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Building blocks for studies of nanoscale magnetism: adsorbates on ultrathin insulating Cu2N
This content has been downloaded from IOPscience. Please scroll down to see the full text. 2014 J. Phys.: Condens. Matter 26 394009 (http://iopscience.iop.org/0953-8984/26/39/394009) View the table of contents for this issue, or go to the journal homepage for more Download details: IP Address: 130.133.8.114 This content was downloaded on 26/04/2017 at 08:52 Please note that terms and conditions apply.
You may also be interested in: Spectroscopic manifestations of the Kondo effect on single adatoms Markus Ternes, Andreas J Heinrich and Wolf-Dieter Schneider Atomically crafted spin lattices as model systems for quantum magnetism A Spinelli, M P Rebergen and and A F Otte Spin excitations and correlations in scanning tunneling spectroscopy Markus Ternes Confinement properties of 2D porous molecular networks on metal surfaces Kathrin Müller, Mihaela Enache and Meike Stöhr Charge transport through molecular switches Sense Jan van der Molen and Peter Liljeroth Spin-polarized spin excitation spectroscopy Sebastian Loth, Christopher P Lutz and Andreas J Heinrich Influence of the local environment on Mn acceptors in GaAs Donghun Lee, David Gohlke, Anne Benjamin et al. Kondo-effect of substitutional cobalt impurities at copper surfaces P Wahl, A P Seitsonen, L Diekhöner et al. Tungsten–Hydrogen complexes on graphene on Ir(111) S J Altenburg and R Berndt
Journal of Physics: Condensed Matter J. Phys.: Condens. Matter 26 (2014) 394009 (8pp)
doi:10.1088/0953-8984/26/39/394009
Building blocks for studies of nanoscale magnetism: adsorbates on ultrathin insulating Cu2N Taeyoung Choi and Jay A Gupta Department of Physics, Ohio State University, Columbus, OH 43210, USA E-mail: [email protected] Received 18 February 2014, revised 2 June 2014 Accepted for publication 5 June 2014 Published 12 September 2014 Abstract
Scanning tunneling microscopy and spectroscopy were performed to study transition metal adatoms (Fe, Co, Cu) and individual metal-dithiol complexes on insulating Cu2N islands. Adsorption of metal adatoms on Cu2N is surprisingly complex and in the case of Fe, we find two distinct adsorption states for each of two distinct adsorption sites. Connection of these metal adatoms to dithiol molecules was pursued to model a single molecule junction, with the aim of understanding further details about the nature of metal/molecule electrical contact. Pronounced changes in local density of states, magnetic anisotropy and Kondo interactions were observed for Co adatoms connected to dithiol molecules. These results illustrate some of the challenges and opportunities for STM studies of nanoscale magnetism in complex systems. Keywords: ultrathin films, scanning tunneling microscopy, magnetism, Kondo, molecular electronics S Online supplementary data available from stacks.iop.org/JPhysCM/26/394009/mmedia (Some figures may appear in colour only in the online journal)
1. Introduction
has fueled considerable interest in molecular junctions for information technologies [8]. Understanding the details of the molecule/electrode contact and the resultant influence on spin and charge transport has remained a grand challenge in the field [9] and motivates STM studies of transport through molecular units. Here, we provide a snapshot of our current studies of nanomagnetism on Cu2N. We have found that the adsorption landscape of transition metals (Fe, Co, Cu) on the Cu2N/Cu(100) surface is surprisingly complex. Upon low-temperature deposition, Co and Cu adatoms each adsorb at two distinct sites with significantly different apparent heights in STM images. In contrast, four adsorption states are observed for Fe adatoms on Cu2N, which are associated with only two distinct binding sites. Tunneling spectroscopy was used to probe how the electronic and magnetic properties vary among the respective states. We then connected individual Co atoms to alkanedithiol molecules on Cu2N as a model for single-molecule junctions. Tunneling spectroscopy indicates changes in electronic and
