Jingsheng Chen
Email Address
msecj@nus.edu.sg
Organizational Units
COLLEGE OF DESIGN & ENG
faculty
ENGINEERING
faculty
165 results
Publication Search Results
Now showing 1 - 10 of 165
Publication Growth and characterization of bamboo-shaped carbon nanotubes using nanocluster-assembled ZnO:Co thin films as catalyst(2010) Zhao, Z.W.; Lei, W.; Zhang, X.B.; Tay, B.K.; Chen, J.S.; MATERIALS SCIENCE AND ENGINEERINGCarbon nanotubes (CNTs) exhibits many extraordinary thermal, electronic, magnetic, and mechanical properties, which make them important materials for applications such as nanoelectronic devices, hydrogen storage devices, biological probes, atomic probes, optical switches and fuel cells [1-2]. CNTs with special structures such as bamboo-shaped, octopus, fishbone, Y-shaped have attracted immense interest from scientists around the world. © 2010 IEEE.Publication Artificial Synapses Based on Multiterminal Memtransistors for Neuromorphic Application(Wiley-VCH Verlag, 2019-04-22) Wang, Lin; Liao, Wugang; Wong, Swee Hang; Yu, Zhi Gen; Li, Sifan; Lim, Yee-Fun; Feng, Xuewei; Tan, Wee Chong; Huang, Xin; Chen, Li; Liu, Liang; Chen, Jingsheng; Gong, Xiao; Zhu, Chunxiang; Liu, Xinke; Zhang, Yong-Wei; Chi, Dongzhi; Ang, Koh-Wee; ELECTRICAL AND COMPUTER ENGINEERING; MATERIALS SCIENCE AND ENGINEERINGNeuromorphic computing, which emulates the biological neural systems could overcome the high-power consumption issue of conventional von-Neumann computing. State-of-the-art artificial synapses made of two-terminal memristors, however, show variability in filament formation and limited capacity due to their inherent single presynaptic input design. Here, a memtransistor-based arti?cial synapse is realized by integrating a memristor and selector transistor into a multiterminal device using monolayer polycrys-talline-MoS2 grown by a scalable chemical vapor deposition (CVD) process. Notably, the memtransistor offers both drain- and gate-tunable nonvolatile memory functions, which efficiently emulates the long-term potentiation/depression, spike-amplitude, and spike-timing-dependent plasticity of biological synapses. Moreover, the gate tunability function that is not achievable in two-terminal memristors, enables significant bipolar resistive states switching up to four orders-of-magnitude and high cycling endurance. First-principles calculations reveal a new resistive switching mechanism driven by the diffusion of double sulfur vacancy perpendicular to the MoS2 grain boundary, leading to a conducting switching path without the need for a filament forming process. The seamless integration of multiterminal memtransistors may offer another degree-of-freedom to tune the synaptic plasticity by a third gate terminal for enabling complex neuromorphic learning. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimPublication Highly chemical ordered L11 CoPt (111) films with perpendicular anisotropy grown on glass substrates(2011-04-01) Yang, Y.; Chen, J.S.; Chow, G.M.; MATERIALS SCIENCE AND ENGINEERINGIn this study, L11 CoPt (111) films were deposited on glass substrates at 300°C with observed superlattice (111) and (333) peaks and easy axis distribution of 2°. The magnetic anisotropy constant was in the order of 107 erg/cm3. The effect of CoPt layer thickness on domain structure and magnetic properties was investigated. With increasing film thickness, the squareness was reduced and the nucleation field changed from negative to positive, indicating low impedance to domain wall motion and increased demagnetizing energy. Magnetic force microscopy images demonstrated the magnetic domain structure changed from irregular and large domains to highly interconnected stripes with increasing CoPt layer thickness. © 2011 American Institute of Physics.Publication L10 ordered FePt based double-layered perpendicular recording media with (002) oriented FeCo films as a soft magnetic underlayer(2008-02-29) Hu, J.F.; Chen, J.S.; Lim, B.C.; Zhou, T.J.; MATERIALS SCIENCE AND ENGINEERINGThe introduction of the soft magnetic underlayer (SUL) in perpendicular recording