The Research On Preparation And Dielectric Properties Of High Dielectric Constant Thin Film CCTO

The polycrystalline and epitaxial Ca Cu3 Ti4O12(CCTO) thin film were both prepared successfully on the surface of Au, Pt and La Al O3(001) single crystal substrate through the high polymer assisted deposition(PAD). Through the constantly adjustment and optimization of the preparation process, we can prepare a dense thin film with high quality, both polycrystalline and epitaxial sample. The samples have good dielectric constant, but the dielectric loss is too high to be applied. In order to explore the nature of dielectric loss of CCTO, this paper has find two kinds of effective methods to lower the dielectric loss:1, In a certain scope of high pressure, under the condition of high purity oxygen, through the PAD technique. On one hand, by applying a certain pressure of pure oxygen, can significantly reduce the oxygen vacancy defects inside, and then reduce the dielectric loss of thin film, on the other hand, when high pressure to a certain extent, between film and substrate of the lattice mismatch, thermal expansion mismatch and pressure of the pressure, all will cause a big change in cell volume, which will trigger a series of dislocation, defects, domain boundary and lattice distortion, and these changes will lead to a new space charge, make the dielectric loss of low frequency surge. When pressure is among 0.35~0.75 Mpa, the atmosphere of high pure oxygen(99.999%) of the atmosphere, the dielectric loss is 0.002~0.01(10-100 k Hz). When pressure is 0.55 Mpa, dielectric loss reaches the lowest,tanδ is as low as 0.002(10-100 k Hz).2, Compared with other chemical methods, the biggest advantage of PAD is the accurately control of measurement, and more conducive to doping modification of CCTO thin films, this paper selects Zr doping modification through the growth of CCTO film, the results show that when the doping sintering under high pressure, the dielectric loss of CCTO increased after the first decrease, but when under normal preparation, dielectric loss, decreased after the first increase, one of the reason is that Zr ions doped, part into the grain boundary, hinder the free electrons move, reduce the leakage, increasing the insulation of the grain boundary, the other part into the grain, to replace the replacement of Ti ions, cause the Ti O6 octahedral structure more imbalances, asymmetric, causing polarization, dielectric loss increases sharply, so when the pressure is different, he doping ratio is different, so the main accumulation location of Zr ion is different as well, therefore, the impact on dielectric loss is different, the results show that when under ordinary conditions, 5%-10% doping amount, the lower dielectric loss of CCTO film to get the biggest, loss tangent value in 10-100 k Hz frequency range can keep within 0.001-0.006.