AI Article Synopsis
- Current reports on the thermal expansion coefficients (TEC) of 2D materials show significant variation, largely due to the challenges in directly measuring these properties of ultra-thin and transparent samples.
- The study introduces a new methodology using four-dimensional scanning transmission electron microscopy (4D-STEM) to directly measure the TEC of monolayer WSe during controlled heating from 18-564 °C.
- The results indicate specific TEC values for WSe that align well with historical data for bulk crystals, providing improved clarity in understanding thermal properties of 2D materials.
Article 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 WSe using four-dimensional scanning transmission electron microscopy (4D-STEM). Experimentally, WSe 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 WSe was determined to be (3.5 ± 0.9) × 10 K and (5.7 ± 2) × 10 K for the in- and out-of-plane TEC, respectively, and (3.6 ± 0.2) × 10 K for the unit cell volume TEC, in good agreement with historically determined values for bulk crystals.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC11238620 | PMC |
| http://dx.doi.org/10.1021/acsnano.4c02996 | DOI Listing |
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