Research
Our laboratory studies the relationship between atomic structure and physical properties in surfaces, two-dimensional materials, quasi-one-dimensional materials, and their heterostructures. Such materials exhibit interesting low-dimension physics such as charge density wave states. Furthermore, we use molecular beam epitaxy technique, thermal treatment, intercalation, to form a variety of defect structures or new (metastable) phases. Our main tools are ultrahigh-vacuum scanning tunneling microscopy and spectroscopy at low temperature, which allows us to investigate atom-scale structure and electronic properties. With two TMD molecular beam epitaxy systems, we can prepare many kinds of samples and they are studied through in-situ transfer without cotaminations. We could also use portable suitcases to deliver samples overseas. Our research thus deepens the understanding of structure-property correlations in 2D quantum materials.
Low-dimensional materials often host electronic phases that are extremely sensitive to atomic structure, defects, interfaces, strain, symmetry, and dimensionality. Our goal is to directly visualize these microscopic ingredients and connect them to electronic behavior and emergent collective phenomena.
By combining sample growth, atomic-scale imaging, local spectroscopy, and close collaboration with theory and complementary experiments, we aim to understand how material properties can be designed and controlled from the atomic scale upward.
We use scanning tunneling microscopy and spectroscopy to probe surfaces and low-dimensional materials with atomic spatial resolution and local electronic sensitivity. These measurements allow us to examine atomic defects, domain boundaries, charge ordering, interface states, and spatial variations of electronic structure. We also do instrumentation development. A patented radio-frequency reflectometry microscope is developed in house.
A major focus of the group is two-dimensional materials, especially transition-metal dichalcogenides and Xenes (germanene). We are interested in how heterostructures, stacking, defects, lattice mismatch, and symmetry breaking modify electronic states and collective phases.
Molecular beam epitaxy provides a controlled route to prepare atomically thin films, interfaces, and heterostructures under well-defined ultrahigh-vacuum conditions. We use growth control as a tool to create model systems for atomic-scale structural and spectroscopic studies. The samples thus grown do not only help our own research, but are the materials used in two international reserach projects (Taiwan-US, Taiwan-France)
We study quasi-one-dimensional materials, mainly transition-metal trichalcogenides, where reduced dimensionality can enhance electronic instabilities, anisotropic behavior, and charge dnesity wave (CDW) transport properties.
Charge density waves and related symmetry-broken states are central themes in our research. We investigate how lattice structure, defects, dimensionality, and interfaces influence charge ordering and how these changes connect to electronic and transport properties.
We seek to establish direct correlations between local atomic structure and material properties. This includes connecting surface morphology, defects, domain structures, heterointerfaces, and spectroscopic signatures to macroscopic or complementary measurements. Often, our experiments use thermal procedure, intercalation, or other surface functionalization methods to create new structures.
1. 3D alkali intercalation in TMD materials
2. Correlation of CDW and intercalation
3. Group IV, V TMD heterostructure and their thermal stability
4. 1D long range stacking fault lines in TMD materials
5. Microscopy and preparation (under UHV) of TMD Janus monolayers
6. CDW phases in TMD heterostructure
7. quasi-1D NbS3 CDW and its correlation to defect structures
8. (through collaboration) THz-STM studies of CDW materials and nanofabrication.
Many questions in low-dimensional quantum materials require multiple experimental and theoretical perspectives. Our laboratory actively collaborates with researchers specializing in computation, spectroscopy, and optical characterization.
Collaboration with density functional theory experts helps us interpret atomic structures, electronic states, defect energetics, and interface-driven phenomena observed in STM/STS.
Angle-resolved photoemission spectroscopy provides momentum-resolved electronic structure information that complements our local real-space and spectroscopic measurements.
Raman, photoluminescence, and related optical measurements provide additional information on vibrational modes, excitonic response, strain, defects, and layer-dependent properties.
Our group has maintained active international collaborations through joint research projects, exchange activities, and collaborative studies of two-dimensional and low-dimensional materials.
We are currently involved in Taiwan-France international research activities through the ENTER2D project, focusing on emergent phenomena in two-dimensional materials and related heterostructures.
We also participate in Taiwan-US collaborative research supported through a Taiwan-AFOSR grant, linking our surface science and low-dimensional materials studies with broader international research efforts.
Previous collaborative projects include several ORCHID projects and an ANR-MOST Taiwan-France project, which supported international collaboration and exchange in related research directions.
Previous collaboration on quasi-1D materials.