Experimental Condensed Matter and Material Science Group

I. Experimental Condensed Matter


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

People

Academic staff

Research staff

Students

Prof. Xiaodong CUI
Dr. D.K. Ki
Prof. Shijie XU
Dr. Sihong LI
Dr. Tengfei YAN
Dr. Bairen ZHU
Mr. Yitian BAO (PhD)
Mr. Chi Ming KAN (MPhil)
Mr. Xiangzhou LAO (PhD)
Mr. Dian LI (PhD)
Mr. Qiye LIU (PhD)
Mr. Xiaorui WANG (PhD)
Mr. Xiong WANG (PhD)
Ms. Chengrong WEI (PhD)
Mr. Ke XIAO (PhD)
Mr. Siyuan YANG (PhD)

 

Research Activities

The facilities of the experimental condensed matter group consists of a number of experimental laboratories, carrying out concerted research in various fields of condensed matter physics, including the key areas below:

  1. Experimental Solid State Physics (X.D. Cui)
    The emphasis of this research lab is on characterizations and applications of low dimensional materials, particularly emerging low dimensional semiconductors. Recently we focus on optical properties of atomic 2 dimensional (2D) crystals, particularly atomic layers of transition metal dichalcogenides (TMD). We explore the interplay of electron’s spin, valley degrees of freedom and electron-electron interactions with semiconductor optics techniques.
     
  2. Quantum Nanoelectronic Devices (D.K. Ki)
    We investigate quantum transport phenomena in various nano-electronic devices, realized by using state-of-art nano-fabrication and engineering techniques—the techniques that include electron-beam lithography, metal depositions and etching, micro-manipulation of atomically thin crystals and more. Materials of current interest are graphene and emerging 2D crystals, topological materials, and artificial heterostructures, and we take various experimental routes (e.g., rotating magnetic fields, inducing strain, etc) to discover or engineer new quantum effects in these systems. Since these effects are often fragile against finite temperature and electrical noises (e.g., fractional quantum Hall effect), we also implement cryogenic and low-noise measurement techniques. Throughout the investigation, we aim to understand and learn to control the underlying physical processes as it not only expands our view of electronic materials but also brings us one-step closer to the realization of new device applications that fully harness the quantum nature of electrons in solids. In this context, we are currently focusing on the topics below:
          (1) Quantum transport in graphene and 2D materials
          (2) ‘Designer’ electronic heterostructures and interfaces
          (3) New topological states of matter


    More details can be found at http://www.physics.hku.hk/~dkkilab/

  3. Novel Optical Properties of Semiconductor Nanostructures (S.J. Xu)
    Optical properties including nonlinear optical properties, electronic structures, electron-phonon interactions, ultrafast phenomena, phonon and defect states in new semiconductor nanostructures such as self-assembled quantum dots, nanocrystals and new two-dimensional transition metal dichalcogenides are our current research interests. In addition, optoelectronic device applications of the semiconductor nanostructures are also our research interest. The materials being investigated by us include III-nitrides, SiC, traditional III-V and II-VI compound semiconductors as well as new 2D transition metal dichalcogenides. The laboratory has been already equipped by variable-temperature (4.2 K-300 K) photoluminescence system, scanning confocal micro-Raman image/spectroscopy system, variable-temperature (10 K-330 K) broadband (200 nm-1700 nm) emission/absorption/reflection spectroscopy, pump-probe based ultrafast (sub-ps) and gated integrator + boxcar averager based (20 ns to ms) time-resolved photoluminescence system, and newly-established low-temperature magneto-photoluminescence spectroscopy with super high spectral resolution. Currently, a pump-probe based fs laser source + scanning confocal microscopy system is being implemented by us, which enables us optically investigate ultrafast quantum processes and even imagine such processes occurring in individual semiconductor nanostructures.

    Further information of the group can be found at http://www.physics.hku.hk/~laser.
     

