By Scanning Probe Microscope

Due to their ultra-sharpness of scanning probe, scanning probe microscopes have been used to fabricate nanoscale p-n junction in silicon [172], and submicron bipolar transistors in CuInSe2 [173, 174]. It was found that application of local, strong electric fields, at ambient temperatures, to originally electrically homogeneous crystals of doped Si and CuInSe2 semiconductors induces nonequilibrium doping profiles in them. Conductive atomic force tips are used to induce a strong electric field between tip and semiconductor surface. Davidsson et al. [175] exposed thin resist layer with electrons by using atomic force microscope. Fifty nanometer long, 6-nm-thick Al lines were fabricated which can be used to define small tunnel junctions.

It is worth noting that another type of nanojunctions can be made by simply laying one nanowire or nanotube across another. Nanotube-V2O5 nanofiber junction is an example [176]. Nanowire cross-junctions can be routinely obtained by microfluidic alignment method [177, 178]. However, in order to achieve high density and reliable nanojunction arrays, tremendous technical breakthroughs are necessary.

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