BiFeO 3 ͑BFO͒ films of pure perovskite phase were deposited on Pt/TiOx/SiO 2 /Si ͑Pt͒, LaNiO 3 /Pt/TiOx/SiO 2 /Si ͑LNO͒, and BaPbO 3 /Pt/TiOx/SiO 2 /Si ͑BPO͒ substrates by rf magnetron sputtering. The BFO film was grown with random orientations on Pt whereas highly ͑100͒-oriented and ͑111͒-oriented ones were obtained on LNO and BPO, respectively. The influence of the bottom electrode on crystal growth, surface topography, leakage behavior, dielectric and ferroelectric properties was investigated. Twice remnant polarizations ͑2Pr͒ and coercive fields ͑2Ec͒ of the ͑100͒-oriented BFO film were measured to be about 100 C/cm 2 and 596 kV/cm, while those of ͑111͒-oriented ones were approximately 205 C/cm 2 and 675 kV/cm. Magnetoelectric multiferroics, with coupled electric, magnetic, and structural order parameters in the same phase, have attracted considerable interest for their simultaneous ferroelectricity, ferromagnetism, and ferroelasticity. 1,2 Ferroelectricity rarely coexists with ferromagnetism because ferroelectric material is an insulator while ferromagnets are electrically conductive due to the high density states near the Fermi level. Among multiferroic materials, BiFeO 3 ͑BFO͒ exhibits a simple crystal structure, a high Curie temperature, and a high Neel temperature, which are advantageous for research and various applications.BFO crystallizes in a rhombohedrally distorted perovskite structure with both ferroelectric ͑T c = 1103 K͒ and antiferromagnetic ͑T N = 643 K͒ characteristics. [2][3][4][5][6][7][8][9][10][11] The easy axis of spontaneous polarization in BFO films was laid close to ͑111͒ planes in this distorted structure. 3 In the G-type antiferromagnetic order of BFO films, 5,6 the magnetic moments of Fe are coupled ferromagnetically within the ͑111͒ planes and fully compensated in others. The multiferroic properties and physical phenomenon of BFO films are significantly dependent on the crystalline orientations, which have mainly been controlled by the epitaxial growth method. The dramatic enhancement in the multiferroic properties and magnetoelectric coupling was found to result from the epitaxial-induced transitions. 2-5 However, some arguments suggested the enhanced multiferroic behavior needed more consideration and further study. 7 Recent research reported good ferroelectric properties of polycrystalline BFO films, which implied that epitaxial stress was not the only method to enhance the ferroelectric behaviors. 8,9 Therefore, the crystal growth and the ferroelectric properties of highly oriented BFO films deserve more attention.It is well known that the bottom electrode, such as SrRuO 3 , LaNiO 3 , and BaPbO 3 , is promising for inducing the preferred orientation and improving the film/electrode interface of the perovskite-type ferroelectric oxide. [12][13][14][15][16][17] The conventional leakage problem of BFO films was greatly improved by the use of conductive SrRuO 3 bottom electrodes. 2-4 Most BFO films have been fabricated by pulsed-laser deposition ͑PLD͒ or chemical solution depositi...

BaPbO 3  (BPO)/PbZr0.53Ti0.47 (PZT)/BPO heterostructures were fabricated by combining the sol-gel and rf-magnetron sputtering techniques. Experimental results indicate that the BPO bottom electrodes effectively prevent the formation of the rosette structure of PZT, producing smooth surfaces. Additionally, ferroelectric, fatigue, and leakage current properties were markedly improved when both the top and the bottom electrodes were changed from Pt to BPO. These improvements are due to a superior electrode/ferroelectric interface. BPO is better than Pt and other oxide electrodes for use in PZT ferroelectric capacitors due to its remarkably improved properties and quite low growth temperature.

