Condensed Matter Experiments Group

AFM image, PL/ PLE spectra and theoretical results of self-assembled InGaAs QDs uncapped with GaAs layer

People

Research Activities

1. Characterization of defects in semiconductors (such as SiC, GaN, GaAs and InP) using Positron Annihilation Spectroscopy (PAS) and various conventional optical/electrical techniques. We house a submillimeter diameter positron beam facility operating in UHV condition, and the techniques available include Coincidence Doppler Broadening Spectroscopy, Positron Lifetime Spectroscopy, Deep Level Transient Spectroscopy and Deep Level Optical Spectroscopy..
2. Optical properties, including nonlinear optical properties, electronic structures, electron-phonon interactions, and ultrafast phenomena, in semiconductor nanostructures (e.g., quantum wells, dots and nanocrystals). The laboratory is equipped with variable-temperature (4.2K-300K) photoluminescence system, confocal micro-Raman system combined with a 77K-500K variable-temperature cooler, variable-temperature (10K-330K) broadband (200nm-1700nm) emission/absorption spectroscopy, ultrafast (sub-ps) time-resolved photoluminescence, and the near-field scanning optical microscopy.
3. Characterizations and applications of nanomaterials, such as carbon nanotubes, nanowires and molecular nanostructures, for fundamental physics and potential applications. Facilities include electric probe station, semiconductor parameter analyzer, and confocal microscopic spectroscopy system.
4. Spintronics research on electron spin related phenomenon, particularly spin current generation, detection and manipulation in non-magnetic semiconductors. Electric transport and optical spectroscopy are the major tools to probe the spin related physics.  Facilities include cryostat (4K-300K), electromagnet, and time-resolved Kerr rotation spectroscopy.  
    

Some Representative Publications

Dr. X.D. Cui

1. "Controlling the Energy Level Alignments at SWNT/Au Interfaces", X.D. Cui, M. Freitag, R. Martel, L. Brus and P. Avouris, Nano Letters, 3 (6), 783-787 (2003) 
2. "Changes in the Electronic Properties of a Molecule When It Is Wired into a Circuit", X.D. Cui, J. Thomfor, O.F. Sankey, X. Zarate, A. Primak, A. Moore, T.A. Moore, D. Gust, L. Nagahara and S.M. Lindsay, Journal of Physical Chemistry B, 106 (34), 8609-8614 (2002) 
3. "Making Electrical Contacts to Molecular Monolayers", X.D. Cui, X. Zarate, J. Thomfohr, A. Primak, A.L. Moore, T.A. Moore, D. Gust. G. Harris, O.F. Sankey and S.M. Lindsay, Nanotechnology, 13 (1), 5-14 (2002) 
4. "Bias-induced Forces in Conducting Atomic Force Microscopy and Contact Charging of Organic Monolayers", X.D. Cui, X. Zarate, A. Primak, A. Moore, T.A. Moore, D. Gust, O.F. Sankey, J. Thomfor and S.M. Lindsay, Ultramicroscopy, 92 (2), 67-76 (2002) 
5. "Reliable and Unambiguous Measurement of Conductivity of a Single-molecule", X.D. Cui, J. Thomfor, O.F. Sankey, X. Zarate, A. Primak, A. Moore, T.A. Moore, D. Gust, G. Harris and S.M. Lindsay, Science, 294 (5542), 571-574 (2001) 

For details, please refer to the Homepage of Nanostructure Characterizations Lab.

