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Raji A, Krieger G, Viart N, Preziosi D, Rueff JP, Gloter A. Charge Distribution across Capped and Uncapped Infinite-Layer Neodymium Nickelate Thin Films. Small 2023:e2304872. [PMID: 37594722 DOI: 10.1002/smll.202304872] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 07/07/2023] [Indexed: 08/19/2023]
Abstract
Charge ordering (CO) phenomena have been widely debated in strongly-correlated electron systems mainly regarding their role in high-temperature superconductivity. Here, the structural and charge distribution in NdNiO2 thin films prepared with and without capping layers, and characterized by the absence and presence of CO are elucidated. The microstructural and spectroscopic analysis is done by scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) and hard X-ray photoemission spectroscopy (HAXPES). Capped samples show Ni1+ , with an out-of-plane (o-o-p) lattice parameter of around 3.30 Å indicating good stabilization of the infinite-layer structure. Bulk-sensitive HAXPES on Ni-2p shows weak satellite features indicating large charge-transfer energy. The uncapped samples evidence an increase of the o-o-p parameter up to 3.65 Å on the thin film top with a valence toward Ni2+ in this region. Here, 4D-STEM demonstrates (303)-oriented stripes which emerge from partially occupied apical oxygen. Those stripes form quasi-2D coherent domains viewed as rods in the reciprocal space with Δqz ≈ 0.24 reciprocal lattice units (r.l.u.) extension located at Q = (± 1 3 , 0 , ± 1 3 $\pm \frac{1}{3},0,\pm \frac{1}{3}$ ) and (± 2 3 , 0 , ± 2 3 $\pm \frac{2}{3},0,\pm \frac{2}{3}$ ) r.l.u. The stripes associated with oxygen re-intercalation concomitant with hole doping suggest a possible link to the previously reported CO in infinite-layer nickelate thin films.
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Affiliation(s)
- Aravind Raji
- Laboratoire de Physique des Solides, CNRS, Université Paris-Saclay, Orsay, 91405, France
- Synchrotron SOLEIL, L'Orme des Merisiers, BP 48 St Aubin, Gif sur Yvette, 91192, France
| | - Guillaume Krieger
- Universite de Strasbourg, CNRS, IPCMS UMR 7504, Strasbourg, F-67034, France
| | - Nathalie Viart
- Universite de Strasbourg, CNRS, IPCMS UMR 7504, Strasbourg, F-67034, France
| | - Daniele Preziosi
- Universite de Strasbourg, CNRS, IPCMS UMR 7504, Strasbourg, F-67034, France
| | - Jean-Pascal Rueff
- Synchrotron SOLEIL, L'Orme des Merisiers, BP 48 St Aubin, Gif sur Yvette, 91192, France
- LCPMR, Sorbonne Université, CNRS, Paris, 75005, France
| | - Alexandre Gloter
- Laboratoire de Physique des Solides, CNRS, Université Paris-Saclay, Orsay, 91405, France
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Cho J, Suwandaratne NS, Razek S, Choi YH, Piper LFJ, Watson DF, Banerjee S. Elucidating the Mechanistic Origins of Photocatalytic Hydrogen Evolution Mediated by MoS 2/CdS Quantum-Dot Heterostructures. ACS Appl Mater Interfaces 2020; 12:43728-43740. [PMID: 32866372 DOI: 10.1021/acsami.0c12583] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Solar fuel generation mediated by semiconductor heterostructures represents a promising strategy for sustainable energy conversion and storage. The design of semiconductor heterostructures for photocatalytic energy conversion requires the separation of photogenerated charge carriers in real space and their delivery to active catalytic sites at the appropriate overpotentials to initiate redox reactions. Operation of the desired sequence of light harvesting, charge separation, and charge transport events within heterostructures is governed by the thermodynamic energy offsets of the two components and their photoexcited charge-transfer reactivity, which determine the extent to which desirable processes can outcompete unproductive recombination channels. Here, we map energetic offsets and track the dynamics of electron transfer in MoS2/CdS architectures, prepared by interfacing two-dimensional MoS2 nanosheets with CdS quantum dots (QDs), and correlate the observed charge separation to photocatalytic activity in the hydrogen evolution reaction. The energetic offsets between MoS2 and CdS have been determined using hard and soft X-ray photoemission spectroscopy (XPS) in conjunction with density functional theory. A staggered type-II interface is observed, which facilitates electron and hole separation across the interface. Transient absorption spectroscopy measurements demonstrate ultrafast electron injection occurring within sub-5 ps from CdS QDs to MoS2, allowing for creation of a long-lived charge-separated state. The increase of electron concentration in MoS2 is evidenced with the aid of spectroelectrochemical measurements and by identifying the distinctive signatures of electron-phonon scattering in picosecond-resolution transient absorption spectra. Ultrafast charge separation across the type-II interface of MoS2/CdS heterostructures enables a high Faradaic efficiency of ∼99.4 ± 1.2% to be achieved in the hydrogen evolution reaction (HER) and provides a 40-fold increase in the photocatalytic activity of dispersed photocatalysts for H2 generation. The accurate mapping of thermodynamic driving forces and dynamics of charge transfer in these heterostructures suggests a means of engineering ultrafast electron transfer and effective charge separation to design viable photocatalytic architectures.