Scanning tunneling microscopy and spectroscopy (STM/STS) has been one of the leading surface science tools to investigate the electronic, optical and magnetic properties of nanostructures with atomic precision. Ultrathin insulating films (e.g. Al2O3, MgO, NaCl, Cu2N) have proven useful for decoupling nanostructures from substrate electron density and enable promising concepts for devices based on individual atoms or molecules. For example, the STM can be used to build atomically precise nanostructures of metal adatoms on Cu2N with relatively high magnetic anisotropy, allowing for nanoscale magnetic memories [1–4]. Atomic-scale switches based on the multi-stable charge states of adatoms on NaCl can also be envisioned [5, 6]. In addition, ultrathin insulating islands can provide a good platform to study aspects of electrical contact to molecular wires [7]. The promise of low-cost fabrication, inherently small size and chemically-tunable properties 0953-8984/14/394009+8$33.00
1
© 2014 IOP Publishing Ltd Printed in the UK
T Choi and J A Gupta
J. Phys.: Condens. Matter 26 (2014) 394009
Figure 1. Fe adatoms on Cu2N. (a) STM image of two Fe adatoms on Cu and two on Cu2N. On Cu2N, the Fe adatoms have apparent heights of 3.4 Å (Fe-1) and 3.8 Å (Fe-2). (b) STM image after the two adatoms are switched to adsorption states with smaller apparent heights of 2.7 Å (Fe-1) and 3.8 Å (Fe-2) (0.5 V, 1 nA). (c) Topographic linecuts from (a) and (b), along an identical trajectory shown by the overlays in (a-black) and (b red). (d) A Laplacian filtered STM image to emphasize local contrast of three Fe atoms (with 2.7 Å 2.7 Å and 3.1 Å apparent heights from left to right).Adsorption sites are determined by the overlay of the Cu2N lattice.
magnetic properties upon complex formation. These studies represent a preliminary step toward a greater understanding of the electrical contact to molecular devices.
V at constant tip height after disabling the STM feedback loop. By adding a small modulation voltage (~800 Hz), a lock-in amplifier simultaneously measured the differential conductance, dI/dV. At low voltages, dI/dV approximates the convolved tip and sample local density of states (LDOS). Modulations of 10 or 1 mVrms were used for measuring conductance over a large ( > 0.5 V) or small (
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My IOPscience
Building blocks for studies of nanoscale magnetism: adsorbates on ultrathin insulating Cu2N
This content has been downloaded from IOPscience. Please scroll down to see the full text. 2014 J. Phys.: Condens. Matter 26 394009 (http://iopscience.iop.org/0953-8984/26/39/394009) View the table of contents for this issue, or go to the journal homepage for more Download details: IP Address: 130.133.8.114 This content was downloaded on 26/04/2017 at 08:52 Please note that terms and conditions apply.
You may also be interested in: Spectroscopic manifestations of the Kondo effect on single adatoms Markus Ternes, Andreas J Heinrich and Wolf-Dieter Schneider Atomically crafted spin lattices as model systems for quantum magnetism A Spinelli, M P Rebergen and and A F Otte Spin excitations and correlations in scanning tunneling spectroscopy Markus Ternes Confinement properties of 2D porous molecular networks on metal surfaces Kathrin Müller, Mihaela Enache and Meike Stöhr Charge transport through molecular switches Sense Jan van der Molen and Peter Liljeroth Spin-polarized spin excitation spectroscopy Sebastian Loth, Christopher P Lutz and Andreas J Heinrich Influence of the local environment on Mn acceptors in GaAs Donghun Lee, David Gohlke, Anne Benjamin et al. Kondo-effect of substitutional cobalt impurities at copper surfaces P Wahl, A P Seitsonen, L Diekhöner et al. Tungsten–Hydrogen complexes on graphene on Ir(111) S J Altenburg and R Berndt
Journal of Physics: Condensed Matter J. Phys.: Condens. Matter 26 (2014) 394009 (8pp)
doi:10.1088/0953-8984/26/39/394009
Building blocks for studies of nanoscale magnetism: adsorbates on ultrathin insulating Cu2N Taeyoung Choi and Jay A Gupta Department of Physics, Ohio State University, Columbus, OH 43210, USA E-mail: [email protected] Received 18 February 2014, revised 2 June 2014 Accepted for publication 5 June 2014 Published 12 September 2014 Abstract
