Alkali-deficiency driven charged out-of-phase boundaries for giant electromechanical response

AbstractTraditional strategies for improving piezoelectric properties have focused on phase boundary engineering through complex chemical alloying and phase control. Although they have been successfully employed in bulk materials, they have not been effective in thin films due to the severe deterioration in epitaxy, which is critical to film properties. Contending with the opposing effects of alloying and epitaxy in thin films has been a long-standing issue. Herein we demonstrate a new strategy in alkali niobate epitaxial films, utilizing alkali vacancies without alloying to form nanopillars enclosed with out-of-phase boundaries that can give rise to a giant electromechanical response. Both atomically resolved polarization mapping and phase field simulations show that the boundaries are strained and charged, manifesting as head-head and tail-tail polarization bound charges. Such charged boundaries produce a giant local depolarization field, which facilitates a steady polarization rotation between the matrix and nanopillars. The local elastic strain and charge manipulation at out-of-phase boundaries, demonstrated here, can be used as an effective pathway to obtain large electromechanical response with good temperature stability in similar perovskite oxides.

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Stress, Microstructure and Temperature Stability of Reactive Sputter Deposited WNx Thin Films

MRS Proceedings ◽

10.1557/proc-612-d9.20.1 ◽

2000 ◽

Vol 612 ◽

Author(s):

K. D. Leedy ◽

M. J. O'Keefe ◽

J. G. Wilson ◽

R. Osterday ◽

J. T. Grant

Keyword(s):

Thin Films ◽

Nitrogen Content ◽

Photoelectron Spectroscopy ◽

Temperature Stability ◽

Tungsten Nitride ◽

Film Properties ◽

Sputter Deposited ◽

Temperature Exposure ◽

Low K ◽

Post Deposition

AbstractTungsten nitride (WNx) thin films can be used as Schottky barriers in high power, high temperature semiconductor devices or as diffusion barriers between Cu, low-k dielectric and silicon because each application requires a thermally stable film. Therefore, it is important to understand the thin film properties of WNx as a function of deposition conditions and elevated temperature exposure. In this investigation, the influence of nitrogen content and post deposition annealing on the stress and microstructure of reactive dc magnetron sputter deposited WNx films was analyzed. With an increasing N2 to Ar flow ratio, the as-deposited crystal structure of the films changed from α-W to β-W to amorphous WNx and finally to W2N. Rapid thermal anneals up to 650°C resulted in large tensile stress increases and phase transformations to W2N in the nitrogen-containing films. Grain growth during annealing decreased as the concentration of nitrogen in the film increased. The nitrogen content in the films was determined using x-ray photoelectron spectroscopy (XPS).

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Thermoelectric properties of epitaxial and topotaxial NaxCoO2 thin films

MRS Proceedings ◽

10.1557/proc-0886-f02-02 ◽

2005 ◽

Vol 886 ◽

Cited By ~ 1

Author(s):

Adyam Venimadhav ◽

Z Ma ◽

Qi Li ◽

A Soukiassian ◽

X. X. Xi ◽

...

Keyword(s):

Thin Films ◽

Pulsed Laser Deposition ◽

Sapphire Substrate ◽

Room Temperature ◽

Pulsed Laser ◽

Epitaxial Films ◽

Laser Deposition ◽

Vapor Pressures ◽

Film Properties ◽

Deposition Parameters

ABSTRACTWe report structural, electrical, and thermopower properties of epitaxial and topotaxial NaxCoO2 thin films on (0001) sapphire substrate. Topotaxial NaxCoO2 films were prepared by converting an epitaxial Co3O4 film to NaxCoO2 by annealing in Na vapor and epitaxial NaxCoO2 films were obtained by pulsed laser deposition. All the films are c-axis oriented. For topotaxial films, annealing in different Na vapor pressures resulted in films with different Na concentrations, which showed distinct transport properties. For directly deposited epitaxial films by pulsed laser deposition, deposition parameters are found to control the Na concentration and hence the film properties. The largest thermoelectric power of the samples made by different methods is found to be similar in the range of 70-100 μV/K at room temperature

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Critical effect of the bottom electrode on the ferroelectricity of epitaxial Hf0.5Zr0.5O2 thin films

Journal of Materials Chemistry C ◽

10.1039/d0tc05853j ◽

2021 ◽

Author(s):

Saúl Estandía ◽

Jaume Gàzquez ◽

María Varela ◽

Nico Dix ◽

Mengdi Qian ◽

...

Keyword(s):

Thin Films ◽

Bottom Electrode ◽

Orthorhombic Phase ◽

Epitaxial Films ◽

Critical Effect

Comparison of a set of perovskite electrodes shows that La1−x(Ca,Sr)xMnO3 is critical to stabilize the ferroelectric orthorhombic phase in epitaxial films. The stabilization is favored if the La content in the manganite is high.

