1
|
Masia F, Langbein W, Fischer S, Krisponeit JO, Falta J. Low-energy electron microscopy intensity-voltage data - Factorization, sparse sampling and classification. J Microsc 2023; 289:91-106. [PMID: 36288376 PMCID: PMC10108219 DOI: 10.1111/jmi.13155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Revised: 09/15/2022] [Accepted: 10/17/2022] [Indexed: 01/14/2023]
Abstract
Low-energy electron microscopy (LEEM) taken as intensity-voltage (I-V) curves provides hyperspectral images of surfaces, which can be used to identify the surface type, but are difficult to analyse. Here, we demonstrate the use of an algorithm for factorizing the data into spectra and concentrations of characteristic components (FSC3 ) for identifying distinct physical surface phases. Importantly, FSC3 is an unsupervised and fast algorithm. As example data we use experiments on the growth of praseodymium oxide or ruthenium oxide on ruthenium single crystal substrates, both featuring a complex distribution of coexisting surface components, varying in both chemical composition and crystallographic structure. With the factorization result a sparse sampling method is demonstrated, reducing the measurement time by 1-2 orders of magnitude, relevant for dynamic surface studies. The FSC3 concentrations are providing the features for a support vector machine-based supervised classification of the surface types. Here, specific surface regions which have been identified structurally, via their diffraction pattern, as well as chemically by complementary spectro-microscopic techniques, are used as training sets. A reliable classification is demonstrated on both example LEEM I-V data sets.
Collapse
Affiliation(s)
- Francesco Masia
- School of Biosciences, Cardiff University, Cardiff, UK.,School of Physics and Astronomy, Cardiff University, Cardiff, UK
| | | | - Simon Fischer
- Institute of Solid State Physics, University of Bremen, Bremen, Germany
| | - Jon-Olaf Krisponeit
- Institute of Solid State Physics, University of Bremen, Bremen, Germany.,MAPEX Center for Materials and Processes, University of Bremen, Bremen, Germany
| | - Jens Falta
- Institute of Solid State Physics, University of Bremen, Bremen, Germany.,MAPEX Center for Materials and Processes, University of Bremen, Bremen, Germany
| |
Collapse
|
2
|
Gura L, Soares EA, Paier J, Stavale F, Freund HJ. Models for Reactions in Confined Space: Can Surface Science Contribute? A Review and Perspective. Top Catal 2023. [DOI: 10.1007/s11244-023-01787-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
AbstractThis paper reports and discusses some of our recent advances in surface science research on a silica film supported on a Ru(0001) substrate. This system is unique, as the silica is bound to the metal surface by dispersive forces only, and thus opens the possibility to study reactions in the confined space between the metal substrate and the silica film, acting as a permeable membrane. We demonstrate that this system allows for detailed insights into the complexity of reactions in confined space, including phenomena due to the response of the confined space to the presence of the reactants, and direct comparison to the situation when the same reaction occurs in open space.
Collapse
|
3
|
Flege JI, Krisponeit JO, Höcker J, Hoppe M, Niu Y, Zakharov A, Schaefer A, Falta J, Krasovskii EE. Nanoscale analysis of the oxidation state and surface termination of praseodymium oxide ultrathin films on ruthenium(0001). Ultramicroscopy 2017; 183:61-66. [PMID: 28526269 DOI: 10.1016/j.ultramic.2017.05.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 04/18/2017] [Accepted: 05/09/2017] [Indexed: 10/19/2022]
Abstract
The complex structure and morphology of ultrathin praseodymia films deposited on a ruthenium(0001) single crystal substrate by reactive molecular beam epitaxy is analyzed by intensity-voltage low-energy electron microscopy in combination with theoretical calculations within an ab initio scattering theory. A rich coexistence of various nanoscale crystalline surface structures is identified for the as-grown samples, notably comprising two distinct oxygen-terminated hexagonal Pr2O3(0001) surface phases as well as a cubic Pr2O3(111) and a fluorite PrO2(111) surface component. Furthermore, scattering theory reveals a striking similarity between the electron reflectivity spectra of praseodymia and ceria due to very efficient screening of the nuclear charge by the extra 4f electron in the former case.
Collapse
Affiliation(s)
- J I Flege
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany; MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany.
| | - J-O Krisponeit
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany; MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany
| | - J Höcker
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - M Hoppe
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - Y Niu
- MAX IV Laboratory, Box 118, 221 00 Lund, Sweden
| | - A Zakharov
- MAX IV Laboratory, Box 118, 221 00 Lund, Sweden
| | - A Schaefer
- Division of Synchrotron Radiation Research, Lund University, 221 00 Lund, Sweden
| | - J Falta
- Institute of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany; MAPEX Center for Materials and Processes, University of Bremen, 28359 Bremen, Germany
| | - E E Krasovskii
- Departamento de Física de Materiales, Universidad del Pais Vasco UPV/EHU, 20080 San Sebastián/Donostia, Basque Country, Spain; Donostia International Physics Center (DIPC), 20018 San Sebastián/Donostia, Basque Country, Spain; IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
| |
Collapse
|
4
|
Flege JI, Herd B, Goritzka J, Over H, Krasovskii EE, Falta J. Nanoscale Origin of Mesoscale Roughening: Real-Time Tracking and Identification of Three Distinct Ruthenium Oxide Phases in Ruthenium Oxidation. ACS NANO 2015; 9:8468-8473. [PMID: 26171635 DOI: 10.1021/acsnano.5b03393] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The structural modification of the Ru(0001) surface is followed in real-time using low-energy electron microscopy at elevated temperatures during exposure to molecular oxygen. We observe the nucleation and growth of three different RuO2 facets, which are unambiguously identified by single-domain microspot low-energy electron diffraction (μLEED) analysis from regions of 250 nm in diameter. Structural identification is then pushed to the true nanoscale by employing very-low-energy electron reflectivity spectra R(E) from regions down to 10 nm for structural fingerprinting of complex reactions such as the oxidation of metal surfaces. Calculations of R(E) with an ab initio scattering theory confirm the growth of (110), (100), and (101) orientations of RuO2 and explain the shape of the R(E) spectra in terms of the conducting band structure. This methodology is ideally suited to identify the structure of supported ultrathin films and dynamic transformations at multicomponent interfaces down to few nanometer lateral resolution at elevated temperature and in reactive environments.
Collapse
Affiliation(s)
- Jan Ingo Flege
- Institute of Solid State Physics, University of Bremen , Otto-Hahn-Allee 1, 28359 Bremen, Germany
| | - Benjamin Herd
- Department of Physical Chemistry, Justus-Liebig-University , Heinrich-Buff-Ring 58, 35392 Gießen, Germany
| | - Jan Goritzka
- Department of Physical Chemistry, Justus-Liebig-University , Heinrich-Buff-Ring 58, 35392 Gießen, Germany
| | - Herbert Over
- Department of Physical Chemistry, Justus-Liebig-University , Heinrich-Buff-Ring 58, 35392 Gießen, Germany
| | - Eugene E Krasovskii
- Departamento de Física de Materiales, Universidad del Pais Vasco UPV/EHU , 20080 San Sebastián/Donostia, Basque Country, Spain
- Donostia International Physics Center (DIPC) , 20018 San Sebastián/Donostia, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science , 48011 Bilbao, Spain
| | - Jens Falta
- Institute of Solid State Physics, University of Bremen , Otto-Hahn-Allee 1, 28359 Bremen, Germany
- MAPEX Center for Materials and Processes, University of Bremen , 28359 Bremen, Germany
| |
Collapse
|