Origin of Prestress-Driven Optical Modulations of Flexible ZnO Thin Films Processed in Stretching Mode

Choi, Hong Je; Jang, Woosun; Mohanty, Bhaskar Chandra; Jung, Ye Seul; Soon, Aloysius; Cho, Yong Soo

doi:10.1021/acs.jpclett.8b02474

Cited by 15 publications

(21 citation statements)

References 37 publications

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“…We find that the impact of η on the band gap of ZnO thin films is practically negligible (at least in comparison to the CeO 2 and TiO 2 cases), which is consistent with previous experimental observations [16]. For instance, according to our first-principles calculations, E g for the wurtzite phase increases by just 2% at η = +5% and decreases by 3% at η = −5%; in comparison, a reduction of 4% was obtained at η ≈ −5% in experimental work [16]. Meanwhile, the band gap for the zinc-blende phase is changed by even smaller amounts, with only a 0.5% reduction at η = +7% and a 0.5% increase at η = −7% (note the opposite sign in the strain-driven E g change as compared to the wurtzite case, Fig.5d).…”

Section: Zinc-blende and Wurtzite Zno (001)supporting

confidence: 92%

“…Both compressive (η < 0) and tensile (η > 0) biaxial strains ranging from zero up to a maximum absolute value of 7% have been considered in the simulations. These values are comparable in magnitude to the η's achieved experimentally in the same materials [14][15][16]. At the end of this section, we introduce a simple analytical model that depends only on structural and dielectric susceptibility changes and reproduces qualitatively, and helps in understanding, the general band gap trends induced by η.…”

Section: Resultssupporting

confidence: 54%

“…Such potential enhancements in photocatalytic activity result from sizeable band gap reductions (∼ 10%) and correct positioning of the valence and conduction-band edges under η. Meanwhile, the effects of epitaxial strain on the band gap of ZnO, another well-known semiconductor photocatalyst [16], are found to be only marginal (|∆E g |/E g ∼ 1%). We present quantitative and physically intuitive arguments that explain the origins of such irregular η-driven effects on E g in terms of dielectric susceptibility and metal-oxygen bond length changes.…”

Section: Introductionmentioning

confidence: 99%

“…However, a clear and general understanding of how biaxial strain affects the photocatalytic performance of binary oxides is still missing. For instance, the relative E g variations induced by tensile biaxial strain are negative in some materials (band gap decreases in TiO 2 and SnO 2 [17,19]) whereas positive in others (band gap increases in ZnO [16]). Likewise, the E g changes driven by compressive biaxial strain are positive in some materials (TiO 2 and SnO 2 [17,19]) whereas negative or almost null in others (ZnO [16] and CdO [20]).…”

Section: Introductionmentioning

confidence: 99%

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Strain engineering of oxide thin films for photocatalytic applications

et al. 2020

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Photocatalytic materials are pivotal for the implementation of disruptive clean energy applications such as conversion of H2O and CO2 into fuels and chemicals driven by solar energy. However, efficient and cost-effective materials able to catalyze the chemical reactions of interest when exposed to visible light are scarce due to the stringent electronic conditions that they must satisfy. Chemical and nanostructuring approaches are capable of improving the catalytic performance of known photoactive compounds however the complexity of the synthesized nanomaterials and sophistication of the employed methods make systematic design of photocatalysts difficult. Here, we show by means of first-principles simulation methods that application of biaxial stress, η, on semiconductor oxide thin films can modify their optoelectronic and catalytic properties in a significant and predictable manner. In particular, we show that upon moderate tensile strains CeO2 and TiO2 thin films become suitable materials for photocatalytic conversion of H2O into H2 and CO2 into CH4 under sunlight. The band gap shifts induced by η are reproduced qualitatively by a simple analytical model that depends only on structural and dielectric susceptibility changes. Thus, epitaxial strain represents a promising route for methodical screening and rational design of photocatalytic materials.

