Needle-Shaped Single-Crystalline Molybdenum Micro-Nano Structure with High Conductivity and Excellent Field Emission Properties: Implications for Large-Current Cold-Cathodes

Abstract

High-melting point metallic micro-nano structural materials are well recognized as good conductors and electron emitters, particularly in the field of cold-cathode electron source and vacuum electron device applications. Developing their singlecrystalline structures helps to further obtain large-current and highpower output performance; however, the controllable preparation of materials is always a difficult problem. In this study, we successfully realized the controllable self-assembled growth of high-quality needleshaped molybdenum (Mo) micro-nano structures, by developing a modified thermal vapor deposition method. The Mo needle typically exhibits ultralong quasi-one dimension (up to ∼1.5 mm) and a sharp tip-end, with a perfect single-crystalline nature. Based on this structural feature, a type of Mo individual with a continuous structure is demonstrated to show an excellent conductivity of approximately 5 × 10 5 Ω −1 cm −1 and very large field emission current up to 93.1 μA with a corresponding current density of 1.2 × 10 5 A cm −2 , standing out from most of the reported cold-cathode nanomaterials. This study provides a potential cold-cathode material with high conductivity and large current for vacuum electronic applications and also indicates a feasible path to achieve the preparation of high-quality single crystals of high-melting-point metals.