Structure, optical properties and visible-light-induced photochemical activity of nanocrystalline ZnO films deposited by atomic layer deposition onto Si(100)

Abstract

Nano-layers of ZnO (thickness 2–300nm) were deposited on the surface of p-Si(100), SiOx/p-Si(100), and n-Si(111) using the atomic layer deposition technique. Morphology, microstructure, and electronic structure of the ZnO/Si(100), ZnO/SiOx/Si(100), and n- Si(111) films were characterized using scanning electron microscopy, X-ray diffraction and reflectometry, and X-ray photoelectron spectroscopy. The layers have good adhesion to the substrate, polycrystalline structure, and uniform thickness. Starting from the thickness of 4nm, the hexagonal crystal structure of zincite (wurtzite-type) could be detected with a weak texture changing from [100] to [001] with increasing thickness of the layer. Desorption of H2O and CO2 at ~10−4Pa from the surface under irradiation with visible light (λ>500nm)—the interval of ZnO transparency—was measured by mass-spectrometry. This proves a sensitization of the photocatalytically active ZnO films to the visible light by silicon substrate and opens possibilities of using the composite Si/ZnO materials.