Articles you may be interested inEffect of concurrent Mg/Nb-doping on dielectric properties of Ba0.45Sr0.55TiO3 thin films Dielectric properties and microstructure of nano-MgO dispersed Ba 0.3 Sr 0.7 Ti O 3 thin films prepared by sputter deposition Effect of oxygen to argon ratio on properties of (Ba,Sr)TiO 3 thin films prepared by radio-frequency magnetron sputteringThe systematic study of the oxygen partial pressure (OPP) and total chamber gas pressure (TGP) effects on the stoichiometry and crystal structure of rf sputtered Ba 0.45 Sr 0.55 TiO 3 (BST) films and their phase purity allowed identifying close to optimal sputtering parameters for BST single phase polycrystalline film. The film with a Ba/Sr ratio equal to that of the source target and (Ba þ Sr)/Ti ratio close to unity demonstrated the enhanced permittivity value of 553 and tunability of 69%. It was confirmed that the increase of TGP enables better match of the film and target stoichiometry. However, using O 2 /Ar ratio as a parameter should be utilized cautiously since exceeding a threshold OPP (2 mTorr in our case) may facilitate secondary phase formation. Relatively large dielectric losses were observed in both films sputtered at high (30 mTorr) and low (5 mTor) TGPs. The presence of oxygen vacancies was identified as a probable cause of losses, which is indirectly confirmed by the deviation of the film lattice constant from that of the bulk target. V C 2013 AIP Publishing LLC. [http://dx.
Composition, microstructure, and dielectric properties of undoped and Ba(Mg1/3Nb2/3)O3 (BMN) doped Ba0.45Sr0.55TiO3 (BST) thin films deposited via rf. magnetron sputtering on platinized alumina substrates have been investigated. The analysis of microstructure has shown that despite the sizable effect of doping on the residual stress, the latter is partially compensated by the thermal expansion coefficient mismatch, and its influence on the BST film crystal structure is insignificant. It was revealed that BMN doped film demonstrated an average (over 2000 devices) of 52.5% tunability at 640 kV/cm, which is ∼8% lower than the value for the undoped film. This drop is associated with the presence of Mg ions in BMN; however, the effect of Mg doping is partially compensated by that of Nb ions. The decrease in grain size upon doping may also contribute to the tunability drop. Doping with BMN allows achievement of a compensation concentration yielding no free carriers and resulting in significant leakage current reduction when compared with the undoped film. In addition, the presence of large amounts of empty shallow traps related to NbTi• allows localizing free carriers injected from the contacts thus extending the device control voltage substantially above 10 V.
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