Research Interests
The eternal mystery of the world is its comprehensibility ------- Albert Einstein
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Our world is made of matter, while the matter is dynamic. The basic microscopic structures and related dynamic fashion of matters determine their physical and chemical properties and thus the potential applications. For example, series of physical and chemical changes occur in the microscopic structures of the energy and information materials during their functions, including the morphology change, phase transition, charge transfer, and valance variation etc.. Most of these dynamics occur on the femtosecond (fs, 10^-15 s) to nanosecond (ns, 10^-9 s) time scale. Therefore, direct imaging and visualization of the transient atomic structures, the transport, interaction and inter-conversion dynamics of different energy carriers including electrons, holes, excitons, phonons, polarons, magnons and photons etc., on the ultrafast timescales are vital for understanding and improving the physical and chemical properties of energy and information materials for their applications in modern energy and information science, but still rather technically challenging. Moreover, direct visualization and recording of atomic and electronic motions as well as molecular dynamics in real space and time is always one of scientists' greatest aspirations. Alongside ultrafast X-ray techniques, transient optical spectroscopy, and conventional electron microscopy (EM), four-dimensional ultrafast electron microscopy (4D UEM, pioneered by the Nobel Laureate Prof. Zewail group in 2005 at Caltech) combing the atomic spatial resolution of EM and the fs time resolution of ultrafast laser provides unprecedented spatiotemporal resolution and unlimited potential for yielding unheard-of insights into the rapid physical, chemical and biological dynamical processes.
Our research interests are to invoke several key advanced technologies including the state-of-the-art electron microscopy, ultrafast fs lasers, and ultrafast optoelectronic techniques to develop a new-generation 4D UTEM, 4D USEM and 4D TRCL techniques with unprecedented spatiotemporal resolution for probing transient structures and nanoscale energy carrier transport/interaction dynamics in energy and information materials to advance their applications.
1. 4D UTEM for probing ultrafast dynamics in functional nanomaterials
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Developing innovative in-situ 4D UTEM techniques, including in-situ direct electron imaging, Lorentz phase imaging, electron diffraction, tomography, holography and EELS etc.
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Ultrafast dynamics of structural phase transition, energy transfer, charge transfer, electron-phonon, electron-photon interaction in energy and information nanomaterials;
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Ultrafast magnetization dynamics in functional magnetic systems, such as magnetic vortex, skyrmion and magnon etc.
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​In-situ study of structure and carrire dynamical process in photocatalytic reactions;
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Evanescent surface plasmon in nanostructures and interference dynamics;
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Quantum interaction between optical near field and free electrons.
For more information and knowledge of 4D UTEM, please refer to the following review articles:
1) Four-Dimensional Electron Microscopy
2) 4D Electron Microscopy: Principles and Applications
3) Attomicroscopy: from femtosecond to attosecond electron microscopy
4D UTEM system and working mechanism
2. 4D USEM and 4D TRCL for probing ultrafast exciton and carrier dynamics in functional nanomaterials
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Developing innovative in-situ 4D USEM technique combining with a four-dimensional ultrafast time-resolved cathodoluminescence (4D TRCL) ;
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Ultrafast energy carrier transport and interaction dynamics in functional optoelectronic nanomaterials and nanodevices, including nano-semiconductors, 2D materials, perovskites etc.;
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Ultrafast excition and polariton dynamics in low-dimensional optoelectronic materials for applications in photovoltaics and optical sensing.
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For more information and knowledge of 4D USEM, please refer to the following review article:
1) Scanning ultrafast electron microscopy
4D USEM system and working mechanism
3. Static cathodoluminescence and photoluminescence for probing fine electronic structures and optical properties of semiconducting nanostructures.
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​Developing high spatial resolution static cathodoluminescence and photoluminescence with low temperature capabilities;
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Investigation of multiple external fields (eg. elastic strain field and electrific field etc.) coupling effect on the electronic structures and optical properties of nanostructural semiconductors as well as their applications in optoelectronic devices;
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Tailoring electronic structure and optoelectronic properties of low dimensional semiconductors by elastic strain engineering and application in optoelectronic devices.
​High spatial resolution cathodoluminescence