2024-06-28 ロスアラモス国立研究所(LANL)
＜関連情報＞
- https://discover.lanl.gov/news/0627-atomically-thin-materials/
- https://pubs.acs.org/doi/10.1021/acsnano.4c02996
四次元走査透過電子顕微鏡によるエピタキシャルWSe2の熱膨張係数の直接測定 Direct Measurement of the Thermal Expansion Coefficient of Epitaxial WSe2 by Four-Dimensional Scanning Transmission Electron Microscopy
Theresa M. Kucinski, Rohan Dhall, Benjamin H. Savitzky, Colin Ophus, Rijan Karkee, Avanish Mishra, Enkeleda Dervishi, Jung Hoon Kang, Chul-Ho Lee, Jinkyoung Yoo, and Michael T. Pettes
ACS Nano Published:June 27, 2024
DOI:https://doi.org/10.1021/acsnano.4c02996
Abstract
Current reports of thermal expansion coefficients (TEC) of two-dimensional (2D) materials show large discrepancies that span orders of magnitude. Determining the TEC of any 2D material remains difficult due to approaches involving indirect measurement of samples that are atomically thin and optically transparent. We demonstrate a methodology to address this discrepancy and directly measure TEC of nominally monolayer epitaxial WSe2 using four-dimensional scanning transmission electron microscopy (4D-STEM). Experimentally, WSe2 from metal–organic chemical vapor deposition (MOCVD) was heated through a temperature range of 18–564 °C using a barrel-style heating sample holder to observe temperature-induced structural changes without additional alterations or destruction of the sample. By combining 4D-STEM measurements with quantitative structural analysis, the thermal expansion coefficient of nominally monolayer polycrystalline epitaxial 2D WSe2 was determined to be (3.5 ± 0.9) × 10–6 K–1 and (5.7 ± 2) × 10–5 K–1 for the in- and out-of-plane TEC, respectively, and (3.6 ± 0.2) × 10–5 K–1 for the unit cell volume TEC, in good agreement with historically determined values for bulk crystals.
