Crossover from Efros–Shklovskii variable range hopping to nearest-neighbor hopping in silicon nanocrystal random network

Abstract

We investigate how random structure affects the electrical transport of a silicon nanocrystal network. The temperature dependence of conductivity follows G ∼ exp[−(T0/T)1/2] between 70 and 160 K. By using T0 = 5765 K obtained by data fitting, the electron localization length is estimated to be 4.1 nm, which corresponds to the mean diameter of silicon nanocrystals. Above 160 K, G follows Arrhenius-like behavior. These temperature dependences are well described by Efros–Shklovskii variable range hopping (ES VRH) with a Coulomb gap and nearest-neighbor hopping (NNH). A crossover between ES VRH and NNH is observed at 160 K.