Pulsed Laser Deposition And Structure Control Of BaTi₂O₅ Thin Films

In this work, the polycrystalline samples of BaTi2O5 compounds were prepared by hot pressing technique used the BaTi2O5 powders that synthesized by arc melting technique. The structure and dielectric properties had been studied in the sintering process (sintering temperature, sintering pressure, holding time). As a new environmentally friendly ferroelectric film, BaTi2O5 films have a broad application on function devices. It's very important to deposit it on Si substrate which is easily integrated with semiconductor industry. However, there is a big lattice mismatch between BaTi2O5 materials and Si(100) substrates. Therefore we prepared the BaTi2O5 films on Si(100) substrates with MgO buffer layer by pulsed-laser deposition (PLD).The results showed that:The decomposition of BaTi2O5 ceramics can be avoided by arc-melting technique. It's found that sintering temperature, sintering pressure and holding time can improve the density and grain size. The best preparation condition was 1190℃-50MPa-2h. There would be less oxygen vacancies in BaTi2O5 ceramics after annealing and the phase almost no change. The dielectric constant and loss tangent of sample decreased with the frequency increasing, which can reach 33 and 0.03 at 1 MHz. The dielectric constant increased with the temperature increasing, and it would reach the maximum,660 near the Curie temperature (Tc=410℃).MgO buffer layers deposited on Si(100) substrates by pulsed laser deposition technique. With the increasing substrate temperature, MgO films had completed (200) orientation. And the grain became larger and closely arranged. The crystallinity of MgO film would be better when there was larger laser energy density. In our experiment, MgO films (deposited at 400℃of substrate temperature,50mm of substrate-target distance,1.18J/cm2 of laser energy, vacuum atmosphere) were (200) preferred orientation with good crystallinity and surface.BaTi2O5 films deposited on Si(100) substrates with MgO buffer layers by pulsed laser deposition technique. In our experiment, BaTi2O5 films (deposited at 715℃of substrate temperature,50mm of substrate-target distance,1.58J/cm2 of laser energy, 15 Pa of oxygen pressure) were (020) preferred orientation with good crystallinity and surface. And the quality of MgO buffer layers played an important role on growing BaTi2O5 films.