Atomic layer deposition of ZnO on thermal SiO_2 and Si surfaces using N_2-diluted diethylzinc and H_2O_2 precursors

摘要

ZnO nanodots are attracting more and more attention in various photoelectrical applications due to multiple excition generation. In this article, atomic layer deposition (ALD) growth of ZnO nanodots has been realized for the first time on both thermal SiO_2 and Si surfaces using N_2-diluted gaseous DEZn and H_2O_2 precursors. The experimental results indicate that the ALD ZnO exhibits a nano-crystalline film with corrugated surfaces in the case of the deposition temperature of 200 ℃, likely due to concrescence among ZnO nanodots. When the deposition temperature is increased up to 300 ℃, ZnO is grown in the form of well-discrete nanodots. This is due to increased desorption of the reacting molecules and a reduction of nucleation sites on the growing surfaces at 300 ℃, thus leading to the reaction between DEZn and -OH groups only on some favorable sites from thermodynamic and energy points of view. In terms of the thermal SiO_2 surface, ZnO nanodots with a density of around 5 × 10~(10) cm~(-2) are obtained for 100 cycles. As for the Si surface, ZnO nanodots with a density as high as ～ 1 × 10~(11) cm~(-2) are achieved for 50 cycles. Finally, the X-ray photoelectron spectroscopy and X-ray diffraction analyses reveal that the ALD ZnO at 300 ℃ is dominated by Zn-O bonds together with a small quantity of Zn-OH bonds, and the deposition temperature of 300 ℃ can result in preferential growth of ZnO (002) orientation and a bigger crystallite size.