Observation of photovoltaic effect within locally doped silicon nanojunctions using conductive probe AFM

Localized p-doped nanojunctions (200–300 nm in diameter) were formed in n-type crystalline silicon substrates and were characterized using scanning electron microscopy (SEM) and conductive-probe atomic force microscopy (C-AFM). Localized doping was performed by diffusion through sub-micron sized holes in a silicon-oxide mask defined using self-organized polystyrene nanoparticles. After oxide removal, a significant brightness contrast in the SEM top and side view images strongly suggested the successful local doping of these areas. Furthermore, local current-voltage measurements performed by C-AFM revealed an open circuit voltage and a short-circuit current only in the areas defined as nanojunctions. This photovoltaic effect is driven by the laser used to control cantilever deflection in the AFM.