Tunable Visible-Light Surface Plasmon Resonance of Molybdenum Oxide Thin Films Fabricated by E-beam Evaporation

Currently plasmonic metal oxides are present in the form of free-standing nanoparticles because they are synthesized with wet chemistry methods. In contrast, this report presents the preparation of chip-based plasmonic molybdenum oxide (MoO 3– x ) thin films on glass substrates by e-beam evaporation and subsequent heat treatment at various temperatures in the nitrogen atmosphere. Localized surface plasmon resonance (LSPR) of MoO 3– x thin films has been studied with experiments and simulation to determine the dependence of the LSPR on the morphological and electronic properties of the films. Heating these films in the nitrogen atmosphere induces the oxygen vacancies, which results in the add-on density of states right below the Fermi level and increases the free charge carrier concentration and the conductivity of the film. The LSPR band of the MoO 3– x film could be blue-shifted and becomes stronger with an increase in the free charge carrier concentration, conductivity, and film roughness of the film. These parameters can be controlled by tuning the heating temperature under nitrogen. This work has presented a new route to fabricate chip-based plasmonic semiconductor nanostructures and to tune the plasmon properties.