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Modeling the temperature dependence of the optical properties of anisotropic SnS0.52Se0.48
Nguyen Xuan Au,Kim Bogyu,Kim Kyujin,Lee Wonjun,Kim Young Dong,Kim Tae Jung,Van Long Le,Nguyen Hoang Tung 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.4
We report the parameter values of the model dielectric function (ε = ε1 + iε2 ) of SnS0.52Se0.48 in the spectral range from 0.74 to 6.42 eV and the temperature range from 27 to 350 K. An analytic representation, obtained using the Tauc–Lorentz (TL) dispersion model, allows interpolation of the parameters with respect to both energy and temperature. We used reported experimental spectra as the basis of our approach and verified that the TL model can parameterize the model dielectric function so as to reproduce the experimental data well and yield values of the dielectric function and the refractive index at arbitrary temperatures that are useful for device applications.
Azimuthal angle dependent dielectric function of SnS by ellipsometry
Nguyen Xuan Au,Jung Yong Woo,Kim Young Dong,Van Le Long,Nguyen Hoang Tung,Kim Tae Jung 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.80 No.1
Since α-SnS has optically strong anisotropic characteristics, a simple method to determine its crystal orientation is strongly needed in device engineering. In this report, by measuring dielectric function ε = ε1 + iε2 of α-SnS in the 1–5 eV spectral region with the full azimuthal angle range, we could find a simple relationship between measured dielectric function values and the orientation of the α-SnS crystal axis. Therefore, during the device manufacturing process, one can use spectroscopic ellipsometry to quickly measure the dielectric response of the α-SnS region of the device to correctly orient the SnS along the preferred direction for the best performance of the device. We also performed the azimuthal angle-dependent analysis of the critical points (CP) analysis, which shows that the positions of CP energies are basically invariant, while their amplitudes and lineshapes strongly depend on the azimuthal angle.
Optical Properties of Anisotropic SnSxSe1−x for Arbitrary Compositions
Nguyen Xuan Au,Kim Tae Jung,Le Van Long,Nguyen Hoang Tung,Kim Young Dong 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.12
Here, we report parameter values for the model dielectric function (ε = ε1 + iε2) of the SnSxSe1-x alloy in the spectral range from 0.74 to 6.4 eV and the composition range 0 ≤ x ≤ 1 by using the Tauc-Lorentz (TL) model. The experimentally reported dielectric function data for SnSxSe1-x along the zigzag (a) and the armchair (b) directions were borrowed from a previous study for selected compositions. We successfully reproduced the asymmetric nature of the dielectric function with TL lineshapes. The ε data are parameterized by using six and seven TL components for the zigzag and the armchair directions, respectively. The obtained parameters at several compositions were fit with cubic polynomials, which can be used to determine the dielectric function and the refractive index as continuous functions of the energy and the composition. Our results will be useful for optoelectronic device design based on SnSxSe1-x materials.
Modeling of the Temperature Dependence of the Dielectric Function of Biaxial α-SnS
Nguyen Hoang Tung,Le Van Long,Kim Tae Jung,Nguyen Xuan Au,Kim Young Dong 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.11
The dielectric functions of biaxial α-SnS at temperatures from 27 to 350 K are modeled with an analytic expression for Tauc-Lorentz oscillators. The temperature dependence of all the obtained parameters are fitted to third-order polynomial equations. The results provide a comprehensive database of the coefficients, which allows the construction of the dielectric function of biaxial α-SnS at arbitrary temperatures from 27 to 350 K and in the spectra range from 0.73 to 6.0 eV, which can be converted to optical constant values such as refractive indices and the absorption coefficients along the armchair-, zigzag-, and c-axes directions for designing optoelectronic devices based on the SnS material.
