Accurate modeling of defects in graphene transport calculations

Linhart, Lukas; Burgdörfer, Joachim; Libisch, Florian

doi:10.1103/physrevb.97.035430

Cited by 19 publications

(11 citation statements)

References 51 publications

(73 reference statements)

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“…A detailed theoretical analysis of the intriguing new measurements that can become possible with two STM tips and thus transport across very short distances, especially in presence of impurities, can be found in refs. [32][33][34] . Double-tip experiments might also enable probing the strain induced shifts in the band gaps and piezoresistivity in 2D materials' membranes 35 , or studying the strain induced magnetic properties of 2D van der Waals magnetic semiconductors by using specialized tips 36 .…”

Section: Discussionmentioning

confidence: 99%

New imaging modes for analyzing suspended ultra-thin membranes by double-tip scanning probe microscopy

Elibol

Hummel

Bayer

et al. 2020

Sci Rep

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Scanning probe microscopy (SpM) techniques are amongst the most important and versatile experimental methods in surface-and nanoscience. Although their measurement principles on rigid surfaces are well understood and steady progress on the instrumentation has been made, SPM imaging on suspended, flexible membranes remains difficult to interpret. Due to the interaction between the SPM tip and the flexible membrane, morphological changes caused by the tip can lead to deformations of the membrane during scanning and hence significantly influence measurement results. On the other hand, gaining control over such modifications can allow to explore unknown physical properties and functionalities of such membranes. Here, we demonstrate new types of measurements that become possible with two SPM instruments (atomic force microscopy, AFM, and scanning tunneling microscopy, STM) that are situated on opposite sides of a suspended two-dimensional (2D) material membrane and thus allow to bring both SPM tips arbitrarily close to each other. One of the probes is held stationary on one point of the membrane, within the scan area of the other probe, while the other probe is scanned. This way new imaging modes can be obtained by recording a signal on the stationary probe as a function of the position of the other tip. The first example, which we term electrical crosstalk imaging (ECT), shows the possibility of performing electrical measurements across the membrane, potentially in combination with control over the forces applied to the membrane. Using ECT, we measure the deformation of the 2D membrane around the indentation from the AFM tip. In the second example, which we term mechanical cross-talk imaging (MCT), we disentangle the mechanical influence of a scanning probe tip (e.g. AFM) on a freestanding membrane by means of independently recording the response of the opposing tip. In this way we are able to separate the tip-induced membrane deformation topography from the (material-dependent) force between the tip and the membrane. Overall, the results indicate that probing simultaneously both surfaces of ultra-thin membranes, such as suspended 2D materials, could provide novel insights into the electronic properties of the materials.Scanning probe microscopes (SPMs) using small physical probes have become highly versatile tools for imaging and manipulation on rigid surfaces due to the many different types of interaction between the probe and the object that can be exploited. SPMs are typically able to map different types of forces, electric fields, currents, thermo power, and many other features of the sample, depending on the structure and materials of the tips and operation and feedback mode during the scan 1,2 . SPMs are also often used for nanoscale manipulation 3,4 , scanning probe lithography 5 and electric contacting on very small areas 6 . Especially for the latter two purposes, multi-probe SPMs have become popular 7 . In this way, transport over very short length scales has been achieved 8-13 , however, the distance betw...

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Section: Discussionmentioning

confidence: 99%

New imaging modes for analyzing suspended ultra-thin membranes by double-tip scanning probe microscopy

Elibol

Hummel

Bayer

et al. 2020

Sci Rep

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“…We find no strong dependence of the interlayer coupling on the spin–orbit interaction induced by Mo. Using the Wannier90 code, we obtained tight-binding parameters for the separate layers and then fitted a coupling strength of ∼60 meV to reproduce the DFT splitting obtained from DFT in tight-binding. We then calculated the interlayer conductance of a 30 nm ribbon with periodic boundary conditions in the Landau–Büttiker approximation …”

Section: Experimental Methodsmentioning

confidence: 97%

Atomic-Scale Carving of Nanopores into a van der Waals Heterostructure with Slow Highly Charged Ions

et al. 2020

Self Cite

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The growing family of 2D materials led not long ago to combining different 2D layers and building artificial systems in the form of van der Waals heterostructures. Tailoring of heterostructure properties postgrowth would greatly benefit from a modification technique with a monolayer precision. However, appropriate techniques for material modification with this precision are still missing. To achieve such control, slow highly charged ions appear ideal as they carry high amounts of potential energy, which is released rapidly upon ion neutralization at the position of the ion. The resulting potential energy deposition is thus limited to just a few atomic layers (in contrast to the kinetic energy deposition). Here, we irradiated a freestanding van der Waals MoS 2 /graphene heterostructure with 1.3 keV/amu xenon ions in high charge states of 38, which led to nanometer-sized pores that appear only in the MoS 2 facing the ion beam, but not in graphene beneath the hole. Reversing the stacking order leaves both layers undamaged, which we attribute to the high conductivity and carrier mobility in graphene acting as a shield for the MoS 2 underneath. Our main focus is here on monolayer MoS 2 , but we also analyzed areas with few-layer structures and observed that the perforation is limited to the two topmost MoS 2 layers, whereas deeper layers remain intact. Our results demonstrate that in addition to already being a valuable tool for materials processing, the usability of ion irradiation can be extended to mono- (or bi)layer manipulation of van der Waals heterostructures when the localized potential energy deposition of highly charged ions is also added to the toolbox.

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“…We therefore adjust our Hamiltonian in Eq. ( 1) by making the hopping parameter t site-dependent, choosing values near these defects from the density functional theory results existing in the literature [81,82].…”

Section: B Dislocationsmentioning

confidence: 99%

Thermodefect voltage in graphene nanoribbon junctions

Aydin,

Sisman,

Fransson

et al. 2021

Preprint

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Thermoelectric junctions are often made of components of different materials characterized by distinct transport properties. Single material junctions, with the same type of charge carriers, have also been considered to investigate various classical and quantum effects on the thermoelectric properties of nanostructured materials. We here introduce the concept of defect-induced thermoelectric voltage, namely, thermodefect voltage, in graphene nanoribbon (GNR) junctions under a temperature gradient. Our thermodefect junction is formed by two GNRs with identical properties except the existence of defects in one of the nanoribbons. At room temperature the thermodefect voltage is highly sensitive to the types of defects, their locations, as well as the width and edge configurations of the GNRs. We demonstrate that the thermodefect voltage can be as high as 1.7 mV/K for 555-777 defects in semiconducting armchair GNRs. We further investigate the Seebeck coefficient, electrical conductance, and electronic thermal conductance, and also the power factor of the individual junction components to explain the thermodefect effect. Taken together, our study presents a new pathway to enhance the thermoelectric properties of nanomaterials.

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Accurate modeling of defects in graphene transport calculations

Cited by 19 publications

References 51 publications

New imaging modes for analyzing suspended ultra-thin membranes by double-tip scanning probe microscopy

New imaging modes for analyzing suspended ultra-thin membranes by double-tip scanning probe microscopy

Atomic-Scale Carving of Nanopores into a van der Waals Heterostructure with Slow Highly Charged Ions

Thermodefect voltage in graphene nanoribbon junctions

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