Pulsed Laser Deposition and Characterization of Sr and Zn Co-Substituted BiFeO₃Thin Films

Abstract

O 3 (BFZO) thin films have been prepared on Pt/TiO 2 /SiO 2 /Si substrates by pulsed laser deposition, and their ferroelectric and ferromagnetic properties have been characterized. X-ray diffraction (XRD) patterns of BSFO and BFZO thin films show a peroveskite single phase and BSFO thin films show shifting and splitting of peaks with increasing fraction of Sr. The BFZO thin film shows a lower leakage current than the BFO thin film and their P-E and M-H hysteresis loops are obtained. The XRD peaks of BSFZO thin films also shift to an angle lower than that of BFO thin films. The P-E hysteresis loop is obtained at 80 K and the reamanent polarizations of the Bi 1:1 Sr x Fe 0:9 Zn 0:1 O 3 thin film are 79 and 58 mC/ cm 2 for x ¼ 0:05 and 0.1, respectively. The M-H hysteresis loop is also obtained at 80 K and the reamanent magnetization and coercive field are 1.1 and 6 emu/cm 3 , and 222 and 792 Oe at a maximum magnetic field of 10 kOe for x ¼ 0:05 and 0.1, respectively.

A giant polarization value in bismuth ferrite thin films

“…Several different measurements have been conducted for improving the ferroelectric properties of BFO thin films by reducing the leakage current density at room temperature, such as the employment of a single crystal substrate [3,8], the use of an appropriate buffer layer [9][10][11], the construction of a multilayer structure [12,13], and the cation substitutions for the Bi and Fe sites in the crystal structure [14][15][16][17]. However, the ferroelectric properties are not ideal for the BFO thin films except for the use of a single crystal substrate together with the orientation modification [3,8].…”

“…Moreover, a larger polarization of P r ∼ 100 C/cm 2 has been induced for the (1 1 1)-oriented BFO thin film deposited on the SrRuO 3 /SrTiO 3 (1 1 1) substrate [8]. The Zn -modified BFO thin film with a polycrystalline perovskite grown on the Pt/TiO 2 /SiO 2 /Si(1 0 0) substrate has exhibited a large remanent polarization of P r ∼ 73 C/cm 2 when measured at the low temperature of 80 K, but it is very difficult to get good P-E loops at E-mail address: yuanyuwang0216@163.com room temperature due to the involvement of a high leakage current density [15]. Moreover, a giant remanent polarization value of P r ∼ 146 C/cm 2 is only obtained for the BFO thin film with a tetragonal structure when measured at a low temperature of 90 K [18].…”

“…The introduction of Zn affects the saturation magnetizations (M s ) value of BFO thin films, that is, the BFZO thin film has a lower M s value than that of the BFO thin film. The decrease in M s value can be attributed to the introduction of the nonmagnetic Zn composition [15,21]. The Zn 2+ substitution for Fe 3+ can suppress the formation of Fe 2+ , and generates more oxygen vacancies in BFO [20].…”

“…The switchable polarization obtained by the PUND measurement is a little smaller as compared to that obtained from the P-E measurement, confirming that the leakage current density only plays a smaller role in affecting the ferroelectric behavior for the BFZO thin film deposited on the SrRuO 3 /SrTiO 3 (1 1 1) substrate. The BFZO thin film has a giant 2P r value of ∼268.5 C/cm 2 when measured at room temperature, which is superior to those of pure BFO thin films with (1 1 1) and other orientations [3,[8][9][10][11][12][13][14][15][16][17], and is also much larger than that (2P r ∼ 180.8 C/cm 2 ) of the BFO thin film deposited on the SrRuO 3 /SrTiO 3 (1 1 1) substrate in this work [ Fig. 5(b)].…”

“…5(b)]. The crystal structure [18], the site engineering [14][15][16][17], and the orientation [3,[8][9][10] usually contribute to the improvement in the polarization of BFO thin films. In the present work, the (1 1 1) orientation should largely contribute to the improvement in the polarization value for the BFZO thin film, where the largest spontaneous polarization occurs in the (1 1 1) direction because the ions are displaced along [1 1 1] directions from their equilibrium positions [23].…”