Structural and electrical properties of (Na0.85K0.15)0.5Bi0.5TiO3 thin films deposited on LaNiO3 and Pt bottom electrodes

doi:10.1016/j.apsusc.2009.12.026

Applied Surface Science

Volume 256, Issue 10, 1 March 2010, Pages 3316-3320

https://doi.org/10.1016/j.apsusc.2009.12.026 Get rights and content

Abstract

(Na_0.85K_0.15)_0.5Bi_0.5TiO₃ thin films were deposited on LaNiO₃(LNO)/SiO₂/Si(1 0 0) and Pt/Ti/SiO₂/Si(1 0 0) substrates by metal–organic decomposition, and the effects of bottom electrodes LNO and Pt on the ferroelectric, dielectric and piezoelectric properties were investigated by ferroelectric tester, impedance analyzer and scanning probe microscopy, respectively. For the thin films deposited on LNO and Pt electrodes, the remnant polarization 2P_r are about 22.6 and 8.8 μC/cm² under 375 kV/cm, the dielectric constants 238 and 579 at 10 kHz, the dielectric losses 0.06 and 0.30 at 10 kHz, the statistic d_33eff values 95 and 81 pm/V. The improved piezoelectric properties could make (Na_1−xK_x)_0.5Bi_0.5TiO₃ thin film as a promising candidate for piezoelectric thin film devices.

Introduction

Lead-free piezoelectric materials are desired inevitably as alternate materials of lead-based materials for the sake of environmental protection and biocompatibility, because the lead toxicities of producing, using and recycling are problematic for devices associated with PbZrO₃–PbTiO₃ (PZT) and other lead-based piezoelectrics [1]. As bismuth sodium titanate Na_0.5Bi_0.5TiO₃ (NBT) exhibits strong ferroelectricity (P_r = 38 μC/cm²) at room temperature and high Curie temperature T_c of 320 °C [2], it has been considered as one of the key lead-free piezoelectric materials. In comparison with pure NBT, NBT-based solid solutions modified with BaTiO₃ or Bi_0.5K_0.5TiO₃ show the improved piezoelectric and dielectric properties because of the existent rhombohedral–tetragonal morphotropic phase boundary [3], [4]. Recently, (Na_0.82K_0.18)_0.5Bi_0.5TiO₃ thick film on Pt coated alumina substrate shows high remnant polarization (2P_r) 56.6 μC/cm², dielectric constant 810 and excellent piezoelectric coefficient 109 pm/V [5], whereas (Na_0.85K_0.15)_0.5Bi_0.5TiO₃ (NBT-KBT15) thin film on Pt/Ti/SiO₂/Si substrate appears remnant polarization (2P_r) 27.6 μC/cm² and dielectric constant 360 [6]. (Na_1−xK_x)_0.5Bi_0.5TiO₃ (NBT-KBT100x) thin films deposited on Pt electrodes are only focused on the ferroelectric and dielectric properties [6], and never be involved in the piezoelectric performance. For device applications, it is very important to select a suitable bottom electrode for the ferroelectric thin films since the structural and electrical properties such as surface roughness, leakage current and dielectric properties are strongly related with the bottom electrode [7], [8]. Therefore, several kinds of metal oxide and compound metallic electrodes have been suggested instead of the conventional pure metal electrodes such as Pt and Au. Among metal compounds, LaNO₃ (LNO) has been considered as a promising candidate for the thermally stable bottom electrodes because of the low room temperature resistivity, chemical stability and pseudocubic perovskite crystal structure with a lattice parameter a = 3.84 Å matching with most of the perovskite ferroelectric materials [8], [9], [10]. The enhancement of dielectric and piezoelectric properties observed with PZT thin films grown on electrode LNO compared with those on electrode Pt may be ascribed to the difference of grain size and of crystallographic orientation of the thin films [9]. We naturally associate whether the change of grain size and crystallographic orientation can improve dielectric and piezoelectric properties for NBT-KBT100x thin film deposited on LNO bottom electrode?

