Effects of an adsorbed water layer and self-assembled organosilane monolayers on scanning probe microscopy of silicon pn structures

Kelvin probe force microscopy (KFM) and scanning capacitance microscopy (SCM) were applied to two-dimensional profiling of silicon pn-structures covered with a thin oxide layer. The surface potential contrast between the p- and n-type regions depended on the hydrophobicity of the oxide surface when KFM imaging was conducted in humid air. Since samples with less adsorbed water on their surface showed greater potential contrast, the contrast degradation in KFM imaging is attributed to a shielding effect of the adsorbed water layer. The contrast in SCM imaging became smaller by applying organosilane self-assembled monolayers (SAM) on the sample surface of the silicon pn structures. The effects of the SAM monolayers to n and p silicon regions were different. These SCM results imply band bending of the substrate silicon.