Controlled synthesis of aligned Bi2S3nanowires, sharp apex nanowires and nanobelts with its morphology dependent field emission investigations

Abstract

Well-aligned ultra-long Bi₂S₃ nanowire arrays with three kinds of apex morphology – abruptly sharpened apex, thin belt and flat – have been systematically fabricated on tungsten (W) foil by a facile hydrothermal method. The structural and morphological studies reveal formation of distinct tip morphologies, possessing high aspect ratio, single crystalline nature and growth along the orthorhombic [001] axis. A plausible growth mechanism has been proposed on the basis of observed experimental results. The field emission properties of Bi₂S₃ nanowires and sharp apex Bi₂S₃ nanowires are investigated. From the field emission studies, the values of the turn-on field, required to draw emission current density of ∼0.1 μA cm⁻², are observed to be ∼2.01 and 1.21 V μm⁻¹ for nanowires and sharp apex nanowires, respectively. Furthermore, ultra-long Bi₂S₃ nanowires are also grown on the W microtip (brush-like) from which very high emission current density ∼11 mA cm⁻² has been drawn. These results are helpful for the design, fabrication and optimization of integrated field emitters using 1D nanostructures as cold cathode material.