Experiments of deep‐level transient spectroscopy and transmission electron microscopy (TEM) observations have been carried out on heat‐treated &Sgr;=25 silicon bicrystals precontaminated with nickel before being heat treated at various temperaturesTa. For the lowestTavalue (600 °C), the electronic interface states were found to be shared between two overlapping narrow continua aroundEc−0.63 eV andEc−0.52 eV. Upon increasingTa, these states shift toward shallow positions and exhibit a marked tendency to shrink and to turn into a unique trap level. While the annealing at 900 °C has led to a single state atEc−0.50 eV, this later moved toEc−0.48 eV for 1000 °C and then toEc−0.44 eV for 1100 °C, with an accompanying consistent lowering in the barrier height (BH). TEM observations demonstrated the formation of pure type‐B NiSi2platelets for 800 °C, but indicated an increasingly important growth of type A for increasingly higherTavalues. While the existence of a unique trap level at highTacould be explained, like previous findings, by some ‘‘uniform’’ coverage of the boundary by the precipitates, the displacement of the interface state(s) toward shallower positions, together with the reduction of the potential barrier, are interpreted in terms involving the increasing contribution of A‐type plates with their low BH in addition to that of B‐type silicides with their high BH. ©1995 American Institute of Physics.