Direct Observation on Impurity Distribution in Phosphorous/Boron Co-Doped Si Nanocrystals

Doping in Si nanocrystals is an interesting topic and to directly study the dopants distribution in phosphorous/boron co-doping circumstance is one of the important issue nowadays. In this study, atom probe tomography is performed to study the structures and impurity distribution in phosphorous/boron co-doped Si nanocrystals/SiO2 multilayers. Comparing with phosphorous singly-doped Si nanocrystals, it is interesting to find the phosphorous concentration in co-doped samples can be significantly improved. Theoretical simulation suggests that phosphorous-boron pairs are formed in co-doped Si nanocrystals with the lowest formation energy, which also reduce the formation energy of phosphorous in Si nanocrystals. The results indicate co-doping can promote more phosphorous impurities enter into the near-surface and inner sites of Si nanocrystals, which provides an interesting way to regulate the electronic and optical properties of Si nanocrystals like the observed enhancement of conductivity and sub-band light emission.