Enhanced structural, optical and dielectric properties of the Se/CdBr2 interfaces designed as terahertz optical receivers

Abstract

Herein monoclinic selenium thin films are used as substrates to grow hexagonal cadmium bromide thin films. It is found that selenium substrates enhance the growth of larger crystallites and reduces the microstrain and defect density in CdBr2. The conduction and valance band offsets of the Se/CdBr2 interfaces are found to be 1.25 eV and 0.54 eV, respectively. With these band offset values the light absorbability of CdBr2 in the visible range of light are remarkably increased. In addition, interfacing of Se with CdBr2 significantly increased the real part of dielectric constant and forced dielectric resonance in the infrared and visible ranges of light. Moreover, the optical conductivity parameters including the drift mobility, the scattering time at femtosecond level and the plasmon frequency for Se/ CdBr2 is optimized using Drude-Lorentz approach. It found that coating CdBr2 onto Se result in enhancement of the drift mobility and plasmon frequency values allowing them reaching ~ 44 cm2/Vs and 0.77 GHz and 22 cm2/Vs and 5.69 GHz, when exposed to infrared and ultraviolet radiation, respectively. It is also observed that Se/CdBr2 optical receivers can perform as terahertz band filters showing constant cutoff frequency values of 3.0 THz and 15.0 THz in the infrared and visible ranges of light, respectively.