MoO 3 films grown on polycrystalline Cu: Morphological, structural, and electronic properties

Abstract

In this work, the authors investigated MoO3 films with thickness between 30 nm and 1\u2009μm grown at room temperature by solid phase deposition on polycrystalline Cu substrates. Atomic force microscopy, scanning electron microscopy, and scanning tunneling microscopy revealed the presence of a homogenous MoO3 film with a “grainlike” morphology, while Raman spectroscopy showed an amorphous character of the film. Nanoindentation measurements evidenced a coating hardness and stiffness comparable with the copper substrate ones, while Auger electron spectroscopy, x-ray absorption spectroscopy, and secondary electron spectroscopy displayed a pure MoO3 stoichiometry and a work function ΦMoO3\u2009=\u20096.5\u2009eV, 1.8\u2009eV higher than that of the Cu substrate. MoO3 films of thickness between 30 and 300\u2009nm evidenced a metallic behavior, whereas for higher thickness, the resistance–temperature curves showed a semiconducting character.In this work, the authors investigated MoO3 films with thickness between 30 nm and 1\u2009μm grown at room temperature by solid phase deposition on polycrystalline Cu substrates. Atomic force microscopy, scanning electron microscopy, and scanning tunneling microscopy revealed the presence of a homogenous MoO3 film with a “grainlike” morphology, while Raman spectroscopy showed an amorphous character of the film. Nanoindentation measurements evidenced a coating hardness and stiffness comparable with the copper substrate ones, while Auger electron spectroscopy, x-ray absorption spectroscopy, and secondary electron spectroscopy displayed a pure MoO3 stoichiometry and a work function ΦMoO3\u2009=\u20096.5\u2009eV, 1.8\u2009eV higher than that of the Cu substrate. MoO3 films of thickness between 30 and 300\u2009nm evidenced a metallic behavior, whereas for higher thickness, the resistance–temperature curves showed a semiconducting character.