“…where E t denotes the demarcation energy between the Urbach tail transitions and the band-to-band transitions and E u is the so-called Urbach energy, representing the width of tail states in the forbidden gap, with the TL or CL oscillator [34,35,60,61]. In some cases, this approach demonstrated an improved description of the optical dielectric response for the materials such as, for example, high-κ dielectric films [40,62,63], hydrogenated amorphous silicon nitride (a-SiN x :H) films [64] and titanium dioxide (TiO 2 ) thin films [65,66].…”