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43 results on '"Asensio, Maria-Carmen"'

1. Nano-mosaic of Topological Dirac States on the Surface of Pb5Bi24Se41 Observed by Nano-ARPES

Author

Nakayama, Kosuke, Souma, Seigo, Trang, Chi Xuan, Takane, Daichi, Chen, Chaoyu, Avila, Jose, Takahashi, Takashi, Sasaki, Satoshi, Segawa, Kouji, Asensio, Maria Carmen, Ando, Yoichi, and Sato, Takafumi

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science
Abstract

We have performed scanning angle-resolved photoemission spectroscopy with a nanometer-sized beam spot (nano-ARPES) on the cleaved surface of Pb5Bi24Se41, which is a member of the (PbSe)5(Bi2Se3)3m homologous series (PSBS) with m = 4 consisting of alternate stacking of the topologically-trivial insulator PbSe bilayer and four quintuple layers (QLs) of the topological insulator Bi2Se3. This allows us to visualize a mosaic of topological Dirac states at a nanometer scale coming from the variable thickness of the Bi2Se3 nano-islands (1-3 QLs) that remain on top of the PbSe layer after cleaving the PSBS crystal, because the local band structure of topological origin changes drastically with the thickness of the Bi2Se3 nano-islands. A comparison of the local band structure with that in ultrathin Bi2Se3 films on Si(111) gives us further insights into the nature of the observed topological states. This result demonstrates that nano-ARPES is a very useful tool for characterizing topological heterostructures., Comment: 6 pages, 3 figures

Published
2019
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2. Nanospot Angle-Resolved Photoemission Study of Bernal-Stacked Bilayer Graphene on Hexagonal Boron Nitride: Band Structure and Local Variation of Lattice Alignment

Author

Joucken, Frédéric, Quezada-López, Eberth A., Avila, Jose, Chen, Chaoyu, Davenport, John L., Chen, Hechin, Watanabe, Kenji, Taniguchi, Takashi, Asensio, Maria Carmen, and Velasco Jr, Jairo

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Hexagonal boron nitride (hBN) is the supporting substrate of choice for two-dimensional material devices because it is atomically flat and chemically inert. However, due to the small size of mechanically exfoliated hBN flakes, electronic structure studies of 2D materials supported by hBN using angle-resolved photoemission spectroscopy (ARPES) are challenging. Here we investigate the electronic band structure of a Bernal-stacked bilayer graphene sheet on a hexagonal boron nitride (BLG/hBN) flake using nanospot ARPES (nanoARPES). By fitting high-resolution energy vs. momentum electronic band spectra, we extract the tight-binding parameters for BLG on hBN. In addition, we reveal spatial variations of the alignment angle between BLG and hBN lattices via inhomogeneity of the electronic bands near the Fermi level. We confirmed these findings by scanning tunneling microscopy measurements obtained on the same device. Our results from spatially resolved nanoARPES measurements of BLG/hBN heterostructures are instrumental for understanding experiments that utilize spatially averaging techniques such as electronic transport and optical spectroscopy.

Published
2019
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3. Visualizing the Effect of an Electrostatic Gate with Angle-Resolved Photoemission Spectroscopy

Author

Joucken, Frédéric, Avila, Jose, Ge, Zhehao, Quezada, Eberth, Yi, Hemian, Goff, Romaric Le, Baudin, Emmanuel, Davenport, John L., Watanabe, Kenji, Taniguchi, Takashi, Asensio, Maria Carmen, and Velasco Jr, Jairo

Subjects
Condensed Matter - Materials Science
Abstract

Electrostatic gating is pervasive in materials science, yet its effects on the electronic band structure of materials has never been revealed directly by angle-resolved photoemission spectroscopy (ARPES), the technique of choice to non-invasively probe the electronic band structure of a material. By means of a state-of-the-art ARPES setup with sub-micron spatial resolution, we have investigated a heterostructure composed of Bernal-stacked bilayer graphene (BLG) on hexagonal boron nitride and deposited on a graphite flake. By voltage biasing the latter, the electric field effect is directly visualized on the valence band as well as on the carbon 1s core level of BLG. The band gap opening of BLG submitted to a transverse electric field is discussed and the importance of intralayer screening is put forward. Our results pave the way for new studies that will use momentum-resolved electronic structure information to gain insight on the physics of materials submitted to the electric field effect.