The charging characteristics of metal-oxide-semiconductor ͑p-type͒ structures containing Au nanocrystals in SiO 2 gate oxide were studied. The Au nanocrystals of 2-3 nm in diameter are self-assembled from the agglomeration of an ultrathin Au layer embedded in SiO 2 matrix by annealing at 600°C. A large hysteresis loop is found in the capacitance-voltage ͑C-V͒ relation even at a low operating voltage ͑2 V͒, indicating its significant charge storage effect. Different charging rates for two kinds of trapped carriers ͑electron and hole͒ were found from C-V measurement under various scan rates. The relatively stable retention characteristic for holes trapped in the Au nanocrystals at room temperature was also demonstrated.

Multiferroic BiFeO 3 -based thin films were heteroepitaxially grown on LaNiO 3 /LaFeO 3 /MgO͑001͒ substrates by radio frequency magnetron sputtering. The epitaxial BFO-based films were grown with pure perovskite phase and a cube-on-cube relationship at a low processing temperature of 450°C. The partial substitution of La ions for Bi ions increased lattice parameters of the BFO film. With the La substitution, the significant improvement in dielectric, ferroelectric, and magnetic properties of the BFO films was observed.Magnetoelectric multiferroics have attracted considerable attention in current studies for their simultaneous ferroelectricity, ferromagnetism, and ferroelasticity. 1-6 These materials which have electric, magnetic, and structural order parameters in the same phase are rarely observed in nature because ferroelectricity is not compatible with ferromagnetism. The magnetism originated from the d-electrons of transition metal, which reduce the off-center tendency of ferroelectric materials. 1 BiFeO 3 ͑BFO͒ crystallizes in a rhombohedrally distorted perovskite structure with both ferroelectric ͑T C = 1103 K͒ and anti-ferromagnetic ͑T N = 643 K͒ characteristics. 3-10 The specific characteristics, such as a simple crystal structure, a high Curie temperature, and a high Néel temperature, are advantageous for research and various applications.Recently, Wang et al. reported dramatically enhanced multiferroic performance of epitaxial BFO films fabricated on SrRuO 3 -buffered SrTiO 3 substrates. 3,4 A dramatic enhancement of ferroelectric performance and magnetoelectric behavior were found to result from epitaxial-induced transition. 3,4 The excellent ferroelectric properties and magnetoelectric behavior of the BFO films provide an alternative choice of lead-free ferroelectric materials. 5,6 However, some challenges, including leakage problems, 7 high electric coercivity, 3-6,8-10 and inhomogeneous magnetic spin structure, 11,12 are necessary to be overcome in future applications. In previous studies, the leakage problems were markedly improved by well-controlled chemistry and interface of BFO films. 10,13 However, high electric coercivity and inhomogeneous magnetic spin structure of BFO films lead to difficulty of polarization switching and cancellation of macroscopic magnetization. 11 Previous studies suggest that electric coercivity 14-16 and inhomogeneous spin structure 17-19 can be effectively improved by La substitution. Therefore, the influence of La substitution on multiferroic properties of the epitaxial BFO films deserves more attention.Most epitaxial BFO-based films have been fabricated by pulsedlaser deposition ͑PLD͒ methods, at high processing temperatures above 670°C. 3-5,7,8 A low-temperature process of sputtering method is a promising method for growing bismuth-based materials without problems such as interdiffusion, phase decomposition, and chemical fluctuations. 13,20 This study reports the low-temperature preparation of the epitaxial BFO-based films by radio frequency ͑rf͒-magnetron sputterin...

Highly non-(001)-oriented Pb(Zr,Ti)O3 (PZT) films have been fabricated by rf-magnetron sputtering. The preferential (110)-oriented BaPbO3 (BPO) deposited on Ru buffer layer induces the growth of (110)-oriented PZT film. With the aid of self-organized growth of PZT, the orientation of the film deposited on random-oriented BPO∕Pt(111)∕Ru(002) is (111)-preferred. The insertion of Pt layer between BPO and Ru changes the orientation of PZT from (110) to (111) and prevents the oxygen diffusion. These non-(001)-oriented PZT films possess more superior ferroelectric, fatigue, and retention properties than those of (001)-oriented PZT films.