Stacked Layers of Nb₂O₅/Pt/Nb₂O₅ Designed as Conducting Oxides, Terahertz Band Filters, and Semitransparent Light Absorbers

Herein, stacked layers of Nb₂O₅ structured with platinum nanosheets were fabricated to handle multifunctional electro-optic operations. The stacked layers of Nb₂O₅/Pt/Nb₂O₅ (NPN) were prepared by the ion coating technique and exhibited an amorphous structure. A remarkable increase in light absorption by more than 480% was achieved via the insertion of Pt nanosheets between layers of Nb₂O₅. Pt nanosheets with thicknesses of 50 nm and 100 nm successfully increased the electrical conductivity of the NPN layers by five and eight orders of magnitude, respectively, without losing transparency. This feature makes the NPN stacks suitable for transparent conducting oxide applications. The insertion of Pt nanosheets between layers of Nb₂O₅ also converted the conductivity from p- to \(n\) $n$ -type. In addition, NPN stacked layers exhibited highly enhanced dielectric properties, demonstrating an increase in the dielectric constant by 190%, making the NPN stacked layers suitable for use in the design of high-κ gate dielectric devices. Moreover, when treated as optical filters, Drude–Lorentz fittings of the dielectric spectra showed that Pt nanosheets increased the free carrier density and the plasmon frequency. The terahertz cutoff frequency of the NPN devices steadily increased with increasing Pt nanosheet thickness. The terahertz cutoff frequency for NPN optical filters comprising a 100-nm-thick layer of Pt displayed values of 7.5 THz and 5.0 THz in the infrared and visible light ranges. The NPN stacks have potential for use in terahertz applications.