In this paper, NBT-KBT15 thin films were deposited on LNO/SiO₂/Si(1 0 0) and Pt/Ti/SiO₂/Si(1 0 0) substrates by using metal–organic decomposition (MOD), and the bottom electrode effects on ferroelectric, dielectric and piezoelectric properties of NBT-KBT15 thin films were investigated by ferroelectric tester, impedance analyzer and scanning probe microscopy. It is expected that the present research may offer useful guidelines to the design and application of piezoelectric NBT-based thin films and devices.

Section snippets

Experimental

LNO thin film was firstly fabricated on SiO₂/Si(1 0 0) substrate by sol–gel process. Stoichiometric amounts of lanthanum acetate (La(CH₃COO)₃·1.5H₂O) and nickel acetate (Ni(CH₃COO)₂·xH₂O) were dissolved in acetate acid (CH₃COOH) and water (with CH₃COOH/H₂O ratio of 5:1). The mixture was constantly stirred until a transparent and stable green precursor solution was obtained, and the final concentration of the solution was about 0.2 M. The precursor solution was spun at 400 rpm for 10 s and 4000 rpm

Results and discussion

Fig. 1 presents XRD patterns of LNO thin film and NBT-KBT15 thin films deposited on LNO and Pt bottom electrodes. It can be seen that LNO thin film shows a perovskite structure, and NBT-KBT15 thin films are polycrystalline films exhibiting dominant perovskite phase without preferred orientation. In addition, the second phase identified as Bi₂Ti₂O₇ structure of NBT-KBT15 thin films can be observed, and it is consistent with the existences of pyrochlore phase reported for NBT thin films [11]. It

Conclusions

NBT-KBT15 lead-free thin films were deposited on LNO and Pt electrodes by MOD. They are of polycrystalline microstructure and unsaturated P–E loops. For the thin films deposited on LNO and Pt electrodes, the remnant polarization 2P_r are about 22.6 and 8.8 μC/cm² under 375 kV/cm, the dielectric constants 238 and 579 at 10 kHz, the dielectric losses 0.06 and 0.30 at 10 kHz, the statistic d_33eff values 95 and 81 pm/V. In comparison with the thin film deposited on Pt electrode, the thin film deposited

Acknowledgements

This work was supported by NNSF of China (10672139, 10825209 and 50872117), Nature Science Foundation of Hunan Province (07JJ5002), Changjiang Scholar Incentive Program ([2009]17), and Project of Hunan's Prestigious Fu-rong Scholar Award ([2007]362).

References (21)

T. Yu et al.
Mater. Lett.
(2007)
X. Hao et al.
Solid State Commun.
(2007)
N. Sama et al.
J. Cryst. Growth
(2008)
T. Yu et al.
Thin Solid Films
(2007)
X.J. Zheng et al.
Scripta Mater.
(2007)
E. Cross
Nature
(2004)
G.A. Smolenskii et al.
Sov. Phys. Solid State
(1961)
T. Takanaka et al.
Jpn. J. Appl. Phys.
(1991)
A. Sasaki et al.
Jpn. J. Appl. Phys.
(1999)
H. Zhang et al.
Appl. Phys. Lett.
(2008)

There are more references available in the full text version of this article.

Cited by (28)

