Influence of N2 spinning atmosphere on electrical properties of Ba(Ti0.85Sn0.15)O3 ferroelectric thin films for dielectric bolometer mode infrared sensor applications

Polycrystalline Ba(Ti0.85Sn0.15)O-3 (BTS15) thin films have been prepared on Pt/Ti/SiO2/Si wafers by Metal-Organic Decomposition (MOD) process. Spin-coating was performed in N-2 atmosphere using different gas flow rates from 0 to 5 l/min while keeping the other fabrication steps the same. The influence of N-2 gas during the spin-coating was investigated. Investigations using XRD and AFM revealed that nitrogen gas flow plays an important role in obtaining films with a good crystallinity and a good grain size/RMS roughness ratio. Also, XPS and UV-PYS investigations revealed that, for the samples obtained when using 4 l/min N-2 flow during spinning, the concentration of oxygen vacancies has the smallest value among the investigated samples. The BTS samples with nitrogen flow rate of 4 l/min have the highest polarization and the smallest leakage current among the investigated samples. Changes in electrical properties were explained considering the fact that the grain size and the roughness of the sample are affected by the different nitrogen flow rate and that the oxygen vacancy concentration is also influenced by the N-2 gas flow. Temperature Coefficient of Dielectric constant (TCD), a parameter of infrared sensitivity, becomes more than 1%/K for a large temperature range when the N-2 flow rate was 4 l/min, making this film suitable for infrared sensing applications.