Transparent In/SeO2 Thin Film Transistors Designed for Gigahertz/Terahertz Technologies

Synthesis of Copper Nanosheets Coatings onto Glass and Glass/CrSe2 Substrates Using Ion Coating Technique for Terahertz Technology

“…As an important point of study, the absorption coefficient (α) spectra for CS and CSC films were calculated with the help of the equation, [ 21,22 ] $$$$\begin{equation}T\ = \ \left( {1 - {R}_{{\mathrm{glass}}}} \right)\left( {1 - {R}_{{\mathrm{glass}}/{\mathrm{CrSe}}}} \right)(\hbox{1-}{R}_{{\mathrm{glass}}/{\mathrm{CrSe}}2/{\mathrm{Cu}}}){\mathrm{exp}}\left( { - \alpha d} \right)\end{equation}$$$$…”

“…Information about the energy bandgap is gained from the Tauc's equation ($${( {\alpha E} )}^2 \propto ( {E - {E}_g} )$$) [ 21,22 ] fittings that are shown in Figure a. For chromium selenide thin films a direct allowed transitions energy bandgap is determined from the $$\alpha - E$$ variation in absorption ranges (1.73–3.72 eV).…”

“…Hence it is possible to think that the copper coating does not strongly affect the optical dynamics and optical transitions in chromium selenide. On the other hand by fitting the absorption coefficient spectra in accordance with the Urbach rule ($$\alpha \ = {\alpha }_o{\mathrm{\ exp}}(\frac{E}{{{E}_u}}$$), $${\alpha }_o:$$preexponential factor) for optical absorption, [ 21,22 ] it is possible to gain information about the changes in the energy band tails ($${E}_u$$) that exist in electronic band structure of CrSe 2. The fitting of the Urbach equation is shown in Figure 4b.…”

“…The dielectric constant is determined from the refractive index ( n ) using Fresnel's equations for light entering normal to the plane. The following relations lead to the identification of the real ($${\varepsilon }_r$$) and imaginary ($${\varepsilon }_{im}$$) parts of dielectric constant and terahertz cutoff frequency ($${f}_T$$) [ 21,22 ] $$$$\begin{equation}R\ = \frac{{{{\left( {n - 1} \right)}}^2 + {{\left( {\alpha \lambda /\left( {4\pi } \right)} \right)}}^2}}{{{{\left( {n + 1} \right)}}^2 + {{\left( {\alpha \lambda /\left( {4\pi } \right)} \right)}}^2}}\ \end{equation}$$$$ $$$$\begin{equation}\ {\varepsilon }_r = {n}^2\ - {\left( {\alpha \lambda /\left( {4\pi } \right)} \right)}^2.\end{equation}$$$$ $$$$\begin{equation}\ {\varepsilon }_{im} = \ 2n\left( {\alpha \lambda /\left( {4\pi } \right)} \right)\end{equation}$$$$ …”

“…[20] The experimentally observed increased surface roughness could also account for the decreased reflectivity of the films. As an important point of study, the absorption coefficient (𝛼) spectra for CS and CSC films were calculated with the help of the equation, [21,22] T =…”