The effect of the underlying substrate on crystallization kinetics of TiNi thin films

The crystallization kinetics of amorphous thin TiNi films deposited on SiO2 (or NaCl)/Al foils substrates were investigated. A dramatic acceleration of the crystallization rate was observed for amorphous attached-substrate films. The acceleration originated from the presence of the thin film/middle-wafer interface which served as a two-dimensional nucleus for the growth of the crystalline phase. In the process of non-isothermal annealing by DSC, apparent activation energies for two kinds of underlying thin TiNi films were determined to be 352.96 and 403.69 kJ/mol, respectively, which was lower than those free-standing films studied in previous works. For the process of isothermal annealing, the crystallization kinetics parameters had remarked drop, reflected from the lower Avrami exponent n (the range of 1.35–2.11) and shorter incubation time τ (the range of 0.1–0.4 min) between 758 and 775 K.