Growth and Field Emission Study of Molybdenum Oxide Nanostars

Abstract

The field emission properties of MoO2 nanostars grown on a silicon substrate and their emission performance in various vacuum gaps are reported in this article. A new structure of molybdenum oxides, named a nanostar, is grown by thermal vapor deposition with a length of ∼1 μm, a thickness of ∼50 nm, and its width in the range of 500−700 nm. The morphology, structure, composition, and chemical states of the prepared nanostars were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). According to XRD analysis, the grown nanostructures are composed of both crystalline Mo4O11 and crystalline MoO2 structures. XPS analysis showed that the synthesized nanostructures contained ∼21.2% Mo6+, ∼16.2% Mo5+, ∼39.8% Mo4+, and ∼22.8% Moδ+ (where 0 < δ < 4). TEM observations indicate that the synthesized sample consists of MoO2 nanostars over a crystalline thin film containing Mo4O11 nanoparticles. The turn-on ...