Effects of Annealing in Ar Gas on Ferroelectric Properties of SrBi 2 Ta 2 O 9 Thin Films

Structural and electrical properties of SrBi 2 Ta 2 O 9 (SBT) thin films crystallized upon annealing in an N 2 ambient were investigated. These thin films were prepared on Pt/TiO 2 /SiO 2 /Si substrates by the chemical solution deposition (CSD) method. The films crystallized in N 2 after calcination at a high O 2 partial pressure in an N 2 /O 2 mixed ambient showed good ferroelectric properties with remanent polarization 2P r = 13-14 µC/cm 2 , coercive field 2E c = 70-80 kV/cm, and leakage current density less than 1 × 10 −7 A/cm 2 at an applied voltage of 3 V. These ferroelectric properties are the same as those of the SBT crystallized in O 2 . However, the films crystallized in N 2 after calcination at a low O 2 partial pressure in an N 2 /O 2 mixed ambient did not form SBT. TDS data showed that the carbon content of the film calcined in poor O 2 was higher than that of the film calcined in rich O 2 . These results showed that the carbon residue within the film might disturb the formation of SBT.

Section: Surface Morphologies and Crystalline Structuressupporting

confidence: 58%

Crystallization of SrBi₂Ta₂O₉ Thin Films in N₂ Ambient by Chemical Solution Deposition Method

Ogata¹,

Nagata²

2001

“…1) The crystal structure and phase transitions of SBT crystal have been studied and discussed. [2][3][4] The formation processes of SBT thin films have been widely researched, [5][6][7][8][9][10][11][12][13][14] and also the crystallization of the SBT film 5,[15][16][17] and its grain growth 18) have been investigated. Although the crystal structure of ferroelectric SBT is orthorhombic with the space group A2 1 am (Bi-layered Aurivillius phase), 19) it is a serious problem that the fluorite-type phase (space group: Fm3m) easily grows at a low temperature.…”

Section: Introductionmentioning

confidence: 99%

Crystallization and Structural Phase Transformation in Sub-100-nm-Thick SrBi₂Ta₂O₉ Thin Film

Kohno

Sakamoto

Matuo

2005

Crystal phase and structural properties in sub-100-nm-thick SrBi2Ta2O9 (SBT) thin films deposited on silicon substrates have been quantitatively investigated by X-ray diffraction (XRD) and X-ray reflection (XRR) analyses. The simulation fitting of XRR showed that the density and the surface roughness of the SBT film increased and saturated as the annealing temperature increased, indicating the phase transformation from fluorite to Aurivillius and the grain growth were enhanced by the high-temperature annealing. The SBT film was composed of small crystals of fluorite-type and Bi-layered Aurivillius phase after crystallization at temperatures of 730–785°C for 1 h. When annealing temperature was higher than 800°C, the film crystallized into a single phase of Bi-layered Aurivillius. It was also shown that the average crystal size in the SBT film increased with annealing temperature and saturated to be ∼75 nm at annealing temperatures higher than 800°C. The annealing temperature dependence of the integrated intensity of the diffraction suggested that the activation energy of the crystallization into the Aurivillius phase was significantly changed at ∼800°C. The change in the activation energy had a close relationship with the structural phase transformation of fluorite to Aurivillius and the grain growth.

“…In recent years, Bi 4 Ti 3 O 12 (BIT), 1,2) SrBi 2 Ta 2 O 9 (SBT), [3][4][5] and (Bi,Nd) 4 Ti 3 O 12 (BNT), [6][7][8][9] which are members of the bismuth layer-structured ferroelectric (BLSF) family, have attracted much attention as promising alternatives to lead zirconate (PZT) 10,11) because they are lead-free and have a low environmental load and excellent ferro-and piezoelectric functionalities. In our previous studies, 12,13) we succeeded in fabricating heteroepitaxially grown (Bi 3.25 Nd 0.75 )Ti 3 O 12 (BNT-0.75) nanoplates with aand b-axis orientations by high-temperature sputtering using conductive Nb:TiO 2 (101) substrates with 0.79 mass % Nb.…”

Section: Introductionmentioning

confidence: 99%

Lattice distortions and piezoelectric properties in (Bi_3.25Nd_0.75− _xEu_x)Ti₃O₁₂ nanoplates with a- and b-axis orientations

Kobune¹,

Kugimiya²,

Kaneko³

et al. 2014

a- and b-axis-oriented (Bi3.25Nd0.75− x Eu x )Ti3O12 (BNEuT, x = 0–0.75) films of 3.0 µm thickness were fabricated on conductive Nb:TiO2(101) substrates containing 0.79 mass % Nb by high-temperature sputtering at 650 °C, and their structural and piezoelectric characteristics were investigated. The room-temperature remanent polarization (2P r) and effective piezoelectric coefficient (d 33) values for the BNEuT films exhibited maxima of 87 µC/cm2 and 15 pm/V, respectively, at x = 0.10, which were approximately 1.3 times larger than those (2P r = 65 µC/cm2 and d 33 = 12 pm/V) of the nondoped (Bi3.25Nd0.75)Ti3O12 (BNT) nanoplate. The BNEuT film with x = 0.10 had a high a-axis orientation judging from the X-ray diffraction measurement and the observation of the phase image by piezoresponse force microscopy. It is shown that adequate Eu3+ doping of BNT nanoplates produces a larger displacement magnitude of the octahedra than that in the nondoped BNT nanoplate, resulting in an improvement of piezoelectric properties in addition to the ferroelectricity.