Research Interests

My current research foci are: (1) Materials for Electronics and Photonics; (2) Adaptive Devices; (3) Materials for Energy Transformation.

Electronic and Optical Materials

Correlated compounds serve as model systems to study interactions among lattice, spin, charge and orbital degree of freedom. Understanding the correlation and phase transition mechanisms in these compounds is paramount for the innovation of next-generation ultrafast and high-efficiency electronic/photonic devices. Exploring the intricate properties and the underlying mechanisms of these compounds require fundamental understanding of design and control of materials growth. Emergence of nanotechnology provides an efficient and powerful tool for engineering the morphology, interface, structure, composition and strain for properties analysis and devices development. Introducing nanostructure to correlated compounds may bring novel properties, as the degree of the interaction between charge and phonon could be greatly manipulated. Specific research topics are exemplified as: thermodynamics of materials growth, driving force of phase transition, doping-driven electronic correlations, and electron-phonon interactions.

Adaptive Electrical/Optical Devices

Unlike conventional semiconductors, in strongly correlated compounds such as nickelates, disorder often induces a drastically nonlinear shift of their electronic conductivity. A tiny amount of foreign dopants or environmental energy fluctuations could leverage a large phase transition. Physically, the increase of synapse weight in neural synapse is manifested by augmentation of the quantity of neurotransmitters and dendritic receptors. Such similarities between disrupted correlated oxides and synapse render them promising candidates in high-efficiency adaptive electronics components. Besides, the extreme sensitivity of nanoscale (e.g., nanowires) correlated oxides to electrical disturbances (e.g., neuron electrical spikes) would make them ideal probes for monitoring and storing neural actions, which is essential for certain emergent psychiatrical therapy methods.

Materials for Energy Transformation

When interfaces are introduced in oxides (especially transition metal oxides), unprecedented electronic properties may emerge due to symmetry breaking. Renewable energy harvesting has attracted increasing attentions due to the increasing economic and environmental costs associated with fossil fuels. Energy storage, as a symbiotic task to energy production, is indispensable for efficient utilization of energy. The sluggish charge transfer dynamics between adjacent oxides or oxides and liquids seriously limits the applications of oxides for energy conversion/storage. Oxides with transition metal ions of unique d-electron filling is revealed to be a favorable material system for high-efficiency oxygen reduction reaction. In rare-earth nickelates, in terms of charge transfer, Ni ions have preferable electron configuration and strong oxygen 2p character which facilitates charge transfer as well. Therefore, the implementation of nickelates in photoelectrochemical water splitting may yield high solar energy conversion efficiency. In addition, introducing ferroelectric/piezoelectric oxides as growth substrates allows us to have additional degree of freedom to probe oxides’ physical properties in an in situ manner, for example, by using electromechanical coupling. Specific research topics include: design and growth of oxides heterostructures, electronic structure tuning in interfaces, electronic structure modification by electron-phonon interactions, transport behaviors of interfaces, charge transfer dynamics between oxides and solution, design and fabrication of transition metal oxides photoelectrochemcal and energy storage devices.

Our Laboratory Equipment

(1) a Customized Atomic Layer Deposition System (MRC 161)

(2) a Customized Pulsed Laser Deposition System (MRC 161)

(3) a Customized RF Sputtering System (MRC 139)

(4) a Customized Chemical Vapor Deposition System (MRC 161)

(5) a Cryogenic Transport Measurement System (MRC 161)

(6) a Cryogenic Optical Stage (MRC 161)

(7) a Customized Ultrafast Optical Spectroscopy (MRC 161)

(8) a Micron Optical Second-harmonic Generation Measurement System (MRC 161)

(9) a High-pressure (200 bar) High-temperature Reactor (MRC 139)

(10) a High-Frequency/High-Voltage Transport Measurement System (MRC 161)

(11) an Electrochemical Measurement System (MRC 161)

(12) a Small Signal Measurement System - SR830 DSP Dual Phase Lock-In Amplifier (MRC 161)

(13) a Supercontinuum Laser (pulse width: 100 ps) (MRC 161)

(14) a 6.5 GHz Network Analyzer (MRC 137)

(15) a High-voltage Supply (20 kV) (MRC 161)

Databases

Quality of Heterostructures by Different Approaches: arxiv, 2019 See Table 1

Space Group Diagrams and Tables: Link

Fourier Analysis of Signals: Link

Crystal Structure Database: Link