Published
2019
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4. A novel artificial condensed matter lattice and a new platform for one-dimensional topological phases

Author

Belopolski, Ilya, Xu, Su-Yang, Koirala, Nikesh, Liu, Chang, Bian, Guang, Strocov, Vladimir N., Chang, Guoqing, Neupane, Madhab, Alidoust, Nasser, Sanchez, Daniel, Zheng, Hao, Brahlek, Matthew, Rogalev, Victor, Kim, Timur, Plumb, Nicholas C., Chen, Chaoyu, Bertran, François, Fèvre, Patrick Le, Taleb-Ibrahimi, Amina, Asensio, Maria-Carmen, Shi, Ming, Lin, Hsin, Hoesch, Moritz, Oh, Seongshik, and Hasan, M. Zahid

Subjects
Condensed Matter - Materials Science
Abstract

Engineered lattices in condensed matter physics, such as cold atom optical lattices or photonic crystals, can have fundamentally different properties from naturally-occurring electronic crystals. Here, we report a novel type of artificial quantum matter lattice. Our lattice is a multilayer heterostructure built from alternating thin films of topological and trivial insulators. Each interface within the heterostructure hosts a set of topologically-protected interface states, and by making the layers sufficiently thin, we demonstrate for the first time a hybridization of interface states across layers. In this way, our heterostructure forms an emergent atomic chain, where the interfaces act as lattice sites and the interface states act as atomic orbitals, as seen from our measurements by angle-resolved photoemission spectroscopy (ARPES). By changing the composition of the heterostructure, we can directly control hopping between lattice sites. We realize a topological and a trivial phase in our superlattice band structure. We argue that the superlattice may be characterized in a significant way by a one-dimensional topological invariant, closely related to the invariant of the Su-Schrieffer-Heeger model. Our topological insulator heterostructure demonstrates a novel experimental platform where we can engineer band structures by directly controlling how electrons hop between lattice sites.

Published
2017

5. Experimental Observation of Two Massless Dirac-Fermion Gases in Graphene-Topological Insulator Heterostructure

Author

Bian, Guang, Chung, Ting-Fung, Liu, Chang, Chen, Chaoyu, Chang, Tay-Rong, Wu, Tailung, Belopolski, Ilya, Zheng, Hao, Xu, Su-Yang, Sanchez, Daniel S., Alidoust, Nasser, Pierce, Jonathan, Quilliams, Bryson, Barletta, Philip P., Lorcy, Stephane, Avila, Jose, Chang, Guoqing, Lin, Hsin, Jeng, Horng-Tay, Asensio, Maria-Carmen, Chen, Yong P., and Hasan, M. Zahid

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Graphene and topological insulators (TI) possess two-dimensional Dirac fermions with distinct physical properties. Integrating these two Dirac materials in a single device creates interesting opportunities for exploring new physics of interacting massless Dirac fermions. Here we report on a practical route to experimental fabrication of graphene-Sb2Te3 heterostructure. The graphene-TI heterostructures are prepared by using a dry transfer of chemical-vapor-deposition grown graphene film. ARPES measurements confirm the coexistence of topological surface states of Sb2Te3 and Dirac {\pi} bands of graphene, and identify the twist angle in the graphene-TI heterostructure. The results suggest a potential tunable electronic platform in which two different Dirac low-energy states dominate the transport behavior.

Published
2015
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6. Experimental observation of two massless Dirac-fermion gases in graphene-topological insulator heterostructure

Author

Bian, Guang, Chung, Ting-Fung, Chen, Chaoyu, Liu, Chang, Chang, Tay-Rong, Wu, Tailung, Belopolski, Ilya, Zheng, Hao, Xu, Su-Yang, Sanchez, Daniel S, Alidoust, Nasser, Pierce, Jonathan, Quilliams, Bryson, Barletta, Philip P, Lorcy, Stephane, Avila, José, Chang, Guoqing, Lin, Hsin, Jeng, Horng-Tay, Asensio, Maria-Carmen, Chen, Yong P, and Hasan, M Zahid

Subjects
Physical Sciences, Condensed Matter Physics, graphene, topological insulator, proximity effect, heterostructure, ARPES, cond-mat.mes-hall, Macromolecular and Materials Chemistry, Materials Engineering, Nanotechnology, Materials engineering, Condensed matter physics
Abstract

Graphene and topological insulators (TI) possess two-dimensional (2D) Dirac fermions with distinct physical properties. Integrating these two Dirac materials in a single device creates interesting opportunities for exploring new physics of interacting massless Dirac fermions. Here we report on a practical route to experimental fabrication of graphene-Sb2Te3heterostructure. The graphene-TI heterostructures are prepared by using a dry transfer of chemical-vapor-deposition grown graphene film. ARPES measurements confirm the coexistence of topological surface states of Sb2Te3and Dirac 7rbands of graphene, and identify the twist angle in the graphene-TI heterostructure. The results suggest a potential tunable electronic platform in which two different Dirac low-energy states dominate the transport behavior.

