Characterization and Field‐Emission Properties of Needle‐like Zinc Oxide Nanowires Grown Vertically on Conductive Zinc Oxide Films

Abstract

Needle‐like ZnO nanowires with high density are grown uniformly and vertically over an entire Ga‐doped conductive ZnO film at 550 °C. The nanowires are grown preferentially in the c‐axis direction. The X‐ray diffraction (XRD) θ‐scan curve shows a full width at half maximum (FWHM) value of 2°. This indicates that the c‐axes of the nanorods are along the normal direction of the substrate surface. The investigation using high‐resolution transmission electron microscopy (HRTEM) confirmed that each nanowire is a single crystal. A room‐temperature photoluminescence (PL) spectrum of the wires consists of a strong and sharp UV emission band at 380 nm and a weak and broad green–yellow band. It reveals a low concentration of oxygen vacancies in the ZnO nanowires and their high optical quality. Field electron emission from the wires was also investigated. The turn‐on field for the ZnO nanowires was found to be about 18 V μm–1 at a current density of 0.01 μA cm–2. The emission current density from the ZnO nanowires reached 0.1 mA cm–2 at a bias field of 24 V μm–1.

Effect of Preheating Temperature on Microstructure and Optical Properties of ZnO Thin Films Prepared by Sol-Gel Spin Coating Technique

“…On the other hand, MEA can chelate with Zn 2+ , which also accelerate the reversible reaction (1) along the hydrolysis direction. At this stage, the reactions involved can be described by reactions (1) to (4). Reactions (3) and (4) …”

“…Owning to its excellent physical properties, ZnO has been a promising material in piezoelectric and optoelectronic fields [3]. ZnO thin films are widely used to light-emitting diodes (LED) [4], UV sensors [5,6], solar cells [7,8], surface acoustic wave (SAW) devices and optical wave-guide devices as well [9]. It is well known that ZnO thin films can be prepared by variety of techniques such as sputtering [10,11], laser ablation [12][13][14], chemical vapor deposition [15,16] and sol-gel spin-coating technique [17][18][19][20][21].…”

Swift Synthesis of ZnO Nanorods by Microwave Hydrothermal Method

“…ZnO nanorods are attracting much interest several applications such as nanophotonics [2], dyesensitized solar cells [3,4], electron field emitters [5,6], field effect transistors [7] and piezotronics [8]. Among various synthesis methods the microwave assisted hydrothermal synthesis has emerged as a powerful method for the synthesis of ZnO nanorods with some significant advantages such as cost effective large yield and less complicated technique [9].…”

Synthesis, microstructure and photoluminescence of well-aligned ZnO nanorods on Si substrate

“…Using this simple method, 1D ZnO nanostructures (especially aligned nanowire or nanorod) were grown on Si or ZnO thin film with or without catalyst [7,[12][13][14][15]. For the 1D ZnO nanowires grown through VLS process, the commonly used catalyst was Au [16].…”