Influence of electrochemical deposition parameters on morphological properties of ZnO on Si (100)

Abstract

In this study, ZnO layer was deposited on Si (100) by electrochemical deposition (ECD) technique. Mixture of zinc chloride (ZnCl2) and potassium chloride (KCl) at different volume ratio was used as the electrolyte. The current density was fixed at 10 mA cm−2 with deposition time of 50 and 30 min. The effect of substrate treatment has also been observed to improve the adhesion of the deposited layer. The morphology of the ZnO layer was analyzed using field emission scanning electron microscopy (FESEM), and variable pressure scanning electron microscopy (VPSEM) equipped with energy dispersive x-ray (EDX) module. Four types of ZnO structure had been obtained; needle, flake, coral and pillar-like structures at different deposition conditions. These structures were obtained by changing several parameters such as substrate doping and chloride medium of electrolyte. It was found that the flake-size become smaller as the amount of Chloride ion (Cl−) in electrolyte increased. In addition, substrate type also found to affect the deposition process. As indicated by the EDX spectra, the ZnO is managed to fully cover the target area of deposition for the n-type Si substrate but a bit poor on p-type Si substrate. The targeted EDX ratio of Zn:O is 1:1, which indicates balance stoichiometry of ZnO. However, the best EDX ratio of Zn:O found in this study was only 1.4:1 which was achieved from deposition on p-type Si substrate with no post-annealing applied. The thickness of deposited ZnO was found to decrease with decreasing deposition time. The average thickness was more than 150 μm for 50 min deposition while 30 min deposition yielded thickness less than 100 μm. It is clearly shown that parameters such as time, electrolyte volume ratio and substrate doping have influence on the morphology and thickness of the deposited ZnO on Si (100) by ECD process.