Crystal Growth and Characterizations of Highly Oriented BiFeO[sub 3] Thin Films

Abstract

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...

BiFeO3 thin films of (1 1 1)-orientation deposited on SrRuO3 buffered Pt/TiO2/SiO2/Si(1 0 0) substrates

“…The (1 1 1) peak intensity first increases with increasing deposition temperature, reaches a maximum value at T d = 590°C, before it decreases with further increase in the deposition temperature. This phenomenon is similar to what has been observed with the BFO thin film buffered by BaPbO 3 underlayer [10], confirming that the deposition temperature plays an important role in the orientation development of the BFO thin film, when deposited on the SRO-buffered Pt/TiO 2 /SiO 2 /Si(1 0 0) substrate. The film texture is also dependent on the deposition temperature.…”

Emerging Multiferroic Memories

“…Today, much progress has been made in understanding the structure, properties, and growth of thin films of BiFeO 3 . High quality epitaxial BiFeO 3 films have been grown via molecular beam epitaxy [115,116], pulsed laser deposition [17,117], radio-frequency (RF) sputtering [118,119], metal-organic chemical vapor deposition (MOCVD) [120,121], and chemical solution deposition (CSD) [122] on a wide range of substrates including traditional oxide substrates as well as Si [117,123] and GaN [124]. This work has shown that high quality films, like those shown in Fig.…”

Electrical and piezoelectric properties of BiFeO3 thin films grown on SrxCa1−xRuO3-buffered SrTiO3 substrates

“…In addition, the expected stress state would be compressive. Although previous work used thin SrRuO 3 -buffered layers (10-80 nm thick) as the bottom electrode in BFO films and varied the strain state by using different substrates, such as SrTiO 3 , LaAlO 3 , YAlO 3 , and Pt, [18][19][20][21] the effects of conductive buffer layers on the performance of BFO thin films has not yet been studied systematically.…”