Published
2016

7. Visualizing crystal twin boundaries of bismuth by high-spatial-resolution ARPES

Author

Moriya, Ayumi, primary, Nakayama, Kosuke, additional, Kawakami, Tappei, additional, Maeda, Kensaku, additional, Tokuyama, Atsuya, additional, Souma, Seigo, additional, Chen, Chaoyu, additional, Avila, José, additional, Asensio, Maria Carmen, additional, Kitamura, Miho, additional, Horiba, Koji, additional, Kumigashira, Hiroshi, additional, Takahashi, Takashi, additional, Fujiwara, Kozo, additional, Segawa, Kouji, additional, and Sato, Takafumi, additional

Published
2023
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9. Chiral Photocurrent in a Quasi-1-D TiS3 (001) Phototransistor

Author

Gilbert, Simeon James, primary, Li, Mingxing, additional, Chen, Jia-Shiang, additional, Yi, Hemian, additional, Lipatov, Alexey, additional, Avila, Jose, additional, Sinitskii, Alexander, additional, Asensio, Maria Carmen, additional, Dowben, Peter A, additional, and Yost, Andrew J, additional

Published
2023
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11. Structural and Electronic Properties of Graphene on Vicinal Iridium Surface

Author

Mikšić Trontl, Vesna, Šrut Rakić, Iva, Kralj, Marko, Jolie, Wouter, Lazić, Predrag, Wenhao, Sun, Avila, Jose, Asensio, Maria-Carmen, Craes, Fabian, Busse, Carsten, Pervan, Petar, and Gradišnik, Vera

Subjects
graphene, vicinal surface
Abstract

Since its discovery, graphene has become a very interesting material for the application in a variety of fields, such as photonics, plasmonics, spintronics or nanoelectronics. It is attracting ever growing interest due to its remarkable properties which have origin in graphene’s crystal and electronic structure. The electronic structure of graphene was resolved in angular-resolved photoemission (ARPES) experiments and its most characteristic feature is a Dirac cone. The Dirac cone could be modified in interaction with the substrate by charge carriers doping or by structural modification. We have studied a periodically modulated graphene grown on Ir(332) substrate where graphene growth induces reversible, well defined faceting of iridium surface into alternating terraces and step bunches which we investigated in scanning tunneling microscopy (STM) experiments [1][2]. Measurements of the electronic band structure by ARPES showed the Dirac cone anisotropy which was attributed to the 1D periodicity present in the system and lateral variation of the charge carrier concentration (on terraces and step bunches) [2]. [1] Šrut, Iva ; Mikšić Trontl, Vesna ; Pervan, Petar ; Kralj, Marko ; Temperature dependence of graphene growth on a stepped iridium surface.// Carbon 56 (2013) ; 193-200 [2] Iva Šrut Rakić, Marko Kralj, Wouter Jolie, Predrag Lazić, Wenhao Sun, José Avila, Maria- Carmen Asensio, Fabian Craes, Vesna Mikšić Trontl, Carsten Busse, and Petar Pervan ; Step-induced faceting and related electronic effects for graphene on Ir(332) // Carbon 110, (2016) 267-277

Published
2022

15. Nanospot angle-resolved photoemission study of Bernal-stacked bilayer graphene on hexagonal boron nitride: Band structure and local variation of lattice alignment

Author

Joucken, Frédéric, primary, Quezada-López, Eberth A., additional, Avila, Jose, additional, Chen, Chaoyu, additional, Davenport, John L., additional, Chen, Hechin, additional, Watanabe, Kenji, additional, Taniguchi, Takashi, additional, Asensio, Maria Carmen, additional, and Velasco, Jairo, additional

Published
2019
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16. Visualizing the Effect of an Electrostatic Gate with Angle-Resolved Photoemission Spectroscopy

