  The electrical conductivity behavior of highly crystallized undoped
hydrogenated microcrystalline silicon films having different microstructures
was studied. The dark conductivity is seen to follow Meyer Neldel rule (MNR) in
some films and anti MNR in others, depending on the details of microstructural
attributes and corresponding changes in the effective density of states
distributions. A band tail transport and statistical shift of Fermi level are
used to explain the origin of MNR as well as anti-MNR in our samples. We
present the evidence of anti-MNR in the various experimental transport data of
microcrystalline silicon materials reported in literature and analyze these
data together with ours to show the consistency and physical plausibility of
statistical shift model. The calculated MNR parameters and other significant
material parameters derived therefrom are tenable for a wide microstructural
range of the microcrystalline silicon system.