Prof. S. Fung

1. "Current Transport Property of N-GaN/N-SiC Heterojunction: Influence of Interface States", Y. Huang, X.D. Chen, S. Fung, C.D. Beling, C.C. Ling, X.Q. Dai and M.H. Xie, Applied Physics Letters, 86, 122102-1-3 (2005) 
2. "Memory Effect of Al-Rich AIN Films Synthesized with RF Magnetron Sputtering", Y. Liu, T.P. Chen, P. Zhao, S. Zhang, S. Fung and Y.Q. Fu, Applied Physics Letters, 87, 033112-1-3 (2005) 
3. "A Quantitative Study of the Relationship between the Oxide Charge Trapping over the Drain Extension and the Off-State Drain Leakage Current", J.Y. Huang, T.P. Chen, C.H. Ang, S. Manju and S. Fung, Applied Physics Letters, 85 (18), 4211-4213 (2004) 
4. "Millimeter Positron Focusing Using a Hybrid Lens Design", C.K. Cheung, P.Y. Kwan, Y.Y. Shan, P.S. Naik, H.M. Weng, C.D. Beling and S. Fung, Material Science Forum, 445 446, 465 467 (2004). 
5. "Deep Level Defect in Si-Implanted GaN N+-P Junction", X.D. Chen, Y. Huang, S. Fung, C.D. Beling, C.C. Ling, J.K. Sheu, M.L. Lee, G.C. Chi and S.J. Chang, Applied Physics Letters, 82 (21), 3671-3673 (2003) 
6. "Creation and Suppression of Point Defects through a Kick-out Substitution Process of Fe in InP", Y.W. Zhao, H.W. Dong, Y.H. Chen, Y.H. Zhang, J.H. Jiao, J.Q. Zhao, L.Y. Lin and S. Fung, Applied Physics Letters, 80 (16), 2878-2879 (2002) 
7. "Submillimeter Focusing of the University of Hong Kong Positron Beam", P.Y. Kwan, S. Fung and C.D. Beling, Applied Surface Science, 194, 32 37 (2002). 
8. "On the Possible Identification of Defects Using the Autocorrelation Function Approach in Double Doppler Broadening of Annihilation Radiation Spectroscopy", C.D. Beling, W. Liming, Y.Y. Shan, S.H. Cheung, S. Fung, B.K. Panda and A.P. Seitsonen, Journal of Physics: Condensed Matter, 10, 46, 10475-10492 (1998). 
9. "Deep-Level Traps in the Extended Tail Region of Boron-Implanted N-Type 6H-SiC", M. Gong, C.V. Reddy, C.D. Beling, S. Fung, G. Brauer, H. Wirth and W. Skorupa, Applied Physics Letters, 72, 21, 2739-2741 (1998). 
10. "Positron Deep Level Transient Spectroscopy - a New Application of Positron Annihilation to Semiconductor Physics", C.D. Beling, S. Fung, H.L. Au, C.C. Ling, C.V. Reddy, A.H. Deng and B.K. Panda, Applied Surface Science, 116, 121-128 (1997). 

For details, please refer to the Homepage of Semiconductor and Positron Physics Lab.

Dr. S.J. Xu

1. "Ultrafast Kerr Rotations and Zero-field Dephasing Time of Electron Spins in InAs/GaAs Quantum Disks", J.Q. Ning, S.J. Xu, Z.F. Wei, X.Z. Ruan, Y. Ji, H.Z. Zheng and H.C. Liu, Physics Letters A, in press (2010). 
2. "Influence of Capping Layer and Atomic Interdiffusion on the Strain Distribution in Single and Double Self-assembled InAs/GaAs Quantum Dots", M. Yang, S.J. Xu and J. Wang, Applied Physics Letters, 92, 083112: 1-3 (2008). 
3. "418 cm^-1 Raman Scattering from Gallium Nitride Nanowires: Is it a Vibration Mode of N-rich Ga-N Bond Configuration?", J.Q. Ning, S.J. Xu, D.P. Yu, Y.Y. Shan and S.T. Lee, Applied Physics Letters, 91, 103117: 1-3 (2007). 
4. "Impact of the Cap Layer on the Electronic Structures and Optical Properties of Self-assembled InAs/GaAs Quantum Dots", H.B. Wu, S.J. Xu and J. Wang, Physical Review B, 74, 205329: 1-6 (2006). 
5. "Green Luminescence Band in ZnO: Fine Structures, Electron-phonon Coupling, and Temperature Effect", S.L. Shi, G.Q. Li, S.J. Xu, Y. Zhao and G.H. Chen, Journal of Physical Chemistry B, 110, 10475-10478 (2006). 
6. "Quantum Dissipation and Broadening Mechanisms due to Electron-phonon Interactions in Self-formed InGaN Quantum Dots", S.J. Xu, G.Q. Li, Y.J. Wang, Y. Zhao, G.H. Chen, D.G. Zhao, J.J. Zhu, H. Yang, D.P. Yu and J.N. Wang, Applied Physics Letters, 88, 083123: 1-3 (2006). 
7. "Efficient Multiphoton-absorption-induced Luminescence in Single-crystalline ZnO at Room Temperature", D.C. Dai, S.J. Xu, S.L. Shi, M.H. Xie and C.M. Che, Optics Letters, 30, 3377-3379 (2005). 
8. "Resonant Coupling of Bound Excitons with LO Phonons in ZnO: Excitonic Polaron States and Fano Interference", S.J. Xu, S.J. Xiong and S.L. Shi, The Journal of Chemical Physics, 123, 221105: 1-5 (2005).

For details, please refer to the Homepage of Laser Spectroscopy Lab.