic
Hanul Kim, Jihoon Kim, Inayat Uddin, Nhat Anh Nguyen Phan, Dongmok Whang, Gil-Ho Kim
Summary: We report a dual-channel field-effect transistor based on n-type WS2 and p-type WSe2 layered heterostructure using multilayered graphene as electrodes to enable electron-dominated ambipolar electrical transport. WS2 exhibits a mobility of 20 cm2 V-1 s-1 and an on/off ratio of 105, whereas WSe2 exhibits a mobility of 5 cm2 V-1 s-1 and an on/off ratio of 104. The proposed design reduces complications in the fabrication of devices with integrated heterostructures, particularly for complementary metal-oxide semiconductor inverter applications.
ACS APPLIED ELECTRONIC MATERIALS
(2023)
Article
Engineering, Environmental
Elisabeth Cuervo Lumbaque, Jelena Radjenovic
Summary: Borophene and hexagonal boron nitride-modified graphene sponge anode and N-doped graphene sponge cathode were used for electrochemical degradation of persistent organic contaminants. The use of intermittent current and the functionalization of graphene improved the contaminant removal efficiency while reducing energy consumption.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Chemistry, Multidisciplinary
Jacob D. Bagley, Dorte R. Danielsen, Nai-Chang Yeh
Summary: Graphene is an attractive supercapacitor electrode material, but tends to stack together during electrode processing, reducing the surface area. In situ exfoliation of graphene nanostripes can greatly enhance capacitance by maintaining electrical connectivity and increasing the total surface area for supercapacitor applications.
Article
Energy & Fuels
Ahmed G. Saad, Ahmed Emad-Eldeen, Wael Z. Tawfik, Ahmed G. El-Deen
Summary: Graphene-based nanocomposites have strong potential as high-capacity supercapacitor electrodes in energy storage systems. Developing an accurate and effective prediction technique using machine learning models is crucial for reducing the time needed to design and test electrode materials. Experimental data from over two hundred research papers was examined to predict the specific capacitance of graphene-based electrode structures, with the artificial neural network (ANN) model demonstrating the highest accuracy in predictions.
JOURNAL OF ENERGY STORAGE
(2022)
Article
Engineering, Electrical & Electronic
Cheng Huang, Jiakun Song, Chen Ji, Jianing Yang, Xiangang Luo
Summary: The paper presents a tunable radar absorber based on graphene and varactor, which can independently control the absorption amplitude and frequency, and has polarization-insensitive characteristics.
IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION
(2021)
Article
Optics
Bin Sun, Feifeng Xie, Yu Luo, Shuai Kang, Jianqiang Liu
Summary: A hybrid system based on graphene/metal electrodes was successfully used to efficiently excite and control plasmonic modes in graphene ribbons, leading to the design of a low-voltage controlled multi-band absorber. This structure has potential applications in integrated photonics compatible with electronic technology, offering a wide range of potential uses.
OPTICS AND LASER TECHNOLOGY
(2021)
Article
Chemistry, Multidisciplinary
Hassan Idris Abdu, Hamouda Adam Hamouda, Joshua Iseoluwa Orege, Mohammed Hassan Ibrahim, Anas Ramadan, Taslim Aboudou, Hongxia Zhang, Jinjin Pei
Summary: By ball milling graphite in the presence of dry ice, a series of graphitic materials with carboxylated edges (ECGs) were synthesized, which showed excellent electrochemical performance as effective electrodes for supercapacitors.
FRONTIERS IN CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Hwanhui Yun, Supriya Ghosh, Prafful Golani, Steven J. Koester, K. Andre Mkhoyan
Article
Physics, Applied
Yingying Zhang, Qun Su, Jie Zhu, Sandhaya Koirala, Steven J. Koester, Xiaojia Wang
APPLIED PHYSICS LETTERS
(2020)
Article
Nanoscience & Nanotechnology
Prafful Golani, Hwanhui Yun, Supriya Ghosh, Jiaxuan Wen, K. Andre Mkhoyan, Steven J. Koester
Article
Engineering, Electrical & Electronic
V. R. Saran Kumar Chaganti, Tristan K. Truttmann, Fengdeng Liu, Bharat Jalan, Steven J. Koester
IEEE ELECTRON DEVICE LETTERS
(2020)
Article
Multidisciplinary Sciences
Ruitao Su, Jiaxuan Wen, Qun Su, Michael S. Wiederoder, Steven J. Koester, Joshua R. Uzarski, Michael C. McAlpine
Review
Nanoscience & Nanotechnology
A. Chaves, J. G. Azadani, Hussain Alsalman, D. R. da Costa, R. Frisenda, A. J. Chaves, Seung Hyun Song, Y. D. Kim, Daowei He, Jiadong Zhou, A. Castellanos-Gomez, F. M. Peeters, Zheng Liu, C. L. Hinkle, Sang-Hyun Oh, Peide D. Ye, Steven J. Koester, Young Hee Lee, Ph. Avouris, Xinran Wang, Tony Low
NPJ 2D MATERIALS AND APPLICATIONS
(2020)
Article
Chemistry, Multidisciplinary
Seon Namgung, Steven J. Koester, Sang-Hyun Oh
Summary: This study demonstrates an ultraflat nanogap platform based on atomic layer deposition for fabricating 2D material-based optical and electronic devices. Short-channel field-effect transistors based on black phosphorus and MoS2, as well as photodetectors with a nanoscale photosensitive channel, were successfully fabricated on this platform, showing higher photosensitivity compared to microscale gap channels.
