09:45 〜 10:00
▲ [25a-F307-3] Nanostructure control of 2D van der Waals Materials α-MoO3
キーワード：nanostructure, molybdenum oxide, van der Waals Materials
Molybdenum oxides (MoOx) are one of interesting oxides in various applications such as chemical catalysis, bio-sensing, and photovoltaic devices. In particular, α-type MoO3, a 2D van der Waals material, provides low-dimensional electrical and optical characteristics. Additionally, control of the reduction of Mo elements causes change in electronic states from transparent insulating to semi-metals, which produces highly tunable and versatile applications. However, studies of the controlled synthesis of α-MoO3 films and nanostructures are still limited. Here we report on growth of α-MoO3 nanostructured films and their related materials.
α-MoO3 nanostructured films were grown on TiO2-terminated SrTiO3 (100) substrates by pulsed laser deposition (PLD). The x-ray diffraction revealed that the film sample grown under high oxygen pressure of 10 Pa showed a single crystal of α-MoO3 along the [010] direction from the result of 2D reciprocal space mapping, which was also confirmed by μ-Raman scattering. Firstly, remarkable change in valence states of Mo elements was observed when oxygen pressure reduced from 15 Pa to 0.1 Pa by using x-ray photo-emission spectroscopy. Specifically, chemical ratios of the Mo5+ and Mo4+ states gradually increased with reducing oxygen pressure as a result of the decrease in the Mo6+ state. Besides, we observed morphologies on the film surfaces using scanning electron microscopy. The high oxygen pressures at 10 Pa clearly showed nano-needle structures. However, the decrease in oxygen pressure caused change in morphology from nano-needle structures to elongated nanowire structures. The sample grown under a low oxygen pressure of 0.1 Pa showed a smooth surface with a roughness of 5 nm. Hereafter, we will progress plasmonic biosensing applications based on MoOx/MoO3 nanostructures.
α-MoO3 nanostructured films were grown on TiO2-terminated SrTiO3 (100) substrates by pulsed laser deposition (PLD). The x-ray diffraction revealed that the film sample grown under high oxygen pressure of 10 Pa showed a single crystal of α-MoO3 along the [010] direction from the result of 2D reciprocal space mapping, which was also confirmed by μ-Raman scattering. Firstly, remarkable change in valence states of Mo elements was observed when oxygen pressure reduced from 15 Pa to 0.1 Pa by using x-ray photo-emission spectroscopy. Specifically, chemical ratios of the Mo5+ and Mo4+ states gradually increased with reducing oxygen pressure as a result of the decrease in the Mo6+ state. Besides, we observed morphologies on the film surfaces using scanning electron microscopy. The high oxygen pressures at 10 Pa clearly showed nano-needle structures. However, the decrease in oxygen pressure caused change in morphology from nano-needle structures to elongated nanowire structures. The sample grown under a low oxygen pressure of 0.1 Pa showed a smooth surface with a roughness of 5 nm. Hereafter, we will progress plasmonic biosensing applications based on MoOx/MoO3 nanostructures.