Strain-Mediated Substrate Effect on the Dielectric and Ferroelectric Response of Potassium Sodium Niobate Thin Films

Tkach, Alexander; Santos, Andrea M.; Złotnik, Sebastian; Serrazina, Ricardo; Okhay, Olena; Bdikin, Igor; Costa, Maria Elisabete V.; Vilarinho, Paula M.

doi:10.3390/coatings8120449

Cited by 11 publications

(14 citation statements)

References 30 publications

(66 reference statements)

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“…The estimated full-width at half-maximum (fwhm) values of the rocking curves of KNN (001) shown in Figure c are 0.32°, 0.37°, and 0.40° for 20, 50, and 80 nm-thick films, respectively. However, different thermal expansion coefficient of KNN and STO is also responsible for the variation in the lattice parameter . Here, the thickness of the films are estimated from the X-ray reflectivity (XRR) patterns (not shown).…”

Section: Resultsmentioning

confidence: 99%

Thickness-Dependent Domain Relaxation Dynamics Study in Epitaxial K_0.5Na_0.5NbO₃ Ferroelectric Thin Films

Pradhan

Rath

David

et al. 2021

ACS Appl. Mater. Interfaces

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We explored the time dependence of the nanoscale domain relaxation mechanism in epitaxial K0.5Na0.5NbO3 (KNN) thin films grown on La0.67Sr0.33MnO3/SrTiO3 (001) substrates over the thickness range 20–80 nm using scanning probe microscopy. Kelvin probe force microscopy (KFM) and piezoresponse force microscopy were performed on pulsed-laser-deposition-deposited KNN thin films for studying the time evolution of trapped charges and polarized domains, respectively. The KFM data show that the magnitude and retention time of the surface potential are the maxima for 80 nm-thick film and reduce with the reduction in the film thickness. The charging and discharging of the samples reveal the easier and stronger electron trapping compared to hole trapping. This result further indicates the asymmetry between retention of the pulse-voltage-induced upward and downward domains. Furthermore, the time evolution of these ferroelectric nanodomains are found to obey stretched exponential behavior. The relaxation time (T) has been found to increase with increase in thickness; however, the corresponding stretched exponent (β) is reduced. Moreover, the written domain can retain for more than 2300 min in KNN thin films. An in-depth understanding of domain relaxation dynamics in Pb-free KNN thin films can bridge a path for future high-density memory applications.

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Section: Resultsmentioning

confidence: 99%

Thickness-Dependent Domain Relaxation Dynamics Study in Epitaxial K_0.5Na_0.5NbO₃ Ferroelectric Thin Films

Pradhan

Rath

David

et al. 2021

ACS Appl. Mater. Interfaces

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“…Consequently, only a minor polarization switching was observed (Figure 6). Growing the KNN films on a substrate giving tensile in-plane strain (e.g., SrRuO 3 /Pt/MgO [47], Pt/SrTiO 3 [48]) will promote in-plane polarization and should therefore promote polarization saturation when conducting in-plane measurements.…”

Section: Discussionmentioning

confidence: 99%

Controlling Phase Purity and Texture of K0.5Na0.5NbO3 Thin Films by Aqueous Chemical Solution Deposition

et al. 2019

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Aqueous chemical solution deposition (CSD) of lead-free ferroelectric K0.5Na0.5NbO3 (KNN) thin films has a great potential for cost-effective and environmentally friendly components in microelectronics. Phase purity of KNN is, however, a persistent challenge due to the volatility of alkali metal oxides, usually countered by using excess alkali metals in the precursor solutions. Here, we report on the development of two different aqueous precursor solutions for CSD of KNN films, and we demonstrate that the decomposition process during thermal processing of the films is of detrimental importance for promoting nucleation of KNN and suppressing the formation of secondary phases. Based on thermal analysis, X-ray diffraction and IR spectroscopy of films as well as powders prepared from the solutions, it was revealed that the decomposition temperature can be controlled by chemistry resulting in phase pure KNN films. A columnar microstructure with out-of-plane texturing was observed in the phase pure KNN films, demonstrating that the microstructure is directly coupled to the thermal processing of the films.

