Intercalation in 2D nanomaterials for heterostructures with tunable materials properties
Abstract
The objective of the proposed work is to use intercalation as a means to control the structure and properties of transition metal dichalcogenide (TMD) nanostructures and as a probe to understand the van der Waals forces and stresses induced by local defects in two-dimensional (2D) materials. Three aims are proposed to achieve the objective. Aim 1: Fundamental understanding of intercalation-induced phase transition in 2D TMDs and investigation of corresponding changes in material properties due to the phase transition. Aim 2: Intercalation as a means to construct a stack of TMD monolayers that amplify desirable monolayer properties while simultaneously providing encapsulation. Aim 3: Intercalation as a probe to understand van der Waals forces and effects of defects on material properties via in situ transmission electron microscopy (TEM) studies of intercalant diffusion dynamics. Two scientific approaches will be employed to achieve the proposed aims. First, a nanodevice will be used as an electrochemical micro-reactor to perform intercalation electrochemically, which allows precise control of the intercalant concentration and simultaneous, in situ monitoring of structural and property changes during intercalation. In situ Raman spectroscopy will be used to monitor structural changes and phase transition while optical and electrical properties will be measured as a function of the intercalant concentration using the nanodevice. Second, in situ TEM will be used to monitor phase transition and intercalant diffusions at the atomic resolution. The intercalant diffusions will be induced by Joule heating and nanosecond voltage pulses. In situ TEM movies of the intercalant diffusion kinetics will be analyzed to infer interactions between Coulomb and van der Waals forces, and to measure directly ionic conductivity and 2D diffusivity of intercalants as a function of the van der Waals gap and the intercalant size. In addition, comparison of the intercalant diffusion kinetics between the pristine region and the defect region will be carried out to quantitatively deduce the stress and strain induced by local and extended defects such as dislocations and grain boundaries. Experimental results will be compared with ab initio band structure calculations and molecular dynamics simulations, in collaboration with theorists. Scientific questions the proposed work aims to answer are as follows. - What is the critical intercalant concentration that induces phase transition in TMDs? - Is intercalation-induced phase transition truly reversible in TMDS without hysteresis? - How will properties of the TMDs continuously change with the intercalant concentration? - What can the intercalant diffusion kinetics tell us about various forces, such as the van der Waals forces and stress induced by defects? The impact of the proposed work is to answer to what extent intercalation can be used as an effective knob for property tuning of TMD nanostructures for practical applications. Scientifically, in situ TEM investigation of intercalant diffusion kinetics around defects will be the first of its kind, generating quantitative data that can be used to build better theoretical tools to capture van der Waals forces and forces related to defects more accurately and predictably.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810367
Entities
People
- Jeeyoung Cha
Organizations
- Army Contracting Command
- United States Army
- Yale University