Plasmon Interactions at the (Ag,Al)/InSe Thin-Film Interfaces Designed for Dual Terahertz/Gigahertz Applications

In this article, we investigate the plasmon-dielectric spectral interaction in the Ag/InSe and Al/InSe thin-film interfaces. The mechanism is explored by means of optical absorbance and reflectance at terahertz frequencies and by the impedance spectroscopy at gigahertz frequencies. It was observed that the interfacing of the InSe with Ag and Al metals with a film thickness of 250 nm causes an energy band gap shift that suits the production of thin-film optoelectronic devices. The reflectance and dielectric constant and optical conductivity spectral analysis of these devices displayed the properties of wireless band stop filters at 390 THz. The physical parameters which are computed from the conductivity spectra revealed higher mobility of charge carriers at the Al/InSe interface over that of Ag/InSe. The respective electron-bounded plasmon frequencies are found to be 2.61 and 2.13 GHz. On the other hand, the impedance spectral analysis displayed a microwave resonator feature with series resonance peak position at 1.68 GHz for the Al/InSe/Ag interface. In addition, the temperature-dependent impedance spectra, which were recorded in the temperature range of 300–420 K, revealed no significant effect of temperature on the wave trapping properties of the Al/InSe/Ag interface. The sensitivity of the interfaces to terahertz and gigahertz frequencies nominates it as laser light/microwave traps, which are used in fibers and communications.