Microstructure/Process Relations in Sol‐Gel‐Prepared KnbO<sub>3</sub> Thin Films on (100) MgO

Derderian, Garo; Barrie, James D.; Aitchison, Kenneth A.; Adams, P. M.; Mecartney, Martha L.

doi:10.1111/j.1151-2916.1994.tb05371.x

Cited by 25 publications

(9 citation statements)

References 14 publications

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“…So far, KNbO 3 thin films can be synthesized by the following methods: metalorganic chemical vapor deposition (MOCVD), − pulsed-laser deposition, ,− sputtering, , liquid-phase epitaxy, − and sol−gel. − All these synthesis routes share similar disadvantages of high-temperature processing, requiring temperatures ranging between 600 °C and over 900 °C to obtain a crystalline KNbO 3 phase. The high synthesis temperatures cause typical problems such as difficulties to control potassium stoichiometry due to high volatilization of potassium oxide, interdiffusion between film and the substrate, ,, formation of interphase layers (particularly in the case of using MgO substrate), , and multidomain formation during cooling to room temperature. ,− ,,, The presence of pyrochlore and/or amorphous phases, as well as porosity, was reported particularly for the KNbO 3 films synthesized by the sol−gel method. , In addition, liquid-phase epitaxy (LPE) is not well suited for films with thickness under 1 μm …”

Section: Introductionmentioning

confidence: 99%

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Suchanek

2004

Chem. Mater.

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Orthorhombic KNbO 3 thin films were deposited on SrTiO 3 (100) and LiTaO 3 (001) substrates by low-temperature hydrothermal epitaxy at 180-210°C using aqueous solutions containing Nb 2 O 5 and KOH. The films were thoroughly characterized by X-ray diffraction, Rutherford backscattering, and scanning electron microscopy. The KNbO 3 films were uniformly distributed on the entire substrate area, exhibited high stoichiometry, and did not show evidence of interdiffusion or chemical reaction at the film/substrate interface. Their microstructures were determined by the substrate used, the synthesis temperature, and the concentration of the reactants. The KNbO 3 films on SrTiO 3 (100) substrates with thickness of 45 nm to 1.28 µm were smooth and transparent, with microstructures strongly suggesting single crystal growth mechanism. They were pure orthorhombic phase with (011) orientation and probably single-domain. Conversely, the KNbO 3 films with higher thickness (>3.5 µm) exhibited very rough microstructure with textured columnar grains. Such films were also orthorombic but with mixed (100)/(011) orientation. This work demonstrated for the first time deposition of heteroepitaxial KNbO 3 films on single-crystal substrates using low-temperature hydrothermal epitaxy in a well-defined range of synthesis conditions. The low synthesis temperatures, which are below the 225°C phase transition temperature of KNbO 3 , resulted in formation of films that appear to exhibit improved features as compared to the films prepared by high-temperature processing. IntroductionPotassium niobiate (KNbO 3 ) is a very promising material for surface acoustic wave (SAW) devices and high-performance bulk-wave transducers. 1 The elctromechanical coupling coefficient (k 2 ) of the surface wave in a single-crystal KNbO 3 can be as high as 53%, which is one order of magnitude larger than that of LiNbO 3 . 2 The bandwidth is about 20% and insertion losses are 2-6 dB. 2 The acoustic wave velocities in KNbO 3 are 3500-7500 m/s 3 and the temperature coefficient of frequency (TCF) ranges between 0 and 170 ppm/K depending upon crystallographic orientation. 2 The KNbO 3 exhibits large piezoelectric nonlinearity. The 45°r otated Y-cut X-propagated KNbO 3 has 25 dB larger efficiency than Y-Z LiNbO 3 ; thus the KNbO 3 single crystal is considered as a promising material for SAW elastic convolvers with super high efficiency and process gain. 4 In addition to excellent piezoelectric properties, the KNbO 3 has a large electrooptic coefficient, high nonlinear optical coefficient, and excellent photorefractive characteristics 5 that make it a very promising candidate for optical applications such as optical waveguides, frequency doublers, 6 intensity modulators, 7

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Section: Introductionmentioning

confidence: 99%

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Suchanek

2004

Chem. Mater.

