Polarized Thermoreflectance and Reflectance Study of ReS₂ and ReS₂:Au Single Crystals

Abstract

In this article, we present the optical study of undoped and Au-doped rhenium disulphide (ReS 2 and ReS 2 :Au) using temperature-and polarization-dependent thermoreflectance (PTR) and reflectance (R) measurements. We have observed the indirect band gaps (E gk , E g? ), and direct band-edge excitonic transitions (E ex 1 , E ex 2 , E ex 3 and E ex 4 ) at various polarization angles. The amplitudes of E ex 1 and E ex 2 transitions have an orthogonal characteristic and follow the Malus rule. A small blue-shift of indirect band gaps has been observed for the ReS 2 :Au sample, we believe that this result is contributed from the doping effects. We also measured the temperature-dependent PTR spectra in the temperature range from 55 to 300 K, and determined the temperature dependences of the transition energies and broadening parameters of E ex 1 and E ex 2 transitions. Reflectance measurements at various polarizations have been performed to confirm our observations.

A Comprehensive Study on the Optical Properties of Thin Gold-Doped Rhenium Disulphide Layered Single Crystals

“…The angular dependences of the peak intensity show a sinusoidal appearance. The experimental data can be analyzed by the following function: 19)…”

Optical and Electrical Properties of Au- and Ag-Doped ReSe2

“…The growth procedures and parameters were similar to those reported elsewhere. 14) For the absorption measurement, a 130 W tungsten-halogen lamp filtered by a monochromator (25 cm) was used to provide the monochromatic light. This light was then chopped by a mechanical chopper at frequency of 200 Hz, passed through a polarizer and lens, and finally was focused on the sample.…”

“…For the PTR measurement the same instruments as described above were used but the system setup was similar to the reflectance measurement system. [14][15][16] To produce thermo-modulation, a 3.3 k surface-mount device (SMD) resistor was tightly sandwiched between the sample under test and the cryo-head. 14) A function generator and a voltage amplifier were used to provide the electric power to the SMD resistor, which introduced temperature perturbation to the sample.…”

“…[14][15][16] To produce thermo-modulation, a 3.3 k surface-mount device (SMD) resistor was tightly sandwiched between the sample under test and the cryo-head. 14) A function generator and a voltage amplifier were used to provide the electric power to the SMD resistor, which introduced temperature perturbation to the sample. A low frequency (5 Hz) square wave with 50% duty cycle was applied to produce an efficient periodic thermal perturbation on the sample.…”