Nanocomposites and nanomaterials

Electrical properties of Na0.5Bi0.5TiO3 thin films deposited on sitall substrates.
 Kruzina T.V., Popov S.A., Potapovich Yu.N., Ryabtsev S.I., Rutskiy A.S.
Physics and electronics dept., Oles Honchar Dnipro National University, Gagarin Avenue, 72, Dnipro, 49010, Ukraine. 
E-mail: spopov@meta.ua

Despite some technological achievements in preparation of Na0.5Bi0.5TiO3 (NBT) films, the relationship between their electrical properties and such factors as technological parameters, the substrate material, as well as the material of the lower electrode and the state of its surface has not been studied sufficiently. Such important disadvantage of NBT films as presence of significant leakage currents (~10-7A/cm2) [1] can also be influenced by abovementioned factors. Although most often NBT films are formed on Pt/TiO2/SiO2/Si substrates, in this work we investigate electrical properties of NBT films deposited by the RF magnetron sputtering on sitall substrate. A Pt layer (of 85 nm thickness) was used as the lower electrode. To synthesize the ferroelectric phase, deposited NBT films were heat treated in the air at 700°C for 45 minutes. XRD analysis showed the presence of a perovskite polycrystalline structure. Obtained NBT films had the following ferroelectric parameters: ε =~800, Pr = 9 µC/cm2. The measured leakage currents were J=6.8·10-10A/cm2 (200С), J=7.8·10-9A/cm2 (1000С), J=2.2·10-7A/cm2 (1500С) at applied electric field of E=2 kV cm-2. The ln(J)-E graph showed presence of linear sections in the 2–30 kV/cm range of electric fields that indicates involvement of several conduction mechanisms. It is assumed that contribution of the space-charge limited currents predominates in the region of electric fields E<10kV/cm, while the Schottky type emission dominates in the region E>10 kV/cm. Also, the conduction in NBT is determined by oxygen vacancies [1,2]. The J for the films obtained on sitall substrates had lower values compared to films on Pt/TiO2/SiO2/Si substrates [1]. Perhaps that is determined by reduced number of oxygen vacancies at the grain boundaries, whose structure and dimensions are determined by the morphology of the film-substrate interface.

1.	Kruzina T. V., Popov S. A., Potapovich Yu. N., Rutskyi A. S. Effect of thermal treatment on structure and leakage current of Na0.5Bi0.5TiO3 thin films// Journal of physics and electronics.- 2018. - Vol. 26(1).- P. 53-56.
2.	Zhou, Z.H., Xue J.M., Li. W.Z. Leakage current and charge carriers in (Na0.5Bi0.5)TiO3 thin film // J.Phys.D. Appl.Phys.- 2005.- 38.- Р. 642-648.