Our research covers a wide range of topics, focused on nano and atomic scale measurements and in-situ electron and scanning probe microscopy. The materials we study include perovskite ferroelectrics, catalysts, metals, and metal organic frameworks. We also do technique development for vibrational electron energy loss spectroscopy (EELS) and four-dimensional scanning transmission electron microscopy (4D STEM). Current research topics are described briefly below, please visit the research project pages for more details.
Pan Group is also part of the Center for Complex and Active Materials (CCAM), an NSF MERSEC at UCI. Research at the CCAM is focused on creating chemically complex hard materials and bio-inspired dynamic soft materials with superior properties and performance.
Four-dimensional scanning transmission electron microscopy (4D STEM)
4D STEM is an emerging technique in electron microscopy where an entire electron diffraction pattern is collected for every position of the scanning probe. This has only become possible for the last 10 years with the advent of commercially available fast electron detection cameras. A wide variety of properties structural, electronic, and magnetic properties can be studied with 4D STEM. We focus on studying the electric field and charge density in nanostructured thin films. More details
Vibrational Microscopy
Vibrational microscopy focuses on the study of lattice vibrations (phonons) in materials which are important in determining their thermal and electrical conductivity. By combining aberration-correction and monochromation, STEM can provide better spatial resolution than any other technique or probing the vibrational structure of materials. More details
Ferroelectrics and Multiferroics
Oxide heterostructures exhibit a variety of unique physical phenomena due to their additional degrees of freedom compared to conventional semiconductor materials. Ferroelectric oxide material are characterized by a spontaneous electric polarization, which can be reoriented with an applied electric field. We study the fundamental physics of ferroelectric heterostructures, domain walls, and other nanostructures using transmission electron microscopy techniques, including atomic resolution imaging, 4D STEM, vibrational EELS, and in-situ TEM. We have collaborations with many synthesis groups to provide us with cutting edge films including freestanding films and superlattices. More details
Catalysis
The field of catalysis encompasses many different types of hard materials ranging from supported single atoms to unsupported nanoparticles for use in many different types of reactions and environments. Electron microscopy can be used to image many different processes such as the formation, catalytic behavior and dynamics, and degradation mechanisms at high spatial and/or temporal resolution, giving information about the atomic structure, coordination, and local environment of the catalyst. Further characterization of catalysts using spectroscopy inside the microscope provide information about the composition, elemental distribution, and electronic structure. We have collaborations with many synthesis groups to provide us with a variety of catalysts for investigation. More details
Grain Boundary Structure and Dynamics
The properties of polycrystalline materials are greatly influenced by their grain boundary networks. Understanding of the evolution of the grain boundary network (e.g. during thermomechanical processing or during exposure to extreme environments) is therefore necessary to accurately model the material’s performance, as-made and across its lifetime. Electron microscopy can be used to characterize the structure of grain boundaries, and in situ techniques can be used to observe the motion of the defects responsible for grain boundary migration. More details
Solid Electrolyte Battery Material
Batteries are critical components of all mobile electronics and are increasingly being applied for grid level energy storage. The basis of any battery lies in the materials used for the anode and cathode. Electron microscopy can offer key insights into the structure-property relationships of anode/cathode materials through high resolution imaging and in-situ studies. More details