Orientation control of barium titanate films using metal oxide nanosheet layer

Abstract

In the present work, we aim to achieve the preferred crystal orientation of chemical solution deposition (CSD)-derived BaTiO3 films on ubiquitous Si wafers with the assistance of Ca2Nb3O10 nanosheet (ns-CN) template layers. The ns-CN on platinized Si (Pt/Si) substrates aligned the BaTiO3(100) plane to the substrate surface, because of the favorable lattice matching of the ns-CN (001) plane. The CSD process in air required a high crystallization temperature of 900 °C for the preferred crystal orientation of BaTiO3(100) because of the BaCO3 byproduct generated during the combustion reaction of the precursor gel. The processing in vacuum to remove CO2 species enhanced the crystal orientation even at the crystallization temperature of 800 °C, although it can generate oxygen vacancies ( ) that cause distorted polarization behavior under an applied field higher than approximately 150 kV/cm. The relative dielectric constant (εr) of the (100)-oriented BaTiO3 film on the ns-CN-supported Pt/Si substrate (ns-CN/Pt/Si) was generally larger than that of the randomly oriented film on Pt/Si, depending on the degree of crystal orientation.

Solid-solution thin films of ternary BaTiO3–Bi(Mg1/2Ti1/2)O3–BiFeO3system epitaxially grown on SrRuO3//SrTiO3substrates via chemical solution process

“…The BT solution was prepared using (CH 3 COO) 2 Ba and Ti(O-n-C 4 H 9 ) 4 as starting materials and a mixture of 2-methoxyethanol and acetic acid (with volume ratio of 2-methoxyethanol : acetic acid ¼ 4:0 : 1:0) as a solvent. [12][13][14] The BMT solution was prepared using Bi(O-t-C 5 H 11 ) 3 , Mg(OC 2 H 5 ) 2 , and Ti(O-n-C 4 H 9 ) 4 as starting materi-als and 2-methoxyethanol as a solvent. The BF solution was prepared using Bi(O-t-C 5 H 11 ) 3 and Fe(acetylacetonate) 3 .…”

Polarization switching behavior of one-axis-oriented lead zirconate titanate films fabricated on metal oxide nanosheet layer

“…Platinized silicon substrates with ns-CN template layer (ns-CN=Pt=Si) were prepared by the dip coating method, similarly to that in previous reports. [27][28][29][30][31] The size of the substrates was ∼10.0 × 5.0 mm 2 .…”

“…[24][25][26][27] One major advantage of the ns-CN template is that it can be applied to various substrates, including the ubiquitous substrates for device fabrication at room temperature, independent of the crystallographic configuration of the substrate surface. The template layer of ns-CN aided the preferential crystal growth of some simple-perovskite oxides (SrTiO 3 , BaTiO 3 , BiFeO 3 , and LaNiO 3 ) 24,26,28,29) as well as a layered-perovskite compound (CaBi 4 Ti 4 O 15 ) 27) on ubiquitous substrates of Si wafer, glass, and stainless steel. As for the crystal growth of PZT, we have confirmed the preferential crystal growth of tetragonal PZT(001) or (100) films, controlled by in-plane thermal stress, up to the thickness of 300 nm, as well as the enhancement or degradation of their ferroelectric property depending on the crystal orientation.…”

One-axis-oriented growth of PZT thin films on transparent glass substrates using metal oxide nanosheets

“…Nanosheets of calcium niobate (Ca 2 Nb 3 O 10 ; ns-CN) with a pseudo-perovskite-type crystal structure (lattice parameters: a = b = 0.386 nm) exhibit favorable lattice matching with various kinds of ferroelectric materials such as PZT, LNO, SrTiO 3 , BaTiO 3 , and BiFeO 3 , which promotes preferential crystal growth. [22][23][24][25][26][27][28][29][30] We previously reported the deposition of polar-axis-oriented PZT thin films by introducing an ns-CN buffer layer on the surface of ubiquitous substrates such as Si wafers and Inconel alloys. 26,27) A nanosheet buffer layer, such as an ns-CN, can be formed without high-temperature heating, which is a problem for the preferential crystal growth of PZT thin films on glass substrates.…”

“…[22][23][24][25][26][27][28][29][30] We previously reported the deposition of polar-axis-oriented PZT thin films by introducing an ns-CN buffer layer on the surface of ubiquitous substrates such as Si wafers and Inconel alloys. 26,27) A nanosheet buffer layer, such as an ns-CN, can be formed without high-temperature heating, which is a problem for the preferential crystal growth of PZT thin films on glass substrates. On the basis of this concept, we investigated thin film deposition of PZT on glass substrates with an ns-CN buffer layer for the purpose of orientation control and lowtemperature processing of PZT thin films.…”