Dielectric properties of SrTiO<inf>3</inf>/LaNiO<inf>3</inf> composite structure prepared by “sol-gel” method
2023, Ceramics International
In this work, Pt/SrTiO₃(STO)/LaNiO₃(LNO) and Pt/STO/Pt structures were fabricated on Si substrates using sol–gel method. Dielectric tunability characteristics of these two structures are investigated over temperature range of 300–80 K. As temperature decreases, relative dielectric constant and tunability of STO films in both structures increase linearly, while loss tangent (tanẟ) decreases. STO prepared on LNO exhibits better crystallinity and dielectric tunability than that prepared on Pt. Furthermore, LNO top pole array with 0.2 mm diameter was prepared on STO/LNO using photosensitive sol–gel method, resulting in LNO/STO/LNO structure with symmetric electrode. Dielectric tunability tests reveal that, compared with Pt/STO/LNO structure, LNO/STO/LNO structure exhibits similar tunability, lower tanẟ, higher figure-of-merit (FOM) values, and better tunability symmetry. Relative dielectric constant, tunability (350 kV/cm), and FOM are approximately 391, 60%, and 142.6 at 80 K, respectively. Further analysis shows that because of Schottky barrier at Pt/STO interface, the FOM and tunability symmetry of Pt/STO/LNO structure are worse than those of LNO/STO/LNO structure. These results demonstrate that LNO electrode performs better than conventional inert metal electrodes.
Annealing temperature effects on Bi<inf>6</inf>Fe<inf>2</inf>Ti<inf>3</inf>O<inf>18</inf>/LaNiO<inf>3</inf>/Si thin films by an all-solution approach
2017, Journal of Alloys and Compounds
Citation Excerpt :
Compared to others metal oxides electrodes such us SrRuO3 and La0.7Sr0.3MnO3 [15,18], the LaNiO3 can be directly deposit onto silicon substrate by CSD method with relatively low resistivity (ρ ∼ 10−4 Ω cm). Additionally, LaNiO3 has been considered as a promising candidate electrode because of its thermally stability, chemical stability and perovskite structure, which can facilitate the crystallization of the most of perovskite ferroelectric materials and decrease the crystallization temperature [22]. In this paper, BFTO18 thin films are successfully deposited on solution-derived LaNiO3 (LNO) buffered Si wafers by CSD processing, and the effects of annealing temperature on the electrical and magnetic properties are investigated.
An all-solution approach is successfully used to deposit Bi₆Fe₂Ti₃O₁₈ (BFTO18) thin films onto solution-derived LaNiO₃/Si substrates. The effects of annealing temperature on the dielectric, leakage, ferroelectric and magnetic properties are investigated. The mechanisms about the annealing dependence of dielectric, leakage and ferroelectric properties are discussed in detail. Room-temperature weak ferromagnetism is observed for all the derived thin films. The results will provide an effective route to prepare BFTO18 multiferroic thin films with large area by low-cost solution method.
The domain configurations of (Na <inf>0.85</inf> K <inf>0.15</inf> ) <inf>0.5</inf> Bi <inf>0.5</inf> TiO <inf>3</inf> thin film with different bottom electrodes
2016, Applied Surface Science
Citation Excerpt :
Therefore, we used the same methods for sample preparation and same characterization methods. Some results seem also similar to the reference [6]. NBKT15 thin films were deposited on LNO/SiO2/Si and Pt/Ti/SiO2/Si substrates by MOD, annealed at 700 °C in an oxygen atmosphere.
Several researches have shown the bottom electrode can strongly affect the physical properties of thin film. However, they seldom involve with the domain switching performance. Here we investigated emphatically the effects of bottom electrodes LNO and Pt on the domain configurations of (Na_0.85K_0.15)_0.5Bi_0.5TiO₃ (NBKT15) thin films using piezoresponse force microscopy. In comparison with the NBKT15 thin film on Pt electrode, the NBKT15 thin film on LNO electrode shows better performance in crystalline and electrical properties. Moreover the domain configuration of single grain within the NBKT15 thin film on LNO electrode is easier to be reversed under the electric fields, due to the larger grain size. Furthermore, we adopted the domain switching criterion from the perspective of equilibrium state free energy of ferroelectric nanodomain to explain the mechanisms of electric-generated domain switchings.
