Highly (100)-oriented SrTiO3 thin films were sputtered on Si (100) substrates. After the optimization of the deposition conditions, the fraction of (110)-oriented material in the SrTiO3 films was about 3%, but the rocking curve of the SrTiO3 (200) peak was quite large (full width at half maximum (FWHM) 2.3°). Indeed grain boundaries crossing the whole SrTiO3 film and an amorphous layer between Si and SrTiO3 could be observed by transmission electron microscopy. DyBa2Cu3O7−δ (DBCO) films were successively sputtered on the polycrystalline SrTiO3 layers on Si. An Auger analysis revealed the presence of barium at the Si/SrTiO3 interface that presumably diffused along the grain boundaries through SrTiO3 to form barium silicates. By reducing both the DBCO deposition temperature and the SrTiO3 thickness, we could prevent this diffusion and improve the electrical properties (R300/R1001 and Tc (R=0) in the 40–60 K range). The specific problems for the growth of DBCO thin film on SrTiO3-buffered silicon substrates by sputter deposition are finally pointed out.
- Buffer layer