Thermooptic properties of epitaxial BiFeO₃films with different orientations

Abstract

We have fabricated epitaxial BiFeO 3 (BFO) films with various orientations on a SrTiO 3 substrate by chemical solution deposition, and evaluated their optical and thermooptic properties by spectroscopic ellipsometry. The refractive index of the epitaxial BFO films was estimated to range from 2.620 to 2.635 at a wavelength of 1550 nm at room temperature using six Gaussian oscillators, and a thermooptic coefficient ranging from %0.31 ' 10 %4 to %0.81 ' 10 %4 K %1 was obtained at a wavelength of 1550 nm. The refractive index increased with temperature. In addition, the rate of increase in refractive index changed at around the Neel temperature. It is suggested that this change is caused by the magnetovolume effect, because a similar change, the d-spacing change at around the Neel temperature, was also obseved. These results suggest that the BFO films have a high potential for application as an optical material with a high refractive index and that the effectual refractive index change can be controlled by the thermal expansion coefficient, even in the same material.

Investigation of the optical properties of a BiFeO-=SUB=-3-=/SUB=-/SrTiO-=SUB=-3-=/SUB=- heterostructure grown on an Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-(0001) substrate by RF cathode sputtering

“…A detailed analysis of the surface morphology and the structural parameters of thin BFO films is necessary for their practical application. Specifically, the optical characteristics of BFO films are important for the development of optoelectronic devices, since their electrooptic, magnetooptic, and thermooptic properties may be adjusted by modulating the refraction index [8]. Without question, further studies of thin BFO films both on crystalline strontium titanate substrates and with this material used as a buffer layer are theoretically and practically relevant.…”

Composition-driven structural variation in ferrielectric phase of (Bi1/2Na1/2)TiO3-Ba(Mg1/3Nb2/3)O3

“…From an environmental viewpoint, concerns of toxicity in Pb have caused a strong demand to develop Pb-free piezoelectric materials. There has been an intense effort to investigate Pb-free piezoelectric materials such as Ba-based, [10][11][12][13][14] Bi-based 10,[15][16][17][18][19] and Nb-based [20][21][22][23][24][25][26][27] ferroelectrics. Among them, bismuth sodium titanate (Bi 1/2 Na 1/2 )TiO 3 (BNT) and its solid solutions are recognized as promising Pb-free materials due to their superior properties.…”