Hopping conduction in size-controlled Si nanocrystals

We investigate the temperature dependence of conduction in size-controlled silicon nanocrystals. The nanocrystals are similar to 8 nm in diameter, covered by similar to 1.5 nm thick SiO2 shells. In 300 nm thick films for temperatures T from 30 to 200 K, the conductivity sigma follows a ln(sigma) vs 1/T-1/2 dependence. This may be associated with either percolation-hopping conductance or Efros-Shklovskii variable range hopping. Assuming hopping sites only on the nanocrystals, the data agree well with the percolation model. (c) 2006 American Institute of Physics.