Paper TF-WeP4
Continuous Dielectric Function of Monolayer MoSe₂ for Temperature Range from 31 to 300 K by Spectroscopic Ellipsometry

Wednesday, December 5, 2018, 4:00 pm, Room Naupaka Salon 1-3

Molybdenum diselenide (MoSe₂) is a layered material with strong in-plane bonding and weak out-of-plane interactions like many transition metal dichalcogenides (TMDCs). These interactions lead to exfoliation into two-dimensional layers of single unit cell thickness. MoSe₂ is well known as one of TMDCs that has a potential substitute for silicon or organic semiconductors in high-tech transistors, sensors, and photodetectors. Several works reported the dielectric function of monolayer MoSe₂ at low and room temperatures by using spectroscopic ellipsometry (SE). However, In order to apply properly for device applications, the dielectric function of monolayer MoSe₂ had better be well known for continuous temperature.

In this work, monolayer MoSe₂ is formed by selenization of MoO₃ which is fabricated on a sapphire substrate by using pulsed-laser sputtering. We report dielectric function parametric model (DFPM) of optical properties of MoSe₂ over the energy range of 0.74 to 6.42 eV and the temperature range from 31 to 300 K that measured by SE. We could clearly observe the existence of twelve critical point (A^-, A⁰, B₁, B₂, C_a, C_b, E, F, and E_I-IV) structures. The parameters were extracted by fitting the spectra with the reconstruction from twelve dispersive oscillators at each measured data. The dependence of temperature is achieved from the model parameters that are fitted by polynomial and then the dielectric functions of MoSe₂ for continuous temperature is determined. These results are expected to be useful in design and understanding in applied device technologies based on MoSe₂.