Thickness limit of BaTiO_3 thin film capacitors grown on SUS substrates using aerosol deposition method

摘要

We fabricated BaTiO_3 thin films with 2.2-0.1 nm thickness on hard stainless steel (SUS) substrates by using the ADM to confirm the causes of dielectric thickness limit showing in BaTiO_3 thin films prepared on SUS substrates and suggest key factors which can overcome the limit Then, from the measurements of thickness dependence of their dielectric properties, the thickness limit of 0.2 nm was confirmed and to confirm the reason why their dielectric properties could not be measured in the thickness below 0.2 μm, the thickness dependence of leakage current mechanisms in BaTiO_3 films were investigated. As a result, by decreasing the thickness of films from 2.2 to 0.2 μm, the mechanism changed from Poole-Frenkel emission to modified-Schottky emission indicating increase of interface effects. Especially, in the case of 0.2 μm thickness, it was confirmed that the dominant mechanism was Fowler-Nordheim tunneling based on electric field concentration at a high electric field. Consequently, from this investigation of leakage current mechanism, it can be expected that the cause of thickness limits was electric field concentration at rough BaTiO_3/SUS interfaces forming in AD process, and to get over the thickness limit and decrease level of leakage currents, the hard substrates are required to reduce the interface roughness and oxygen vacancies acted as donors should be decreased.