Elucidating the mechanism of water adsorption on aluminum surface by SIMS

This study investigated the adsorption of water on aluminum surface. Aluminum samples exposed to different amounts of water vapor, with or without nitrogen gas mixture, were analyzed by a secondary ion mass spectrometer (SIMS). A two stage load-lock system was used to reduce the water vapor contamination attributed from the transfer of the samples. Experimental results indicate that the background water signal on the sample is linearly proportional to the amount of exposure. However, the intensity of background water signal on the sample displayed a power of 3.8 of the maximum transient pressure in the main chamber during sample transfer. Additionally, the effect of adiabatic expansion on water adsorption was studied by comparing different exposure conditions with respect to the intensity of water signal. According to those results, more water was adsorbed on aluminum surface when the exposure water mixed with nitrogen gas of 1 atm. This finding implies that adiabatic expansion may be a mechanism of water adsorbed on sample surface during evacuation