technology is to further increase the recording areal density. However, problems such as growth of the uncontrollable recording layer and additional media noise contributed from the SUL could be resulted. In this work, a synthetic antiferromagnetically (SAF) coupled (002) oriented Fe65Co35 film as an SUL was developed for L10 ordered FePt based double-layered recording media. The crystallography of hetero-epitaxially grown double-layered media CrRu/(Ru/FeCo)2/Pt/FePt/Ru was demonstrated. The L10 ordered FePt based double-layered perpendicular recording media with SAF coupled FeCo films as the SUL were developed. © 2007 Elsevier B.V. All rights reserved.Publication Large magnetic moment observed in Co-doped ZnO nanocluster-assembled thin films at room temperature(2007) Zhao, Z.W.; Tay, B.K.; Chen, J.S.; Hu, J.F.; Lim, B.C.; Li, G.P.; MATERIALS SCIENCE AND ENGINEERINGCo-doped ZnO nanocluster-assembled films were deposited by nanocluster-beam deposition. Zn0.986Co0.014O nanodusters remained wurtzite in structure with size of 5 nm. Compared with bulk ZnO, a blueshift of 0.28 eV was observed in the absorption edge of the film. Two photoluminescence bands at 378 and 510 nm were detected. Room-temperature ferromagnetism was observed in doped ZnO nanocluster-assembled film. Moreover, it exhibited a large saturated magnetization of 1.4μB/Co and increased to 3.65μB/Co after the film was annealed. The possible mechanisms on the observed ferromagnetism and enhanced magnetic moment were discussed. © 2007 American Institute of Physics.Publication First principles study of magnetic anisotropy and magnetoelectric effect of FePd/MgO(001) ultrathin films(2013-05-07) He, K.H.; Chen, J.S.; MATERIALS SCIENCE AND ENGINEERINGThe magnetic anisotropy and magnetoelectric effect of FePd/MgO(001) ultrathin films were studied by first principles calculations. The calculation results showed that the magnetization easy axis was in the film normal and the magnetic anisotropy energy (MAE) was reduced with the film thickness. Furthermore, the MAE of FePd reached maximum at the lattice constant of 4.05 Å. The MAE of FePd/MgO films decreased with increasing applied electric field, and the magnitude of the interfacial magnetoelectric coefficient was about 1.4 × 10-12 G cm2/V, which was larger than that in previous reports of Fe/MgO. The calculations also suggested that the MAE was largely dependent on the difference in the orbital moment between [001] and [100] magnetization directions. © 2013 American Institute of Physics.Publication FePt patterned media fabricated by deep UV lithography followed by sputtering or PLD(2007-06) Qiu, L.J.; Ding, J.; Adeyeye, A.O.; Yin, J.H.; Chen, J.S.; Goolaup, S.; Singh, N.; ELECTRICAL & COMPUTER ENGINEERING; PHYSICS; MATERIALS SCIENCE AND ENGINEERINGContinuous and patterned FePt films (40 nm) were fabricated on silicon (100) substrates using deep ultraviolet lithography with the wavelength of 248 nm followed by sputter deposition or pulsed laser deposition at room temperature, liftoff, and postannealing in vacuum. The structures and magnetic properties of the films were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and alternating gradient force magnetometry. A buffer layer of Ag or MgO was inserted between the Si substrate and FePt to prevent a chemical reaction between Si and FePt. The phase transformation from face-centered cubic to face-centered tetragonal started after annealing at 400°C for continuous films, while for the patterned FePt films, phase formation was retarded. High coercivities of 10-15 kOe have shown potential in hard magnetic applications. The effects of Ag and MgO top layers on the coercivities were also investigated. © 2007 IEEE.Publication Critical Fe thickness for effective coercivity reduction in FePt/Fe exchange-coupled bilayer(2012-03) Huang, L.S.; Hu, J.F.; Chen, J.S.; MATERIALS SCIENCE AND ENGINEERINGFePt/Fe perpendicular exchange-coupled bilayers with different Fe thicknesses were prepared to study the exchange coupling effect and the magnetization switching mechanism. An Fe