Herein, tungsten oxide thin films comprising excess oxygen are treated as optical resonator suitable for gigahertz/terahertz applications. WO3 thin films which are prepared by the thermal evaporation technique under a vacuum pressure of 10 -5 mbar are structurally, compositionally and optically evaluated. The amorphous WO3.33 films which showed high transparency permit electronic transitions within an indirect allowed energy band gap of 3.05 eV. The band gap comprised energy band tails of width of 190 meV. Four dominant dielectric resonators centered in the infrared (IR), visible (VIS) and ultraviolet (UV) ranges of light are detected. Analysis of the optical conductivity in accordance with the Drude-Lorentz approaches have shown that the drift mobility of free holes in this amorphous layer can be as large as 5.61 cm 2 /Vs an as low as 1.59 cm 2 /Vs when exposed to IR and UV light signals, respectively. In addition, the gigahertz/terahertz cutoff frequency (𝑓 𝑐𝑜 ) spectra demonstrated 𝑓 𝑐𝑜 values in the gigahertz frequency domain when exposed to IR light. Excitations with light signals in the VIS and UV spectral ranges allow 𝑓 𝑐𝑜 values that extends from 0.7-40.0 THz. The wide range of tunability of the WO3 dielectric resonators nominates them as dielectric lenses suitable for optical communications.

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Herein, 𝑝 −WO3 thin films coated onto ytterbium thin film substrates are used as active layers to fabricate a back to back Schottky (BBS) barriers. The Schottky contacts and the tungsten oxide active layers are grown by the thermal evaporation technique under a vacuum pressure of 10-5 mbar. The films are structurally, morphologically, optically and electrically characterized. The physical nature of the grown 𝑝 −WO3 layers is amorphous comprising excess oxygen in its composition. Electrically, the BBS devices displayed a biasing dependent current rectification ratio confirming the tunneling type of Schottky barriers. The current conduction are dominated through tunneling barriers of height of ~0.80 eV. The barriers allow hole tunneling within energy barriers of widths of ~45 nm and of 300 nm under reverse and forward biasing conditions, respectively. In addition, the impedance spectroscopy measurements have shown the ability of wide tunability of the resistance and capacitance of the devices resulting in a microwave cutoff frequency exceeding 2.0 GHz. The resistive and capacitive features of the devices in addition to the microwave cutoff frequency spectra nominate the Yb/𝑝-WO3/Yb BBS devices for use as microwave resonators suitable for 4G/5G technologies.

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/pssa.202100822.

Herein, tungsten oxide thin films comprising excess oxygen are treated as optical resonator suitable for gigahertz/terahertz applications. WO 3 thin films which are prepared by the thermal evaporation technique under a vacuum pressure of 10 -5 mbar are structurally, compositionally and optically evaluated. The amorphous WO 3.33 films which showed high transparency permit electronic transitions within an indirect allowed energy band gap of 3.05 eV. The band gap comprised energy band tails of width of 190 meV. Four dominant dielectric resonators centered in the infrared (IR), visible (VIS) and ultraviolet (UV) ranges of light are detected. Analysis of the optical conductivity in accordance with the Drude-Lorentz approaches have shown that the drift mobility of free holes in this amorphous layer can be as large as 5.61 cm 2 /Vs an as low as 1.59 cm 2 /Vs when exposed to IR and UV light signals, respectively. In addition, the gigahertz/terahertz cutoff frequency ( ) spectra demonstrated values in the gigahertz frequency domain when exposed to IR light. Excitations with light signals in the VIS and UV spectral ranges allow values that extends from 0.7-40.0 THz. The wide range of tunability of the WO 3 dielectric resonators nominates them as dielectric lenses suitable for optical communications.