Article
Engineering, Electrical & Electronic
Nagesh Kallollu Narayanaswamy, Manju Ramrao Bhosle, Krishna Kanth Varma Penmatsa, Ajay Kumar Dwivedi
Summary: In this study, a graphene-based radiator operating at THz frequency is designed and analyzed. The radiator utilizes a tilted dumbbell-shaped aperture loaded on a graphene patch to generate circularly polarized waves. The antenna's frequency response and axial ratio can be tuned by changing the chemical potential of the graphene patch. The proposed antenna operates from 5.85 to 6.05 THz and exhibits good gain and left-handed circular polarization characteristics, making it suitable for sensing applications.
OPTICAL AND QUANTUM ELECTRONICS
(2022)
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
Yongfeng Qu, Jijun Ding, Haiwei Fu, Haixia Chen, Jianhong Peng
Summary: The study systematically investigates the doping effect of boron and sulfur atoms on the electronic and adsorption properties of graphene through density functional theory simulations. The results show that the ratio of B and S atom doping determines the type of conductivity exhibited by graphene, with a ratio less than 2 resulting in n-type and higher ratios leading to p-type conductivity. Additionally, the role of vacancy defects in graphene and the transformation behavior from p to n-type induced by increasing S atom doping are highlighted.
APPLIED SURFACE SCIENCE
(2021)
Article
Biochemistry & Molecular Biology
Xiaoming Ding, Yanli Li, Yubo Zhang
Summary: This study focuses on fabricating VO2 films doped with different contents of tungsten (W) element on high-purity Si substrate. The films exhibited good crystallinity and uniform thickness. X-ray diffraction and X-ray photoelectron spectroscopy characterizations showed that W can be doped into the VO2 lattice, resulting in small lattice distortion. In situ FT-IR measurements revealed that the phase transition temperature of the films can be continuously decreased with increasing W doping content. The doping also significantly enhanced the film's conductivity and reduced optical transmittance. These findings provide important insights into designing doped VO2 films for silicon-based devices.
Article
Chemistry, Multidisciplinary
Bing Liu, Peng Xiao, Chaohui Liu, Jiamin Li, Yingjie Cao, Siguang Ma
Summary: The direct growth of high-quality large graphene crystals with hexagonal shape on the SiO2/Si substrate at low temperatures by PECVD is significant for its electronic and optoelectronic applications. This work successfully reduces the total nucleation density and suppresses subsequent multiple nucleation, ensuring a low total nucleation density all the time during growth and facilitating the successful growth of large graphene crystals. This work will promote the study of low-temperature growth techniques of graphene on dielectric substrates, as well as the large-scale applications of graphene.
Article
Chemistry, Multidisciplinary
Sandra Rodriguez-Villanueva, Frank Mendoza, Alvaro A. Instan, Ram S. Katiyar, Brad R. Weiner, Gerardo Morell
Summary: This study reports the direct synthesis of graphene on SiO2/Si using hot-filament chemical vapor deposition. The results show the growth of few-layers of graphene over the entire SiO2/Si substrate, far beyond the catalytic copper-strip.
Article
Chemistry, Physical
Eunji Ji, Min Jung Kim, Jong-Young Lee, Dongchul Sung, Namwon Kim, Jin-Woo Park, Suklyun Hong, Gwan-Hyoung Lee
Summary: The study investigates the influence of substrate conditions on the doping and degradation of graphene, revealing that the hydroxyl groups on the oxygen-plasma-treated SiO2 substrate alter the characteristics of graphene and lead to decreased reactivity and conductivity.Graphene on P-SiO2 exhibits higher reactivity due to doping induced by -OH groups and shows reduced carrier mobility and larger shift of charge neutral point. Meanwhile, the device on the bare SiO2 shows negligible changes even after UV exposure.
Article
Engineering, Environmental
L. Quan, F. X. Qin, H. T. Lu, D. Estevez, Y. F. Wang, Y. H. Li, Y. Tian, H. Wang, H. X. Peng
Summary: This study successfully prepared sulfur and nitrogen dual doped graphene with different doping sequences, and found that the first doping process has a significant impact on the properties of graphene, while the second doping step further influences the final performance. The dual doped graphene samples exhibited two pronounced absorption peaks and different absorption properties.