II. Materials Science


Transient setup and GaN:Co surface

People

Academic staff

Research staff

Students

Prof. Aleksandra B. DJURIŠIĆ
Dr. Francis C.C. LING

Prof. Mao Hai XIE

Mr. Waqar AZEEM
Dr. Fangzhou LIU
Dr. Caiqin LUO

Mr. Wei CHEN (PhD)
Ms. Yawei DAI (PhD)
Mr. Lok Ping HO (PhD)
Ms. Xiaoqing HU (PhD)
Mr. Dong HUANG (PhD)
Mr. Yuanjun JIN (PhD)
Mr. Tik Lun LEUNG (MPhil)
Mr. Jingyang LIN (PhD)
Mr. Ze MEN (MPhil)
Mr. Rashid RASHAD (PhD)
Miss Yingli Shi (PhD)
Miss Wenting SUN (MPhil)
Mr. Ho Won TAM (PhD)
Mr. Hao TIAN (PhD)
Ms. Jian WANG (PhD)
Mr. Yantao WANG (PhD)
Mr. Yipu XIA (PhD)
Miss Mengfei YUAN (MPhil)
Ms. Junqiu ZHANG (PhD)
Mr. Yu ZHANG (PhD)

 

Research Activities

The material science group conducts researches of various materials in the form of thin films and nanostructures. Examples include perovskite transition metal oxides, organic-inorganic halide perovskites, transition metal dichalcogenides, wide bandgap semiconductors (ZnO and GaN, for example), topological insulators, organic and inorganic nanocomposites. The techniques involved include various high vacuum deposition systems (e.g., sputtering, thermal and e-beam evaporation, pulse laser ablation, chemical vapor deposition, and molecular-beam epitaxy), low temperature and high B field measurement facility, x-ray and electron diffraction, scanning probe microscopy, photoelectron and Auger electron spectroscopy, temperature dependent Hall, IV and CV measurements, UV/Vis/NIR spectrometers, etc.

  1. Optoelectronics and Nanomaterials  (A.B. Djurišić)
    The research activities include fabrication and characterization of organic and organic/inorganic optoelectronic devices (organic light emitting diodes and solar cells), as well as fabrication and characterization of wide band gap semiconductor nanostructures. The laboratory  is  equipped  with fume cupboards, tube furnaces, spin-coater, two thermal evaporators for fabrication of optoelectronic devices, and E-beam/sputtering deposition system, while characterization facilities include UV/Vis/NIR spectrometers for characterization of light emitting diodes and experimental setups for power conversion efficiency and external quantum efficiency measurements for solar cells. The study of optoelectronic devices aims at improving the understanding of the operating principles and processes taking place at interfaces. The obtained results are then used for fabrication of devices with improved performance. The study of wide band gap nanostructures includes comprehensive investigation of influence of the fabrication conditions on structural and optical properties of the nanostructures, and exploring their possible use in energy and environmental applications.
     
  2. Defects characterization and engineering of functional materials  (C.C. Ling)
    The current focused interests of the Material Physics Laboratory include:
    (1) Defects in semiconductors: characterizations and identifications, defects influence on materials electrical, optical and magnetic properties, defect control, defects at semiconductor junctions;
    (2) Electrical and optical properties of semiconductor system: deep level transient spectroscopy, temperature dependent Hall measurement, IV and CV measurements, luminescence spectroscopy;
    (3) Positron annihilation spectroscopic study of vacancy type defects: These research activities are performed with the positron beam line located at the electron LINAC ELBE, Helmoltz Zentrum Dresden Rossendorf, Germany;
    (4) Defects in functional oxides and wide band-gap materials: Tailoring electrical, optoelectronic, and magnetic properties of these materials via defect engineering.
     
  3. Experimental Surface Science (M.H. Xie)
    The surface science laboratory aims at understanding the processes and properties that occur at the boundary of materials - surface.
    Current researches focus on the growth and surface characterizations of low-dimensional materials, such as transition-metal dichalcogenides and their hetero-structures.
    We carry out molecular beam epitaxy (MBE) and surface studies of ultrathin layers MBE is one of the most versatile techniques to grow materials with precise control. It allows fabrication of artificial structures by combining different materials to form the so-called "quantum wells" and "superlattices". Quantum effects and new concepts in material sciences are thus explored for modern device applications. By using STM/S and UPS, we characterize the atomic and electronic structures of film surfaces. The latter are important for the understanding various quantum effects at atomic scale.


Some Representative Publications

(For the complete publication list of the department, please go back to Research.)

