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Grant support

The authors acknowledge the financial support from the Spanish Ministry of Science and Innovation, through the Maria de Maeztu Programme for Units of Excellence in R&D (CEX2018-000805-M and CEX2019-000919-M) and MINECO-FEDER projects PID2019-111742GB-C31, PID2019-111742GB-C32, PCI2018-093081, PID2019-109539GB-C43, MAT2015-666888-C3-3R, MICINN projects FIS2017-82415-R, RTI2018-097895-B-C43 and PID2019-111742GA-I00, the Comunidad Autonoma de Madrid through S2018/NMT-4321 (NanomagCOST-CM), the Generalitat Valenciana (CIDEGENT/2018/001 grant and iDiFEDER/2018/061 co-financed by FEDER) and the Deutsche Forschungsgemeinschaft (DFG, FLAG-ERA AB694/2-1), the European Union Seventh Framework Programme under Grant agreement No. 604391 Graphene Flagship. The authors thank the European Research Council (ERC Starting Grant 2D-PnictoChem 804110 to G.A.). W.S.P. acknowledges the computer resources and assistance provided by the Centro de Computacion Cientifica of the Universidad Autonoma de Madrid and the computer resources at MareNostrum and technical support provided by Barcelona Supercomputing Center (FI-2019-2-0007). Part of the electron microscopy work was carried out at SuperSTEM, the UK National Facility for Advanced Electron Microscopy, supported by the Engineering and Physical Sciences Research Council (EPSRC). The authors thank Marta Alcaraz (ICMol) for her assistance with the TG-GC-MS experiments.

Analysis of institutional authors

Rodriguez-San-Miguel, DAuthorTorres, IAuthorSalagre, EAuthorSegovia, PAuthorMichel, EgAuthorAres, PAuthorGomez-Herrero, JAuthorPalacios, JjAuthorZamora, FCorresponding Author

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March 8, 2021
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Exfoliation of Alpha-Germanium: A Covalent Diamond-Like Structure

Publicated to:ADVANCED MATERIALS. 33 (10): e2006826- - 2021-03-01 33(10), DOI: 10.1002/adma.202006826

Authors: Gibaja, Carlos; Rodriguez-San-Miguel, David; Paz, Wendel S; Torres, Inigo; Salagre, Elena; Segovia, Pilar; Michel, Enrique G; Assebban, Mhamed; Ares, Pablo; Hernandez-Maldonado, David; Ramasse, Quentin; Abellan, Gonzalo; Gomez-Herrero, Julio; Varela, Maria; Jose Palacios, Juan; Zamora, Felix

Affiliations

‎ Friedrich Alexander Univ Erlangen Nurnberg FAU, Dept Chem & Pharm, Dr Mack Str 81, D-90762 Furth, Germany - Author
‎ Friedrich Alexander Univ Erlangen Nurnberg FAU, Joint Inst Adv Mat & Proc ZMP, Dr Mack Str 81, D-90762 Furth, Germany - Author
‎ SuperSTEM, SciTech Daresbury Sci & Innovat Campus, Daresbury WA4 4AD, England - Author
‎ Univ Autonoma Madrid, Condensed Matter Phys Ctr IFIMAC, Madrid 28049, Spain - Author
‎ Univ Autonoma Madrid, Dept Fis Mat Condensada, Madrid 28049, Spain - Author
‎ Univ Autonoma Madrid, Dept Quim Inorgan, Condensed Matter Phys Ctr IFIMAC, Madrid 28049, Spain - Author
‎ Univ Autonoma Madrid, Dept Quim Inorgan, Inst Adv Res Chem Sci IAdChem, Madrid 28049, Spain - Author
‎ Univ Autonoma Madrid, Inst Nicolas Cabrera INC, Madrid 28049, Spain - Author
‎ Univ Complutense Madrid, Fac CC Fis, Madrid 28040, Spain - Author
‎ Univ Complutense Madrid, Inst Pluridisciplinar, Madrid 28040, Spain - Author
‎ Univ Fed Espirito Santo, Dept Fis, BR-29075910 Vitoria, ES, Brazil - Author
‎ Univ Leeds, Sch Chem & Proc Engn, Leeds LS2 9JT, W Yorkshire, England - Author
‎ Univ Leeds, Sch Phys & Astron, Leeds LS2 9JT, W Yorkshire, England - Author
‎ Univ Manchester, Dept Phys & Astron, Oxford Rd, Manchester M13 9PL, Lancs, England - Author
‎ Univ Manchester, Natl Graphene Inst, Oxford Rd, Manchester M13 9PL, Lancs, England - Author
‎ Univ Valencia, Inst Ciencia Mol ICMol, Catedrat Jose Beltran 2, Valencia 46980, Spain - Author
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Abstract

