The growth mechanism and the barrier performance of Al2O3, SiO2 and a binary Si-Al oxide (SiAlxOy) deposited by spatial atomic layer deposition (SALD) were investigated. Alumina and silica were deposited by TMA and BDEAS with growth-per-cycles (GPC) of 0.16 and 0.013 nm, respectively. Interestingly a significant higher GPC of 0.225 nm was found for SiAlxOy. Although alumina in principle has excellent barrier properties, the films easily degraded and lose their barrier performance if exposed to water vapor at elevated temperatures. Therefore, the barrier performances of these films were investigated under harsh environment conditions. We found that the barrier performance of 100 nm Al2O3 failed in less than one day at 70 °C with 70 % relative humidity, whereas 100 nm SiAlxOy sustained for approximately one week. However, the resistivity of those barrier systems was significantly improved by inserting a single 3.3 nm SiO2 layer into the barrier films. In this way the barrier system withstands up to 5 months and the intrinsic water vapor transition rate was reduced by two to three orders of magnitude to ∼10-4 g/m2/day at these tough aging conditions.