Ferroelectric behavior of bismuth titanate thin films grown via magnetron sputtering

Bismuth titanate (BixTiyOz) thin films were grown using the r.f. magnetron sputtering technique on (100) silicon substrates. In the process, annealing was performed in both oxygen and dry air atmospheres at 600 °C for 30 and 120 min. The structure of the thin films was characterized through X-ray diffraction (XRD), and the ferroelectric response was determined with measurements of piezoelectric force microscopy (PFM). Bi4Ti3O12 with a predominant orthorhombic phase was obtained in the annealed thin films. All the annealed films exhibited the characteristic hysteresis and butterfly loops of ferroelectric materials. Thermal annealing of BixTiyOz films in an atmosphere of air for 30 min resulted in the highest d33 value of 78±14 pm/V, which decreased to 64±26 pm/V for 120 min. On the other hand, annealing in an oxygen atmosphere produced BixTiyOz films with more uniform d33 values, 54±3 pm/V and 42±6 pm/V for 30 and 120 min, respectively. Ferroelectric coefficient values decreased with the increase of annealing time in an oxidant atmosphere, which can be explained by the vacancies present. These results are consistent with the experimental measurements carried out in other investigations.