1:00 PM - 1:30 PM
▲ [10p-N404-1] Structure, interlayer interactions, thermal conductivity, and light emission in two-dimensional MoSe2 and MoS2 using optical spectroscopy
Keywords:Raman spectroscopy, 2D materials
Two- dimensional transition metal dichalcogenides have strikingly different electronic and optical properties compared to their bulk counterparts. In particular, the occurrence of a direct band gap renders them useful for optoelectronic devices. Raman spectroscopy is a useful metrology for evaluating diverse material aspects of two-dimensional materials. Our focus here is on two such materials, namely MoSe2 and MoS2.
In the case of MoSe2, we demonstrate Raman spectroscopy for evaluating the (i) stepwise selenization mechanism of the precursor MoO3 to 2D MoSe2 in a Chemical Vapor Deposition fabrication method, (b) interlayer interaction and number of layers through Davydov splitting of the A1g mode and (c) layer variation of the thermal conductivity. The light emission is observed only in triangular flakes with 4 layers or less. The layer variation of the photoluminescence peak position is investigated as also the effect of sulphur incorporation in MoSe2 for bandgap tunability.
In the case of MoS2, nanosheets are synthesized by a grinding-assisted liquid phase exfoliation process. Raman spectroscopy demonstrates that MoS2 is thus exfoliated down to 3-4 layers. Grinding helps to suppress the strong unwanted visible photoluminescence emission due to sonochemical degradation of the solvent, and helps to enhance the excitonic emission.
1. Vineeta Singh, Dattatray J. Late, Shyama Rath, Appl. Surf. Sci.,538,147946 (2021)
2. Vineeta Singh, Dattatray J. Late, Shyama Rath, J.Vac. Sci. Technol. A 38 023402 (2020)
3. Vineeta Singh, Shyama Rath, Physica E, 128, 114617 (2021)
In the case of MoSe2, we demonstrate Raman spectroscopy for evaluating the (i) stepwise selenization mechanism of the precursor MoO3 to 2D MoSe2 in a Chemical Vapor Deposition fabrication method, (b) interlayer interaction and number of layers through Davydov splitting of the A1g mode and (c) layer variation of the thermal conductivity. The light emission is observed only in triangular flakes with 4 layers or less. The layer variation of the photoluminescence peak position is investigated as also the effect of sulphur incorporation in MoSe2 for bandgap tunability.
In the case of MoS2, nanosheets are synthesized by a grinding-assisted liquid phase exfoliation process. Raman spectroscopy demonstrates that MoS2 is thus exfoliated down to 3-4 layers. Grinding helps to suppress the strong unwanted visible photoluminescence emission due to sonochemical degradation of the solvent, and helps to enhance the excitonic emission.
1. Vineeta Singh, Dattatray J. Late, Shyama Rath, Appl. Surf. Sci.,538,147946 (2021)
2. Vineeta Singh, Dattatray J. Late, Shyama Rath, J.Vac. Sci. Technol. A 38 023402 (2020)
3. Vineeta Singh, Shyama Rath, Physica E, 128, 114617 (2021)