Thickness dependence of room temperature permittivity of polycrystalline BaTiO3 thin films by radio-frequency magnetron sputtering

Abstract

Polycrystalline BaTiO3 thin films with thickness ranging from 2100 to 20 000 Å were prepared on platinum substrates using off-axis radio-frequency magnetron sputtering. The variation in room temperature permittivity of the films was investigated with respect to thickness using x-ray diffraction and transmission electron microscopy. All films were ferroelectric and their room temperature permittivity, which was significantly higher than previously reported values, showed a strong dependence on film thickness. Higher permittivity was attributed primarily to the presence of ferroelectric domains. The room temperature permittivity of the thin films showed large variations with grain size, as in the case of BaTiO3 ceramics. The increase in permittivity with increasing film thickness was attributed to the decrease in defect concentration with grain growth. The 20 000 Å film showed an abrupt decrease in permittivity and the presence of an intergranular phase having titanium-excess composition; these phenomena are discussed in terms of domain boundary pinning and recrystallization.

A Mesoscopic Electromechanical Theory of Ferroelectric Films and Ceramics

“…When the poly crystal has (001 } c texture, then it can have a saturation strain and polarization almost equal to that of a single crystal. This is consistent with reported saturation polarization as high as 25//C/cm 2 in BaTiOs thin film of ljum thick [15]. When the film thickness increases to 2/mi, it drops to about 7^C/cm 2 .…”

A strong electro-optically active lead-free ferroelectric integrated on silicon

“…The EO properties of BTO are tightly connected with its crystalline structure, which is described in a non-centrosymmetric tetragonal P4mm space group compatible with a non-vanishing linear Pockels effect 22 . Although the tetragonal phase is stable in bulk BTO crystals at room temperature, polycrystalline BTO thin films tend to stabilize in a cubic symmetry 23 , which originates from the formation of small grains, without Pockels effect. We suppressed such grain formation by depositing our 130-nm-thick BTO film epitaxially on a Si substrate covered by a 4-nm-thin strontium titanate (STO) buffer layer.…”

Microstructure and Dielectric Properties of Barium Titanate Film Prepared by MOCVD

“…25) The smaller grain size means more numbers of grain boundary in the films. They assumed that the grain boundary could be more insulative (15) : sputtering (3) : CSD (7) : sol-gel (10) : bulk (20) 1000 Fig. 11 Relationship between grain size and ε of BaTiO 3 at room temperature.…”

“…BaTiO 3 films generally consisted of fine grains ranging from several tens to hundreds of nanometers in size, whose dielectric constant might change from several tens to thousands decreasing with decreasing the grain size. 3,7,10,14) However, the relationship between dielectric properties and microstructure of BaTiO 3 films has not been well understood.…”

“…1,2) Several methods such as rf-magnetron sputtering, 3,4) reactive evaporation, 5) laser deposition, 6) chemical solution deposition, 7) sol-gel. [8][9][10] and metal-organic chemical vapor deposition (MOCVD) [11][12][13][14][15] have been applied to prepare BaTiO 3 films.…”