Area of Excellence

 

Fast algorithms for propagation of electromagnetic wave and circuit simulators

W.C. Chew has invented a series of fast algorithms for solving electromagnetic scattering and inverse problems. His research group has developed parallel codes that solve dense matrix systems with tens of millions of unknowns for the first time for integral equations of scattering, which has been used to simulate the propagation of electrical signals through integrated circuits. K.L. Wu is an expert in electromagnetic numerical modelling. P. Chan led a team of engineers that defined and developed a CAD system to design multi-chip module products. This effort led to the first functional 486 based multi-chip module at Intel.

Quantum transport in nanoscale and molecular devices

H. Guo and J. Wang have pioneered the field of first-principles simulation of quantum transport through nano-electronic devices. They have developed a density-functional theory coupled to nonequilibrium Green's function theory to calculate the currents through molecular and nanoscopic electronic devices (Phys. Rev. B 63, 245407 (2001), times cited: 362). This work represents a very important step forward in nano-electronics theory and laid the foundation of the first-principles theory and modeling of molecular electronics. G.H. Chen and his group have pioneered the first-principles quantum mechanical simulation of transient currents through molecular and nanoscopic electronic devices (Phys. Rev. B 75, 195445 (2007)). The method developed has been applied to simulate the switch-on or off of a molecular device for the first time from first-principles. Since the quantum transport in nano-devices especially in AC bias is in general a nonequilibrium process, equilibrium quantum transport theory such as scattering matrix theory is not adequate to describe this process. J. Wang is also an expert in nonequilibrium quantum transport theory and has formulated a proper theoretical framework based on the nonequilibrium Green's functions to predict finite frequency AC and nonlinear DC quantum transport properties.

Strongly correlated electron systems and spintronics

Electron-electron correlation continues to be one of the most challenging problems in condensed matter physics. Our team has been in the forefront of this field. In a well known paper, the coordinator and T. M. Rice at ETH-Zurich proposed a microscopic model as a minimum model to understand some essential properties of high transition temperature superconducting copper oxides, which has become a widely adopted mathematic model to study the copper oxides (Phys. Rev. B 39, 3759 (1988), with over 2000 citations). The proposed composite particle of the charge carrier is now called "Zhang-Rice singlet". The theory that the coordinator subsequently developed with his collaborators (Supercon. Sci and Tech. 1, 36 (1988)) has become an important part of so-called "plain vanilla version" of one of the theories to explain high transition temperature superconductivity.

Spintronics, or spin electronics, involves the study of active control and manipulation of electron's magnetic spin (a tiny compass) in materials. Recently, this field has been developing rapidly for its potential applications in electronic devices. Our team has been actively working on recent development in this field. Zhang and his collaborators studied spin Hall effect of a 2-dimensional electron gas in a uniform magnetic field and predicted a resonant spin Hall conductance (Phys. Rev. Lett. 92, 256603 (2004)). J. Wang and H. Guo have studied spin currents and spin Hall conductance fluctuations in mesoscopic systems (Phys. Rev. Lett. 98, 196402 (2007); 100, 066803 (2008)). Cui and J. N. Wang have studied spin current injection and detection by optical and transport means.

Fast algorithm for quantum mechanical simulation of electronic dynamic processes

The computational time of O(N) method scales linearly with the system sizes, and is thus the most efficient method for very large systems. G.H. Chen has developed the first O(N) quantum mechanical method for electronically excited systems (Phys. Rev. B 59, 7259 (1999)). Recently Chen has extended density-functional theory to open systems, and thus laid the rigorous foundation of first-principles method for realistic nanoscopic molecular devices (Phys. Rev. B 75, 195445 (2007)). The method has been used to simulate the transient currents through a carbon nanotube based electronic device. In collaboration with Thomas Frauenheim of Bremen University, Chen and his students have implemented the new method with an approximate density-functional theory (density-functional tight-binding method), and thus make it possible to simulate the transient currents through novel electronic devices with dimension up to 10 nm on a modest PC cluster.

