Autocorrelation function (ACF) analysis has been applied to the high-resolution transmission electron microscope images of amorphous interlayers formed in the interfacial reactions of ultrahigh vacuum (UHV)-deposited titanium thin films on (001) Si. Ti, Ti5Si3 and Ti 5Si4 were found to form in Ti-rich layers in the as-deposited samples. On the other hand, the nanocrystallites of C49-TiSi 2 and C54-TiSi2 were present in Si-rich layers. The thickness of the amorphous intermining layer increases in multilayered structure with annealing temperature. Phases formed in 573-973 K (300-700°C) annealed samples were also determined.