Author

Joucken, Frédéric, primary, Avila, Jose, additional, Ge, Zhehao, additional, Quezada-Lopez, Eberth A., additional, Yi, Hemian, additional, Le Goff, Romaric, additional, Baudin, Emmanuel, additional, Davenport, John L., additional, Watanabe, Kenji, additional, Taniguchi, Takashi, additional, Asensio, Maria Carmen, additional, and Velasco, Jairo, additional

Published
2019
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17. Electroanalytical Performance of Nitrogen-Doped Graphene Films Processed in One Step by Pulsed Laser Deposition Directly Coupled with Thermal Annealing

Author

Bourquard, Florent, primary, Bleu, Yannick, additional, Loir, Anne-Sophie, additional, Caja-Munoz, Borja, additional, Avila, José, additional, Asensio, Maria-Carmen, additional, Raimondi, Gaëtan, additional, Shokouhi, Maryam, additional, Rassas, Ilhem, additional, Farre, Carole, additional, Chaix, Carole, additional, Barnier, Vincent, additional, Jaffrezic-Renault, Nicole, additional, Garrelie, Florence, additional, and Donnet, Christophe, additional

Published
2019
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18. Metal‐Organic Framework Surface Functionalization: GraftFast Surface Engineering to Improve MOF Nanoparticles Furtiveness (Small 40/2018)

Author

Giménez‐Marqués, Mónica, primary, Bellido, Elena, additional, Berthelot, Thomas, additional, Simón‐Yarza, Teresa, additional, Hidalgo, Tania, additional, Simón‐Vázquez, Rosana, additional, González‐Fernández, África, additional, Avila, José, additional, Asensio, Maria Carmen, additional, Gref, Ruxandra, additional, Couvreur, Patrick, additional, Serre, Christian, additional, and Horcajada, Patricia, additional

Published
2018
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19. Electronic band structure of ReS2 by high-resolution angle-resolved photoemission spectroscopy

Author

Webb, James, Hart, Lewis, Wolverson, Daniel, Chen, Chaoyu, Avila, Jose, and Asensio, Maria-Carmen

Abstract

The rhenium-based transition metal dichalcogenides (TMDs) are atypical of the TMD family due to their highly anisotropic crystalline structure and are recognized as promising materials for two-dimensional heterostructure devices. The nature of the band gap (direct or indirect) for bulk, few-, and single-layer forms of ReS2 is of particular interest, due to its comparatively weak interplanar interaction. However, the degree of interlayer interaction and the question of whether a transition from indirect to direct gap is observed on reducing thickness (as in other TMDs) are controversial. We present a direct determination of the valence band structure of bulk ReS2 using high-resolution angle-resolved photoemission spectroscopy. We find a clear in-plane anisotropy due to the presence of chains of Re atoms, with a strongly directional effective mass which is larger in the direction orthogonal to the Re chains (2.2 me) than along them (1.6 me). An appreciable interplane interaction results in an experimentally measured difference of ≈100−200 meV between the valence band maxima at the Z point (0,0,1/2) and the Γ point (0,0,0) of the three-dimensional Brillouin zone. This leads to a direct gap at Z and a close-lying but larger gap at Γ, implying that bulk ReS2 is marginally indirect. This may account for recent conflicting transport and photoluminescence measurements and the resulting uncertainty about the nature of the band gap in this material.

Published
2017

20. Atomic Layer Deposition of a Nanometer-Thick Li3PO4Protective Layer on LiNi0.5Mn1.5O4Films: Dream or Reality for Long-Term Cycling?

Author

Hallot, Maxime, Caja-Munoz, Borja, Leviel, Clement, Lebedev, Oleg I., Retoux, Richard, Avila, José, Roussel, Pascal, Asensio, Maria Carmen, and Lethien, Christophe

Abstract

LiNi0.5Mn1.5O4(LNMO) is a promising 5V-class electrode for Li-ion batteries but suffers from manganese dissolution and electrolyte decomposition owing to the high working potential. An attractive solution to stabilize the surface chemistry consists in mastering the interface between the LNMO electrode and the liquid electrolyte with a surface protective layer made from the powerful surface deposition method. Here, we show that a 7400 nm thick sputtered LNMO film coated with a nanometer-thick lithium-ion-conductive Li3PO4layer was deposited by the atomic layer deposition method. We demonstrate that this “material model system” can deliver a remarkable surface capacity (∼0.4 mAh cm–2at 1C) and exhibits improved cycling lifetime (×650%) compared to the nonprotected electrode. Nevertheless, we observe that mechanical failure occurs within the LNMO and Li3PO4films when long-term cycling is performed. This in-depth study gives new insights regarding the mechanical degradation of LNMO electrodes upon charge/discharge cycling and reveals for the first time that the surface protective layer made from the ALD method is not sufficient for long-term stability applications.

