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Thin Mn germanide films studied with XPS, STM, and XMCD
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. (Materialfysik)ORCID iD: 0000-0003-4165-1515
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. (Materialfysik)
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. (Materialfysik)
2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, no 4, 045311-1-045311-6 p.Article in journal (Refereed) Published
Abstract [en]

Thin Mn germanide films with nanoscale thicknesses on Ge(111) have been studied by low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), core-level spectroscopy (CLS), and x-ray magnetic circular dichroism. The 260 C annealing of 16 monolayers of Mn deposited on Ge(111)c(2×8) resulted in a uniform film with intense threefold split √3×√3 LEED spots and Moiré patterns in the STM images. This ultrathin film shows a clear ferromagnetism with a Curie temperature of ∼250 K. High-resolution Ge 3d CLS spectra were recorded with photon energies between 50 and 90 eV at normal and 60 emission angle. To achieve a consistent fit over the energy and angular range three components were used in the line-shape analysis. The low temperature (260 C) annealed film shows significant differences in terms of electronic structure and magnetism in contrast to the high temperature (330 C or above) annealed ones. Our results indicate that the annealing temperature and the Mn coverage play important roles in the formation of a thin magnetic Mn germanide film.

Place, publisher, year, edition, pages
2013. Vol. 88, no 4, 045311-1-045311-6 p.
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
URN: urn:nbn:se:kau:diva-14506DOI: 10.1103/PhysRevB.88.045311ISI: 000321838800006OAI: oai:DiVA.org:kau-14506DiVA: diva2:544817
Funder
Swedish Research Council
Available from: 2012-08-16 Created: 2012-08-16 Last updated: 2015-12-15Bibliographically approved
In thesis
1. Thin Mn silicide and germanide layers studied by photoemission and STM
Open this publication in new window or tab >>Thin Mn silicide and germanide layers studied by photoemission and STM
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The research presented in this thesis concerns experimental studies of thin manganese silicide and germanide layers, grown by solid phase epitaxy on the Si(111)7×7 and the Ge(111)c(2×8) surfaces, respectively. The atomic and electronic structures, as well as growth modes of the epitaxial Mn-Si and Mn-Ge layers, were investigated by low-energy electron diffraction (LEED), angle-resolved photoelectron spectroscopy (ARPES), core-level spectroscopy (CLS), and scanning tunneling microscopy and spectroscopy (STM and STS). The magnetic properties of the Mn-Ge films were investigated by X-ray magnetic circular dichroism (XMCD).

The Mn-Si layers, annealed at 400 °C, showed a √3×√3 LEED pattern, consistent with the formation of the stoichiometric monosilicide MnSi. Up to 4 monolayers (ML) of Mn coverage, island formation was observed. For higher Mn coverages, uniform film growth was found. Our results concerning morphology and the atomic and electronic structure of the Mn/Si(111)-√3×√3 surface, are in good agreement with a recent theoretical model for a layered MnSi structure and the √3×√3 surface structure.

Similar to the Mn-Si case, the grown Mn-Ge films, annealed at 330 °C and 450 °C, showed a √3×√3 LEED pattern. This indicated the formation of the ordered Mn5Ge3 germanide. A strong tendency to island formation was observed for the Mn5Ge3 films, and a Mn coverage of about 32 ML was needed to obtain a continuous film. Our STM and CLS results are in good agreement with the established model for the bulk Mn5Ge3 germanide, with a surface termination of Mn atoms arranged in a honeycomb pattern. Mn-Ge films grown at a lower annealing temperature, 260 °C, showed a continuous film at lower coverages, with a film structure that is different compared to the structure of the Mn5Ge3 film. XMCD studies showed that the low-temperature films are ferromagnetic for 16 ML Mn coverage and above, with a Curie temperature of ~250 K.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2012. 46 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2012:41
Keyword
Semiconductor surfaces, Si(111), Ge(111), manganese, Mn, silicides, germanides, atomic structure, electronic structure, magnetic properties, LEED, ARPES, XPS, core-level spectroscopy, STM, STS, XMCD
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-14488 (URN)978-91-7063-448-2 (ISBN)
Public defence
2012-09-28, 21A 342, Universitetsgatan 2, Karlstad, 13:15 (English)
Opponent
Supervisors
Available from: 2012-09-11 Created: 2012-08-13 Last updated: 2015-04-15Bibliographically approved

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