Temperature-dependent electrical conduction in porous silicon: Non-Arrhenius behavior
Department of Chemical Engineering, Faculty of Engineering, Hiroshima University
1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan
2 Materials Science & Engineering, Henry Samueli School of Engineering University of California, Irvine, CA92697-2575, USA
Accepted: 13 February 2001
A model for the temperature dependence of electrical conduction in a porous silicon (PS) layer is introduced based on the consideration that the onset of electrical conduction is dependent on the formation of a continuous network of conducting sites extending the entire thickness of a PS layer. At an arbitrary temperature, a PS layer consists of both unblocked and blocked sites (blocking energies are larger than thermal fluctuation energy). The fraction of unblocked sites increases with temperature. At low temperatures () a PS layer is mainly dominated by a continuous network of blocked sites, while discrete unblocked sites do not form any continuous network extending the entire thickness of a PS layer. At medium temperatures () both continuous networks of unblocked and blocked sites appear in a PS layer. And at higher temperatures (), a PS layer is mainly dominated by a continuous network of unblocked sites, while discrete blocked sites do not form any continuous network extending the entire thickness of a PS layer. Contrary to the prevalent views, the overall temperature dependence of the electrical conductivity of a PS is not always Arrhenius: it obeys a Vogel-Tammann-Fulcher (VTF) law at , becomes insulating at , and exhibits the Arrhenius behavior only for . Both T1 and T2 are found to increase with the decrease silicon nanocrytallites sizes. The VTF behavior was derived using the mean-field approximation for Ising model and found to agree with experimental evidences.
PACS: 73.23.-b – Electronic transport in mesoscopic systems / 73.50.-h – Electronic transport phenomena in thin films / 73.61.Tm – Nanocrystalline materials
© EDP Sciences, 2001