where the rate of surface coverage changes consists of (a) the irre- versible reaction rate coefficient k1 (b) the fraction of open sites on substrate surface ð1 hO hAlðCH3Þ2Þ (c) the fraction of available hydroxyl hOH; (d) the depletion of absorbed methyl by R2, ð2 hOHÞ [13]. When the TMA pulse injection and the following up purge process are completed, the second water pulse will be applied, and the surface coverage of methyl and hydroxyl are influ- enced by reaction R3 and R4. Considering the chemisorbed TMA molecules have two methyls on each oxygen bridge site, the related surface coverage changing rates yield,