Acquisition of In Situ and Operando Capabilities in Transmission Electron Microscopy for Materials R&E
Abstract
In situ and operando characterization of materials and processes inside the transmission electron microscope (TEM) is considered to be the next frontier in materials research. This is enabled by innovation in TEM specimen holders that allow such in situ and operando experiments, leading to unprecedented insights into materials phenomena. The acquisition of two TEM specimen holders, one for atmospheric-gas (A-G) in situ observations, and the other for electrical-biasing (E-B) operando observations, is proposed. This will not only enable critical materials-research experiments but also will enhance significantly the state-of-the-art electron microscopy (EM) capabilities at Brown University. The A-G TEM holder is very versatile, and it will allow in situ TEM observation of interaction between a wide variety of materials (nanoparticles, nanowires, thin films) and a broad range of gases (air, oxygen, argon, mixture, etc.) that are stagnant or flowing. The pressure range is up to atmospheric pressure, and the temperature range is 25 to 800 ?C. This is enabled by containing the material and the gas in an electron-transparent cell, with gas-flow control and a heating chip, isolated from the vacuum of the TEM electron-beam column. The E-B TEM holder is also very versatile, and it will allow operando TEM observations of a wide range of active materials (nanoparticles, nanowires, thin films) under electrical field. This is enabled by specially designed chips with multiple electrodes integrated into the E-G holder. Both the A-G and the E-B holders are low-profile, and as such, they will allow scanning TEM (STEM) imaging. In addition, they will also allow the use of energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) inside the TEM for site-specific, high-resolution chemical composition analyses at the nanoscale in real-time during in situ and operando observations. This added in situ and operando capability will benefit a wide range of projects at Brown University, in particular a current project funded by the Office of Naval Research (ONR; No. N00014-17-1-2232; Program Manager: Billy Short, Code 30) pertaining to the emerging thin-film perovskite solar cells (PSCs). PSCs have topped 22% power conversion efficiency, rivalling that of commercial Si-based PVs, and have the advantage of being solution-processed at near room temperature. Their lightweightness, flexibility, and portability are attractive for potential application in distributed and individualized power supply for the military. However, the polycrystalline thin films made of hybrid organic-inorganic perovskites (HOIPs), which are at the heart of PSCs, undergo degradation in ambient atmosphere. Furthermore, significant electric-field-induced migration of ions occurs in HOIP thin films, which also leads to their instability. Thus, the main objectives of the ONR project are to understand the role of grain boundaries (GB) in the environmental degradation and ion-migration of polycrystalline HOIPs, and to mitigate that degradation through design of novel GB structures. The proposed A-G and E-B TEM specimen holders will be extremely beneficial in meeting those objectives. The A-G TEM holder will be used to study the effect of ambient-air, oxygen, and argon (inert) environments on the degradation behavior of various HOIP compositions and microstructures inside the TEM, as a function of temperature. The E-B TEM holder will allow us to monitor ion-migration operando inside the TEM using EDS/EELS at the nanoscale, as a function of electrical bias in HOIP thin films of different compositions and microstructures. A comprehensive education and training program is proposed, one aimed at graduate students and postdoctoral researchers. This program will have the elements of coursework, educational projects, training by technical staff, and training by “super users.”
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 10, 2018
- Source ID
- N000141812311
Entities
People
- Nitin P Padture
Organizations
- Brown University
- Office of Naval Research
- United States Navy