@article{MTMT:31670809, title = {Ab-initio wave packet dynamical simulation of defects in 2D materials}, url = {https://m2.mtmt.hu/api/publication/31670809}, author = {Márk, Géza István and Vancsó, Péter}, doi = {10.3390/ASEC2020-07760}, journal-iso = {PROCEEDINGS}, journal = {PROCEEDINGS}, volume = {2020}, unique-id = {31670809}, year = {2020}, eissn = {2504-3900}, orcid-numbers = {Vancsó, Péter/0000-0003-4333-9787} } @article{MTMT:31670541, title = {Wave-Packet Dynamics Study of the Transport Characteristics of Perforated Bilayer Graphene Nanoribbons}, url = {https://m2.mtmt.hu/api/publication/31670541}, author = {Demin, V. A. and Kvashnin, D. G. and Vancsó, Péter and Márk, Géza István and Chernozatonskii, L. A.}, doi = {10.1134/S0021364020170063}, journal-iso = {JETP LETT+}, journal = {JETP LETTERS}, volume = {112}, unique-id = {31670541}, issn = {0021-3640}, abstract = {The electrical conduction characteristics of perforated bilayer graphene nanoribbons are studied by the wave-packet dynamics method. The transport characteristics for typical examples of such nanostructures, which depend on the specific features of the contacts between the electrodes and the nanostructure under study, are estimated within a theoretical model. The effect of nanopores on the propagation of a wave packet across bilayer nanoribbons having two different configurations is revealed. These studies may become the first necessary prerequisite for the possible applications of such objects as components of electronic and optoelectronic circuits.}, year = {2020}, eissn = {1090-6487}, pages = {305-309}, orcid-numbers = {Vancsó, Péter/0000-0003-4333-9787} } @article{MTMT:30331608, title = {Spontaneous doping of the basal plane of MoS2 single layers through oxygen substitution under ambient conditions}, url = {https://m2.mtmt.hu/api/publication/30331608}, author = {Pető, János and Ollár, Tamás and Vancsó, Péter and Popov, Z.I. and Magda, Gábor Zsolt and Dobrik, Gergely and Hwang, C. and Sorokin, P.B. and Tapasztó, Levente}, doi = {10.1038/s41557-018-0136-2}, journal-iso = {NAT CHEM}, journal = {NATURE CHEMISTRY}, volume = {10}, unique-id = {30331608}, issn = {1755-4330}, year = {2018}, eissn = {1755-4349}, pages = {1246-1251}, orcid-numbers = {Vancsó, Péter/0000-0003-4333-9787; Dobrik, Gergely/0000-0002-6690-274X; Tapasztó, Levente/0000-0002-9377-8465} } @article{MTMT:3390771, title = {Exfoliation of single layer BiTeI flakes}, url = {https://m2.mtmt.hu/api/publication/3390771}, author = {Fülöp, Bálint and Tajkov, Zoltán and Pető, János and Kun, Péter and Koltai, János and Oroszlány, László and Tóvári, Endre and Murakawa, H and Tokura, Y and Bordács, Sándor and Tapasztó, Levente and Csonka, Szabolcs}, doi = {10.1088/2053-1583/aac652}, journal-iso = {2D MATER}, journal = {2D MATERIALS}, volume = {5}, unique-id = {3390771}, issn = {2053-1583}, abstract = {Spin orbit interaction is strongly enhanced in structures where a heavy element is embedded in an inversion asymmetric crystal field. A simple way for realizing such a setup is to take a single atomic layer of a heavy element and encapsulate it between two atomic layers of different elemental composition. BiTeI is a promising candidate for such a 2D crystal. In its bulk form BiTeI consists of loosely coupled three atom thick layers where a layer of high atomic number Bi are sandwiched between Te and I sheets. Despite considerable recent attention to bulk BiTeI due to its giant Rashba spin splitting, the isolation of a single layer remained elusive. In this work we report the first successful isolation and characterization of a single layer of BiTeI using a novel exfoliation technique on stripped gold. Our scanning probe studies and first principles calculations show that the fabricated 100 mu m sized BiTeI flakes are stable at ambient conditions. Giant Rashba splitting and spin-momentum locking of this new 2D crystal opens the way towards novel spintronic applications and synthetic topological heterostructures.}, keywords = {AU; ENERGY; CRYSTALS; Graphene; Graphite; Rashba spin splitting; topological insulator; BiTeI; RASHBA; AU(111) SURFACE; DER-WAALS HETEROSTRUCTURES; SCANNING-TUNNELING-MICROSCOPE; stripped gold exfoliation; van der Waals heterostructures}, year = {2018}, eissn = {2053-1583}, orcid-numbers = {Fülöp, Bálint/0000-0001-6853-2642; Koltai, János/0000-0003-2576-9740; Oroszlány, László/0000-0001-5682-6424; Tóvári, Endre/0000-0002-0000-3805; Bordács, Sándor/0000-0003-0420-5997; Tapasztó, Levente/0000-0002-9377-8465} } @article{MTMT:3327507, title = {Electronic Dynamics in Graphene and MoS2 Systems}, url = {https://m2.mtmt.hu/api/publication/3327507}, author = {Márk, Géza István and Fejer, GR and Vancsó, Péter and Lambin, P and Biró, László Péter}, doi = {10.1002/pssb.201700179}, journal-iso = {PHYS STAT SOL B BASIC RES}, journal = {PHYSICA STATUS SOLIDI B-BASIC RESEARCH}, volume = {254}, unique-id = {3327507}, issn = {0370-1972}, abstract = {We performed