Charging States of Si Quantum Dots as Detected by AFM/Kelvin Probe Technique

Hemispherical Si quantum dots have been self-assembled on thermally grown 3.2-nm-thick SiO2/p-Si(100) by low-pressure chemical vapor deposition of silane. The charging states of the Si quantum dots have been detected as surface potential changes by using an atomic force microscopy/Kelvin force probe method. From the relationship between the measured surface potential changes and the charging energy of a single dot, the number of electrons retained in a dot has been estimated to be one. Furthermore, it is found that electron extraction from neutral dots can be achieved to create a hole at each dot.