Investigation of the Selective Growth of ZnO and Zn(OH)₂Films Deposited by Chemical Bath Near Room Temperature

Abstract

Zinc oxide (ZnO) and zinc hydroxide (Zn(OH)2) thin films were deposited by the chemical bath deposition onto glass substrates at temperatures of 25°C, 35°C and 45°C. The experimental conditions for the selective deposition of the films such as the concentration of the reagents, temperature, and pH of the chemical bath were determined from the predictions of the species distribution diagrams (SDDs) and solubility curves (SCs). SDDs and SCs were elaborated by considering the chemical reagents, temperature, and pH, and give information about the probability of formation of specific compounds. The reagents used were ZnSO4, KOH, and NH4NO3. The physicochemical of the synthesis of both ZnO and Zn(OH)2 films are proposed. X-ray photoelectron spectroscopy and X-ray diffraction indicate the presence of ZnO and/or Zn(OH)2 compounds, where the selective deposition of each material (or coexistence) is dependent on the bath temperature and pH. The crystalline structure was hexagonal (zincite) for ZnO and orthorhombic (wulfingite) for Zn(OH)2. The bandgap energy of the deposited films ranged from 3.32 to 3.51 eV. A better understanding of the selective deposition of specific compounds by controlling the experimental parameters represents an important step toward the fabrication of nanomaterials with tailored properties for a wide range of applications.

Effect of Zn(S,O,OH) Buffer Thin Films Formed on CIGS through Different Stages and Reaction Processes in Chemical Bath Deposition: Interpretations from Mechanisms and Transformation Kinetics Perspective

“…This mechanism focuses more on forming ZnS than ZnO and Zn(OH) 2 on the surface (heterogeneous process). In addition, due to comparable k sp values in the deposition process of ZnS thin films, the formation of Zn(OH) 2 and ZnO can occur as a competitive reaction, [ 34,35 ] as shown in Equations () and ()…”

Deposition of ZnO Thin Films by Chemical Bath Technique: Physicochemical Conditions and Characterization

“…The height of the lines indicates the intensity of the diffraction plane according to the reference JCPDS . For samples obtained at 90°C (Figure 8a 44 By modifying the growth mechanism of the samples, i.e., chemical conditions, important changes in the crystalline structure can be obtained. When the growth mechanism is due only by ammonia complexes (D1 condition) the crystalline structure coincides in relative intensity and position with the standard of ZnO.…”