Transport measurement of a single molecule and novel semiconductor devices

X.D. Cui has developed a method for making electrical contact to single molecules and has performed the first repeatable measurement of current through a single molecule (Science 294, 571 (2001)). The method is a powerful tool to study the electrical properties of molecular mesoscopic systems. The work was highlighted in an article in Science, "It's all about the contacts", and was listed in "Highlights of 2001" in Chemical and Engineering News (Dec. 2001). J.N. Wang has developed a novel technique to fabricate GaAs/AlGaAs quantum wire resonant tunneling diodes. The electronic one-dimensional states and wavefunctions of these devices have been measured for the first time by magneto-resonant tunneling spectroscopy (Phys. Rev. Lett. 73, 1146 (1994); 75, 1996 (1995)).

Exact theory for the real-time dynamics of quantum transport and related systems

Y.J. Yan has constructed a reduced density matrix based theory, which is not just formally exact, but also by far the most tractable approach to the real-time dynamics of general quantum transport and related problems; see J. Chem. Phys. 128, 234703 (2008); 129, 184112 (2008); 130, 164708 (2009).

Computational imaging for optical projection lithography

The design of photomasks used in the optical lithography process must take into account the various optical effects inherent in the system. E. Lam has developed inverse imaging technology for an automatic efficient optical proximity correction design used for mask synthesis. He has also pioneered a phase initialization mechanism which enhances the robustness of mask design against variations in imaging conditions (Opt. Exp. 16, 14746 (2008)). His work has received a best paper award at the SPIE Lithography Asia conference in Taiwan.

 

To be added soon.

 

Conference papers:

 

1. Yuanzhe Xu, Quan Chen, Lijun Jiang, Ngai Wong, “Process-variation-aware electromagnetic- semiconductor coupled simulation,” accepted by Circuits and Systems (ISCAS), 2011.

2. S.H. Lo, H. Borouchaki and P. Laug, “Automatic decomposition of discretized surfaces for parallel processing”, PARENG2O 11: The Second International Conference on Parallel, Distributed, Grid and Cloud Computing for Engineering to be held in Ajaccio, Corsica, France, 12-15 April 2011.

3. Zu-Hui MA, Li-Jun JIANG, Zhi-Guo QIAN, Mao-Kun LI, and Weng Cho CHEW, “Solving Low Frequency Electromagnetic Problems With EPA And A-EFIE”, 2010 AP-RASC

4. Edmund Y. Lam, “Regularization in inverse lithography: Enhancing manufacturability and robustness to process variations,” in China Semiconductor Technology International Conference (CSTIC), March 2010. Published in ECS Transactions, Vol. 27, No. 1, pp. 427-432, March 2010.

5. Zhi-Guo Qian, Mao-Kun Li, Zu-Hui Ma, Li-Jun Jiang, Weng Cho Chew, “Solving multi-scale low frequency electromagnetic problems”, EuCAP2010, April 2010

6. Ningning Jia and Edmund Y. Lam, “Performance analysis of pixelated source-mask optimization for optical microlithography,” in IEEE International Conference on Electron Devices and Solid-State Circuits, December 2010.

7. Lining Zhang, Mansun Chan and Frank He, “The Impact of Device Parameter Variation on Double Gate Tunneling FET and Double Gate MOSFET”, Accepted for presentation in the 2010 IEEE International Conference on Electronic Device and Solid-State Circuits, December 15-17, Hong Kong

8. Ningning Jia and Edmund Y. Lam, “Stochastic gradient descent for robust inverse photomask synthesis in optical lithography,” in IEEE International Conference on Image Processing, pp. 4173-4176, September 2010.

9. Yijiang Shen, Ngai Wong, and Edmund Y. Lam, “Aberration-aware robust mask design with level-set-based inverse lithography,” in Photomask and Next-Generation Lithography Mask Technology, volume 7748 of Proceedings of the SPIE, pp. 77481U, April 2010.

10. Y. P. Chen, J. L. Xiong, and W. C. Chew, “Fast and Broadband Simulation of Large-scale Microstrip Structures,” Progress in Electromagnetics Research Symposium, 2010, Xi’an, China.

