BaO/Se heterojunctions designed as effective light Absorbers, terahertz optical filters and microwave waveguides

• BaO/Se interfaces are designed and experimentally characterized. • BaO/Se exhibited conduction and valence band offsets of 1.22 eV and 0.0 eV, respectively. • The spectral dielectric resonance, optical conductivity and terahertz cutoff frequency are studied. • The impedance spectra in the quad band range of 10–1800 MHz are explored. Herein, hexagonal selenium microrods are deposited onto tetragonal barium oxide substrates by the thermal evaporation technique under a vacuum pressure of 10 -5 mbar. Optical studies indicated that BaO and Se exhibited band gaps of 3.55 eV and 2.33 eV, respectively. BaO/Se interfaces exhibited a valence and conduction band offsets of 0 eV and 1.22 eV, respectively. In addition, depositing Se layers onto BaO substrates, remarkably, enhanced the light absorption of Se by more than 100 % in the spectral range of 1.9–4.0 eV and by 1100 % at 3.0 eV. Moreover, the analyses of the dielectric, the optical conductivity and terahertz cutoff frequency showed the suitability of the BaO/Se heterojunctions for the fabrication of terahertz optical filters. Electrically, Au/BaO/Se/Au planner waveguides exhibited low pass filter and antenna characteristics that suits microwave technology in the gigahertz frequency domain. The features of the BaO/Se devices are promising for using them in electro-optical systems.