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Safari MR, Matthes F, Ernst KH, Bürgler DE, Schneider CM. Deposition of Chiral Heptahelicene Molecules on Ferromagnetic Co and Fe Thin-Film Substrates. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3281. [PMID: 36234411 PMCID: PMC9565510 DOI: 10.3390/nano12193281] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/02/2022] [Accepted: 09/14/2022] [Indexed: 06/16/2023]
Abstract
The discovery of chirality-induced spin selectivity (CISS), resulting from an interaction between the electron spin and handedness of chiral molecules, has sparked interest in surface-adsorbed chiral molecules due to potential applications in spintronics, enantioseparation, and enantioselective chemical or biological processes. We study the deposition of chiral heptahelicene by sublimation under ultra-high vacuum onto bare Cu(111), Co bilayer nanoislands on Cu(111), and Fe bilayers on W(110) by low-temperature spin-polarized scanning tunneling microscopy/spectroscopy (STM/STS). In all cases, the molecules remain intact and adsorb with the proximal phenanthrene group aligned parallel to the surface. Three degenerate in-plane orientations on Cu(111) and Co(111), reflecting substrate symmetry, and only two on Fe(110), i.e., fewer than symmetry permits, indicate a specific adsorption site for each substrate. Heptahelicene physisorbs on Cu(111) but chemisorbs on Co(111) and Fe(110) bilayers, which nevertheless remain for the sub-monolayer coverage ferromagnetic and magnetized out-of-plane. We are able to determine the handedness of individual molecules chemisorbed on Fe(110) and Co(111), as previously reported for less reactive Cu(111). The demonstrated deposition control and STM/STS imaging capabilities for heptahelicene on Co/Cu(111) and Fe/W(110) substrate systems lay the foundation for studying CISS in ultra-high vacuum and on the microscopic level of single molecules in controlled atomic configurations.
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Affiliation(s)
- Mohammad Reza Safari
- Peter Grünberg Institute, Electronic Properties (PGI-6), Forschungszentrum Jülich, 52428 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - Frank Matthes
- Peter Grünberg Institute, Electronic Properties (PGI-6), Forschungszentrum Jülich, 52428 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - Karl-Heinz Ernst
- Molecular Surface Science Group, Empa, Swiss Federal Laboratories for Materials Science and Technology, 8600 Dübendorf, Switzerland
- Nanosurf Laboratory, Institute of Physics, The Czech Academy of Sciences, 16200 Prague, Czech Republic
| | - Daniel E. Bürgler
- Peter Grünberg Institute, Electronic Properties (PGI-6), Forschungszentrum Jülich, 52428 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
| | - Claus M. Schneider
- Peter Grünberg Institute, Electronic Properties (PGI-6), Forschungszentrum Jülich, 52428 Jülich, Germany
- Jülich Aachen Research Alliance (JARA), Fundamentals of Future Information Technology, 52425 Jülich, Germany
- Fakultät für Physik, Universität Duisburg-Essen, 47057 Duisburg, Germany
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Bork J, Onsgaard J, Diekhöner L. Growth and structure of Ag on bilayer Co nanoislands on Cu(111). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2010; 22:135005. [PMID: 21389508 DOI: 10.1088/0953-8984/22/13/135005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have studied the growth of Ag on bilayer high Co nanoislands on Cu(111) using scanning tunneling microscopy. Noble metal capping of magnetic nanostructures is known to influence the magnetism and knowledge of the growth is therefore important. We find that Ag preferentially nucleates on the Co nanoislands, initially leaving the free Cu sites clean. Furthermore we observe that those Co islands which are capped with Ag are almost completely capped, thus making a perfect multilayered system of Ag/Co/Cu(111). We observe a (9 × 9) reconstruction of the Ag overlayer on Co/Cu(111).
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Affiliation(s)
- Jakob Bork
- Institut for Fysik og Nanoteknologi, and Interdisciplinary Nanoscience Center (iNANO), Aalborg Universitet, Skjernvej 4A, Aalborg, Denmark
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Diekhöner L, Schneider MA, Baranov AN, Stepanyuk VS, Bruno P, Kern K. Surface states of cobalt nanoislands on Cu111. PHYSICAL REVIEW LETTERS 2003; 90:236801. [PMID: 12857277 DOI: 10.1103/physrevlett.90.236801] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2002] [Indexed: 05/24/2023]
Abstract
The electronic structure of thin Co nanoislands on Cu(111) has been investigated below and above the Fermi level (E(F)) by scanning tunneling spectroscopy at low temperature. Two surface related electronic states are found: a strong localized peak 0.31 eV below E(F) and a mainly unoccupied dispersive state, giving rise to quantum interference patterns of standing electron waves on the Co surface. Ab initio calculations reveal that the electronic states are spin polarized, originating from d3(z(2)-r(2))-minority and sp-majority bands, respectively.
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Affiliation(s)
- L Diekhöner
- Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
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Monastra S, Manghi F, Rozzi CA, Arcangeli C, Wetli E, Neff HJ, Greber T, Osterwalder J. Quenching of majority-channel quasiparticle excitations in cobalt. PHYSICAL REVIEW LETTERS 2002; 88:236402. [PMID: 12059383 DOI: 10.1103/physrevlett.88.236402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2002] [Indexed: 05/23/2023]
Abstract
The low-energy electronic excitations in cobalt are studied by a theoretical method that includes many-body effects and a realistic description of the band structure. Angle-resolved photoemission spectra measured on a thick film of hexagonal close-packed Co on Cu(111) agree well with calculated spectral functions. Because of many-body effects no sharp quasiparticle peaks exist for binding energies larger than 2 eV and in this energy region the spectrum is essentially incoherent. The many-body corrections are much stronger in the majority-spin channel and drastically affect the spin polarization of the spectra.
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Affiliation(s)
- S Monastra
- INFM-S3 and Dipartimento di Fisica, Università di Modena, Via Campi 213/a, I-41100 Modena, Italy
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Gambardella P, Dhesi SS, Gardonio S, Grazioli C, Ohresser P, Carbone C. Localized magnetic states of Fe, Co, and Ni impurities on alkali metal films. PHYSICAL REVIEW LETTERS 2002; 88:047202. [PMID: 11801162 DOI: 10.1103/physrevlett.88.047202] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2001] [Indexed: 05/23/2023]
Abstract
X-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) have been used to study transition metal impurities on K and Na films. The multiplet structure of the XAS spectra indicates that Fe, Co, and Ni have localized atomic ground states with predominantly d7, d8, and d9 character, respectively. XMCD shows that the localized impurity states possess large, atomiclike, magnetic orbital moments that are progressively quenched as clusters are formed. Ni impurities on Na films are found to be nonmagnetic, with a strongly increased d10 character of the impurity state. The results show that the high magnetic moments of transition metals in alkali hosts originate from electron localization.
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Affiliation(s)
- P Gambardella
- Institut de Physique des Nanostructures, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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