Journal of Colloid and Interface Science, Vol.378, 77-82, 2012
Degradation of bare and silanized silicon wafer surfaces by constituents of biological fluids
The 24 h stability of bare silicon wafers as such or silanized with CH3O-(CH2-CH2-O)-C3H6-trichlorosilane (n = 6-9) was investigated in water, NaCl, phosphate and carbonate solutions, and in phosphate buffered saline (PBS) at 37 degrees C (close to biological conditions regarding temperature, high ionic strength, and pH). The resulting surfaces were analyzed using ellipsometry, X-ray Reflectometry (XRR), X-ray Photoelectron Spectroscopy (XPS), and Atomic Force Microscopy (AFM). Incubation of the silanized wafers in phosphate solution and PBS provokes a detachment of the silane layer. This is due to a hydrolysis of Si-O bonds which is favored by the action of phosphate, also responsible for a corrosion of non-silanized wafers. The surface alteration (detachment of silane layer and corrosion of the non-silanized wafer) is also important with carbonate solution, due to a higher pH (8.3). The protection of the silicon oxide layer brought by silane against the action of the salts is noticeable for phosphate but not for carbonate. (C) 2012 Elsevier Inc. All rights reserved.