 

Prof. X.D. Cui

  1. "Manipulating spin-polarized photocurrents in 2D transition metal dichalcogenides", L. Xie, X. Cui, Proceedings of the National Academy of Sciences, 113, 14, 3746-3750 (2016)
  2. “Anomalously robust valley polarization and valley coherence in bilayer WS2”, B. Zhu, H.L.Zeng, J.F. Dai, Z.R. Gong and X.D. Cui, Proceedings of the National Academy of Sciences of the United States of America (PNAS), 111, 11606-11611 (2014) 
  3. "Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides", H. Zeng, G.B. Liu, J. Dai, Y. Yan, B. Zhu, R. He, L. Xie, S. Xu, X. Chen, W. Yao and X.D. Cui, Scientific Reports, 3, 1068 (2013) 
  4. "Valley polarization in MoS2 monolayers by optical pumping", H.L. Zeng, J.F. Dai, W. Yao, D. Xiao and X.D. Cui, Nature Nanotechnology, 7, 490-493 (2012) 
  5. “Magnetoelectric Photocurrent Generated by Direct Interband Transitions in InGaAs/InAlAs Two-Dimensional Electron Gas”, J.F. Dai, H.F. Lu, C.L. Yang, S.Q. Shen, F.C. Zhang and X.D. Cui; Physical Review Letters, 104, 246601 (2010) 
  6. “Observation of exciton-phonon sideband in individual metallic single-walled carbon nanotubes”, H.L. Zeng, H.B. Zhao, F.C. Zhang and X.D. Cui, Physical Review Letters, 102, 136406 (2009) 


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

Prof. A.B. Djurišić

  1. “Cesium Doped NiOx as an Efficient Hole Extraction Layer for Inverted Planar Perovskite Solar Cells”, W. Chen, F.Z. Liu, X.Y. Feng, A.B. Djurišić, W.K. Chan, Z.B. He, Advanced Energy Materials, 1700722 (2017) 
  2. “Is excess PbI2 beneficial for perovskite solar cell performance?”, F. Z. Liu, Q. Dong, M. K. Wong, A. B. Djurišić, A. Ng, Z. W. Ren, Q. Shen, C. Surya, W. K. Chan, J. Wang, A. M. C. Ng, C. Z. Liao, H. K. Li, K. M. Shih, C. R. Wei, H. M. Su, and J. F. Dai, Advanced Energy Materials, 6, 1502206 (2016)
  3. “Hydrothermally synthesized CuxO as a catalyst for CO oxidation”, M.Y. Guo, F.Z. Liu, J.K. Tsui, A.A. Voskanyan, A.M.C. Ng, A.B. Djurišić, W.K. Chan, K.Y. Chan, C.Z. Liao, K.M. Shih and C. Surya, Journal of Materials Chemistry A, 3, 3627-3632 (2015)
  4. “Mechanisms of Antibacterial Activity of MgO: Non-ROS Mediated Toxicity of MgO Nanoparticles Towards Escherichia coli”, Y.H. Leung, A.M.C. Ng, X.Y. Xu, Z.Y. Shen, L.A. Gethings, M.T. Wong, C.M.N. Chan, M.Y. Guo, Y.H. Ng, A.B. Djurišić, P.K.H. Lee, W.K. Chan, L.H. Yu, D.L. Phillips, A.P.Y. Ma and F.C.C. Leung, Small, 10, 1171-1183 (2014)
  5. “In situ synthesis of CuxO/SnOx/CNT and CuxO/SnOx/SnO2/CNT nanocomposite anodes for lithium ion batteries by a simple chemical treatment process”, X. Liu, F. Z. Liu, Q. Sun, A. M. C. Ng, A. B. Djurišić, M. H. Xie, C. Z. Liao, K. M. Shih,ACS Appl. Mater. & Interfaces , 6, 13478-13486 (2014)

 