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“…Furthermore, in our recent work we have shown that substrates, used for the film deposition, also have a determining role on the final properties of the films [11]. Thus, platinized Si, mainly reported as substrate for KNN [6,7,8] and other piezoelectric films [9,10], has been shown to induce large tensile residual stress in sol–gel derived undoped KNN films due to thermal expansion mismatch, thus diminishing out-of-plane dielectric, ferroelectric, and piezoelectric response of the films [11]. On the other hand, platinized SrTiO 3 substrates, possessing much larger thermal expansion coefficient (TEC), have been shown to induce residual compressive stress in KNN films, significantly enhancing out-of-plane permittivity, polarization, and piezoresponse [11].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, platinized Si, mainly reported as substrate for KNN [6,7,8] and other piezoelectric films [9,10], has been shown to induce large tensile residual stress in sol–gel derived undoped KNN films due to thermal expansion mismatch, thus diminishing out-of-plane dielectric, ferroelectric, and piezoelectric response of the films [11]. On the other hand, platinized SrTiO 3 substrates, possessing much larger thermal expansion coefficient (TEC), have been shown to induce residual compressive stress in KNN films, significantly enhancing out-of-plane permittivity, polarization, and piezoresponse [11]. Therefore, to study only the influence of the solution conditions on the properties of polycrystalline KNN thin films, minimizing the effect of the substrate, one should choose a substrate with similar TEC.…”

Section: Introductionmentioning

confidence: 99%

Effect of Solution Conditions on the Properties of Sol–Gel Derived Potassium Sodium Niobate Thin Films on Platinized Sapphire Substrates

et al. 2019

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If piezoelectric micro-devices based on K0.5Na0.5NbO3 (KNN) thin films are to achieve commercialization, it is critical to optimize the films’ performance using low-cost scalable processing conditions. Here, sol–gel derived KNN thin films are deposited using 0.2 and 0.4 M precursor solutions with 5% solely potassium excess and 20% alkali (both potassium and sodium) excess on platinized sapphire substrates with reduced thermal expansion mismatch in relation to KNN. Being then rapid thermal annealed at 750 °C for 5 min, the films revealed an identical thickness of ~340 nm but different properties. An average grain size of ~100 nm and nearly stoichiometric KNN films are obtained when using 5% potassium excess solution, while 20% alkali excess solutions give the grain size of 500–600 nm and (Na + K)/Nb ratio of 1.07–1.08 in the prepared films. Moreover, the 5% potassium excess solution films have a perovskite structure without clear preferential orientation, whereas a (100) texture appears for 20% alkali excess solutions, being particularly strong for the 0.4 M solution concentration. As a result of the grain size and (100) texturing competition, the highest room-temperature dielectric permittivity and lowest dissipation factor measured in the parallel-plate-capacitor geometry were obtained for KNN films using 0.2 M precursor solutions with 20% alkali excess. These films were also shown to possess more quadratic-like and less coercive local piezoelectric loops, compared to those from 5% potassium excess solution. Furthermore, KNN films with large (100)-textured grains prepared from 0.4 M precursor solution with 20% alkali excess were found to possess superior local piezoresponse attributed to multiscale domain microstructures.

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Strain-Mediated Substrate Effect on the Dielectric and Ferroelectric Response of Potassium Sodium Niobate Thin Films

Cited by 11 publications

References 30 publications

Thickness-Dependent Domain Relaxation Dynamics Study in Epitaxial K_0.5Na_0.5NbO₃ Ferroelectric Thin Films

Thickness-Dependent Domain Relaxation Dynamics Study in Epitaxial K_0.5Na_0.5NbO₃ Ferroelectric Thin Films

Controlling Phase Purity and Texture of K0.5Na0.5NbO3 Thin Films by Aqueous Chemical Solution Deposition

Effect of Solution Conditions on the Properties of Sol–Gel Derived Potassium Sodium Niobate Thin Films on Platinized Sapphire Substrates

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Strain-Mediated Substrate Effect on the Dielectric and Ferroelectric Response of Potassium Sodium Niobate Thin Films

Cited by 11 publications

References 30 publications

Thickness-Dependent Domain Relaxation Dynamics Study in Epitaxial K0.5Na0.5NbO3 Ferroelectric Thin Films

Thickness-Dependent Domain Relaxation Dynamics Study in Epitaxial K0.5Na0.5NbO3 Ferroelectric Thin Films

Controlling Phase Purity and Texture of K0.5Na0.5NbO3 Thin Films by Aqueous Chemical Solution Deposition

Effect of Solution Conditions on the Properties of Sol–Gel Derived Potassium Sodium Niobate Thin Films on Platinized Sapphire Substrates

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Thickness-Dependent Domain Relaxation Dynamics Study in Epitaxial K_0.5Na_0.5NbO₃ Ferroelectric Thin Films

Thickness-Dependent Domain Relaxation Dynamics Study in Epitaxial K_0.5Na_0.5NbO₃ Ferroelectric Thin Films