Design and Characterization of Se/Nb2 O5 Interfaces asHigh Infrared- Absorbers and High Frequency Band Filters

Abstract

Herein a new class of optoelectronic devices beneficial for infrared lightabsorption and high-frequency application in the terahertz frequency domainare designed and fabricated. The devices are formed by coating a highlytransparent thin layer of Nb2 O5 onto a selenium-thin film to form Se/Nb 2 O5(SNO) optical interfaces. Although coating of Nb 2 O5 nanosheets decreasedthe crystallite sizes and increased the strain and defect concentration in thehexagonal structured Se films, they successfully increased the lightabsorption by ≈148% in the infrared range of light. A blueshift in the energyband gap of Se from 2.02 to 2.30 eV is observed. The coating of the Nb2 O5onto Se suppressed the free carrier absorption in Se and Nb 2 O5 . As dielectricactive layers, SNO interfaces showed a major resonance dielectric peakcentered 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 cm 2 Vs−1 and5.0 × 1017 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 of4.0–131 THz showed the suitability of the SNO devices for terahertz technology and other optoelectronics