Dr. F.C.C. Ling

  1. “Thermal evolution of defects in undoped zinc oxide grown by pulsed laser deposition”, Zilan Wang, Shichen Su, Francis Chi-Chung Ling, W. Anwand, and A. Wagner, J. Appl. Phys., 116, 033508 (2014)
  2. “Impedance analysis of secondary phases in a Co-implanted ZnO single crystal”, M. Younas, L. L. Zou, M. Nadeem, Naeem-ur-Rehman, S. C. Su, Z. L. Wang, W. Anwand, A. Wagner, J. H. Hao, C. W. Leung, R. Lortz, and F. C. C. Ling, Phys. Chem. Chem. Phys., 16, 16030 (2014)
  3. “Low-threshold lasing action in an asymmetric double ZnO/ZnMgO quantum well structure”, S.C. Su, H. Zhu, L.X. Zhang, M. He, L.Z. Zhao, S.F. Yu, J.N. Wang and F. C.C. Ling, Appl. Phys. Lett., 103, 131104 (2013)
  4. “Current transport studies of ZnO/p-Si heterostructures grown by plasma immersion ion implantation and deposition”, X. D. Chen, C. C. Ling, S. Fung, C. D. Beling, Y. F. Mei, Ricky K. Y. Fu, G. G. Siu, Paul K. Chu,Appl. Phys. Lett., 88, 132104 (2006)
  5. “Low energy electron irradiation induced deep level defects in 6H-SiC: The implication for the microstructure of the deep levels E1/E2”, X.D. Chen, C.L. Yang, M. Gong, W.K. Ge, S. Fung, C.D. Beling, J.N. Wang, M.K. Lui and C.C. LingPhys. Rev. Lett., 92, 125504 (2004)


Prof. M.H. Xie

  1. "One-dimensional phosphorus chain and two-dimensional blue phosphorene grown on Au (111) by molecular-beam epitaxy", J.P. Xu, J.Q. Zhang, H. Tian, H. Xu, W.K. Ho, M.H. Xie. Phys. Rev. Mater., 1, 061002(R)(2017)
  2. "Inversion Domain Boundary Induced Stacking and Bandstructure Diversity in Bilayer MoSe2", J.H. Hong, C. Wang, H.J. Liu, X.B. Ren, J.L. Chen, G. Wang, J.F. Jia, M.H. Xie, C.H. Jin, W. Ji, J. Yuan, Z. Zhang, Nano Letter, 17, 11, 6653-6660 (2017)
  3. "Quantum effects and phase tuning in epitaxial hexagonal and monoclinic MoTe2 monolayers”, J. Chen, G.Y. Wang, Y.A. Tang, H. Tian, J. Xu, X.Q. Dai, H. Xu, J.F. Jia, W.K. Ho, M.H. Xie, ACS Nano, 11, 3282 (2017)
  4. “Observation of intervalley quantum interference in epitaxial monolayer tungsten diselenide”, H.J. Liu, J.L. Chen, H.Y. Yu, F. Yang, L. Jiao, G.B. Liu, W.K. Ho, C.L. Gao, J.F. Jia, W. Yao, M.H. XieNat. Comm., 6, 8180 (2015)
  5. “Line and point defects in MoSe2 bilayer studied by scanning tunneling microscopy and spectroscopy”, H.J. Liu, H. Zheng, F. Yang, L. Jiao, J.L. Chen, W.K. Ho, C.L. Gao, J.F. Jia, M.H. Xie, ACS Nano., 9, 6619 (2015)
  6. “Molecular-beam epitaxy of monolayer and bilayer WSe2: a scanning tunneling microscopy / spectroscopy study and deduction of exciton binding energy”, H.J. Liu, L. Jiao, L. Xie, F. Yang, J.L. Chen, W.K. Ho, C.L. Gao, J.F. Jia, X.D. Cui, M.H. Xie, 2D Mater.2, 034004 (2015)
  7. “Dense network of one-dimensional midgap metallic modes in monolayer MoSe2 and their spatial undulations”, H.J. Liu, L. Jiao, F. Yang, Y. Cai, X. Wu, W.K. Ho, C.L. Gao, J.F. Jia, N. Wang, H. Fan, W. Yao, M.H. Xie, Phys. Rev. Lett., 113, 066105 (2014)
  8. “Anisotropic topological surface states on high-index Bi2Se3 films”, Z.J. Xu, X. Guo, M.Y. Yao, H.T. He, L. Miao, L. Jiao, H.C. Liu, J.N. Wang, D. Qian, J.F. Jia, W.K. Ho, M.H. XieAdv. Mater., 25, 1557 (2013)


For details, please refer to the Homepage of Optoelectronics and Nanomaterials Lab.