Published
2021
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21. GraftFast Surface Engineering to Improve MOF Nanoparticles Furtiveness

Author

Giménez‐Marqués, Mónica, primary, Bellido, Elena, additional, Berthelot, Thomas, additional, Simón‐Yarza, Teresa, additional, Hidalgo, Tania, additional, Simón‐Vázquez, Rosana, additional, González‐Fernández, África, additional, Avila, José, additional, Asensio, Maria Carmen, additional, Gref, Ruxandra, additional, Couvreur, Patrick, additional, Serre, Christian, additional, and Horcajada, Patricia, additional

Published
2018
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22. Inorganic Ions Assisted the Anisotropic Growth of CsPbCl3 Nanowires with Surface Passivation Effect

Author

Tang, Yingying, primary, Cao, Xianyi, additional, Honarfar, Alireza, additional, Abdellah, Mohamed, additional, Chen, Chaoyu, additional, Avila, José, additional, Asensio, Maria-Carmen, additional, Hammarström, Leif, additional, Sa, Jacinto, additional, Canton, Sophie E., additional, Zheng, Kaibo, additional, Pullerits, Tõnu, additional, and Chi, Qijin, additional

Published
2018
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23. Topology and doping effects in three-dimensional nanoporous graphene

Author

Di Bernardo, Iolanda, primary, Avvisati, Giulia, additional, Chen, Chaoyu, additional, Avila, José, additional, Asensio, Maria Carmen, additional, Hu, Kailong, additional, Ito, Yoshikazu, additional, Hines, Peter, additional, Lipton-Duffin, Josh, additional, Rintoul, Llew, additional, Motta, Nunzio, additional, Mariani, Carlo, additional, and Betti, Maria Grazia, additional

Published
2018
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25. Unraveling the Structural and Electronic Properties at the WSe2–Graphene Interface for a Rational Design of van der Waals Heterostructures

Author

Agnoli, Stefano, primary, Ambrosetti, Alberto, additional, Menteş, Tevfik Onur, additional, Sala, Alessandro, additional, Locatelli, Andrea, additional, Silvestrelli, Pier Luigi, additional, Cattelan, Mattia, additional, Eichfeld, Sarah, additional, Deng, Donna D., additional, Robinson, Joshua. A., additional, Avila, José, additional, Chen, Chaoyu, additional, and Asensio, Maria Carmen, additional

Published
2018
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30. A novel artificial condensed matter lattice and a new platform for one-dimensional topological phases

Author

Belopolski, Ilya, primary, Xu, Su-Yang, additional, Koirala, Nikesh, additional, Liu, Chang, additional, Bian, Guang, additional, Strocov, Vladimir N., additional, Chang, Guoqing, additional, Neupane, Madhab, additional, Alidoust, Nasser, additional, Sanchez, Daniel, additional, Zheng, Hao, additional, Brahlek, Matthew, additional, Rogalev, Victor, additional, Kim, Timur, additional, Plumb, Nicholas C., additional, Chen, Chaoyu, additional, Bertran, François, additional, Le Fèvre, Patrick, additional, Taleb-Ibrahimi, Amina, additional, Asensio, Maria-Carmen, additional, Shi, Ming, additional, Lin, Hsin, additional, Hoesch, Moritz, additional, Oh, Seongshik, additional, and Hasan, M. Zahid, additional

Published
2017
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32. van der Waals epitaxy of monolayer hexagonal boron nitride on copper foil : growth, crystallography and electronic band structure

Author

Wood, Grace E., Marsden, Alexander J., Mudd, James J., Walker, Marc, Asensio, Maria-Carmen, Avila, José, Cheng, Kai, Bell, Gavin R., and Wilson, Neil R.

