The development of rapid thermal annealing (RTA) or sintering (RTS) techniques for processing of Si and compound semiconductor metallizations also opens a new avenue for investigations of the initial stages of high-temperature, solid state reactions in thin amorphous multilayers. Of particular interest in this regard are the nucleation and early growth of silicides. In this study we suggest a method to prepare large numbers of specimens for TEM, using deposition of Si/metal/Si tri layers on electron microscope grids and annealing the grids in an RTA system. The method enables quick determination of first silicide phases, nuclei shape and density, relative nucleation and growth rates and, for some systems, the diffusing species. Seven widely used metals are investigated: Co, Cr, Nb, Ni, Mo, Ti, and Ta. The first silicide phases determined from electron diffraction patterns are listed and compared to first phases reported in longer furnace annealings. TEM cross sections of reacted Si/Ta/Si and Si/Nb/Si show two different growth morphologies, which are discussed in terms of main diffusing species in a proposed model.