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Superconducting Sr2RuO4 Thin Films without Out-of-Phase Boundaries by Higher-Order Ruddlesden–Popper Intergrowth

Nano Letters ◽

10.1021/acs.nanolett.0c04963 ◽

2021 ◽

Author(s):

Jinkwon Kim ◽

Junsik Mun ◽

Carla M. Palomares García ◽

Bongju Kim ◽

Robin S. Perry ◽

...

Keyword(s):

Thin Films ◽

Higher Order ◽

Phase Boundaries

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Detection of nitroaromatic vapours with diketopyrrolopyrrole thin films: exploring the role of structural order and morphology on thin film properties and fluorescence quenching efficiency

Chemical Communications ◽

10.1039/c4cc08468c ◽

2015 ◽

Vol 51 (6) ◽

pp. 1143-1146 ◽

Cited By ~ 18

Author(s):

Monika Warzecha ◽

Jesus Calvo-Castro ◽

Alan R. Kennedy ◽

Alisdair N. Macpherson ◽

Kenneth Shankland ◽

...

Keyword(s):

Thin Film ◽

Thin Films ◽

Fluorescence Quenching ◽

Optical Detection ◽

Film Properties ◽

Structural Order ◽

Quenching Efficiency ◽

First Time

Sensitive optical detection of nitroaromatic vapours with diketopyrrolopyrrole thin films is reported for the first time.

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Random Fourier Features via Fast Surrogate Leverage Weighted Sampling

Proceedings of the AAAI Conference on Artificial Intelligence ◽

10.1609/aaai.v34i04.5920 ◽

2020 ◽

Vol 34 (04) ◽

pp. 4844-4851

Author(s):

Fanghui Liu ◽

Xiaolin Huang ◽

Yudong Chen ◽

Jie Yang ◽

Johan Suykens

Keyword(s):

State Of The Art ◽

Sampling Strategy ◽

Prediction Performance ◽

Current State ◽

Kernel Approximation ◽

Sampling Process ◽

New Strategy ◽

The Matrix ◽

Benchmark Datasets ◽

Random Fourier Features

In this paper, we propose a fast surrogate leverage weighted sampling strategy to generate refined random Fourier features for kernel approximation. Compared to the current state-of-the-art method that uses the leverage weighted scheme (Li et al. 2019), our new strategy is simpler and more effective. It uses kernel alignment to guide the sampling process and it can avoid the matrix inversion operator when we compute the leverage function. Given n observations and s random features, our strategy can reduce the time complexity for sampling from O(ns2+s3) to O(ns2), while achieving comparable (or even slightly better) prediction performance when applied to kernel ridge regression (KRR). In addition, we provide theoretical guarantees on the generalization performance of our approach, and in particular characterize the number of random features required to achieve statistical guarantees in KRR. Experiments on several benchmark datasets demonstrate that our algorithm achieves comparable prediction performance and takes less time cost when compared to (Li et al. 2019).

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Dielectric tunable characteristics of compositional-gradient BaTi1−xSnxO3 thin films

Journal of Advanced Dielectrics ◽

10.1142/s2010135x21500193 ◽

2021 ◽

Vol 11 (04) ◽

pp. 2150019

Author(s):

Chenjing Wu ◽

Manwen Yao

Keyword(s):

Thin Films ◽

Impedance Matching ◽

Sol Gel ◽

Temperature Stability ◽

Dielectric Behavior ◽

Compositional Gradient ◽

Dielectric Tunability ◽

Temperature Range ◽

Si Substrates ◽

Low Leakage

Compositional-gradient [Formula: see text][Formula: see text]O3 thin films on Pt(100)/Ti/SiO2/Si substrates are fabricated with sol–gel using spin coating. All of the structures of the prepared thin films are of single-phase crystalline perovskite with a dense and crack-free surface morphology. BTS10/15/20 thin film exhibits enhanced temperature stability in its dielectric behavior. The temperature coefficient of capacitance [Formula: see text] in the temperature range from [Formula: see text]C to [Formula: see text]C is [Formula: see text]C and that of [Formula: see text] in the temperature range from [Formula: see text]C to [Formula: see text]C is [Formula: see text]C. Furthermore, the thin films show low leakage current density and dielectric loss. High and stable dielectric tunable performances are found in BTS10/15/20 thin films: the dielectric tunability of the thin films is around 20.1% under a bias voltage of 8 V at 1 MHz and the corresponding dielectric constant is in the range between 89 and 111, which is beneficial for impedance matching in circuits. Dielectric tunability can be obtained under a low tuning voltage, which helps ensure safety. The simulated resonant frequency of the compositional-gradient BTS thin films depends on the bias electric field, showing compositional-gradient BTS thin films could be used in electrically tunable components and devices. These properties make compositional-gradient BTS thin films a promising candidate for dielectric tuning.

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