Effect of reaction temperature on surface morphology and photoelectric properties of ZnO grown by hydrothermal method in mixed solvent

Abstract

ZnO thin films were prepared by hydrothermal method in mixed solvent with different reaction temperatures. Microstructure, surface morphology, optical properties and UV photoresponse of the thin films have been investigated by means of X-ray diffractometer, scanning electron microscopy, laser micro-Raman spectrometer, UV-Vis spectrophotometer and interactive source meter instrument. The results indicated that ZnO thin films consist of ZnO nanoparticles with hexagonal wurzite structure. A small quantity of Zn(OH) 2 appear as reaction temperature increase to 125°C. ZnO thin film grown at 175°C consists of many densely vertically aligned ZnO nano rods on the substrate and has the best preferential c-axis orientation. Three peaks centered at about 446, 568 and 1150 cm -1 have been attributed to E 2 (high), A 1 (LO) and 2A 1 (LO) phonon mode. Broadening of the visible emission band may be attributed to abundant surface defects and surface states of the thin films. Variation of the E g may be attributed to the synergy of surface morphology and oxygen-vacancy (V O ) density. The fast and slow UV photo response may be attributed to the adsorption and photo desorption of oxygen molecules on the surface of ZnO thin films and exchange process between oxygen gas and native deep defect level, respectively.

Tuning the Surface Morphologies and Properties of ZnO Films by the Design of Interfacial Layer

“…Previous reports have indicated that lattice mismatch between ZnO and sapphire could persist even in a film as thick as 1 μm, leading to a redshift of 50 meV for the band-edge emission peak [ 45 , 46 ]. In addition, variations of the surface morphology and oxygen vacancy population are also the factors that cause this change [ 47 ]. The PL emissions of the two ridge-like films exhibit much stronger intensities with FWHMs of 123 and 133 meV for ZnO-R1 and ZnO-R2, respectively, which are smaller than that of the particle-like sample and smaller than that of a ZnO film grown on the (111) plane of cubic YSZ [ 48 ].…”

“…Particularly, a green emission band appears at approximately 2.5 eV in ZnO-P, which is similar to that of a ZnO film deposited on MgO(100) [ 49 ]. In general, oxygen vacancies [ 50 ], surface morphology [ 47 , 51 ], and oxygen clusters formed on the surface [ 52 ] are major origins for the green emission band. ZnO films with densely vertically aligned ZnO nanorods have been reported to possess stronger green emission bands relative to films with small particle and nanosheet morphologies [ 47 ].…”

“…In general, oxygen vacancies [ 50 ], surface morphology [ 47 , 51 ], and oxygen clusters formed on the surface [ 52 ] are major origins for the green emission band. ZnO films with densely vertically aligned ZnO nanorods have been reported to possess stronger green emission bands relative to films with small particle and nanosheet morphologies [ 47 ]. Additionally, the stronger visible emission band likely originates from the abundant surface defects and surface states of the thin films with larger specific surface area.…”

Study on the Preparation and Characterizations of an Improved Porous Ti/TiO2/CdS‐CNT/C3N4 Photoelectrode and Photoelectric Catalytic Degradation of Methylene Blue

“…The degradation was 42.5%, 64.6% and 98.3% for the Ti/TiO 2 /CdS‐CNT/C 3 N 4 electrode in the EC, PC and PEC reaction conditions, respectively. It was obvious that PEC efficiency of Ti/TiO 2 /CdS‐CNT/C 3 N 4 electrode is almost the summation of EC and PC efficiency because of the photoelectric synergy …”

Review—Nanostructural ZnO-Based Electrochemical Sensor for Environmental Application

“…76 Small pyramidal particles, ZnO NSs and NRs can also be controlled by changing growth temperatures. 77 Different reaction times affected 61 (d) Ostwald ripening mechanism for the formation of mesoporous hollow spheres (Copyright@ Elsevier 2018. All rights reserved, reprinted with permission).…”