Evidence of shallow band gap in ultrathin 1T′−MoTe2 via infrared spectroscopy
| Autor: | Sangyun Lee, Jin Cheol Park, Jungseek Hwang, Eilho Jung, Young Hee Lee |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Physics
Dc resistivity Band gap Doping Infrared spectroscopy 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Crystallography symbols.namesake Lithium intercalation Phase (matter) 0103 physical sciences symbols van der Waals force 010306 general physics 0210 nano-technology |
| Zdroj: | Physical Review B. 101 |
| ISSN: | 2469-9969 2469-9950 |
| DOI: | 10.1103/physrevb.101.235434 |
| Popis: | Although van der Waals (vdW) layered $\mathrm{Mo}{\mathrm{S}}_{2}$ shows the phase transformation from the semiconducting $2H$ phase to the metallic $1T$ phase through chemical lithium intercalation, vdW $\mathrm{MoT}{\mathrm{e}}_{2}$ is thermodynamically reversible between the $2H$- and $1{T}^{\ensuremath{'}}$ phases, and can be further transformed by energetics, laser irradiation, strain or pressure, and electrical doping. Here, thickness- and temperature-dependent optical properties of $1{T}^{\ensuremath{'}}\text{\ensuremath{-}}\mathrm{MoT}{\mathrm{e}}_{2}$ thin films grown by chemical vapor depsition are investigated via Fourier-transformed infrared spectroscopy. An optical gap of $28\ifmmode\pm\else\textpm\fi{}\phantom{\rule{4pt}{0ex}}2$ meV in a three-layer (or 2-nm)-thick $1{T}^{\ensuremath{'}}\text{\ensuremath{-}}\mathrm{MoT}{\mathrm{e}}_{2}$ is clearly observed at a low-temperature region below 50 K. No discernible optical band gap is observed in samples thicker than \ensuremath{\sim}4 nm. The observed thickness-dependent band-gap results agree with the measured dc resistivity data; the thickness-dependent $1{T}^{\ensuremath{'}}\text{\ensuremath{-}}\mathrm{MoT}{\mathrm{e}}_{2}$ clearly demonstrates the metal-semiconductor transition at a crossover below the 2-nm-thick sample. |
| Databáze: | OpenAIRE |
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