CrO2 (100) and TiO2 (100) film heteroepitaxy on a BaF2 (111)/Si (100) substrate

Multi-domained heteroepitaxial rutile-phase TiO 2 (1 0 0)-oriented films were grown on Si (1 0 0) substrates by using a 30-nm-thick BaF 2 (1 1 1) buffer layer at the TiO 2 –Si interface. The 50 nm TiO 2 films were grown by electron cyclotron resonance oxygen plasma-assisted electron beam evaporation of a titanium source, and the growth temperature was varied from 300 to 600 °C. At an optimal temperature of 500 °C, X-ray diffraction measurements show that rutile phase TiO 2 films are produced. Pole figure analysis indicates that the TiO 2 layer follows the symmetry of the BaF 2 surface mesh, and consists of six (1 0 0)-oriented domains separated by 30° in-plane rotations about the TiO 2 [1 0 0] axis. The in-plane alignment between the TiO 2 and BaF 2 films is oriented as [0 0 1] TiO 2 || BaF 2 [ 1 0 1 ¯ ] or [0 0 1] TiO 2 || BaF 2 [ 1 1 2 ¯ ] . Rocking curve and STM analyses suggest that the TiO 2 films are more finely grained than the BaF 2 film. STM imaging also reveals that the TiO 2 surface has morphological features consistent with the BaF 2 surface mesh symmetry. One of the optimally grown TiO 2 (1 0 0) films was used to template a CrO 2 (1 0 0) film which was grown via chemical vapor deposition. Point contact Andreev reflection measurements indicate that the CrO 2 film was approximately 70% spin polarized.