CHEMICAL ENGINEERING JOURNAL
(2021)
Article
Chemistry, Multidisciplinary
Yiru Ma, Huiqi Qu, Wenna Wang, Yueqin Yu, Xinghao Zhang, Bin Li, Lei Wang
Summary: The Si/SiO2@graphene superstructure, fabricated through reducing silicalite-1 and depositing carbon layers, exhibits excellent structural stability and high ion/electron transport rate. The optimized anode delivers outstanding cycling life, rate capability, areal capacity, and mechanical stability. The full cell test using LiFePO4 as the cathode demonstrates a high capacity and the Si/SiO2@graphene superstructure effectively maintains the film in LIBs.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Physics, Applied
Chen Yue, Xiaomei Lu, Junting Zhang, Fengzhen Huang, Jinsong Zhu
Summary: In investigating the special electrical phenomena in a graphene/ferroelectric field-effect transistor, it was found that the conductivity of graphene can be influenced by the Au counter electrode and water adsorption, with stronger coupling to the negative surface.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2021)
Article
Chemistry, Physical
Yifan Zhang, Yihan Wang, Yuan Gao, Xinwei Wang, Jianming Xue
Summary: This study doped Si atoms into single-layer graphene through ion implantation, with concentrations up to 8.9 at%, which can be accurately controlled by adjusting the ion fluence. Raman spectra revealed that the irradiation damage of graphene mainly consisted of substitutions and adsorptions, with vacancies maintained at a low level. The work function of the doped graphene increased from 4.34 to 4.46 eV with Si concentration varying from zero to 8.9 at%, showing potential in regulating the performance of related electrical applications.
APPLIED SURFACE SCIENCE
(2022)
Article
Chemistry, Physical
Xingxing Zhang, Xiangdong Gao, Yubing Dong, Yongqing Wu, Deng Duan, Xiang Zhao, Xiaomin Li
Summary: In this study, Mg2+ was doped in nanoporous SiO2 nano-particles to modulate the infrared emissivity of intrinsic SiO2. The effects of Mg doping on the crystallinity, morphology, infrared emissivity, and radiative cooling properties were investigated. The results showed that Mg doping induced cristobalite na-nocrystals, transformed the morphology, and improved the infrared emissivity. The Mg-doped SiO2 coatings exhibited high solar reflectivity and significantly improved radiative cooling capacity.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Chemistry, Multidisciplinary
Chun-Chih Tseng, Tiancheng Song, Qianni Jiang, Zhong Lin, Chong Wang, Jaehyun Suh, Kenji Watanabe, Takashi Taniguchi, Michael A. McGuire, Di Xiao, Jiun-Haw Chu, David H. Cobden, Xiaodong Xu, Matthew Yankowitz
Summary: The extreme versatility of van der Waals materials allows them to exhibit new electronic properties when in close proximity to dissimilar crystals. In this study, we investigate heterostructures of graphene and chromium trihalide magnetic insulators and discover unprecedented gate tunability and atypical transport features, providing a roadmap for exploiting proximity effects in graphene coupled to magnetic insulators.
Article
Crystallography
Sisi Wu, Lingyu Wan, Liangmin Wei, Devki N. Talwar, Kaiyan He, Zhechuan Feng
Summary: The temperature-dependent optical properties of graphene on Si and SiO2/Si substrates were systematically investigated using variable angle spectroscopic ellipsometry. The optical constants of graphene showed changes with the substrate and temperature, with significant absorption in the ultraviolet region and anomalous dispersions in the visible and near-infrared region. A like-Sellmeier equation was found suitable for describing the dispersions of graphene on Si and SiO2/Si substrates in the wavelength range of 400-1200 nm.
