Enhanced Photoelectrochemical Activity in All‐Oxide Heterojunction Devices Based on Correlated “Metallic” Oxides

Apgar, Brent A.; Lee, Sungki; Schroeder, Lauren E.; Martin, Lane W.

doi:10.1002/adma.201303144

Cited by 22 publications

(20 citation statements)

References 55 publications

(84 reference statements)

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“…After laser irradiation, the carrier density of the IT zone was increased because of the phase transition and defect formed during laser irradiation. 21,31,32 Based on the observations outlined above, we conclude that a MEF was constructed on the titanium surface, as shown in Figure 1.…”

Section: Resultsmentioning

confidence: 59%

Built-in microscale electrostatic fields induced by anatase–rutile-phase transition in selective areas promote osteogenesis

Ning

Zhu

et al. 2016

NPG Asia Mater

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Bone has a built-in electric field because of the presence of piezoelectric collagen. To date, only externally applied electric fields have been used to direct cell behavior; however, these fields are not safe or practical for in vivo use. In this work, for the first time, we use a periodic microscale electric field (MEF) built into a titanium implant to induce osteogenesis. Such a MEF is generated by the periodic organization of a junction made of two parallel semiconducting TiO2 zones: anatase and rutile with lower and higher electron densities, respectively. The junctions were formed through anatase–rutile-phase transition in selective areas using laser irradiation on the implants. The in vitro and in vivo studies confirmed that the built-in MEF was an efficient electrical cue for inducing osteogenic differentiation in the absence of osteogenic supplements and promoted bone regeneration around the implants. Our work opens up a new avenue toward bone repair and regeneration using built-in MEF.

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Section: Resultsmentioning

confidence: 59%

Built-in microscale electrostatic fields induced by anatase–rutile-phase transition in selective areas promote osteogenesis

Ning

Zhu

et al. 2016

NPG Asia Mater

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“…Knowledge of the Schottky barrier height for metal/semiconductor and band offsets for semiconductor/semiconductor heterostructures are required for the design of future La 1Àx Sr x CoO 3 -based devices of interest in solid state physics, electrochemistry, and photo-electrochemistry. [1][2][3][4][5][6] For electrochemical devices, for instance, optimal energy band alignments at La 0.5 Sr 0.5 CoO 3 /TiO 2 /water interfaces have been proposed to enhance "hot electron" transport through such heterostructures, thereby accounting for their high photoelectrochemical activity. 4 More generally, the location of the valence band (VB) maximum of non-conducting oxide electrocatalysts relative to the redox potential of electrochemical reactions determines the dependence of electrochemical activity on thickness.…”

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confidence: 99%

“…[1][2][3][4][5][6] For electrochemical devices, for instance, optimal energy band alignments at La 0.5 Sr 0.5 CoO 3 /TiO 2 /water interfaces have been proposed to enhance "hot electron" transport through such heterostructures, thereby accounting for their high photoelectrochemical activity. 4 More generally, the location of the valence band (VB) maximum of non-conducting oxide electrocatalysts relative to the redox potential of electrochemical reactions determines the dependence of electrochemical activity on thickness. 5 Unfortunately, band offsets at complex oxide interfaces are difficult to predict, requiring experimental verification.…”

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confidence: 99%

“…[36][37][38] Photons of lower energies may also be converted by LCO with subsequent carrier separation at the LCO/NSTO interface. 4 To summarize, we have investigated the energy band offset, and the atomic and electronic structures at the interface between perovskite La 1Àx Sr x CoO 3 and niobiumdoped strontium titanate. A large valence band offset of 2.8 6 0.1 eV between LaCoO 3 and Nb:SrTiO 3 was measured.…”

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confidence: 99%

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Interface energetics and atomic structure of epitaxial La1−xSrxCoO3 on Nb:SrTiO3

Overmeere

Baniecki

Yamazaki

et al. 2015

Applied Physics Letters

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The energetics at oxide semiconductor/La1−xSrxCoO3 heterojunctions, including the respective alignment of the valence and conduction bands, govern charge transfer and have to be determined for the design of future La1−xSrxCoO3-based devices. In this letter, the electronic and atomic structures of epitaxial La1−xSrxCoO3 on Nb-doped strontium titanate are revealed by scanning transmission electron microscopy, electron energy loss spectroscopy, and in situ x-ray and ultra violet photoelectron spectroscopies. For LaCoO3, a valence band (VB) offset of 2.8 ± 0.1 eV is deduced. The large offset is attributed to the orbital contributions of the Co 3d states to the VB maximum of the LaCoO3 thin films, with no evidence of interface dipole contributions. The sensitivity of the valence band orbital character to spin state ordering and oxygen vacancies is assessed using density functional theory.

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“…20 PEC experiments were performed using a setup and measurement process that have been described previously. 21,22 Photocatalytic activities of the samples were examined by measuring the degradation rate of methylene blue solution, which is an effective method to evaluate the visible light absorption ability of the thin film material. Typically, the STO control sample and 10% doped SLTCO with 5 nm STO protection layer were measured under an AM1.5G spectrum light filtered by a k ¼ 444 nm long-pass filter for 12 h. The filter cuts off light with wavelength shorter than 444 nm (տ2.8 eV), thus eliminating effects of the primary O 2p to Ti 3d absorption in STO.…”

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confidence: 99%

Visible light carrier generation in co-doped epitaxial titanate films

Comès

Smolin

Kaspar

et al. 2015

Applied Physics Letters

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Perovskite titanates such as SrTiO$_{3}$ (STO) exhibit a wide range of important functional properties, including high electron mobility, ferroelectricity, and excellent photocatalytic performance. The wide optical band gap of titanates limits their use in these applications, however, making them ill-suited for integration into solar energy harvesting technologies. Our recent work has shown that by doping STO with equal concentrations of La and Cr we can enhance visible light absorption in epitaxial thin films while avoiding any compensating defects. In this work, we explore the optical properties of photoexcited carriers in these films. Using spectroscopic ellipsometry, we show that the Cr$^{3+}$ dopants, which produce electronic states immediately above the top of the O 2p valence band in STO reduce the direct band gap of the material from 3.75 eV to between 2.4 and 2.7 eV depending on doping levels. Transient reflectance spectroscopy measurements are in agreement with the observations from ellipsometry and confirm that optically generated carriers are present for longer than 2 ns. Finally, through photoelectrochemical methylene blue degradation measurements, we show that these co-doped films exhibit enhanced visible light photocatalysis when compared to pure STO.Comment: 19 pages including supplement, 8 figures (3 main, 5 supplement

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Enhanced Photoelectrochemical Activity in All‐Oxide Heterojunction Devices Based on Correlated “Metallic” Oxides

Cited by 22 publications

References 55 publications

Built-in microscale electrostatic fields induced by anatase–rutile-phase transition in selective areas promote osteogenesis

Built-in microscale electrostatic fields induced by anatase–rutile-phase transition in selective areas promote osteogenesis

Interface energetics and atomic structure of epitaxial La1−xSrxCoO3 on Nb:SrTiO3

Visible light carrier generation in co-doped epitaxial titanate films

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