Effect of Electrolyte Concentration on Epitaxial Growth of ZnO on Cu Substrates through Electrochemical Deposition

Abstract

The roles of zinc and nitrate ions in the electrochemical growth of ZnO were examined in this study. ZnO was deposited on a polycrystalline Cu substrate from electrolyte containing 0.0025–0.08 M zinc nitrate and 0.1–2.0 M potassium nitrate. The morphology, epitaxial orientation relationship, interfacial microstructure, and photoluminescence (PL) properties of the ZnO deposits were characterized. The ZnO morphology was found to be controlled mostly by the zinc ion concentration in the electrolyte. Here, 50–400 nm wide hexagonal pillars were deposited from electrolyte with potassium nitrate concentration as high as 0.4 M. All the deposited films had strong 〈0001〉//ND fibre texture. Most of the ZnO crystallites were grown epitaxially on Cu grains regardless of the electrolyte concentration. The major epitaxial orientation relationship was identified as (0001)ZnO//(103)Cu and [11 2 ¯ 0]ZnO//[010]Cu, and three other epitaxial orientation relationships were also identified. Samples consisting of nanopillars or plates exhibited excellent PL characteristics with near bandgap–deep level emission intensity ratios of 2.4–4.3 and full width at half maximum of the NBE peak of 122–131 meV.

Luminescence properties of epitaxial Cu2O thin films electrodeposited on metallic substrates and Cu2O single crystals

“…In other words, the film deposited on each substrate grain has a specific brightness, indicating that the morphology of the deposited film is affected strongly by the orientation of the substrate grain. This orientationdependent contrast provides an evidence that the films are likely deposited epitaxially [21,25]. Moreover, the SEM micrographs at high magnifications (Fig.…”

Luminescence Properties of Epitaxial Cu2O Thin Films Electrodeposited on Metallic Substrates and Cu2O Single Crystals

“…In other words, the film deposited on each substrate grain has a specific brightness, indicating that the morphology of the deposited film is affected strongly by the orientation of the substrate grain. This orientation-dependent contrast proves that the films are likely deposited epitaxially [ 30 , 37 ]. Moreover, the SEM micrographs at high magnifications ( Figure 1 b,e,h,k) acquired from the squared area in the corresponding low-magnification micrographs show that the films are composed of crystals oriented in the same manner, confirming the hypothesis of epitaxy.…”

“…Five thin film samples were prepared via the electrodeposition method in aqueous solutions containing 0.4 M cupric sulfate (CuSO 4 ·5H 2 O, 99.5% purity) and lactic acid (CH 3 CH(OH)COOH, 90% purity). The pretreatment of the Ag and Cu substrates were reported previously [ 30 , 37 ]. The electrolyte was adjusted to a pH value of 9 or 12 by sodium hydroxide (NaOH, 99% purity).…”