Q. Yao

Site engineering in chemical solution deposited Na1/2Bi1/2TiO3 thin films using Mn acceptor

A series of Mn doped Na1/2Bi1/2TiO3 (NBT) thin films with dopant concentrations from 0 to 4 at% (NBTMn x , x = 0, 0.01, 0.02, 0.04) were fabricated on the indium tin oxide/glass substrates by chemical solution deposition. The effects of Mn doping content on crystalline, ferroelectric and dielectric properties were investigated. All thin films exhibit phase-pure polycrystalline perovskite structures. For the insulating measurement, at low electric field, space charge limited conduction or a grain boundary limited behavior is responsible for the leakage behavior of NBTMn x thin films, whereas at the high electric field, the dominant mechanism is changed to the interface-limited Fowler–Nordheim tunneling except NBTMn0.04. The leakage current density is reduced by more than three orders of magnitude in NBTMn0.02 compared with that of NBT thin film. Also, the enhanced ferroelectric properties of NBTMn0.02 thin film can be observed in polarization–electric filed hysteresis loop with P r of 38 μC cm−2, which is consistent with the result of the normalized capacitance–voltage curve. The dielectric constant and dissipation factor of NBTMn0.02 thin film are 501 and 0.04, respectively at 100 kHz. These electrical property improvements are attributed to the decrease of oxygen vacancy-induced leakage current.

The microstructure, energy storage and dielectric behaviours of (Ti,Zn)-doped Bi0.97Nd0.03FeO3 thin films

Abstract (Ti, Zn)-co-doped Bi0.97Nd0.03FeO3 (BNFTZ) thin films with different thicknesses were prepared directly on indium tin oxide/glass substrates deriving from the precursor solutions with different solution concentrations. The X-ray diffraction, scanning electron microscopy and insulating/ferroelectric/dielectric measurements were utilised to characterise the BNFTZ thin films. Both BNFTZ thin films with the thicknesses of 160 and 320 nm are crystallised into phase-pure perovskite structure without second phase. Compared to the film of 160 nm, a lower leakage current can be obtained in BNFTZ film of 320 nm due to due to its denser microstructure with smaller grain size. The film with 320 nm thickness possesses a high energy-storage efficiency of 87%, which can be ascribed to the slim P–E loop. At 100 kHz, the film of 320 nm owns lower dielectric constant (~91) and dissipation factor (~0.10). The possible contributions are discussed to explain the difference in the related performances for BNFTZ thin films with different thicknesses.

Enhanced energy storage property and dielectric tunability of Na 0.5 Bi 0.5 (Ti,W,Ni)O 3 thin film on Bi(Fe,Mn)O 3 buffered LaNiO 3 (100)/Si substrate

Na0.5Bi0.5(Ti,W,Ni)O3 (NBTWN) thin films were fabricated on the pure and Bi(Fe,Mn)O3 buffered Pt/TiO2/SiO2/Si and LaNiO3(100)/Si substrates by chemical solution deposition, respectively. The crystallization, surface morphology, and electrical properties of the four films are mainly investigated. The films, which are grown on the Pt/TiO2/SiO2/Si substrates, exhibit similar polycrystalline structure. Whereas for films deposited on the LaNiO3 (100)/Si substrates, strong (l00) orientations are observed. Compared with the NBTWN film on pure Pt/TiO2/SiO2/Si, the introduction of Bi(Fe,Mn)O3 buffer layer and LaNiO3 oxide electrode can promote the grain growth of the NBTWN resulting in larger grain size. Large remanent polarization and breakdown strength can be observed in films with Bi(Fe,Mn)O3 buffer layers. Furthermore, the combination of low leakage current and good energy storage capacity, together with high dielectric tunability is achieved in NBTWN/Bi(Fe,Mn)O3/LaNiO3(100)/Si heterostructure. The enhancement in electrical properties may be attributed to the preferred crystalline orientation and optimized grain size depending on both the buffer layer and the electrode that are used.

Microstructure, leakage current and dielectric tunability properties of W6+:Na0.5Bi0.5TiO3/Fe3+:Na0.5Bi0.5TiO3 bilayered thin film

Abstract The bilayered Na0.5Bi0.5Ti0.99W0.01O3/Na0.5Bi0.5Ti0.98Fe0.02O3 (NBTW/NBTFe) structure was grown on indium tin oxide/glass using a modified sol–gel process. The microstructure, and insulating and dielectric properties were investigated. X-ray diffraction indicates that the bilayered thin film is well crystallized with a phase-pure perovskite structure. The thin film shows a uniform surface without crack, and no interface is found between the NBTW/NBTFe structure. In the dielectric constant-electric field curves for dielectric measurement, abnormal loops are observed under the low electric field or high frequency. A maximum value of 35.4% for dielectric tunability is obtained when an electric field of ±500 kV/cm is applied, which can be mainly due to the good insulating characteristic with low leakage current. Furthermore, a dielectric constant of 484, dielectric loss of 0.07 as well as figure of merit of 5.1 can be observed at the frequency of 100 kHz. These findings can be taken as a base for further improving the electrical performance of NBT-based thin films.