Article
Materials Science, Multidisciplinary
Xiang-Yu Sun, Chuan-Gui Wu, Wen-Bo Luo, Yao Shuai, Wang-Li Zhang
Summary: This paper presents a newly produced porous SiO2 film made by traditional sol-gel method. The structural properties of SiO2 aerogel films spin-coated on bare Si and Si with SiO2 buffer layer were observed and compared. Results reveal that the surface of SiO2 aerogel films on bare Si is rough and discontinuous, while flat and smooth surface is observed on sample with SiO2 buffer layer.
Article
Materials Science, Multidisciplinary
Yogeenth Kumaresan, Guanbo Min, Abhishek Singh Dahiya, Ammara Ejaz, Dhayalan Shakthivel, Ravinder Dahiya
Summary: A self-powered stretchable UV photodetector, developed with kirigami-inspired honeycomb-patterned zinc oxide nanowires and coupled with a triboelectric nanogenerator, demonstrates unprecedented stretchability and high performance. This innovative approach has great potential for real-time UV radiation monitoring using wearable healthcare technology.
ADVANCED MATERIALS TECHNOLOGIES
(2022)
Article
Engineering, Electrical & Electronic
Ho-In Lee, So-Young Kim, Seung-Mo Kim, Yongsu Lee, Hae-Won Lee, Sung Ho Yu, Hyeon Jun Hwang, Myung Mo Sung, Byoung Hun Lee
Summary: This work investigates the scaling prospect of ZnO stacked nanosheet channel ternary field effect transistor, as well as the impact of scaling geometric parameters on its performance. The results show that compared to other ternary logic devices, this device has lower power consumption and higher noise margin in the intermediate state. The feasibility for stable ternary circuit operation is also confirmed.
IEEE ELECTRON DEVICE LETTERS
(2022)
Article
Engineering, Electrical & Electronic
Yogeenth Kumaresan, Sihang Ma, Oliver Ozioko, Ravinder Dahiya
Summary: In this study, an innovative approach was proposed to achieve a highly sensitive capacitive pressure sensor by introducing a zinc oxide nanowire interlayer in the conventional metal-insulator-metal architecture. The zinc oxide nanowire interlayer significantly enhanced the performance of the sensor, resulting in a 7-fold increase in sensitivity at a low-pressure range. The improvement in sensitivity was attributed to enhanced charge separation and electric dipole generation due to the displacement of zinc and oxygen atoms under applied pressure.
IEEE SENSORS JOURNAL
(2022)
Article
Engineering, Electrical & Electronic
Sihang Ma, Yogeenth Kumaresan, Abhishek Singh Dahiya, Leandro Lorenzelli, Ravinder S. Dahiya
Summary: This paper presents a flexible tactile sensing system based on ultrathin chips for dynamic contact pressure measurement. The system exhibits high sensitivity and has potential applications in minimal invasive surgical instruments.
IEEE SENSORS JOURNAL
(2023)
Article
Multidisciplinary Sciences
Woochul Kim, Hyeonghun Kim, Tae Jin Yoo, Jun Young Lee, Ji Young Jo, Byoung Hun Lee, Assa Aravindh Sasikala, Gun Young Jung, Yusin Pak
Summary: In response to the explosive demand for data processing, there has been interest in a new logic gate platform that can overcome the limitations of existing electronic logic gates. This study presents an all-in-one optoelectronic logic gate based on the spectral photo-response characteristics of a self-powered perovskite photodetector. Five representative logic gates are demonstrated using a single detector via photocurrent polarity control.
NATURE COMMUNICATIONS
(2022)
Article
Nanoscience & Nanotechnology
Cihyun Kim, Tae Jin Yoo, Min Gyu Kwon, Kyoung Eun Chang, Hyeon Jun Hwang, Byoung Hun Lee
Summary: The structure of a gate-controlled graphene/germanium hybrid photodetector was optimized by splitting the active region, resulting in significantly improved infrared detection capability.
