“…5, which shows CP energy values (represented by dots) acquired through the second-derivative analysis. The t results are depicted as solid lines, obtained using a phenomenological expression that includes the Bose-Einstein statistical factor for phonons 33,34 :…”
Monolayer materials typically display intriguing temperature-dependent dielectric and optical properties, which are crucial for improving the structure and functionality of associated devices. Due to its unique photoelectric capabilities, monolayer WSe2 has recently received a lot of attention in the fields of atomically thin electronics and optoelectronics. In this work, we focus on the evolution of the temperature-dependent dielectric and optical properties of 2D WSe2 over energies from 0.74 to 6.40 eV and temperatures from 40 K to 350 K. We analyze second derivatives with respect to energy to locate the critical points (CP). The dependence of the observed CP energies on temperature is consistent with the alternative domination of the declining exciton binding energy as the temperature increases.
“…5, which shows CP energy values (represented by dots) acquired through the second-derivative analysis. The t results are depicted as solid lines, obtained using a phenomenological expression that includes the Bose-Einstein statistical factor for phonons 33,34 :…”
Monolayer materials typically display intriguing temperature-dependent dielectric and optical properties, which are crucial for improving the structure and functionality of associated devices. Due to its unique photoelectric capabilities, monolayer WSe2 has recently received a lot of attention in the fields of atomically thin electronics and optoelectronics. In this work, we focus on the evolution of the temperature-dependent dielectric and optical properties of 2D WSe2 over energies from 0.74 to 6.40 eV and temperatures from 40 K to 350 K. We analyze second derivatives with respect to energy to locate the critical points (CP). The dependence of the observed CP energies on temperature is consistent with the alternative domination of the declining exciton binding energy as the temperature increases.
“…5 , which shows CP energy values (represented by dots) acquired through the second-derivative analysis. The fit results are depicted as solid lines, obtained using a phenomenological expression that includes the Bose–Einstein (BE) statistical factor for phonons 36 , 37 : Figure 5 Temperature dependences of the CP energies of WSe 2 . …”
Section: Resultsmentioning
confidence: 99%
“…Here, Θ represents the mean frequency of phonons, and E B signifies the interaction strength between electrons and phonons. For other CPs exhibiting negligible curvature in their temperature dependence, we fit a linear equation 35 , 36 : where E L is an adjustable parameter and λ is the temperature coefficient - dE / dT . The best fit parameters are listed in Table 2 .…”
Monolayer materials typically display intriguing temperature-dependent dielectric and optical properties, which are crucial for improving the structure and functionality of associated devices. Due to its unique photoelectric capabilities, monolayer WSe2 has recently received a lot of attention in the fields of atomically thin electronics and optoelectronics. In this work, we focus on the evolution of the temperature-dependent dielectric function (ε = ε1 + i ε2) of monolayer WSe2 over energies from 0.74 to 6.40 eV and temperatures from 40 to 350 K. We analyze the second derivatives of ε with respect to energy to accurately locate the critical points (CP). The dependence of the observed CP energies on temperature is consistent with the alternative domination of the declining exciton binding energy as the temperature increases.
“…At T = 1073 K, the sample with a dull orange glow was detected via the photomultiplier and started to strongly degenerate due to shrinking of the band gap and thermal excitation, where all structures are broadened and shifted to lower energy by as much as 0.4 eV. Temperature-dependent dielectric functions of InSb have been measured by T.J. Kim et al in the photon energy range of 0.7–6.5 eV and T = 31 → 675 K. The critical point features have also been analyzed utilizing the second-derivative method. − The optical properties of AlN films have been investigated at T = RT → 860 K by Y. Liu et al…”
Section: Determination Of Reference Dielectric Functionsmentioning
Among the many available real-time characterization methods,
ellipsometry
stands out with the combination of high sensitivity and high speed
as well as nondestructive, spectroscopic, and complex modeling capabilities.
The thicknesses of thin films such as the complex dielectric function
can be determined simultaneously with precisions down to sub-nanometer
and 10–4, respectively. Consequently, the first
applications of high- and low-temperature real-time ellipsometry have
been related to the monitoring of layer growth and the determination
of optical properties of metals, semiconductors, and superconductors,
dating back to the late 1960s. Ellipsometry has been ever since a
steady alternative of nonpolarimetric spectroscopies in applications
where quantitative information (e.g., thickness, crystallinity, porosity,
band gap, absorption) is to be determined in complex layered structures.
In this article the main applications and fields of research are reviewed.
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