Lead-tungsten oxide interfaces designed as gigahertz/terahertz filters

Abstract

Herein amorphous tungsten oxide thin films of thicknesses of 300 nm are coated onto semitransparent Pb films (100 nm) by the thermal evaporation technique under a vacuum pressure of 10−5 mbar. Optical investigations in these films have shown that Pb nanosheets enhances the light absorbability in the visible and infrared ranges of light without significant change in the energy band gap value. In addition deep analyses of the optical conductivity and terahertz cutoff frequency spectra of the Pb/WO3 optical filters revealed that the cutoff frequency value in the visible range of light is invariant with light signal energy indicating the possibly of filtering none-monochromatic light signals. On the other hand imposing an ac signal between the terminals of Pb/WO3/Au devices has proofed the ability of the device to perform as low pass and as band stop filters workable in the microwave frequency domain. The microwave cutoff frequency for this device reached ∼9 GHz nominating it for use in 5 G mobile technology. The current study showed that coating of tungsten oxide onto semitransparent Pb substrate and coverage small area of the top contact with Au can allow functioning the device as gigahertz/terahertz band filters suitable for communication technology.