Growth of Crystalline SrTiO3 Films on Si Substrates Using Thin Fluoride Buffer Layers and Their Electrical Properties

Strontium titanate ( SrTiO3: STO) films were grown epitaxially on Si (111) and (100) substrates using thin SrF2 buffer layers. The SrF2 buffer layer was used for preventing the formation of an amorphous SiO2 layer on the Si substrate during deposition of an STO film. It was found from X-ray diffraction (XRD) analysis that well (110)-oriented STO films were grown on Si(111) substrates by a two-step growth method, in which a thin (8 nm thick) STO film was predeposited on the SrF2 buffer layer at 450°C and a thick (80 nm thick) STO film was successively deposited at 750°C. It was also found from XRD and Auger electron spectroscopy (AES) measurements that the SrF2 buffer layer was completely dissolved during STO film deposition at 750°C, and no fluorine (F) atoms existed in the buffer layer. The epitaxial relationship on Si(111) substrates revealed by X-ray pole figure measurements was (110) S T O //(111) S i and <110> S T O //<112> S i , while that on Si(100) substrates was (100) S T O //(100) S i and <110> S T O //<110> S i or <110> S T O //<100> S i . Concerning the electrical properties of STO films, the best values of breakdown field (at 1 µ A/cm2), resistivity (at 1 MV/cm), and relative dielectric constant were 2.3 MV/cm, 8.2×1012 Ω· cm and 72, respectively.