Preparation and Properties of Bi_4-xLa_xTi₃O₁₂Ferroelectric Thin Films Using Excimer UV Irradiation

Abstract

Low-temperature processing of Bi 4−x La x Ti 3 O 12 (BLT) thin films was investigated by chemical solution deposition using an excimer UV irradiation, and their ferroelectric properties, crystallinity and microstructure were characterized. BLT thin films were prepared on Pt(200 nm)/TiO 2 (50 nm)/SiO 2 /Si substrates by a spin-coating technique from alkoxide precursor solutions. The excimer UV irradiation onto as-deposited BLT thin films was highly effective in removing organic species of the gel films, leading to the decrease of the crystallization temperature and an increase of the crystallinity. The UV-processed BLT films started to crystallize at 550 • C and showed a high crystallinity and a high (117) preferred orientation for 600 • C-annealed films. BLT thin films prepared at 600 • C showed a homogeneous and dense microstructure with grain sizes of 200-300 nm. The excimer UV irradiation onto as-crystallized BLT thin films was also effective in improving the ferroelectric properties of the thin films. Bi 3.35 La 0.75 Ti 3 O 12 thin films prepared at 600 • C using excimer UV irradiation showed a well-saturated P-E hysteresis loop with a P r of 9.8 µC/cm 2 and E c of 78 kV/cm. Moreover, the Bi 3.35 La 0.75 Ti 3 O 12 thin films exhibited good fatigue endurance up to 10 10 switching cycles.

Preparation and Properties of Bi4 ? xNdxTi3O12 Thin Films by Chemical Solution Deposition

“…In addition, Bi 3+ ions in the BIT structure can be substituted by trivalent rare-earth ions, such as La 3+ , Nd 3+ and Sm 3+ . Recently, the improvement of electrical properties of BIT thin films by rare-earth ion doping has been reported by several researchers [1][2][3][4][5][6][7][8][9][10]. Among them, Bi 4−x Nd x Ti 3 O 12 (BNT) has been receiving much attention due to its larger ferroelectricity than that of the other rare-earth ion doped BIT [5][6][7][8][9][10].…”

Synthesis and properties of ferroelectric Si-doped (Bi, Nd)4Ti3O12 thin films by chemical solution deposition

“…In this study, the amounts of Nd for the Bi site of (Bi,Nd) 4 (Ti,Si) 3 O 12 and excess Bi were set at the same values as those in the previous works [3,5,6]. The Si amount of (Bi,Nd) 4 (Ti,Si) 3 O 12 was determined based upon the most effective amount of Ge for (Bi,Nd) 4 (Ti,Ge) 3 O 12 thin films reported by the authors [8,9].…”

“…Bi 3+ ions in the BiT structure can be substituted by nonvolatile rare earth ions for the improvement of its properties. Rare-earth-modified BiT thin films has been intensively studied as a ferroelectric layer for memory devices because of its excellent properties [1][2][3][4][5][6]. However, the fabrication of high-density FeRAMs is still difficult, because of problems such as insufficient microstructure and ferroelectric properties.…”

“…The ferroelectric properties of the BNTS films were also discussed. 3 and Si(OC 2 H 5 ) 4 corresponding to a Bi 3.35 Nd 0.75 Ti 2.9 Si 0.1 O 12 (BNTS) composition (with 3% of excess Bi) were dissolved in absolute 2-methoxyethanol, and acetylacetone was then added to the solution as a stabilizing agent. The molar ratio of acetylacetone to BNTS precursor was 6.…”

Fabrication and characterization of intergrown Bi4Ti3O12-based thin films using a metal-organic precursor solution

“…[1][2][3][4][5][6] These Bi 4 Ti 3 O 12 -based thin films have attracted much attention for application in several electronic thin-film devices utilizing ferroelectricity, such as nonvolatile ferroelectric random access memories (NvFeRAMs). However, the fabrication of practical NvFeRAMs is still difficult, because the ferroelectric properties of Bi 4 Ti 3 O 12 -based thin films are still insufficient compared with those of Pb-based ferroelectric thin films.…”