Scanning tunneling microscopy and spectroscopy were performed to study transition metal adatoms (Fe, Co, Cu) and individual metal-dithiol complexes on insulating Cu2N islands. Adsorption of metal adatoms on Cu2N is surprisingly complex and in the case of Fe, we find two distinct adsorption states for each of two distinct adsorption sites. Connection of these metal adatoms to dithiol molecules was pursued to model a single molecule junction, with the aim of understanding further details about the nature of metal/molecule electrical contact. Pronounced changes in local density of states, magnetic anisotropy and Kondo interactions were observed for Co adatoms connected to dithiol molecules. These results illustrate some of the challenges and opportunities for STM studies of nanoscale magnetism in complex systems. Keywords: ultrathin films, scanning tunneling microscopy, magnetism, Kondo, molecular electronics S Online supplementary data available from stacks.iop.org/JPhysCM/26/394009/mmedia (Some figures may appear in colour only in the online journal)
1. Introduction
has fueled considerable interest in molecular junctions for information technologies [8]. Understanding the details of the molecule/electrode contact and the resultant influence on spin and charge transport has remained a grand challenge in the field [9] and motivates STM studies of transport through molecular units. Here, we provide a snapshot of our current studies of nanomagnetism on Cu2N. We have found that the adsorption landscape of transition metals (Fe, Co, Cu) on the Cu2N/Cu(100) surface is surprisingly complex. Upon low-temperature deposition, Co and Cu adatoms each adsorb at two distinct sites with significantly different apparent heights in STM images. In contrast, four adsorption states are observed for Fe adatoms on Cu2N, which are associated with only two distinct binding sites. Tunneling spectroscopy was used to probe how the electronic and magnetic properties vary among the respective states. We then connected individual Co atoms to alkanedithiol molecules on Cu2N as a model for single-molecule junctions. Tunneling spectroscopy indicates changes in electronic and
Scanning tunneling microscopy and spectroscopy (STM/STS) has been one of the leading surface science tools to investigate the electronic, optical and magnetic properties of nanostructures with atomic precision. Ultrathin insulating films (e.g. Al2O3, MgO, NaCl, Cu2N) have proven useful for decoupling nanostructures from substrate electron density and enable promising concepts for devices based on individual atoms or molecules. For example, the STM can be used to build atomically precise nanostructures of metal adatoms on Cu2N with relatively high magnetic anisotropy, allowing for nanoscale magnetic memories [1–4]. Atomic-scale switches based on the multi-stable charge states of adatoms on NaCl can also be envisioned [5, 6]. In addition, ultrathin insulating islands can provide a good platform to study aspects of electrical contact to molecular wires [7]. The promise of low-cost fabrication, inherently small size and chemically-tunable properties 0953-8984/14/394009+8$33.00
1
© 2014 IOP Publishing Ltd Printed in the UK
T Choi and J A Gupta
J. Phys.: Condens. Matter 26 (2014) 394009
Figure 1. Fe adatoms on Cu2N. (a) STM image of two Fe adatoms on Cu and two on Cu2N. On Cu2N, the Fe adatoms have apparent heights of 3.4 Å (Fe-1) and 3.8 Å (Fe-2). (b) STM image after the two adatoms are switched to adsorption states with smaller apparent heights of 2.7 Å (Fe-1) and 3.8 Å (Fe-2) (0.5 V, 1 nA). (c) Topographic linecuts from (a) and (b), along an identical trajectory shown by the overlays in (a-black) and (b red). (d) A Laplacian filtered STM image to emphasize local contrast of three Fe atoms (with 2.7 Å 2.7 Å and 3.1 Å apparent heights from left to right).Adsorption sites are determined by the overlay of the Cu2N lattice.
magnetic properties upon complex formation. These studies represent a preliminary step toward a greater understanding of the electrical contact to molecular devices.
V at constant tip height after disabling the STM feedback loop. By adding a small modulation voltage (~800 Hz), a lock-in amplifier simultaneously measured the differential conductance, dI/dV. At low voltages, dI/dV approximates the convolved tip and sample local density of states (LDOS). Modulations of 10 or 1 mVrms were used for measuring conductance over a large ( > 0.5 V) or small (
