Characterization of electronic charged states of P-doped Si quantum dots using AFM/Kelvin probe

Phosphorous doping to Si quantum dots was performed by a pulse injection of 1% PH3 diluted with He during the dot formation on thermally grown SiO2 from thermal decomposition of pure SiH4, and electron charging to and discharging from P-doped Si dots were studied to characterize their electronic charged states using a Kelvin probe technique in atomic force microscopy (AFM). The potential change corresponding to the extraction of one electron from each of the P-doped Si dots was observed after applying a tip bias as low as + 0.2 V while for undoped Si dots, with almost the same size as P-doped Si dots, almost the same amount of the potential change was detectable only when the tip bias was increased to ∼ 1 V. It is likely that, for P-doped Si dots, the electron extraction from the conduction band occurs and results in a positively charged state with ionized P donor.