Prof. S.J. Xu

  1. “Luminescence and thermal behaviors of free and trapped excitons in cesium lead halide perovskite nanosheets”, Xiangzhou Lao, Zhi Yang, Zhicheng Su, Zilan Wang, Honggang Ye, Minqiang Wang, Xi Yao, and Shijie Xu, Nanoscale 10, 9949 (2018)
  2. “Effective Photon Recycling and Super Long Lived Minority Carriers in GaInP/GaAs Heterostructure Solar Cell: A Time-Resolved Optical Study”, Z. C. Su, Shijie Xu, X. H. Wang, J. Q. Ning, Rongxin Wang, Shulong Lu, Jianrong Dong, and Hui Yang, IEEE Journal of Photovoltaics 8, 820 (2018)
  3. “Understanding and manipulating luminescence in carbon nanodots”, Z. C. Su, H. G. Ye, Z. Xiong, Q. Lou, Z. Zhang, F. Tang, J. Y. Tang, J. Y. Dai, C. X. Shan, and S. J. Xu, Carbon 126, 58 (2018)
  4. “Luminescence Anisotropy and Thermal Effect of Magnetic and Electric Dipole Transitions of Cr3+ Ions in Yb: YAG Transparent Ceramic”, Fei Tang, Honggang Ye, Zhicheng Su, Yitian Bao, Wang Guo, and Shijie Xu, ACS Applied Materials & Interfaces 9, 43790 (2017)
  5. “Extinction of the zero-phonon line and the first-order phonon sideband in excitonic luminescence of ZnO at room temperature: the self-absorption effect”, Honggang Ye, Zhicheng Su, Fei Tang, Changcheng Zheng, Guangde Chen, Jian Wang, and Shijie Xu, Science Bulletin 62, 1525 (2017)
  6. “Electroluminescence Probe of Internal Processes of Carriers in GaInP Single Junction Solar Cell”, Z.C. Su, S.J. Xu, R.X. Wang, J.Q. Ning, J.R. Dong, S.L. Lu, and H. Yang, Solar Energy Materials and Solar Cells 168, 201 (2017).
  7. “A generalized model for time-resolved luminescence of localized carriers and applications: Dispersive thermodynamics of localized carriers”, Zhicheng Su and Shijie Xu, Scientific Reports 7, 13 (2017)
  8. “Triplet harvesting in luminescent Cu(I) complexes by thermally activated luminescence mechanism transition: Impact of molecular structure”, Z.C. Su, C.C. Zheng, G. Cheng, C.-M. Che, and S.J. Xu, Journal of Materials Chemistry C, 5, 4488 (2017)
  9. “Excitation Dependent Phosphorous Property and New Model of the Structured Green Luminescence in ZnO”, Honggang Ye, Zhicheng Su, Fei Tang, Mingzheng Wang, Guangde Chen, Jian Wang, and Shijie Xu, Scientific Reports 7, 41460 (2017)
  10. “Carrier Localization Effects in InGaN/GaN Multiple-Quantum-Wells LED Nanowires: Luminescence Quantum Efficiency Improvement and “Negative” Thermal Activation Energy”,Wei Bao, Zhicheng Su, Changcheng Zheng, Jiqiang Ning, and Shijie Xu, Scientific Reports 6, 34545 (2016)
  11. “A set of manganese ions activated fluoride phosphors (A2BF6:Mn4+, A=K, Na, B=Si, Ge, Ti): Synthesis below 0 oC and efficient room-temperature photoluminescence”, F. Tang, Z.C. Su, H.G. Ye, M.Z. Wang, X. Lan, D.L. Philips, Y.G. Cao, and S.J. Xu, Journal of Materials Chemistry C, 4, 9561 (2016)
  12. “Transition of radiative recombination channels from delocalized states to localized states in a GaInP alloy with partial atomic ordering: a direct optical signature of Mott transition?”, Z. C. Su, J. Q. Ning, Z. Deng, X. H. Wang, S. J. Xu, R. X. Wang, S. L. Lu, J. R. Dong, and H. Yang, Nanoscale, 8, 7113-7118 (2016)


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

Last updated on 10 September 2018