Of Ba (zr <sub> 0.2 </ Sub> Of Ti <sub> 0.8 </ Sub>) The O <sub> 3 </ Sub> Dielectric Films Growth And Mn Doping Effects Research

Ba(Zr_xTi_1-x)O₃ (BZT) is obtained by substituting ions at B site of BaTiO₃ with Zr in compounds of the perovskite structure of ABO₃. This is possible because Zr4+ is chemically more stable than the Ti4+ that the substitution of Ti⁴⁺ with Zr⁴⁺ would depress the conduction caused by electronic hoping between Ti⁴⁺ and Ti³⁺. Therefore, BZT could exhibit high dielectric tunability with low dielectric loss. So BZT has been widely invested as a possible material of tunable microwave device applications. So in this thesis, Ba(Zr0.2Ti0.8)O3 (BZT) and 2 mol % additional Mn-doped Ba(Zr_0.2Ti_0.8)O₃ (Mn-BZT) thin films had been prepared on single crystal oxide substrates and Pt/Ti/SiO₂/Si by pulse laser deposition (PLD) technique. The growth of films and the effect of Mn doping, deposition temperature, thickness of films and bottom electrodes on the structural and electric properties had been systematically investigate. This dissertation had touched the following aspects:Firstly, BZT and Mn-BZT films were deposited on LaNiO3 (LNO) coated LaAlO3(001)and SrRuO3 (SRO) coated MgO(001) single crystal oxide substrate. It had been found that both films could be with a cube-on-cube arrangement on single crystal oxygen substrates at 600℃. The dielectric tunability increased from 49.1% to 59.4% and the dielectric loss at zero bias decreased from 2.5% to 1.8% by Mn doping for BZT films on LNO/LAO. The dielectric tunability increased from 42.7% to 52.4% and the dielectric loss at zero bias decreased from 2.6% to 2.0% by Mn doping for BZT films on SRO/MgO. Additionally, the effect of film thickness on the dielectric properties of BZT films was studied. With the derease of film thickness, the dielectric tanubility first increased and then decreased, whicn can be interpreted by the competition between the interface stress and dielectric"dead layer".Secondly, BZT and Mn-BZT films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates by PLD. It indicated both films were deposited with a preferential (111) grain orientation at 700℃. And the properties of crystallization for BZT films were enhanced by Mn doping. The dielectric tunability of preferential (111)-oriented BZT film on Pt/Ti/SiO2/Si increased from 60.9% to 69.0% and the dielectric loss at zero bias decreased from 6.5‰to 5.0‰by Mn doping. Meanwhile, it was found that the dielectric properties were affected by deposition temperature. With the increase of deposition temperature, the tunability increased and the loss decreased. Furthermore, the ferroelectricity was enhanced at higher deposition temperature. It would be due to the large mismatch of themal expansion coefficient between BZT films and silicon substrates.The mechanism of Mn doping had been investigated. The enhanced dielectric behavior by Mn doping could be mainly attributed to enhanced crystallization and the lowering of Fermi levels of BZT films and the decrease of electron concentration and free electrons, and the reorientation of the defect complex of Mn T' ' i ? VO...