Abstract
Two-dimensional materials exhibit great potential for high-performance electronics applications and the knowledge of their thermal properties is extremely necessary, since they are closely related to efficient heat dissipation and electron-phonon interactions. In this study we report the temperature-dependence of the out-of-plane A1g Raman mode of suspended and supported CVD-grown single-crystalline tungsten diselenide (WSe2) monolayer. The A1g phonon wavenumber is linearly red-shifted for temperature ranging from 98 to 513 K, with first-order temperature coefficients β of -0.0044 and -0.0064 cm−1/K for suspended and supported monolayer WSe2, respectively. The higher β module value for supported sample is attributed to the increase of the phonon anharmonicity due to the phonon scattering with the surface roughness of the substrate. Our analysis of the temperature-dependent phonon dynamics reveal the influence of the substrate on thermal properties of monolayer WSe2 and provide fundamental information for developing of atomically-thin 2D materials devices.
Highlights
WSe2 exhibits an electronic band structure similar to its sulfide counterpart, i.e. it experiences an indirect-to-direct band gap transition as the crystal is reduced from bulk to monolayer.18,19 The unique band structure along with the reduced dimensionality of few-layer WSe2 enables atomically thin systems to display numerous novel phenomena, such as pronounced photoluminescence and the manipulation of the valley degrees of freedom of charge carries.18,20,21 The strong light-matter interactions observed in WSe2 thin layers make them excellent candidates to be used in optoelectronic circuits.22–24 All these remarkable electronic properties are related to the thermal characteristics and an efficient heat dissipation is necessary to reach high-performance on electronic devices
In order to understand the vibrational properties of transition metal dichalcogenides (TMDs), it is important to correlate them with the phonon transport and the electron-phonon interactions, which can determine the performance of electronic devices, due to non-harmonic effects in the lattice potential energy
To the best of our knowledge, temperature-dependent Raman spectroscopy of suspended monolayer WSe2 has not been investigated yet and the thermal properties study of this suspended TMD it is very important for future applications based on WSe2
Summary
WSe2 exhibits an electronic band structure similar to its sulfide counterpart, i.e. it experiences an indirect-to-direct band gap transition as the crystal is reduced from bulk to monolayer.18,19 The unique band structure along with the reduced dimensionality of few-layer WSe2 enables atomically thin systems to display numerous novel phenomena, such as pronounced photoluminescence and the manipulation of the valley degrees of freedom of charge carries.18,20,21 The strong light-matter interactions observed in WSe2 thin layers make them excellent candidates to be used in optoelectronic circuits.22–24 All these remarkable electronic properties are related to the thermal characteristics and an efficient heat dissipation is necessary to reach high-performance on electronic devices. In this study we report the temperature-dependence of the out-of-plane A1g Raman mode of suspended and supported CVD-grown single-crystalline tungsten diselenide (WSe2) monolayer.
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