2D materials have opened a new field in materials science with outstanding scientific and technological impact. A largely explored route for the preparation of 2D materials is the exfoliation of layered crystals with weak forces between their layers. However, its application to covalent crystals remains elusive. Herein, a further step is taken by introducing the exfoliation of germanium, a narrow-bandgap semiconductor presenting a 3D diamond-like structure with strong covalent bonds. Pure alpha-germanium is exfoliated following a simple one-step procedure assisted by wet ball-milling, allowing gram-scale fabrication of high-quality layers with large lateral dimensions and nanometer thicknesses. The generated flakes are thoroughly characterized by different techniques, giving evidence that the new 2D material exhibits bandgaps that depend on both the crystallographic direction and the number of layers. Besides potential technological applications, this work is also of interest for the search of 2D materials with new properties.

Keywords

2d materialsalpha-germanium nanolayersbandgap modulationgram-scale preparation2-dimensional materials2d materialsAlpha&#8208Alpha-germanium nanolayersBandgap modulationCrystalsGermanium nanolayersGram&#8208Gram-scale preparationGrapheneLiquid&#8208Liquid-phase exfoliationPhase exfoliationRoadmapScale preparation

Quality index

Bibliometric impact. Analysis of the contribution and dissemination channel

The work has been published in the journal ADVANCED MATERIALS due to its progression and the good impact it has achieved in recent years, according to the agency WoS (JCR), it has become a reference in its field. In the year of publication of the work, 2021, it was in position 4/165, thus managing to position itself as a Q1 (Primer Cuartil), in the category Nanoscience & Nanotechnology. Notably, the journal is positioned above the 90th percentile.

From a relative perspective, and based on the normalized impact indicator calculated from World Citations provided by WoS (ESI, Clarivate), it yields a value for the citation normalization relative to the expected citation rate of: 2.22. This indicates that, compared to works in the same discipline and in the same year of publication, it ranks as a work cited above average. (source consulted: ESI Nov 14, 2024)

This information is reinforced by other indicators of the same type, which, although dynamic over time and dependent on the set of average global citations at the time of their calculation, consistently position the work at some point among the top 50% most cited in its field:

  • Weighted Average of Normalized Impact by the Scopus agency: 2.73 (source consulted: FECYT Feb 2024)
  • Field Citation Ratio (FCR) from Dimensions: 5.03 (source consulted: Dimensions Jul 2025)

Specifically, and according to different indexing agencies, this work has accumulated citations as of 2025-07-22, the following number of citations:

  • WoS: 30
  • Scopus: 30
  • Europe PMC: 6

Impact and social visibility

From the perspective of influence or social adoption, and based on metrics associated with mentions and interactions provided by agencies specializing in calculating the so-called "Alternative or Social Metrics," we can highlight as of 2025-07-22:

  • The use, from an academic perspective evidenced by the Altmetric agency indicator referring to aggregations made by the personal bibliographic manager Mendeley, gives us a total of: 40.
  • The use of this contribution in bookmarks, code forks, additions to favorite lists for recurrent reading, as well as general views, indicates that someone is using the publication as a basis for their current work. This may be a notable indicator of future more formal and academic citations. This claim is supported by the result of the "Capture" indicator, which yields a total of: 39 (PlumX).

With a more dissemination-oriented intent and targeting more general audiences, we can observe other more global scores such as:

  • The Total Score from Altmetric: 18.05.
  • The number of mentions on the social network X (formerly Twitter): 15 (Altmetric).
  • The number of mentions in news outlets: 1 (Altmetric).

It is essential to present evidence supporting full alignment with institutional principles and guidelines on Open Science and the Conservation and Dissemination of Intellectual Heritage. A clear example of this is:

Leadership analysis of institutional authors

This work has been carried out with international collaboration, specifically with researchers from: Brazil; Germany; United Kingdom.

There is a significant leadership presence as some of the institution’s authors appear as the first or last signer, detailed as follows: First Author (Gibaja, C) and Last Author (ZAMORA ABANADES, FELIX JUAN).

the author responsible for correspondence tasks has been ZAMORA ABANADES, FELIX JUAN.