Field emission properties originated from 2D electronics gas successively tunneling for 1D heterostructures of ZnO nanobelts decorated with In₂O₃ nanoteeth

Abstract

ZnO–In₂O₃ one-dimensional (1D) nanosized heterostructures constructed by ZnO belts and In₂O₃ tooth-like particles were self-assembled on single crystal silicon substrate using thermal chemical vapor transport and condensation without being aided by any metal catalyst. The morphology, structure, and composition of the as-synthesized 1D heterostructures were analyzed in detail. The widths of the ZnO nanobelts ranged from several tens of nanometers to one micrometer, and the lengths ranged from several tens to one hundred of micrometers. In₂O₃ tooth-like nanoparticles with sizes of about 50–100 nm were found grown at two edges of ZnO nanobelts. ZnO nanobelts grew along [$10\overline{1} 0$] direction, whereas In₂O₃ nanoteeth grew along [$31\overline{1}$], [$3\overline{1} 1$], [$\overline{3} \overline{1} 1$], and [$\overline{3} 1\overline{1}$] directions so as to form rhombus-shaped structures. The growth mechanism of the nanosized heterostructures was discussed on the basis of the vapor–solid process and polar surface effect of ZnO nanobelts. Field emission characteristics of the as-prepared heterostructures were measured and explained by energy band theory of heterostructure in detail. It is important to note that the 2D electronics gas (2DEG) was formed between the ZnO energy band bending down and the interface of the heterostructure. The successive tunneling of 2DEG that took place from ZnO to In₂O₃ and then from In₂O₃ to vacuum was the main reason resulting in electronics emission for the nanosized heterostructures in the process of field emission.