Article
Chemistry, Multidisciplinary
Chunhui Dai, Kriti Agarwal, Hans A. Bechtel, Chao Liu, Daeha Joung, Andrei Nemilentsau, Qun Su, Tony Low, Steven J. Koester, Jeong-Hyun Cho
Summary: By utilizing a plasma-triggered self-assembly process, 3D graphene nanocylinders are introduced, which induce significantly stronger plasmon fields compared to 2D graphene patterns. Synchrotron nanospectroscopy measurements confirm the preservation of hybridized 3D graphene plasmons in high precision curved nanocylinders.
Article
Physics, Applied
V. R. Saran Kumar Chaganti, Prafful Golani, Tristan K. Truttmann, Fengdeng Liu, Bharat Jalan, Steven J. Koester
Summary: This study investigated the metal contact resistance of Nd-doped n-type SrSnO3 films, finding significant differences in conductivity among different contact layers. The Ti contact showed the best Ohmic behavior after Al2O3 passivation, with the lowest specific contact resistivity. Temperature-dependent analysis was used to extract barrier height and doping effects for annealed Ti contacts, indicating their potential for high-performance and transparent electronic applications.
APPLIED PHYSICS LETTERS
(2021)
Article
Nanoscience & Nanotechnology
Nezhueyotl Izquierdo, Jason C. Myers, Prafful Golani, Adonica De Los Santos, Nicholas C. A. Seaton, Steven J. Koester, Stephen A. Campbell
Summary: Black arsenic phosphorus single crystals were grown using a short-way transport technique, characterized using various analytical methods to provide valuable insights into the growth mechanism. By adapting a previously developed thin film growth technique, devices fabricated from exfoliated bulk-b-AsP grown in the same reaction condition showed promising performance with an on-off current ratio of 10(2) and peak field-effect hole mobility of 23 cm(2) V-1 s(-1).
Review
Multidisciplinary Sciences
Sang-Hyun Oh, Hatice Altug, Xiaojia Jin, Tony Low, Steven J. Koester, Aleksandar P. Ivanov, Joshua B. Edel, Phaedon Avouris, Michael S. Strano
Summary: This article introduces the unique advantages of low-dimensional van der Waals (vdW) materials in nanophotonic biosensing, including the dimensional reduction effect, enhanced electrostatic tunability of polariton modes due to reduced dielectric screening in vdW materials, and the implications for new sensing functionalities. It discusses basic sensing principles, technological challenges, and the progress in implementing vdW materials for advanced sensing applications.
NATURE COMMUNICATIONS
(2021)
Article
Engineering, Electrical & Electronic
Jiaxuan Wen, V. R. Saran Kumar Chaganti, Steven J. Koester
Summary: This study demonstrates back-gated, multifinger graphene RF varactors with a de-embedded quality factor frequency product, Qx f, above 300 GHz. The effects of different design parameters on tuning ratio and quality factor at 77 K and room temperature are explored at frequencies between 1 MHz and 18 GHz. Small signal equivalent circuit modeling is performed to further explain the impact of design parameters on RF performance. These results hold promise for future integration of graphene varactors in high-speed analog applications.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Jiaxuan Wen, V. R. Saran Kumar Chaganti, Tristan K. Truttmann, Fengdeng Liu, Bharat Jalan, Steven J. Koester
Summary: The study presents a SrSnO3 high-frequency field-effect transistor (FET) with performance parameters such as maximum drain current and transconductance, and provides relevant data in radio frequency (RF) characterization. This represents a significant advancement in the development of perovskite materials for RF applications.
IEEE ELECTRON DEVICE LETTERS
(2021)
Article
Chemistry, Physical
Youngdong Yoo, Jong Seok Jeong, Rui Ma, Steven J. Koester, James E. Johns
CHEMISTRY OF MATERIALS
(2020)
Article
Nanoscience & Nanotechnology
Qun Su, Xue Zhen, Justin T. Nelson, Ruixue Li, Philippe Buhlmann, Gregory Sherwood, Steven J. Koester
ACS APPLIED NANO MATERIALS
(2020)