11. Yang G. Liu, Weng Cho Chew, Li Jun Jiang and Zhi Guo Qian, “A memory saving vector fast multipole algorithm for solving the augmented EFIE (invited)”, pp. 140-143, URSI Commission B International Symposium on Electromagnetic Theory, August, 2010.

12. Yang G. Liu and Weng Cho Chew, “A vector fast multipole algorithm for low frequency problems”, pp. 728-731, URSI Commission B International Symposium on Electromagnetic Theory, August, 2010.

Journal papers:

 

1. Y.P. Chen, L. Jiang, Z.G. Qian, and W.C. Chew, “An augmented electric field integral equation for layered medium Green’s function,” IEEE Trans. Antennas Propagat., vol. 59, no. 3, pp. 960-968, March, 2011.

2. Y.P. Chen, J.L. Xiong, and W. C. Chew, “A mixed-form thin-stratified medium fast-multipole algorithm for both low and mid-frequency problems,” IEEE Trans. Antennas Propagat., vol. 59, no. 6, pp. 2341-2349, June, 2011.

3. Quan Chen, Wim Schoenmaker, Peter Meuris and Ngai Wong, “An effective formulation of coupled electromagnetic-TCAD simulation for extremely high frequency onwards,” IEEE Trans. Computer-Aided Design of Integrated Circuits and Systems, Vol. 30, No. 6, pp. 866-876, 2011.

4. S.Z. Wen, S.K. Koo, C.Y. Yam, X. Zheng, Y.J. Yan, Z.M. Su, K.N. Fan, L. Cao, W.P. Wen, and G.H. Chen, “Time-dependent current distributions of a two-terminal carbon nanotube-based electronic device”, Journal of Physical Chemistry B, Vol. 115, No. 18, pp. 5519-5525, 2011.

5. C.Y. Yam, G.H. Chen, Y. Wang, Th. Frauenheim and T. Niehaus, “Time-dependent versus static quantum transport simulations beyond linear response” Physical Review B, Vol. 83, No. 24, 245448, 2011.

6. Yang G. Liu, Weng Cho Chew, Li Jun Jiang and Zhi Guo Qian, “A Memory Saving Fast A-EFIE Solver for Modeling Low-Frequency Large Scale Problems”, Accepted by Applied Numerical Mathematics, 2010.

7. Yang G. Liu and Weng Cho Chew, “A Low Frequency Vector Fast Multipole Algorithm with Vector Addition Theorem”, Communications in Computational Physics, Vol. 8, No. 5, pp. 1183-1207, November 2010.

8. P.R. Atkins and W.C. Chew, "Fast computation of the dyadic green's function for layered media via interpolation," IEEE Antennas Wireless Propag. Lett., Vol. 9, pp. 493-496, 2010.

9. X. Zheng, G.H. Chen, Y. Mo, S.K. Koo. H. Tian, C.Y. Yam and Y.J. Yan, “Time-dependent density functional theory for quantum transport”, Journal of Chemical Physics, Vol. 133, 114101, 2010. *Top 20 Most Downloaded Articles in September 2010*

10. Edmund Y. Lam and Alfred K. Wong, “Nebulous hotspot and algorithm variability in computation lithography” Journal of Micro/Nanolithography, MEMS, and MOEMS, 9, 033002, 2010.

11. Ningning Jia and Edmund Y. Lam, “Machine learning for inverse lithography: Using stochastic gradient descent for robust photomask synthesis,” Journal of Optics, 12, 045601, 2010.

12. J.L. Xiong, M.S. Tong, P. Atkins, and W.C. Chew, "Efficient evaluation of casimir force in arbitrary three-dimensional geometries by integral equation methods," Physics Letter A, Vol. 374, pp. 2517-2520, 2010.

13. Junfeng Dai, Hai-Zhou Lu, C. L. Yang, Shun-Qing Shen, Fu-Chun Zhang, and Xiaodong Cui, “Magnetoelectric Photocurrent generated by direct interband transition in InGaAs/InAlAs two dimensional electron gas”, Physical Review Letters, 104, 246601, 2010.