Effects of Plasma Pretreatment on ZnO Deposition by SILAR on SiO₂, HfO₂, and Glass Substrates

Abstract

Zinc oxide (ZnO) films are deposited onto glass, silicon oxide, and hafnium oxide substrates via the successive ionic layer adsorption and reaction (SILAR) method. The substrates are subjected to an oxygen plasma treatment prior to the deposition to increase the hydrophilic character of the film surface and improve the morphological and structural properties of the resulting ZnO films. Crystallinity, surface morphology, and thickness of the films with and without the plasma treatment are thoroughly evaluated by multiple characterization techniques. The oxygen plasma treatment increases the substrate's surface roughness significantly which results in an increase in the nucleation sites. The plasma treatment yields thicker films in all the substrates compared with substrates without the plasma treatment. The thickness of the ZnO deposited on glass substrates increases as the rinsing time increases, while the opposite is observed for films deposited on both silicon and hafnium oxide substrates. The higher porosity of the ZnO films grown on silicon dioxide and hafnium dioxide substrates leads to a higher surface area that increases the removal of the deposited ZnO on these substrates with the rinsing during the SILAR deposition, resulting in an overall thickness reduction of the film.

SILAR Deposition of Metal Oxide Nanostructured Films

“…For example, in a comparative study ZnO films have been deposited via SILAR on glass, pure SiO 2 and HfO 2 substrates, with and without a prior plasma cleaning. [200] The oxygen plasma pre-treatment caused a significant increase in surface energy which was demonstrated by a reduction in the water contact angles for all three substrate types (Figure 7a). [Zn(NH 3 ) 4 ] 2+ at a pH of 11 was utilized as the cationic precursor while ethylene glycol at 120 °C was employed as the anionic precursor.…”

“…Figure 7. a) Reduction in contact angles in untreated (top images) and treated (bottom images) substrates; b) SEM images of ZnO films deposited on treated (O 2 plasma) and untreated substrates. Adapted with permission [200]. Copyright 2018, Wiley-VCH.…”