Nanoscale electrical and crystallographic properties of ultra-thin dielectric films

Thin SrTiO3 (STO) films with a thickness of 14 nm were grown on the Pt/Ti/SiO2/Si (STO/Pt) and Ru/SiO2/Si (STO/Ru) substrates at room temperature by radio-frequency magnetron sputtering. The as-deposited STO films were then post-annealed at 450–650 °C in an oxygen atmosphere in order to obtain various crystallographic features. The crystalline STO/Pt and STO/Ru films were obtained at an annealing temperature above 550 °C. The results of X-ray photoelectron spectroscope reveal that the crystalline STO films have a microscopically homogeneous film structure. Besides, secondary ion mass spectrometry depth profiles show an increase of interface roughness with an increasing annealing temperature of the STO films. Atomic force microscope images also show that the surface of the crystalline STO/Ru film is smoother than that of the STO/Pt film at a given annealing temperature. The effective improvement in the chemical homogeneity and surface roughness of the STO films results in a considerable decrease in the nanostructural leakage current of the STO films upon the use of a Ru electrode.