Optical study on the size effects in BaTiO3 thin films

Abstract

To study the size effects in ferroelectric thin film, we measured the optical transmittance and Raman spectra in BaTiO3 thin films deposited by the rf-magnetron sputtering technique on fused quartz and (111) Si substrates. A variation in the energy gap and Raman peaks with film thickness and grain size was observed and the possible origin was analyzed.

The size-effect on luminescence properties of BaTiO3:Eu3+ nanocrystallites prepared by the sol–gel method

“…To determine the Ω λ parameters we have used the relation between the 5 D 0 → 7 F J transitions assuming that the matrix element U (6) is close to zero for the 5 D 0 → 7 F 6 transition (U (6) = 0.0005) and that it is equal zero for all other transitions. Then the Einstein coefficient A 0-λ for spontaneous emission can be expressed as…”

“…Moreover due to "clearing" matrix elements U (4) , U (6) and U (2) , U (6) for the 5 D 0 → 7 F 2 and 5 D 0 → 7 F 4 transitions, respectively, we can get the values of Ω 2 and Ω 4 by determining A 0-λ directly from luminescence spectra taking 5 D 0 ||U (2) || 7 F 2 2 = 0.0035 and 5 D 0 ||U (4) || 7 F 4 2 = 0.0030. It can be done by using the relation between the integral intensity I and the transition energy hυ given as I = hυAN, where A is the Einstein coefficient for spontaneous emission and N is the population of the emitting 5 D 0 level.…”

“…Therefore, the investigation of size-dependence of the ferroelectric phase transition in small BaTiO 3 particles has been a subject of many reports [5][6][7][8][9][10][11]. It has been found that the ferroelectric tetragonal phase disappears for grain sizes less than 100 nm at room temperature [9,10].…”

Microstructure and dielectric properties of (Ba,Sr)TiO3 thin film produced by the polymeric precursor method

“…On the other hand, the increase of the solution viscosity affected the shape of the cutoff, as shown in Figure 5 layered films also presented a high transmission (>70%) in the spectral region of 400-800 nm. However, a slight shift of the cutoff to longer wavelength for the 4-layered films (F9 and F11) was observed, which may have been due to the large increase in film thickness, as suggested by Zhu et al 32 Table III summarizes the refractive indices of the different films, calculated from the ellipsometric measurements. As lithium niobate presents anisotropic properties, the refractive index depends on the crystallographic orientation.…”

Progress and prospect for high temperature single-phased magnetic ferroelectrics

“…Recently, more detailed analysis of experimental measurements of electric field dependence of leakage current density (J-E) for the BiFeO 3 and related ceramics and thin films reveal that J increases linearly with low electric field, elucidating an ohmic conduction mechanism in this region, while the most probable conduction mechanism for high electric field region seems extrinsic due to the thermal excitation of inner charged defects, described by the conduction mechanisms of space-charge-limited current characterized by the linear relationship of J-E 2 [53,54] , Schottky by lnJ-E 1/2 [55,56] and/or Poole-Frenkel by ln(J/E)-E 1/2 [45,[57][58][59] . On the other hand, the band structure of BiFeO 3 was calculated to be indirect with band gap of 2.8 eV by the density-functional based screened exchange method [60] and determined as direct 2.36 eV through transmission spectroscopy measurements of BiFeO 3 films on fused silica [61] and 2.5 eV in the single crystal sample [35] , which is much smaller than 3.2 eV of BaTiO 3 [62] .…”