Metalorganic chemical vapor deposition of lead-free ferroelectric BiFeO3 films for memory applications

Abstract

We have grown BiFeO3 thin films on SrRuO3∕SrTiO3 and SrRuO3∕SrTiO3∕Si using liquid delivery metalorganic chemical vapor deposition. Epitaxial BiFeO3 films were successfully prepared through the systematic control of the chemical reaction and deposition process. We found that the film composition and phase equilibrium are sensitive to the Bi:Fe ratio in the precursor. Fe-rich mixtures show the existence of α-Fe2O3, while Bi-rich mixtures show the presence of β-Bi2O3 as a second phase at the surface. In the optimized films, we were able to obtain an epitaxial single perovskite phase thin film. Electrical measurements using both quasistatic hysteresis and pulsed polarization measurements confirm the existence of ferroelectricity with a switched polarization of 110–120μC∕cm2, ΔP(=P*−P̂). Out-of plane piezoelectric (d33) measurements using an atomic force microscope yield a value of 50–60pm∕V.

The structural and piezoresponse properties of c-axis-oriented Aurivillius phase Bi5Ti3FeO15 thin films deposited by atomic vapor deposition

“…It is reported that the film composition and structure are sensitively affected by the substrate temperature and the precursor delivery ratio. 21 It is found that at the substrate temperature of 610 C the film composition is very close to the precursor delivery ratio, which means the liquid precursor supply mixing ratio can be transferred into the as-grown film. In this case, the atomic element ratio in the as-grown film is approximately 5.4:3:1, similar to the liquid precursor supply mixing ratio mentioned above.…”

“…In this case, the atomic element ratio in the as-grown film is approximately 5.4:3:1, similar to the liquid precursor supply mixing ratio mentioned above. We speculate that there are two reasons for the accurate ratio transferring: the first is that due to the relative high vaporization temperature all liquid precursors can be vaporized completely and the tube between vaporizer and reactor is maintained at 240 C without any condensation of gas precursors; 21 the second is that the substrate surface has similar absorption/desorption efficiency for all gas precursors. The accurate controllability of composition in the deposited film will facilitate the deposition of more complex Bi 4 Ti 3 O 12 -BiFeO 3 system thin films with integer or fractional n values.…”

“…[11][12][13][14][15][16][17][18][19] While methods such as sol-gel, 12,19 solid-state reaction, 17,18 and pulsed laser deposition 4 20,21 Atomic vapor deposition (AVD) is based on pulsed liquid-injection chemical vapor deposition with a volume of each pulse of the order of microlitres. 22 It has been proved that AVD can deposit high-quality high-k dielectric or ferroelectric films with a largely uniform film thickness, composition, and electrical properties and is highly suitable for mass production.…”

Dielectric dynamics of epitaxial BiFeO3 thin films

“…3 This is similar with many other large dielectric materials like CaCu 3 Ti 4 O 12 , LuFe 2 O 4 , LaMnO 3 et al In literatures and our previous results, it was shown that both giant dielectric constant and magnetocapacitance can be attributed to the interfacial effects in leaky oxide. [4][5][6][7] Therefore, although the leakage current can be suppressed in fabricated BFO thin films dramatically, [8][9][10] one should still be careful about the conclusions deduced from the dielectric results.…”

Tetragonal BiFeO3 on yttria-stabilized zirconia

“…BFO is an ideal platform for manipulating the lattice, charge, orbital, and spin degrees of freedom via an electric field and therefore serves as a fertile playground for exploring new possibilities for next-generation electronics. [1][2][3][4][5][6][7][8] Recently, through an assistance of strain engineering in thin film process, BFO exhibits a rich variety of phases including rhombohedral, monoclinic, and orthorhombic structures. [9][10][11][12][13][14] Numerous efforts have also been made to reveal the fundamental understanding of correlation between structure and electric/magnetic order parameters.…”