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Section: Zinc-blende and Wurtzite Zno (001)supporting

confidence: 92%

Section: Resultssupporting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Strain engineering of oxide thin films for photocatalytic applications

et al. 2020

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“…It has been reported that the bandgap narrowing of piezoelectric ZnO is induced under a tensile strain along the c-axis by the respective downward and upward shifts of the CB and the VB. [71,72] Thus, this red-shift in the UV peak position was possibly due to the inhomogenous band bending at the AuNI/ZNT interface due to the laser-induced AuNI reconstruction and the resulting applied tensile strain. Some concerns may be raised regarding the impact of laser exposure on the PL measurement in the UV range because the laser irradiation can produce defect states in ZnO.…”

Section: In Situ Photothermal Surface Restructuring/melting Behavior In the Auni-znts Hybrid: Desorption And Ionizationmentioning

confidence: 98%

Photothermal Structural Dynamics of Au Nanofurnace for In Situ Enhancement in Desorption and Ionization

Kim

Yun

Noh

et al. 2021

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202103745. in the AuNI-ZNT hybrid, which modulates the overall band structure and thereby promotes the ionization process. Ultimately, high LDI-MS performance is demonstrated by analyzing small metabolites of fatty acids and monosaccharides, which are challenged to be detected in conventional LDI-MS. This study emphasizing the understanding of matrix properties can provide insights into the design and development of a novel nanomaterial as an efficient LDI matrix. Furthermore, the developed hybrid matrix can overcome the major hurdles existing in conventional LDI-MS.

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Contribution of Anisotropic Lattice‐Strain to Piezoelectricity and Electromechanical Power Generation of Flexible Inorganic Halide Thin Films

Kim

Park

et al. 2022

Advanced Energy Materials

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even higher strain-stress field is likely created within the perovskite lattices than in the case of rigid substrates because of the larger thermal expansion mismatch with the flexible polymer substrates and the operations that induce intense stress, such as bending, stretching, twisting, and folding. [8][9][10] On the other hand, the additional strain present in the flexible perovskite structure can positively influence the piezoelectric properties of the materials, if properly applied, by inducing the extensive distortion of octahedral structure and thus the surface polarization.Herein, we propose a strain-engineering technique that enables intentionally imposing in situ compressive or tensile strain. As a representative all-inorganic halide material, we employed CsPbBr 3 in the form of a flexible thin film to explore its strain-dependent piezoelectricity for use in harvesting electromechanical energy under bending operation. Despite the variety of potential anisotropic halide compounds, piezoelectricity in perovskite halides has rarely been demonstrated experimentally, probably because of the difficulty of securing high-quality samples due to the limited availability of appropriate chemical precursors and synthesis methods. Table S1 (Supporting Information) summarizes the reported piezoelectric coefficients of halide materials, [11][12][13][14][15][16][17][18][19][20][21] which were obtained from both experiments and theoretical simulations. Apart from the reported theoretical estimations of piezoelectricity, [11,12] the local piezoresponse as characterized by piezoresponse force microscopy (PFM) is usually used to define the effective piezoelectric coefficient d 33,eff for synthesized halide materials. [13][14][15][19][20][21] For example, a d 33,eff value of 6 pm V −1 was reported for methylammonium lead iodide (MAPbI 3 ) thin films as a result of PFM measurements. [14] As another example, MASnI 3 thin films revealed a high d 33,eff of 20.8 pm V −1 with a well-developed butterfly loop. [15] Typically, the experimental piezoelectric coefficient ranged from 0.32 to 38 pm V −1 , [13][14][15][16][17][18][19][20][21] while the theoretical values were in the range of 4.1 to 31.4 pC N −1 , [11,12] which depended on halide composition (e.g., organic-inorganic versus inorganic compounds and B-site substitutions in ABX 3 structure) and the type of material (e.g., single-crystal, nanoparticle, and thin film) as summarized in Table S1 (Supporting Information).The enhanced piezoelectricity achieved by applying the in situ strain here was further verified by demonstrating the

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Origin of Prestress-Driven Optical Modulations of Flexible ZnO Thin Films Processed in Stretching Mode

Cited by 15 publications

References 37 publications

Strain engineering of oxide thin films for photocatalytic applications

Strain engineering of oxide thin films for photocatalytic applications

Photothermal Structural Dynamics of Au Nanofurnace for In Situ Enhancement in Desorption and Ionization

Contribution of Anisotropic Lattice‐Strain to Piezoelectricity and Electromechanical Power Generation of Flexible Inorganic Halide Thin Films

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