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“…Different macroscopic phases develop indicating an inadequate distribution of metal ions in the film. This aspect was observed before, 22 but interfering hydrolysis was not excluded. The unintended interaction with ambient humidity is therefore definitively ruled out as the primary explanation for the depicted results.…”

Section: Resultsmentioning

confidence: 73%

Precursor Homogeneity and Crystallization Effects in Chemical Solution Deposition‐Derived Alkaline Niobate Thin Films

Röscher

Tappertzhofen

Schneller

2011

Journal of the American Ceramic Society

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Chemical solution deposition‐derived potassium niobate and sodium niobate thin films have been prepared under protective atmosphere using an alkoxide approach. A profound dependency of the quality and homogeneity of the resulting thin films on the preparation of the alkaline precursor has been found. In addition to this, an additional increase in microstructure homogeneity for the significantly more sensitive potassium niobate system is obtainable if the precursor solution is further stabilized by acetylacetone although ambient humidity is already strongly suppressed. The observed behavior is attributed to the stabilization of the heterometallic complex in the precursor solution until film deposition commenced. Further on, the crystallization pathway of the respective alkaline niobate thin films has been evaluated and indication of crystallization through a metastable phase has been provided which seems to play a key role in orientation control. Finally, the temperature dependency of the lattice parameter spacing for potassium niobate and sodium niobate thin films has been presented and evidence of a strong substrate‐induced lattice deformation has been given.

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“…The lattice spacing along the growth and lateral direction are 0.397 and 0.409 nm, respectively, whereas the spacing in bulk KNO was reported to be 0.3984 and 0.4035 nm, respectively. 31 The average crystallite size in the nanofiber sample was around 20 ± 5 nm and estimated by direct measurement of the size distribution using enhanced microscopy images as shown in Figure S2.…”

Section: Methodsmentioning

confidence: 99%

Decoding Apparent Ferroelectricity in Perovskite Nanofibers

Ganeshkumar

Somnath²,

Cheah

et al. 2017

ACS Appl. Mater. Interfaces

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Ferroelectric perovskites are an important group of materials underpinning a wide variety of devices ranging from sensors and transducers to nonvolatile memories and photovoltaic cells. Despite the progress in material synthesis, ferroelectric characterization of nanoscale perovskites is still a challenge. Piezoresponse force microscopy (PFM) is one of the most popular tools for probing and manipulating nanostructures to study the ferroelectric properties. However, the interpretation of hysteresis data and alternate signal origins are critical. Here, we use a family of scanning probe microscopy (SPM) techniques to systematically investigate the ferroelectric behavior of electrospun potassium niobate (KNbO) nanofibers. Band Excitation (BE) SPM scans reveal that PFM signals are dominated by changes in resonant frequency due to rough nanofiber surfaces, rather than the actual local piezoelectric strength. We investigate the bias-induced charge injection properties and electrostatic interactions on the PFM response of the nanofiber using contact mode Kelvin probe force microscopy (cKPFM). Furthermore, the impact of relative humidity on the KNbO nanofiber's piezoresponse, switching behavior, and tip-induced charges are explored. The resultant data from BE scans were utilized to estimate the piezoelectric constants of the KNO nanofiber. These observations will provide clarity in studying newly developed ferroelectric nanostructures and unambiguously interpreting the PFM data.

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Microstructure/Process Relations in Sol‐Gel‐Prepared KnbO₃ Thin Films on (100) MgO

Cited by 25 publications

References 14 publications

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Precursor Homogeneity and Crystallization Effects in Chemical Solution Deposition‐Derived Alkaline Niobate Thin Films

Decoding Apparent Ferroelectricity in Perovskite Nanofibers

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Microstructure/Process Relations in Sol‐Gel‐Prepared KnbO3 Thin Films on (100) MgO

Cited by 25 publications

References 14 publications

Synthesis of Potassium Niobiate (KNbO3) Thin Films by Low-Temperature Hydrothermal Epitaxy

Synthesis of Potassium Niobiate (KNbO3) Thin Films by Low-Temperature Hydrothermal Epitaxy

Precursor Homogeneity and Crystallization Effects in Chemical Solution Deposition‐Derived Alkaline Niobate Thin Films

Decoding Apparent Ferroelectricity in Perovskite Nanofibers

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Microstructure/Process Relations in Sol‐Gel‐Prepared KnbO₃ Thin Films on (100) MgO

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy

Synthesis of Potassium Niobiate (KNbO₃) Thin Films by Low-Temperature Hydrothermal Epitaxy