Epitaxial Relationships and Electrical Properties of SrTiO3 Films on Various Thin -Fluoride/Si Structures

Abstract

AbstractCrystalline strontium titanate (SrTiO3:STO) films were grown on Si(111) and Si(100) substrates using thin SrF2 and CaF2 buffer layers by two-step growth method. In all cases, fluoride buffer layers were effective in growing STO films on Si substrates, which is probably due to that fluoride buffer layers have excellent crystallinity and they can prevent formation of amorphous SiO2 layers on Si substrates at the initial stage of the STO deposition. It was found from X-ray diffraction and pole-figure measurements that (110)-oriented STO crystallites with three different positions to the substrate were grown on Si(111) substrates for both SrF2 and CaF2 buffer layers. In constrast, (100)-oriented STO films with 12-fold symmetry were grown on a SrF2/Si(100), and mixed (110)- and (100)-oriented STO crystallites were grown on a CaF2/Si(100) structure. It was concluded from these results that better crystallinity of STO films can be obtained on the SrF2 buffer layer in case of Si(111) and on the CaF2 buffer layer in case of Si(100). It was also found from I-V and C-V analyses that the STO films have good insulating and dielectric characteristics. For a SrTiO3 film on SrF2/Si(111) structure, the best values of breakdown field (at l.μA/cm2), resistivity (at IMV/cm) and dielectric constant were 2.3MV/cm, 8.2 × 1012 Ωcm and 72, respectively.