Different ZnO Nanostructures Fabricated by a Seed-Layer Assisted Electrochemical Route and Their Photoluminescence and Field Emission Properties

Abstract

A simple seed-layer assisted electrochemical deposition (ECD) route has been successfully developed for preparation of different ZnO nanostructures, and their optical and field emission properties are also studied. ZnO films, nanowires, and nanosheets could be prepared in a rational way by just controlling the ECD current density. The corresponding growth mechanisms are also discussed on the basis of the characteristics of the ZnO crystal structure and the influences of the seed-layer and ECD current density. Except for ZnO nanosheets, both the room-temperature and low-temperature photoluminescence measurements of the ZnO films and nanowire arrays show strong ultraviolet excitonic emission, which proves their good crystal quality. Detailed analysis of the field emission (FE) properties indicates that the hierarchical ZnO nanowire array shows good FE property due to their high aspect ratio, small radius curvature, and proper density.

Ultraviolet Sensors Based on Two-Dimensional Zinc Oxide Structures

“…This band was related to the surface defects; the source of these defects may be attributed to the oxygen vacancies or zinc interstitials [57,60]. Furthermore, the strong dependence of the PL peak locations and intensities of ZnO nanostructures on the size and shape of the nanostructures was noted [35,61].…”

“…Several 2D ZnO structures, such as 2D plate [27], nanodisk [35], and nanosheet [59] ZnO structures, show low intensity of the near edge UV emission, which was attributed to the surface states being nonradioactive centres due to their large surface-to-volume ratio [60] and higher intensity in the visible broadband. This was attributed to the wide surface area of the 2D structures that make the density of surface defects higher compared to the other ZnO structures, such as nanorods and nanowires [57,60].…”

One-dimensional ZnO nanostructures: Solution growth and functional properties

“…A photoluminescence spectrum of ZnO nanowires at 4.2 K is shown in Fig. 40(b) [338]. Generally as the temperature was decreased from room temperature to 4.2 K, the photoluminescence intensity increased [104], and its temperature dependence [184].…”

“…Density of emitters plays an important role. If it is too low, then the emission current density will be low; if it is too high, then the local electric field around the emitter tips will have an electrostatic screening effect induced by the neighboring nanowires, which generally lowers the β value [112,338]. Φ is the emitter work function, which is about 5.4 eV for ZnO [337].…”

Optical Properties of ZnO/ZnS and ZnO/ZnTe Heterostructures for Photovoltaic Applications

“…In addition, more complicated structures such as nanobelts 7,8 , nanohelices 9 , and others [10][11][12] have been synthesized. Unfortunately, the ZnO band gap (3.4 eV) is too large for use in efficient photovoltaic devices.…”