Photocurrent mapping with submicron resolution on the silicon-electrolyte junction by using near-field optics

We have developed a technique allowing photocurrent (PC) mapping of silicon surface in contact with an electrolyte which offers an unprecedented spati al resolution. The photocurrent is generated by near-field optics using an optical tip with a 100 nm diameter aperture as an illumination source. The comparison between topographic and photocurrent mapping of SiO2/Si mesas is used to demonstrate the feasibility of such a technique. Topographic and P C images show 300 nm lateral resolution. It is shown that this resolution i s topography limited, i.e., determined by the tip-topography interaction. I ndeed, PC mapping on topography-less patterned porous silicon/silicon sampl es shows that the lateral resolution can be as good as 100 nm, limited by t he aperture size. (C) 2001 American Institute of Physics.