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Rothhardt D, Kimouche A, Klamroth T, Hoffmann-Vogel R. Local work function on graphene nanoribbons. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2024; 15:1125-1131. [PMID: 39224533 PMCID: PMC11368052 DOI: 10.3762/bjnano.15.91] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Accepted: 07/30/2024] [Indexed: 09/04/2024]
Abstract
Graphene nanoribbons show exciting electronic properties related to the exotic nature of the charge carriers and to local confinement as well as atomic-scale structural details. The local work function provides evidence for such structural, electronic, and chemical variations at surfaces. Kelvin prove force microscopy can be used to measure the local contact potential difference (LCPD) between a probe tip and a surface, related to the work function. Here we use this technique to map the LCPD of graphene nanoribbons grown on a Au(111) substrate. The LCPD data shows charge transfer between the graphene nanoribbons and the gold substrate. Our results are corroborated with density functional theory calculations, which verify that the maps reflect the doping of the nanoribbons. Our results help to understand the relation between atomic structure and electronic properties both in high-resolution images and in the distance dependence of the LCPD.
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Affiliation(s)
- Daniel Rothhardt
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24–25, 14476 Potsdam-Golm, Germany
- current address: Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
- current address: Department of Physics, University of Basel, CH-4056 Basel, Switzerland
| | - Amina Kimouche
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24–25, 14476 Potsdam-Golm, Germany
| | - Tillmann Klamroth
- Institute of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24–25, 14476 Potsdam-Golm, Germany
| | - Regina Hoffmann-Vogel
- Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24–25, 14476 Potsdam-Golm, Germany
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2
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Zanjani SM, Naseem MT, Müstecaplıoğlu ÖE, Onbaşlı MC. All optical control of magnetization in quantum confined ultrathin magnetic metals. Sci Rep 2021; 11:15976. [PMID: 34354127 PMCID: PMC8342544 DOI: 10.1038/s41598-021-95319-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 07/21/2021] [Indexed: 02/07/2023] Open
Abstract
All-optical control dynamics of magnetization in sub-10 nm metallic thin films are investigated, as these films with quantum confinement undergo unique interactions with femtosecond laser pulses. Our theoretical analysis based on the free electron model shows that the density of states at Fermi level (DOSF) and electron-phonon coupling coefficients (Gep) in ultrathin metals have very high sensitivity to film thickness within a few angstroms. We show that completely different magnetization dynamics characteristics emerge if DOSF and Gep depend on thickness compared with bulk metals. Our model suggests highly efficient energy transfer from femtosecond laser photons to spin waves due to minimal energy absorption by phonons. This sensitivity to the thickness and efficient energy transfer offers an opportunity to obtain ultrafast on-chip magnetization dynamics.
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Affiliation(s)
- Saeedeh Mokarian Zanjani
- grid.15876.3d0000000106887552Graduate School of Materials Science and Engineering, Koç University, Sarıyer, 34450 Istanbul, Turkey
| | - Muhammad Tahir Naseem
- grid.15876.3d0000000106887552Department of Physics, Koç University, Sarıyer, 34450 Istanbul, Turkey
| | | | - Mehmet Cengiz Onbaşlı
- grid.15876.3d0000000106887552Graduate School of Materials Science and Engineering, Koç University, Sarıyer, 34450 Istanbul, Turkey ,grid.15876.3d0000000106887552Department of Electrical and Electronics Engineering, Koç University, Sarıyer, 34450 Istanbul, Turkey
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Schneider S, Hoffmann-Vogel R. Electrostatic forces above graphene nanoribbons and edges interpreted as partly hydrogen-free. NANOSCALE 2020; 12:17895-17901. [PMID: 32844849 DOI: 10.1039/d0nr03348k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Graphene nanoribbons' electronic transport properties strongly depend on the type of edge, armchair, zigzag or other, and on edge functionalization that can be used for band-gap engineering. For only partly hydrogenated edges interesting magnetic properties are predicted. Electric charge accumulates at edges and corners. Scanning force microscopy has so far shown the centre of graphene nanoribbons with atomic resolution using a quartz crystal tuning fork sensor of high stiffness. Weak long-range electrostatic forces related to the charge accumulation on the edges of graphene nanoribbons could not be imaged so far. Here, we show the electrostatic forces at the corners and edges of graphene nanoribbons are amenable to measurement. We use soft cantilevers and a bimodal imaging technique to combine enhanced sensitivity to weak long-range electrostatic forces with the high resolution of the second-frequency shift. Additionally, in our work the edges of the nanoribbons are mainly hydrogen-free, opening to the route to investigations of partly hydrogenated magnetic nanoribbons.
