講演情報
[15a-WL2_101-5]First-Principles Study of Transparent Conductive Oxides for Surface Plasmon Resonance–Based Propane Gas Sensing
〇Muhammad Arifin1,2, Kohji Nakamura2 (1.Department of Physics, Gadjah Mada Univ., 2.Graduate School of Engineering, Mie Univ.)
キーワード：
transparent conductive oxides、surface plasmon resonance、sensitivity
Surface plasmon resonance (SPR) sensitivity is strongly influenced by the dielectric environment, and transparent conductive oxide (TCO) overlayers can enhance plasmonic field confinement through low optical loss and tunable permittivity. In this work indium oxide, gallium oxide, and aluminum oxide are systematically investigated as dielectric overlayers in Au-based SPR sensors. Their dielectric functions are obtained from first-principles calculations using the FLAPW method combined with the Kubo formalism [1], with all oxides modeled in a rhombohedral crystal structure. The localized d orbitals are treated within a second-variational +U approach, and the band gap is corrected by applying a scissor shift to the conduction bands [2]. The SPR sensing performance is then simulated using the transfer-matrix method at a wavelength of 633 nm for propane gas detection [3].
Electronic structure analysis shows that the d-orbital DOS is highly localized at the valence band maximum in indium oxide, moderately reduced in gallium oxide, and shifted further away in aluminum oxide. The conduction band minima are dominated by metal 5s states with parabolic Γ-centered dispersions typical of TCOs [4]. In the visible range, the imaginary dielectric function decreases from indium oxide to aluminum oxide, consistent with the higher absorption onset of aluminum oxide.
SPR simulations at a propane concentration of 24000 ppm (approximately the lower explosive limit, LEL) show resonance angle shifts of 0.128°, 0.112°, and 0.100° for indium oxide, gallium oxide, and aluminum oxide overlayers, respectively. A linear sensing response is observed below the LEL, with sensitivities of 7270, 6388, and 5621 °/RIU. Indium oxide exhibits the highest sensitivity owing to its easily modulated dielectric response, highlighting the role of dielectric engineering in optimizing TCO-based SPR gas sensors.
Electronic structure analysis shows that the d-orbital DOS is highly localized at the valence band maximum in indium oxide, moderately reduced in gallium oxide, and shifted further away in aluminum oxide. The conduction band minima are dominated by metal 5s states with parabolic Γ-centered dispersions typical of TCOs [4]. In the visible range, the imaginary dielectric function decreases from indium oxide to aluminum oxide, consistent with the higher absorption onset of aluminum oxide.
SPR simulations at a propane concentration of 24000 ppm (approximately the lower explosive limit, LEL) show resonance angle shifts of 0.128°, 0.112°, and 0.100° for indium oxide, gallium oxide, and aluminum oxide overlayers, respectively. A linear sensing response is observed below the LEL, with sensitivities of 7270, 6388, and 5621 °/RIU. Indium oxide exhibits the highest sensitivity owing to its easily modulated dielectric response, highlighting the role of dielectric engineering in optimizing TCO-based SPR gas sensors.