Hydrophobic to hydrophilic transition of HF-treated Si surface during Langmuir-Blodgett film deposition

HF-treated Si surface, which is hydrophobic in nature and quite stable in air and inside pure water, can become completely hydrophilic during nickel arachidate Langmuir-Blodgett film growth. Such transition is clearly evident from the structures of films deposited by different number of strokes and can be understood by considering partial oxidation of Si surface inside subphase water and further or complete oxidation in air, in presence of Ni head-groups. Attached Ni head-groups weaken the nearby Si-Si covalent bonding and easily oxidize those Si atoms. Depending upon the amount of those head-groups and its distribution, oxidation or transition can even complete. (C) 2010 Elsevier B.V. All rights reserved.