Controllable synthesis and field emission enhancement of Al2O3 coated In2O3 core-shell nanostructures

Four types of indium oxide (In2O3) nanostructures were synthesized on Au-catalysed silicon substrate via a VLS method. A rod-like In2O3 nanostructure was chosen to fabricate In2O3-Al2O3 core-shell nanostructures with different shell thicknesses via a two-step method. Core-shell nanostructures with shell thickness of 30 nm are reprocessed by annealing and H2 plasma treating. Field emission (FE) properties of all the samples were measured and compared. It is found that Al2O3 coatings remarkably decrease the effective work function and improve the FE capabilities of In2O3 nanostructures (turn-on field decreases from 1.34 to 1.26 V μm-1, threshold field decreases from 3.60 to 2.64 V μm-1). Annealing and H2 plasma treating can promote the improvement even further (turn-on field 1.23 V μm-1, 1.21 V μm-1 and threshold field 2.50 V μm-1, 2.14 V μm-1, respectively). The FE enhancement is attributed to the electron accumulation in the insulating Al2O3 nanostructure and the electron redistribution at the heterojunction.