Subjects
QD, TS, QC
Abstract

We investigate the growth of hexagonal boron nitride (h-BN) on copper foil by low pressure chemical vapour deposition (LP-CVD). At low pressure, h-BN growth proceeds through the nucleation and growth of triangular islands. Comparison between the orientation of the islands and the local crystallographic orientation of the polycrystalline copper foil reveals an epitaxial relation between the copper and h-BN, even on Cu(100) and Cu(110) regions whose symmetry is not matched to the h-BN. However, the growth rate is faster and the islands more uniformly oriented on Cu(111) grains. Angle resolved photoemission spectroscopy measurements reveal a well-defined band structure for the h-BN, consistent with a band gap of 6 eV, that is decoupled from the copper surface beneath. These results indicate that, despite a weak interaction between h-BN and copper, van der Waals epitaxy defines the long range ordering of h-BN even on polycrystalline copper foils and suggest that large area, single crystal, monolayer h-BN could be readily and cheaply produced.

Published
2015

38. Nanomosaic of Topological Dirac States on the Surface of Pb5Bi24Se41Observed by Nano-ARPES

Author

Nakayama, Kosuke, Souma, Seigo, Trang, Chi Xuan, Takane, Daichi, Chen, Chaoyu, Avila, Jose, Takahashi, Takashi, Sasaki, Satoshi, Segawa, Kouji, Asensio, Maria Carmen, Ando, Yoichi, and Sato, Takafumi

Abstract

We have performed scanning angle-resolved photoemission spectroscopy with a nanometer-sized beam spot (nano-ARPES) on the cleaved surface of Pb5Bi24Se41, which is a member of the (PbSe)5(Bi2Se3)3mhomologous series (PSBS) with m= 4 consisting of alternate stacking of the topologically trivial insulator PbSe bilayer and four quintuple layers (QLs) of the topological insulator Bi2Se3. This allows us to visualize a mosaic of topological Dirac states at a nanometer scale coming from the variable thickness of the Bi2Se3nanoislands (1–3 QLs) that remain on top of the PbSe layer after cleaving the PSBS crystal, because the local band structure of topological origin changes drastically with the thickness of the Bi2Se3nanoislands. A comparison of the local band structure with that in ultrathin Bi2Se3films on Si(111) gives us further insights into the nature of the observed topological states. This result demonstrates that nano-ARPES is a very useful tool for characterizing topological heterostructures.

Published
2019
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39. Inorganic Ions Assisted the Anisotropic Growth of CsPbCl3Nanowires with Surface Passivation Effect

Author

Tang, Yingying, Cao, Xianyi, Honarfar, Alireza, Abdellah, Mohamed, Chen, Chaoyu, Avila, José, Asensio, Maria-Carmen, Hammarström, Leif, Sa, Jacinto, Canton, Sophie E., Zheng, Kaibo, Pullerits, Tõnu, and Chi, Qijin

Abstract

All-inorganic halide perovskite nanowires (NWs) exhibit improved thermal and hydrolysis stability and could thus play a vital role in nanoscale optoelectronics. Among them, blue-light-based devices are extremely limited because of the lack of a facile method to obtain high-purity CsPbCl3NWs. Herein, we report a direct and facile method for the synthesis of CsPbCl3NWs assisted by inorganic ions that served both as a morphology controlling agent for the anisotropic growth of nanomaterials and a surface passivation species modulating the surface of nanomaterials. This new approach allows us to obtain high-purity and size-uniform NWs as long as 500 nm in length and 20 nm in diameter with high reproducibility. X-ray photoelectron spectroscopy and ultrafast spectroscopic measurements confirmed that a reduced band gap caused by the surface species of NWs relative to nanocubes (NCs) was achieved at the photon energy of 160 eV because of the hybrid surface passivation contributed by adsorbed inorganic ions. The resulting NWs demonstrate significantly enhanced photoelectrochemical performances, 3.5-fold increase in the photocurrent generation, and notably improved stability compared to their NC counterparts. Our results suggest that the newly designed NWs could be a promising material for the development of nanoscale optoelectronic devices.

Published
2018
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41. <italic>In situ</italic> characterization of the deposition of anatase TiO2 on rutile TiO2(110).

