Multiple layers of aluminum silicate and silicon dioxide deposited by room-temperature atomic layer deposition for enhanced cation sorption

Abstract

Multiple layers of aluminum silicate and SiO2 are deposited at room temperature (RT) by repeating a combination of aluminum-silicate atomic layer deposition (ALD) and a plural number of SiO2 ALDs. The RT-ALD is performed by using precursors of tris(dimethylamino)silane and trimethyl aluminum (TMA). The oxidizing gas is plasma excited humidified Ar. A cross-sectional transmission electron microscope and angle resolved x-ray photoelectron spectroscopy suggest that aluminum from the TMA molecule is diffused to SiO2 to form an aluminum silicate layer with the Al rich surface at RT. The deposited film shows an enhanced Na sorption in an NaCl aqueous solution of 10 mM, compared with the pure aluminum silicate layer without the SiO2 layer. It is assumed that the bond formation of Al–O–Al in the aluminum silicate film is suppressed by limiting the thickness of the aluminum silicate layer. Multiple films are also applicable for Cs and K ion sorption. The effects of the multiple layers on the ion sorptivity are discussed in the paper.