Monofunctional alkylsilanes, CH3(CH2)n-1Si(CH3)2R with n varying from 4 to 30 and the hydrolyzable group R = Cl or N(CH3)2, were deposited on quartz slides and on nanometric silica. Due to the presence of only one hydrolyzable group for these alkylsilanes, silane monolayers result from the grafting process. Two methods for silanization were considered: deposition from a solvent (derived from Sagiv's process) and vapor phase deposition (derived from Kovats's process). In vapor phase deposition, the physisorbed water is mainly removed from the surface during the conditioning of the specimens, whereas this is not the case for the solvent method. In addition, the two deposition processes do not take place at the same temperature: the silane needs to be heated under vacuum for the vapor deposition method, whereas the reaction takes place at room temperature for the solvent method. Characterizations of the grafting efficiency and of the structure of the grafted layers were performed with different techniques ...