Author

Head, Ashley R., Johansson, Niclas, Niu, Yuran, Snezhkova, Olesia, Chaudhary, Shilpi, Schnadt, Joachim, Bluhm, Hendrik, Chen, Chaoyu, Avila, José, and Asensio, Maria-Carmen

Subjects
TITANIUM dioxide, RUTILE, ATOMIC layer deposition, CHEMICAL precursors, BIOCHEMICAL substrates, X-ray absorption spectra, CHEMICAL vapor deposition
Abstract

Growing additional TiO2 thin films on TiO2 substrates in ultrahigh vacuum (UHV)-compatible chambers have many applications for sample preparation, such as smoothing surface morphologies, templating, and covering impurities. However, there has been little study into how to control the morphology of TiO2 films deposited onto TiO2 substrates, especially using atomic layer deposition (ALD) precursors. Here, the authors show the growth of a TiO2 film on a rutile TiO2(110) surface using titanium tetraisopropoxide (TTIP) and water as the precursors at pressures well below those used in common ALD reactors. X-ray absorption spectroscopy suggests that the relatively low sample temperature (175 °C) results in an anatase film despite the rutile template of the substrate. Using ambient pressure x-ray photoelectron spectroscopy, the adsorption of TTIP was found to be self-limiting, even at room temperature. No molecular water was found to adsorb on the surface. The deposited thickness suggests that an alternate chemical vapor deposition growth mechanism may be dominating the growth process. This study highlights the possibility that metal oxide film deposition from molecular precursors is an option for sample preparations in common UHV-compatible chambers. [ABSTRACT FROM AUTHOR]

Published
2018
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42. Atomic Layer Deposition of a Nanometer-Thick Li 3 PO 4 Protective Layer on LiNi 0.5 Mn 1.5 O 4 Films: Dream or Reality for Long-Term Cycling?

Author

Hallot M, Caja-Munoz B, Leviel C, Lebedev OI, Retoux R, Avila J, Roussel P, Asensio MC, and Lethien C

Abstract

LiNi 0.5 Mn 1.5 O 4 (LNMO) is a promising 5V-class electrode for Li-ion batteries but suffers from manganese dissolution and electrolyte decomposition owing to the high working potential. An attractive solution to stabilize the surface chemistry consists in mastering the interface between the LNMO electrode and the liquid electrolyte with a surface protective layer made from the powerful surface deposition method. Here, we show that a 7400 nm thick sputtered LNMO film coated with a nanometer-thick lithium-ion-conductive Li 3 PO 4 layer was deposited by the atomic layer deposition method. We demonstrate that this "material model system" can deliver a remarkable surface capacity (∼0.4 mAh cm -2 at 1C) and exhibits improved cycling lifetime (×650%) compared to the nonprotected electrode. Nevertheless, we observe that mechanical failure occurs within the LNMO and Li 3 PO 4 films when long-term cycling is performed. This in-depth study gives new insights regarding the mechanical degradation of LNMO electrodes upon charge/discharge cycling and reveals for the first time that the surface protective layer made from the ALD method is not sufficient for long-term stability applications.

Published
2021
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43. Inorganic Ions Assisted the Anisotropic Growth of CsPbCl 3 Nanowires with Surface Passivation Effect.

Author

Tang Y, Cao X, Honarfar A, Abdellah M, Chen C, Avila J, Asensio MC, Hammarström L, Sa J, Canton SE, Zheng K, Pullerits T, and Chi Q

Abstract

All-inorganic halide perovskite nanowires (NWs) exhibit improved thermal and hydrolysis stability and could thus play a vital role in nanoscale optoelectronics. Among them, blue-light-based devices are extremely limited because of the lack of a facile method to obtain high-purity CsPbCl 3 NWs. Herein, we report a direct and facile method for the synthesis of CsPbCl 3 NWs assisted by inorganic ions that served both as a morphology controlling agent for the anisotropic growth of nanomaterials and a surface passivation species modulating the surface of nanomaterials. This new approach allows us to obtain high-purity and size-uniform NWs as long as 500 nm in length and 20 nm in diameter with high reproducibility. X-ray photoelectron spectroscopy and ultrafast spectroscopic measurements confirmed that a reduced band gap caused by the surface species of NWs relative to nanocubes (NCs) was achieved at the photon energy of 160 eV because of the hybrid surface passivation contributed by adsorbed inorganic ions. The resulting NWs demonstrate significantly enhanced photoelectrochemical performances, 3.5-fold increase in the photocurrent generation, and notably improved stability compared to their NC counterparts. Our results suggest that the newly designed NWs could be a promising material for the development of nanoscale optoelectronic devices.

Published
2018
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