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Affiliation(s)
- Sebastian Schneider
- Physikalisches Institut, Karlsruhe Institute of Technology, Karlsruhe, Germany
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Späth T, Popp M, Hoffmann-Vogel R. Film Thickness of Pb Islands on the Si(111) Surface. PHYSICAL REVIEW LETTERS 2020; 124:016101. [PMID: 31976694 DOI: 10.1103/physrevlett.124.016101] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 08/27/2019] [Indexed: 06/10/2023]
Abstract
We analyze topographic scanning force microscopy images together with Kelvin probe images obtained on Pb islands and on the wetting layer on Si(111) for variable annealing times. Within the wetting layer we observe negatively charged Si-rich areas. We show evidence that these Si-rich areas result from islands that have disappeared by coarsening. We argue that the islands are located on Si-rich areas inside the wetting layer such that the Pb/Si interface of the islands is in line with the top of the wetting layer rather than with its interface to the substrate. We propose that the Pb island heights are one atomic layer smaller than previously believed. For the quantum size effect bilayer oscillations of the work function observed in this system, we conclude that for film thicknesses below 9 atomic layers large values of the work function correspond to even numbers of monolayers instead of odd ones. The atomically precise island height is important to understand ultrafast "explosive" island growth in this system.
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Affiliation(s)
- Th Späth
- Physikalisches Institut, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | - M Popp
- Physikalisches Institut, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
| | - R Hoffmann-Vogel
- Department of Physics, University of Konstanz, Universitätsstrasse 10, 78464 Konstanz, Germany
- Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany
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5
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Lytvyn PM, Kuchuk AV, Mazur YI, Li C, Ware ME, Wang ZM, Kladko VP, Belyaev AE, Salamo GJ. Polarization Effects in Graded AlGaN Nanolayers Revealed by Current-Sensing and Kelvin Probe Microscopy. ACS APPLIED MATERIALS & INTERFACES 2018; 10:6755-6763. [PMID: 29381323 DOI: 10.1021/acsami.7b19160] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We experimentally demonstrate that the conductivity of graded AlxGa1-xN increases as a function of the magnitude of the Al concentration gradient (%Al/nm) due to polarization doping effects, without the use of impurity dopants. Using three up/down-graded AlxGa1-xN nanolayers with Al gradients ranging from ∼0.16 to ∼0.28%Al/nm combined in one structure, the effects of polarization engineering for localized electric fields and current transport were investigated. Cross-sectional Kelvin probe force microscopy and conductive atomic force microscopy were used to directly probe the electrical properties of the films with spatial resolution along the thickness of the growth. The experimental profiles of the built-in electric fields and the spreading current found in the graded layers are shown to be consistent with simulations of the field distribution as well as of the electron and hole densities. Finally, it was directly observed that for gradients less than 0.28%Al/nm the native n-type donors still limit polarization-induced hole doping, making p-type conductivity still a challenge due to background impurities and defects.
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Affiliation(s)
- Petro M Lytvyn
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China , Chengdu 610054, P. R. China
- Institute for Nanoscience & Engineering, University of Arkansas , W. Dickson 731, Fayetteville, Arkansas 72701, United States
- V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine , Pr. Nauky 41, 03680 Kyiv, Ukraine
| | - Andrian V Kuchuk
- Institute for Nanoscience & Engineering, University of Arkansas , W. Dickson 731, Fayetteville, Arkansas 72701, United States
| | - Yuriy I Mazur
- Institute for Nanoscience & Engineering, University of Arkansas , W. Dickson 731, Fayetteville, Arkansas 72701, United States
| | - Chen Li
- Institute for Nanoscience & Engineering, University of Arkansas , W. Dickson 731, Fayetteville, Arkansas 72701, United States
| | - Morgan E Ware
- Institute for Nanoscience & Engineering, University of Arkansas , W. Dickson 731, Fayetteville, Arkansas 72701, United States
| | - Zhiming M Wang
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China , Chengdu 610054, P. R. China
| | - Vasyl P Kladko
- V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine , Pr. Nauky 41, 03680 Kyiv, Ukraine
| | - Alexander E Belyaev
- V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine , Pr. Nauky 41, 03680 Kyiv, Ukraine
| | - Gregory J Salamo
- Institute for Nanoscience & Engineering, University of Arkansas , W. Dickson 731, Fayetteville, Arkansas 72701, United States
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Handschuh-Wang S, Wang T, Zhou X. Recent advances in hybrid measurement methods based on atomic force microscopy and surface sensitive measurement techniques. RSC Adv 2017. [DOI: 10.1039/c7ra08515j] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
This review summaries the recent progress of the combination of optical and non-optical surface sensitive techniques with the atomic force microscopy.
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Affiliation(s)
- Stephan Handschuh-Wang
- College of Chemistry and Environmental Engineering
- Shenzhen University
- Shenzhen 518060
- P. R. China
| | - Tao Wang
- Functional Thin Films Research Center
- Shenzhen Institutes of Advanced Technology
- Chinese Academy of Sciences
- Shenzhen 518055
- P. R. China
| | - Xuechang Zhou
- College of Chemistry and Environmental Engineering
- Shenzhen University
- Shenzhen 518060
- P. R. China
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