Glancing angle synthesized indium nanoparticles covered TiO₂ thin film and its structural, optoelectronic properties

Abstract

Surface plasmon resonance is one of the most interesting phenomena shown by noble metal nanoparticles (NPs) in nanoscale dimension. Gold, silver NPs used to show enhancement in absorption at their selective plasmon resonance frequency. But indium (In) shows broader resonance, and hence, In NPs can be employed for the purpose of wideband detection. Here, glancing angle deposition is incorporated in an e-beam chamber to obtain controlled growth of 5, 10 and 30 nm In NPs array over TiO₂ thin film (TF) on ITO-coated glass plate. The 5-nm In NPs on TiO₂ TF process superior performances in terms of enhanced Raman scattering and optical absorption. Optical absorption spectrophotometry shows averagely two times enhancement in absorption for 5-nm In NPs compared to bared TiO₂ TF on Si substrate. The plasmonic detector (TiO₂ TF/5-nm In NPs/TiO₂ TF/Si) produced dark current of 0.36 µA/cm² at 5 V, which increased to 0.51 µA/cm² under white light illumination. The maximum 116 times photosensitivity at −2 V was calculated for the plasmonic device. The NPs-designed plasmonic device shows twofold photoresponsivity in visible region (400–650 nm) with respect to the bared TiO₂TF device. The external quantum efficiency for plasmonic device was calculated to be 65 %.