Controllable Low-Temperature Chemical Vapor Deposition Growth and Morphology Dependent Field Emission Property of SnO₂ Nanocone Arrays with Different Morphologies

Vertically aligned SnO2 nanocones with different morphologies have been directly grown on fluorine-doped tin oxide (FTO) glass substrates in a large area by heating a mixture of stannous chloride dihydrate (SnCl2·2H2O) and anhydrous zinc chloride (ZnCl2) at 600 °C in air. Control over the SnO2 nanocone arrays with different morphologies is achieved by adjusting the heat treatment time. The SnO2 nanocones are single crystalline with the tetragonal structure. A single-layer SnO2 nanoparticle film is first formed via the vapor-solid (VS) process due to the decentralization function of ZnCl2 vapor, and the SnO2 nanoparticles served as seeds and grew into nanocone arrays via the VS process. The sharp-tipped nanostructure formation may originate from a concentration gradient of reactant in the growth process. The as-obtained whiskerlike nanocone arrays exhibit enhanced field emission properties in comparison with typical nanoconelike structure arrays and other SnO2 nanostructured materials reported previously, and the turn-on field and field-enhancement factor is 1.19 V/μm and 3110, respectively. The experimental result is consistent with the Utsumi's relative figure of merit for pillar-shaped emitters.