Hopping conduction in size-controlled Si nanocrystals

We investigate the temperature dependence of conduction in size-controlled silicon nanocrystals. The nanocrystals are ∼8nm in diameter, covered by ∼1.5nm thick SiO2 shells. In 300nm thick films for temperatures T from 30to200K, the conductivity σ follows a ln(σ) vs 1∕T1∕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.