thickness of 3 nm was found to be the critical point where the coercivity reduction became saturated and had the largest thermal stability gain factor of 2.25. This thickness was close to the exchange length between the magnetically hard and soft layers. Within the exchange length the soft phase strongly coupled to the hard phase and the magnetization of the bilayer processed single switching; beyond the exchange length reversible magnetization increased with the Fe thickness and exchange spring effect was found. Our simulation results also revealed that the exchange length was the critical Fe thickness for effective coercivity reduction and for maintaining high remanence. © 2011 Elsevier B.V. All rights reserved.Publication Controlling the Magnetic Properties of LaMnO3/SrTiO3 Heterostructures by Stoichiometry and Electronic Reconstruction: Atomic-Scale Evidence(Wiley-VCH Verlag, 2019-05-17) Li, Mengsha; Tang, Chunhua; Paudel, Tula R.; Song, Dongsheng; Lu, Weiming; Han, Kun; Huang, Zhen; Zeng, Shengwei; Wang, Xiao Renshaw; Yang, Ping; Ariando; Chen, Jingsheng; Venkatesan, Thirumalai; Tsymbal, Evgeny Y.; Li, Changjian; Pennycook, Stephen John; DEPT OF PHYSICS; ELECTRICAL AND COMPUTER ENGINEERING; MATERIALS SCIENCE AND ENGINEERING; SINGAPORE SYNCHROTRON LIGHT SOURCE; NUS NANOSCIENCE & NANOTECH INITIATIVEInterface-driven magnetic effects and phenomena associated with spin–orbit coupling and intrinsic symmetry breaking are of importance for fundamental physics and device applications. How interfaces affect the interplay between charge, spin, orbital, and lattice degrees of freedom is the key to boosting device performance. In LaMnO3/SrTiO3 (LMO/STO) polar–nonpolar heterostructures, electronic reconstruction leads to an antiferromagnetic to ferromagnetic transition, making them viable for spin filter applications. The interfacial electronic structure plays a critical role in the understanding of the microscopic origins of the observed magnetic phase transition, from antiferromagnetic at 5 unit cells (ucs) of LMO or below to ferromagnetic at 6 ucs or above, yet such a study is missing. Here, an atomic scale understanding of LMO/STO ambipolar ferromagnetism is offered by quantifying the interface charge distribution and performing first-principles density functional theory (DFT) calculations across this abrupt magnetic transition. It is found that the electronic reconstruction is confined within the first 3 ucs of LMO from the interface, and more importantly, it is robust against oxygen nonstoichiometry. When restoring stoichiometry, an enhanced ferromagnetic insulating state in LMO films with a thickness as thin as 2 nm (5 uc) is achieved, making LMO readily applicable as barriers in spin filters. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimPublication Engineering the topological states of Weyl ferromagnetic CoxMnGay films grown by molecular beam epitaxy(American Institute of Physics, 2024-04-25) Lizhu Ren; Zhao, Tieyang; Chen, Jingsheng; Teo, Kie Leong; LIZHU, Ren; ELECTRICAL AND COMPUTER ENGINEERING; MATERIALS SCIENCE AND ENGINEERINGDue to its nontrivial topological state, a magnetic Weyl semimetal often exhibits exotic transport properties that are important for both fundamental physics and potential spintronics applications. In this Letter, we investigate the composition dependences of the structural order, magnetism, and transport properties for the epitaxial Heusler alloy CoxMnGay (CMG) topological Weyl semimetal films grown via molecular beam epitaxy. Our results show that the saturated magnetization, anomalous Hall conductivity, and anomalous Hall angle of CMG are influenced by its composition and structural order. Specifically, we observed that the optimized L21–Co2MnGa alloy exhibits a high intrinsic anomalous Hall conductivity of approximately 913 X 1 cm 1 at its maximum, which is attributed to the substantial Berry curvature within its electronic band structures. This study provides valuable insights into how to engineer the topological ferromagnetic state of the Weyl semimetals for future applications.