Effect of annealing temperature on piezoelectric and mechanical properties of (Bi<inf>0.5</inf>Na<inf>0.5</inf>)TiO<inf>3</inf>-(Bi<inf>0.5</inf>K<inf>0.5</inf>)TiO<inf>3</inf>-BaTiO<inf>3</inf> thin films
2016, Ceramics International
Polycrystalline piezoelectric lead-free 85 mol% (Bi_0.5Na_0.5)TiO₃–10 mol% (Bi_0.5K_0.5)TiO₃–5 mol% BaTiO₃ (85BNT–10BKT–5BT) thin films were fabricated at different annealing temperatures by a chemical solution deposition method on Pt/Ti/SiO₂/Si substrates. Perovskite phase was achieved during annealing at 650–800 °C. The effect of annealing temperature on piezoelectric and mechanical properties was investigated. The results show that 85BNT–10BKT–5BT thin films annealed at 700 °C exhibit the largest effective d₃₃ value of 140.4 pm/V, and the highest elastic modulus 142.0 GPa. The optimal properties can be attributed to dense domain and homogenous microstructure. Results show that 85BNT–10BKT–5BT thin films may be a good candidate for lead-free piezoelectric-based micro-electromechanical systems.
Effects of LaNiO<inf>3</inf> seeding layers on the crystal structure and electrical properties in 0.94(Bi<inf>0.5</inf>Na<inf>0.5</inf>)TiO<inf>3</inf>-0.06BaTiO<inf>3</inf> thin films
2015, Ceramics International
In this work, the high-quality 0.94(Bi_0.5Na_0.5)TiO₃–0.06BaTiO₃ (hereafter abbreviated as BNT–BT) lead-free piezoelectric thin films were synthesized by introducing LaNiO₃ (hereafter abbreviated as LNO) seeding layers. The effects of LNO seeding layers on the crystal structure and electrical properties were systematically investigated. The X-ray diffraction patterns indicate that highly (100)-oriented BNT–BT films were prepared through utilizing LNO seeding layers. The maximum piezoelectric coefficient d₃₃^⁎ of ~100 pm/V, remanent polarization 2P_r of ~18 μC/cm² and dielectric constant ɛ_r ~410 have been obtained in the highly (100)-oriented BNT–BT films. The observed tremendous enhancement of piezoresponse, ferroelectric and dielectric properties in LNO-seeded films can be attributed to the better crystallization quality, higher degree of (100)-preferred orientation and reduced leakage current density. These findings demonstrate that LNO-seeded BNT–BT thin films integrating with silicon substrates may provide a wide range of applications in high-performance MEMS devices.
Enhanced ferroelectric and dielectric properties of Nb<sup>5+</sup>-doped Na<inf>0.5</inf>Bi<inf>0.5</inf>TiO<inf>3</inf> thin film deposited under nitrogen annealing atmosphere
2015, Ceramics International
Na_0.5Bi_0.5(Ti_0.98Nb_0.02)O_3+δ (NBTNb) thin films are fabricated under N₂ and O₂, respectively. For comparison, the Na_0.5Bi_0.5TiO₃ (NBT) thin film under O₂ is also prepared. The co-effects of Nb⁵⁺-doping and annealing atmosphere on microstructure, ferroelectric and dielectric properties of NBT thin film are investigated. The XRD results show that all the thin films have crystallized into phase-pure polycrystalline perovskite structure. Under O₂ annealing ambience, compared with NBT thin film, enhanced ferroelectricity is achieved for NBTNb, which can be ascribed to the reduced leakage current and TiO₆ octahedral distortion. Furthermore, the NBTNb annealed under N₂ exhibits a well-defined polarization–electric field hysteresis loop with a larger remanent polarization (P_r) of 10.7 μC/cm², which can be due to the well-crystallized structure with smooth surface and high densification. Also, the dielectric constant (ε_r) and dissipation factor (tanδ) versus frequency show smaller dispersion with a ε_r of 402 and tanδ of 0.065 at 100 kHz.

View all citing articles on Scopus

View full text

Structural and electrical properties of (Na0.85K0.15)0.5Bi0.5TiO3 thin films deposited on LaNiO3 and Pt bottom electrodes

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusions

Acknowledgements

Mater. Lett.

Solid State Commun.

J. Cryst. Growth

Thin Solid Films

Scripta Mater.

Nature

Sov. Phys. Solid State

Jpn. J. Appl. Phys.

Jpn. J. Appl. Phys.

Appl. Phys. Lett.

Structural and electrical properties of (Na_0.85K_0.15)_0.5Bi_0.5TiO₃ thin films deposited on LaNiO₃ and Pt bottom electrodes