Hopping conduction in Mn-doped ZnO

The dc and ac conductivities of Mn-doped ZnO were investigated at temperatures from 10 to 100 K. The temperature dependence of the dc conductivity from 10 to 100 K shows an abrupt change at similar to18 K, manifesting a much lower activation energy for conduction below 18 K. From 10 to 18 K, the ac conductivity, sigma(ac)(omega), varies as sigma(ac)(omega)=Aomega(s) in the frequency range from 10(2) to 10(6) Hz with s in the range of 0.6-1. The dc and ac conductivity observations suggest that the dominant conduction mechanism at temperatures between 10 to 18 K in these samples is a hopping conduction. (C) 2003 American Institute of Physics.