Structural properties of epitaxial SrHfO3 thin films on Si (001)

Thin films of SrHfO3 have been grown by MBE on Si (001). Synchrotron X-ray diffraction (XRD) and grazing incidence extended X-ray absorption spectroscopy (GI-EXAFS) were employed to elucidate the epitaxial relationship between the SrHfO3 and Si (001). The SrHfO3 film was unstrained and exhibited a lattice mismatch of 6% with silicon; the orientation was SrHfO3(001)[110] || Si(001)[100]. The SrHfO3 (200) plane demonstrated the expected four fold symmetry with a peak positioned every 90° in the phi scan of X-ray diffraction. Excellent fits of the GI-EXAFS showed that Hf was coordinated to about 6 oxygen atoms at a bonding distance of 2.080 Å and about 8 Sr neighbors at 3.53 Å. The short range order determined by GI-EXAFS corroborated the long range order determined by XRD, where nearly epitaxial growth, good crystalline quality, low disorder and minimal defects observed make SrHfO3 a viable dielectric candidate in Si based complementary metal-oxide-semiconductor field effect transistors.