Design and Characterization of Se/Nb2O5 Interfaces as High Infrared- Absorbers and High Frequency Band Filters

Herein a new class of optoelectronic devices beneficial for infrared light absorption and high-frequency application in the terahertz frequency domain are designed and fabricated. The devices are formed by coating a highly transparent thin layer of Nb₂O₅ onto a selenium-thin film to form Se/Nb₂O₅ (SNO) optical interfaces. Although coating of Nb₂O₅ nanosheets decreased the crystallite sizes and increased the strain and defect concentration in the hexagonal structured Se films, they successfully increased the light absorption by ≈148% in the infrared range of light. A blueshift in the energy band gap of Se from 2.02 to 2.30 eV is observed. The coating of the Nb₂O₅ onto Se suppressed the free carrier absorption in Se and Nb₂O₅. As dielectric active layers, SNO interfaces showed a major resonance dielectric peak centered at 1.67 eV. The optical conductivity and terahertz cutoff frequency analyses which are handled using the Drude-Lorentz approach revealed the highest drift mobility and free carrier concentration of 17.17 cm² Vs⁻¹ and 5.0 $\times {10}^{17}$ cm⁻³ when an oscillator of energy of 1.75 eV is activated. In addition, the terahertz cutoff frequency spectra which varied in the range of 4.0–131 THz showed the suitability of the SNO devices for terahertz technology and other optoelectronics.