Crystallization of sputtered BaTiO3-based thin films: A differential scanning calorimetry study

Crystallization behavior of sputtered BaTiO3 and Nb-doped BaTiO3 thin films has been characterized by means of the differential scanning calorimetry (DSC). The crystallization of as-deposited amorphous structure to the equilibrium crystalline structure is confirmed as an irreversible, exothermic, first-order transition. Our in situ DSC result confirming the metastable nature of sputtered films is in agreement with that of a conventional, ex situ x-ray diffraction result. At a heating rate of 20 °C/min, the crystallization peak temperature of BaTiO3 film is found to be 467.6 °C and to increase with the addition of Nb. Activation energies for crystallization are determined by Kissinger's method to be 139.2, 99.3, and 81.0 kJ/mol for pure BaTiO3, BaTiO3–2 at. % Nb, and BaTiO3–3 at. % Nb films, respectively. The decrease in activation energy suggests the addition of Nb tends to assist the thermal-activated crystallization process in sputtered films.