Growth mechanism and interface magnetic properties of Co nanostructures on graphite

Research output: Contribution to journalArticleAcademicpeer-review

19 Citations (Scopus)

Abstract

We investigated structural, electronic, and magnetic properties of Co adsorbed on highly oriented pyrolytic graphite (HOPG). Distribution and atomic sites of 3d transition-metal Co nanoislands and adatoms on HOPG were experimentally investigated by scanning tunneling microscopy with atomic resolution. In the very low thickness regime (0.6 A° ), a strong nucleation mechanism and a preferred Co nanoisland diameter of ∼3.4 nm have been observed. Co adatoms were found to preferentially occupy β sites of the HOPG surface graphene layer and the atoms aggregated by further occupation of either α or overbond sites. This is in contrast to predictions based on density functional theory, which indicates that the hollow sites are the most energetically stable sites for Co adsorption. The presence of surface hydrocarbon contamination on graphite might be one possible cause of the observed active nucleation and stabilized nanoisland diameter of Co. The formation of Co carbide was evidenced by x-ray absorption spectroscopy. More importantly, the Co magnetic spin moment at the interface of Fe-capped ferromagnetic Co nanostructures and graphite, as determined by x-ray magnetic circular dichroism and sum-rule analysis, was found to be only 63% of the bulk value, implying a magnetically defective spin contact for carbon spintronics applications.
Original languageUndefined
Pages (from-to)0544201-0544206
Number of pages6
JournalPhysical review B: Condensed matter and materials physics
Volume84
Issue number5
DOIs
Publication statusPublished - 5 Aug 2011

Keywords

  • EC Grant Agreement nr.: FP7/228424
  • EWI-21084
  • METIS-285217
  • IR-79221
  • TSTNE-Probe-STM: Scanning Tunneling Microscope

Cite this

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title = "Growth mechanism and interface magnetic properties of Co nanostructures on graphite",
abstract = "We investigated structural, electronic, and magnetic properties of Co adsorbed on highly oriented pyrolytic graphite (HOPG). Distribution and atomic sites of 3d transition-metal Co nanoislands and adatoms on HOPG were experimentally investigated by scanning tunneling microscopy with atomic resolution. In the very low thickness regime (0.6 A° ), a strong nucleation mechanism and a preferred Co nanoisland diameter of ∼3.4 nm have been observed. Co adatoms were found to preferentially occupy β sites of the HOPG surface graphene layer and the atoms aggregated by further occupation of either α or overbond sites. This is in contrast to predictions based on density functional theory, which indicates that the hollow sites are the most energetically stable sites for Co adsorption. The presence of surface hydrocarbon contamination on graphite might be one possible cause of the observed active nucleation and stabilized nanoisland diameter of Co. The formation of Co carbide was evidenced by x-ray absorption spectroscopy. More importantly, the Co magnetic spin moment at the interface of Fe-capped ferromagnetic Co nanostructures and graphite, as determined by x-ray magnetic circular dichroism and sum-rule analysis, was found to be only 63{\%} of the bulk value, implying a magnetically defective spin contact for carbon spintronics applications.",
keywords = "EC Grant Agreement nr.: FP7/228424, EWI-21084, METIS-285217, IR-79221, TSTNE-Probe-STM: Scanning Tunneling Microscope",
author = "P.K.J. Wong and {de Jong}, {Machiel Pieter} and L. Leonardus and Siekman, {Martin Herman} and {van der Wiel}, {Wilfred Gerard}",
note = "10.1103/PhysRevB.84.054420",
year = "2011",
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language = "Undefined",
volume = "84",
pages = "0544201--0544206",
journal = "Physical review B: Condensed matter and materials physics",
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Growth mechanism and interface magnetic properties of Co nanostructures on graphite. / Wong, P.K.J.; de Jong, Machiel Pieter; Leonardus, L.; Siekman, Martin Herman; van der Wiel, Wilfred Gerard.

In: Physical review B: Condensed matter and materials physics, Vol. 84, No. 5, 05.08.2011, p. 0544201-0544206.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Growth mechanism and interface magnetic properties of Co nanostructures on graphite

AU - Wong, P.K.J.

AU - de Jong, Machiel Pieter

AU - Leonardus, L.

AU - Siekman, Martin Herman

AU - van der Wiel, Wilfred Gerard

N1 - 10.1103/PhysRevB.84.054420

PY - 2011/8/5

Y1 - 2011/8/5

N2 - We investigated structural, electronic, and magnetic properties of Co adsorbed on highly oriented pyrolytic graphite (HOPG). Distribution and atomic sites of 3d transition-metal Co nanoislands and adatoms on HOPG were experimentally investigated by scanning tunneling microscopy with atomic resolution. In the very low thickness regime (0.6 A° ), a strong nucleation mechanism and a preferred Co nanoisland diameter of ∼3.4 nm have been observed. Co adatoms were found to preferentially occupy β sites of the HOPG surface graphene layer and the atoms aggregated by further occupation of either α or overbond sites. This is in contrast to predictions based on density functional theory, which indicates that the hollow sites are the most energetically stable sites for Co adsorption. The presence of surface hydrocarbon contamination on graphite might be one possible cause of the observed active nucleation and stabilized nanoisland diameter of Co. The formation of Co carbide was evidenced by x-ray absorption spectroscopy. More importantly, the Co magnetic spin moment at the interface of Fe-capped ferromagnetic Co nanostructures and graphite, as determined by x-ray magnetic circular dichroism and sum-rule analysis, was found to be only 63% of the bulk value, implying a magnetically defective spin contact for carbon spintronics applications.

AB - We investigated structural, electronic, and magnetic properties of Co adsorbed on highly oriented pyrolytic graphite (HOPG). Distribution and atomic sites of 3d transition-metal Co nanoislands and adatoms on HOPG were experimentally investigated by scanning tunneling microscopy with atomic resolution. In the very low thickness regime (0.6 A° ), a strong nucleation mechanism and a preferred Co nanoisland diameter of ∼3.4 nm have been observed. Co adatoms were found to preferentially occupy β sites of the HOPG surface graphene layer and the atoms aggregated by further occupation of either α or overbond sites. This is in contrast to predictions based on density functional theory, which indicates that the hollow sites are the most energetically stable sites for Co adsorption. The presence of surface hydrocarbon contamination on graphite might be one possible cause of the observed active nucleation and stabilized nanoisland diameter of Co. The formation of Co carbide was evidenced by x-ray absorption spectroscopy. More importantly, the Co magnetic spin moment at the interface of Fe-capped ferromagnetic Co nanostructures and graphite, as determined by x-ray magnetic circular dichroism and sum-rule analysis, was found to be only 63% of the bulk value, implying a magnetically defective spin contact for carbon spintronics applications.

KW - EC Grant Agreement nr.: FP7/228424

KW - EWI-21084

KW - METIS-285217

KW - IR-79221

KW - TSTNE-Probe-STM: Scanning Tunneling Microscope

U2 - 10.1103/PhysRevB.84.054420

DO - 10.1103/PhysRevB.84.054420

M3 - Article

VL - 84

SP - 544201

EP - 544206

JO - Physical review B: Condensed matter and materials physics

JF - Physical review B: Condensed matter and materials physics

SN - 1098-0121

IS - 5

ER -