Oxygen ions are implanted into BiFeO3 films on LaNiO3/SrTiO3(1 0 0) substrates. The evolution of films is characterized by x-ray diffraction, scanning electron microscopy and cross-sectional transmission electron microscopy. The leakage current density of the implanted films is lowered by two orders of magnitude in comparison with unimplanted BFO films. The mechanisms for reduced leakage current in BiFeO3 thin films are discussed.

We investigated the structural and electrical properties of HfO2 films fabricated by the pulsed laser deposition technique. HfO2 films were deposited directly on n-Si (100) substrates and Pt coated silicon substrates, respectively, at 300°C in a 20 Pa N2 ambient, and in situ post-annealed in a 20 Pa N2 ambient. X-ray diffraction indicates that films post-annealed at temperatures more than 500°C exhibit a polycrystalline monoclinic structure. High-resolution transmission electron microscopy images clearly show that an interfacial layer (IL) between an amorphous HfO2 layer and the Si substrate exists. An x-ray photoelectron spectroscopy measurement was performed to identify this IL as nonstoichiometric Hf-silicate. The dielectric constant of amorphous HfO2 was determined to be about 26 by measuring the Pt/HfO2/Pt capacitor structures. Capacitance–voltage measurements show that a small equivalent oxide thickness of 1.26 nm for the 5 nm HfO2 film on the n-Si substrate, with a leakage current of 2.2 mA cm−2 at 1 V gate voltage was obtained.

YBCO films with different levels of excess yttrium were prepared on single-crystal LaAlO 3 with metal-organic deposition using trifluoroacetates (TFA-MOD). X-ray diffraction and transmission electron microscope measurements revealed excess yttrium in YBCO in the form of nanoscale Y 2 O 3 with (400) preferred orientation. The field dependence of J c demonstrated that YBCO films with Y 2 O 3 doping had enhanced J c in comparison with stoichiometric YBCO films in the magnetic fields. We think the reason for this is that the Y 2 O 3 nanoparticles act as pinning centres. YBCO films with 60% yttrium excess display 43% increased J c compared to stoichiometric YBCO films at a magnetic field of 1 T.

Solution deposition is a promising method for YBCO coated conductor fabrication. We developed a new fluorine-reduced 'metal-organic deposition using trifluoroacetates' (TFA-MOD) method with copper acetate as one of the starting materials. Using the fluorine-reduced TFA-MOD method, we were able to get high performance YBCO films with good out-of-plane and in-plane orientations within a shortened calcining time, which was reduced by at least 4 h in comparison with that for the normal TFA-MOD process. Good superconducting properties, with J c of 2 MA cm −2 at 77 K and T c of 88.3 K ( T c = 0.9 K), have been obtained for 350 nm epitaxial YBCO thin films on LaAlO 3 single-crystal substrates. Owing to the low price of copper acetate and the shorter calcining time, fluorine-reduced TFA-MOD is a very effective and cost-cutting process.