Dielectric Function and Critical Points of SnS0.52Se0.48 in the Temperature Range from 27 to 350 K
Kim Tae Jung,Nguyen Xuan Au,Kim Bogyu,Kim Kyujin,Lee Wonjun,Kim Young Dong,르반롱,Nguyen Hoang Tung 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.11
We report the dielectric function ε = ε1+iε2 and the critical point (CP) energies of the orthorhombic SnS0.52Se0.48 alloy for the zigzag (a) and the armchair (b) directions in the spectral energy range from 0.74 to 6.42 eV and the temperature range from 27 to 350 K using spectroscopic ellipsometry. The CP energies were determined from the 2nd derivative spectra by using the standard analytic method. We observed sharpenings and blue-shifts of the CPs with decreasing temperature. We found thirteen and twelve CPs for the a- and the b-directions, respectively, at the lowest temperature while only eight and nine CPs were detected at room temperature. Also, an exciton effect was observed only in the armchair direction at low temperatures. The temperature dependences of the CP energies were determined by fitting the data to a phenomenological expression that contain the Bose-Einstein statistical factor and the temperature coefficient to describe the electron-phonon interaction.
Approximated dielectric tensor of the biaxial α-SnSe crystal
Le Long Van,Nguyen Hoang Tung,Kim Tae Jung,Nguyen Xuan Au,Kim Young Dong 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.78 No.4
We present the principal components of the dielectric tensor for α-SnSe biaxial single crystal in the spectral range from 0.74 to 6.42 eV at room temperature (300 K) using spectroscopic ellipsometry. Aspnes’ first-order approximation method was applied to obtain approximated pseudodielectric response from the pseudodielectric tensor measured at an angle of incidence of ϕ = 68.8°. Multilayer calculations were then performed to extract the pure dielectric tensor without surface roughness artifacts. The Tauc–Lorentz model was applied to describe the critical point structures, and the optical constants along the principal axes of biaxial α-SnSe single crystal can be now calculated at arbitrary wavelength for device applications.
Modeling of the Optical Properties of Monolayer WS2
Kim Tae Jung,Le Van Long,Nguyen Hoang Tung,Nguyen Xuan Au,Kim Young Dong 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.4
We report parametric modeling of the optical properties of monolayer WS2 so its dielectric response can be calculated at temperatures from 41 to 300 K from 1.5 to 6 eV. Parameterization of dielectric function was performed by dielectric-function parametric model, using previously reported dielectric function data which was obtained by spectroscopic ellipsometry. We interpolated the obtained parameters by using cubic polynomials to reconstruct optical properties at arbitrary temperatures. Blue shifts of the bandgap energies and reductions of linewidths of the critical point structures are clearly observed. Given these results, refractive indices and absorption coefficients of the monolayer WS2 follow also at arbitrary temperatures.
Parameterization of the Dielectric Function of GaAsSb Alloy Films
Kim Tae Jung,Le Van Long,Nguyen Hoang Tung,Nguyen Xuan Au,Kim Bogyu,Kim Young Dong 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.77 No.10
The GaAsxSb1-x alloys are particularly promising materials for near-infrared light-emitting diode and detector devices. The optical properties, such as the dielectric function, complex refractive index, and absorption coefficient, are needed to properly design and understand semiconductor devices. Here, we report a method to obtain the optical properties of GaAsxSb1-x for the energy range from 1.5 to 6 eV and for an As composition from 0 to 1 at arbitrary wavelengths and compositions. The parameterization of the dielectric function of GaAsxSb1-x for specific compositions at x = 0, 0.183, 0.397, 0.528, 0.8, and 1 were realized by using the dielectric function parametric model.
Dielectric Functions and Critical Points of GaAsSb Alloys
김태중,박한결,변준석,Van Long Le,Hoang Tung Nguyen,Xuan Au Nguyen,김영동,송진동,David E. Aspnes 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.6
We report the pseudodielectric functions and the critical points of GaAs$_x$Sb$_{1-x}$ ternary alloy films. Data were obtained by performing spectroscopic ellipsometry on 1-$\upmu$m-thick films grown on (001) GaAs by using molecular beam epitaxy. Artifacts from surface contaminants, including oxide overlayers, were minimized by using in-situ chemical cleaning, leading to accurate representations of the bulk dielectric responses of these materials. We determined the energies of the $E_1$, $E_1+\Delta_1$, $E_0'$, $E_0'+\Delta_0'$, $E_2$, $E_2'$, and $E_1'$ critical points from numerically calculated second energy derivatives, as well as their compositional dependences by using lineshape fitting.