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Affiliation(s)
- Junsang Cho
- Departments of Chemistry and Materials Science and Engineering, Texas A&M University, College Station, Texas 77842-3012, United States
- Department of Chemistry, Duksung Women's University, Seoul 01369, South Korea
| | - Nuwanthi S Suwandaratne
- Department of Chemistry, University at Buffalo The State University of New York, Buffalo, New York 14260-3000, United States
| | - Sara Razek
- Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, New York 13902, United States
| | - Yun-Hyuk Choi
- Departments of Chemistry and Materials Science and Engineering, Texas A&M University, College Station, Texas 77842-3012, United States
- School of Advanced Materials and Chemical Engineering, Daegu Catholic University, Gyeongsan, Gyeongbuk 38430, South Korea
| | - Louis F J Piper
- Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, New York 13902, United States
| | - David F Watson
- Department of Chemistry, University at Buffalo The State University of New York, Buffalo, New York 14260-3000, United States
| | - Sarbajit Banerjee
- Departments of Chemistry and Materials Science and Engineering, Texas A&M University, College Station, Texas 77842-3012, United States
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Wu MY, Huang QS, Le Guen K, Ilakovac V, Li BX, Wang ZS, Giglia A, Rueff JP, Jonnard P. Characterization of Pd/Y multilayers with B 4C barrier layers using GIXR and X-ray standing wave enhanced HAXPES. J Synchrotron Radiat 2018; 25:1417-1424. [PMID: 30179181 DOI: 10.1107/s1600577518009402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 06/29/2018] [Indexed: 06/08/2023]
Abstract
Pd/Y multilayers are high-reflectance mirrors designed to work in the 7.5-11 nm wavelength range. Samples, prepared by magnetron sputtering, are deposited with or without B4C barrier layers located at the interfaces of the Pd and Y layers to reduce interdiffusion, which is expected from calculating the mixing enthalpy of Pd and Y. Grazing-incident X-ray reflectometry is used to characterize these multilayers. B4C barrier layers are found to be effective in reducing Pd-Y interdiffusion. Details of the composition of the multilayers are revealed by hard X-ray photoemission spectroscopy with X-ray standing wave effects. This consists of measuring the photoemission intensity from the samples by performing an angular scan in the region corresponding to the multilayer period and an incident photon energy according to Bragg's law. The experimental results indicate that Pd does not chemically react with B nor C at the Pd-B4C interface while Y does react at the Y-B4C interface. The formation of Y-B or Y-C chemical compounds could be the reason why the interfaces are stabilized. By comparing the experimentally obtained angular variation of the characteristic photoemission with theoretical calculations, the depth distribution of each component element can be interpreted.
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Affiliation(s)
- M Y Wu
- Laboratoire de Chimie Physique - Matière et Rayonnement, Sorbonne University, UMR CNRS 7614, 4 Place Jussieu, 75005 Paris, France
| | - Q S Huang
- Key Laboratory of Advanced Micro-Structured Materials MOE, Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
| | - K Le Guen
- Laboratoire de Chimie Physique - Matière et Rayonnement, Sorbonne University, UMR CNRS 7614, 4 Place Jussieu, 75005 Paris, France
| | - V Ilakovac
- Laboratoire de Chimie Physique - Matière et Rayonnement, Sorbonne University, UMR CNRS 7614, 4 Place Jussieu, 75005 Paris, France
| | - B X Li
- Laboratoire de Chimie Physique - Matière et Rayonnement, Sorbonne University, UMR CNRS 7614, 4 Place Jussieu, 75005 Paris, France
| | - Z S Wang
- Key Laboratory of Advanced Micro-Structured Materials MOE, Institute of Precision Optical Engineering, School of Physics Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
| | - A Giglia
- CNR, Istituto Officina Materiali, 34149 Trieste, Italy
| | - J P Rueff
- Laboratoire de Chimie Physique - Matière et Rayonnement, Sorbonne University, UMR CNRS 7614, 4 Place Jussieu, 75005 Paris, France
| | - P Jonnard
- Laboratoire de Chimie Physique - Matière et Rayonnement, Sorbonne University, UMR CNRS 7614, 4 Place Jussieu, 75005 Paris, France
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