Electrical properties of K0.5Na0.5NbO3 thin films grown on Nb:SrTiO3 single-crystalline substrates with different crystallographic orientations

Abstract

To attain a deep understanding of ferroelectric and piezoelectric characteristics of K0.5Na0.5NbO3 as a promising lead-free compound, the ferroelectric and piezoelectric responses of its epitaxially grown films with three primary orientations of [001], [110], and [111] were investigated with an emphasis on the influence of crystallographic orientation. The films were prepared by sol-gel processing using Nb-doped SrTiO3 single-crystalline substrates with various cutting directions. A peak remnant polarization value (Pr) of 17.3 μC/cm2 was obtained along the [110] direction due to the coincidence between the spontaneous polarization and the film orientation, which is significantly higher than 10.5 μC/cm2 in [111]-oriented and 10.1 μC/cm2 in [001]-oriented ones. However, a better piezoelectric response was achieved in the [001]-oriented films with an average local effective piezoelectric coefficient (d33) of 50.5 pm/V, as compared with 45.1 pm/V and 39.7 pm/V in [110]- and [111]-oriented films, respectively.

Determination of crystallographic orientation of lead-free piezoelectric (K,Na)NbO3 epitaxial thin films grown on SrTiO3 (100) surfaces

“…5,6 Previous studies revealed that KNN films with high phase purity could be synthesized by a sol-gel process on Pt/Ti/SiO 2 /Si substrates or perovskite oxides like single-crystalline SrTiO 3 (abbreviated as STO) wafer. 7,8 Even though it is possible to prepare oriented KNN films on Pt/Ti/SiO 2 /Si substrates, epitaxial ones grown on STO substrates are more attractive not only due to their outstanding performance but also because the specimens are ideal for structural investigation. Such studies are particularly necessary for the KNN-based system, which has a more complicated phase structure than the well-studied Pb(Zr,Ti)O 3 (abbreviated as PZT) counterpart.…”

“…Our previous study showed that epitaxial KNN films grown on the (100) surface of STO substrates possess higher piezoelectric property than the counterparts on the (110) and (111) surfaces, which could not be fully understood by the knowledge of spontaneous polarization and domain configuration. 8 It is known that PZT-based films grown on SrTiO 3 (100) surfaces are [001] oriented with an out-of-plane direction as c-axis. 11 However, more detailed studies are needed to investigate the precise crystallographic structure of KNN films on cubic substrates because of the lattice parameter differences existing between KNN and PZT systems.…”

Ferroelectric properties in thin film barium titanate grown using pulsed laser deposition

“…However, the ferroelectric phase is subject to varying degrees of intrinsic and/or extrinsic influences, ranging from elemental composition, 9 annealing, growth technique, 10 and straining, 11 among others. [12][13][14][15][16] Therefore, it is important to understand the quality of perovskites in terms of their demonstrated ferroelectric properties.…”

Growth and physical properties of highly oriented La-doped (K,Na)NbO3 ferroelectric thin films

“…This, in turn, implies that KNN films are coherently in-plane oriented. Similar behaviour has been reported when preparing KNN thin films by sol-gel processing using STO(100) as substrate [23]. In addition, the rocking curves or ω-scan, Figure 3b, of the pure KNN(70/70) films deposited onto STO(100) were performed using the (400) reflection, 2θ = 100.8 º.…”