Article
Nanoscience & Nanotechnology
Sihang Ma, Yogeenth Kumaresan, Abhishek Singh Dahiya, Ravinder Dahiya
Summary: Heterogeneous integration is a promising approach for combining printed electronics and silicon technology in high-performance hybrid flexible electronics. A non-contact printing method is demonstrated here as an easy and cost-effective way to access UTCs on flexible foils. The research shows that a small increase in electrical resistance from printed interconnects can lead to an acceptable level of variation in device mobility of MOSFETs. The bonded UTCs exhibit robust device performance under bending conditions, indicating high reliability in both chip thinning and bonding methods.
ADVANCED ELECTRONIC MATERIALS
(2022)
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, Analytical
Myeongseop Kim, Bobae Cho, Hansol Lee, Taeil Yoon, Byeongha Lee
Summary: In this study, a hemispherical resonator gyroscope (HRG) was implemented using a consumer wineglass as the resonator and 3 x 3 optical interferometers as the detectors. The low quality of the off-the-shelf wineglass as a resonator was overcome by the high performance of the optical interferometer. The asymmetries in stiffness and absorption of the resonator were analyzed theoretically and confirmed experimentally. The straightness of the amplitude ratio of two n = 2 fundamental resonant modes of the resonator in a complex plane was proven. By utilizing this straightness and the high performance of the optical interferometer, four real constant parameters characterizing the HRG system were extracted. Experimental results showed that it was possible to measure the Coriolis force at the level of industrial grade using a resonator with an average resonance frequency of 444 Hz and Q value of 1477.2, and achieve a small bias stability of 2.093 degrees/h.
Article
Materials Science, Multidisciplinary
Soo Cheol Kang, Hyun-Wook Jung, Sung-Jae Chang, Ilgyu Choi, Sang Kyung Lee, Seung Mo Kim, Byoung Hun Lee, Ho-Kyun Ahn, Jong -Won Lim
Summary: AlGaN/GaN MIS-HEMTs fabricated with a recess gate exhibit sensitivity to changes in the polarity of the gate voltage. Under negative gate bias stress, electron detrapping requires overcoming an energy barrier, leading to increased temperature dependence. Degradation occurs primarily at the Al2O3/AlGaN interface rather than in the channel or mobility. During relaxation, the time exponent of V-T shift is relatively low, which may be attributed to further degradation at the broader energy levels of the Al2O3/AlGaN interface.
CURRENT APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Hyeon Jun Hwang, So-Young Kim, Sang Kyung Lee, Byoung Hun Lee
Summary: This study investigated the performance of a thermoelectric device made of centimeter-scale monolayer graphene. The carrier type and junction profile of the active graphene layer were modified through chemical doping. After device optimization, improvements in carrier concentration of at least 200% and enhancements in power factor of at least 600% were achieved. Under optimal conditions, a maximum Seebeck coefficient of -350 mu V/K and power factor of -14000 mu W/mK^2 were obtained, which are at least three times higher than the best values reported for other graphene-based thermoelectric devices.
Article
Nanoscience & Nanotechnology
Hongliang Li, Jin Tae Kim, Jin-Soo Kim, Duk-Yong Choi, Sang-Shin Lee
Summary: A spectrometer-free liquid identification scheme based on optofluidic refractive index sensing and vision intelligence algorithms was demonstrated. The integration of a metasurface device into an optofluidic channel provided a highly sensitive polarization-independent focused vortex beam at a single wavelength, serving as the optical fingerprints of liquid chemicals. Deep learning architectures were adopted to classify the beam patterns, achieving a successful identification accuracy of over 99% for various liquid chemicals.
Article
Chemistry, Multidisciplinary
Hyeon Jun Hwang, So-Young Kim, Sang Kyung Lee, Byoung Hun Lee
Summary: By modifying the Fermi level of large-area graphene using an external electric field, researchers have experimentally investigated a reconfigurable passive device that can manipulate its resonant frequency by controlling its quantum capacitance value without complicated equipment. When the total capacitance change caused by the gate bias increased to 60% compared to the initial state, a 6% shift in the resonant frequency could be achieved. Although the signal characteristics of the graphene antenna are slightly inferior to conventional metal antennas, simplifying the device structure allows reconfigurable characteristics to be implemented using only the gate bias change.