wave packet dynamical calculations for graphene-and MoS2 monolayers by a new formulation of the split-operator FFT method utilizing ab initio band structure results into the kinetic energy operator. While the time dependent dynamics is available through the solution of the time dependent Schrodinger equation in wave packet dynamics, the energy dependent dynamics is calculated by the application of the time-energy Fourier transform to the wave function. Time dependent probability results show an anisotropic spreading of the probability density current. The magnitude and angular dependence of the anisotropy is dependent (i) on the process creating the initial wave packet (e.g., injection from an STM tip or scattering on an impurity) and (ii) on the details of the band structure.}, year = {2017}, eissn = {1521-3951}, orcid-numbers = {Vancsó, Péter/0000-0003-4333-9787; Biró, László Péter/0000-0001-7261-0420} } @article{MTMT:3266108, title = {Novel graphene/Sn and graphene/SnOx hybrid nanostructures: Induced superconductivity and band gaps revealed by scanning probe measurements}, url = {https://m2.mtmt.hu/api/publication/3266108}, author = {Pálinkás, András and Molnár, György and Magda, Gábor Zsolt and Hwang, Chanyong and Tapasztó, Levente and Samuely, Peter and Szabó, Pavol and Osváth, Zoltán}, doi = {10.1016/j.carbon.2017.09.026}, journal-iso = {CARBON}, journal = {CARBON}, volume = {124}, unique-id = {3266108}, issn = {0008-6223}, abstract = {Abstract The development of functional composite nanomaterials based on graphene and metal nanoparticles (NPs) is currently the subject of intense research interest. In this study we report the preparation of novel type of graphene/Sn and graphene/SnOx (1 ≤ x ≤ 2) hybrid nanostructures and their investigation by scanning probe methods. First, we prepare Sn NPs by evaporating 7–8 nm tin on highly oriented pyrolytic graphite substrates. Graphene/Sn nanostructures are obtained by transferring graphene on top of the tin NPs immediately after evaporation. We show by scanning tunnelling microscopy (STM) and spectroscopy (STS) that tin NPs reduce significantly the environmental p-type doping of graphene. Furthermore, we demonstrate by low-temperature STM and STS measurements that superconductivity is induced in graphene, either directly supported by Sn NPs or suspended between them. Additionally, we prepare SnOx NPs by annealing the evaporated tin at 500 °C. STS measurements performed on hybrid graphene/SnOx nanostructures reveal the electronic band gap of SnOx NPs. The results can open new avenues for the fabrication of novel hybrid superconducting nanomaterials with designed structures and morphologies.}, year = {2017}, eissn = {1873-3891}, pages = {611-617}, orcid-numbers = {Molnár, György/0000-0002-4792-5516; Tapasztó, Levente/0000-0002-9377-8465; Osváth, Zoltán/0000-0003-0440-5446} } @article{MTMT:3253435, title = {Preparing local strain patterns in graphene by atomic force microscope based indentation}, url = {https://m2.mtmt.hu/api/publication/3253435}, author = {Nemes Incze, Péter and Kukucska, Gergő and Koltai, János and Kürti, Jenő and Hwang, C and Tapasztó, Levente and Biró, László Péter}, doi = {10.1038/s41598-017-03332-5}, journal-iso = {SCI REP}, journal = {SCIENTIFIC REPORTS}, volume = {7}, unique-id = {3253435}, issn = {2045-2322}, abstract = {Patterning graphene into various mesoscopic devices such as nanoribbons, quantum dots, etc. by lithographic techniques has enabled the guiding and manipulation of graphene's Dirac-type charge carriers. Graphene, with well-defined strain patterns, holds promise of similarly rich physics while avoiding the problems created by the hard to control edge configuration of lithographically prepared devices. To engineer the properties of graphene via mechanical deformation, versatile new techniques are needed to pattern strain profiles in a controlled manner. Here we present a process by which strain can be created in substrate supported graphene layers. Our atomic force microscope-based technique opens up new possibilities in tailoring the properties of graphene using mechanical strain.}, year = {2017}, eissn = {2045-2322}, orcid-numbers = {Nemes Incze, Péter/0000-0002-1222-3020; Kukucska, Gergő/0000-0002-8715-8075; Koltai, János/0000-0003-2576-9740; Kürti, Jenő/0000-0001-9752-2769; Tapasztó, Levente/0000-0002-9377-8465; Biró, László Péter/0000-0001-7261-0420} } @article{MTMT:3205234, title = {A magnetic phase-transition graphene transistor with tunable spin polarization}, url = {https://m2.mtmt.hu/api/publication/3205234}, author = {Vancsó, Péter and Hagymási, Imre and Tapasztó, Levente}, doi = {10.1088/2053-1583/aa5f2d}, journal-iso = {2D MATER}, journal = {2D MATERIALS}, volume = {4}, unique-id = {3205234}, issn = {2053-1583}, abstract = {Graphene nanoribbons (GNRs) have been proposed as potential building blocks for field effect transistor (FET) devices due to their quantum confinement bandgap. Here, we propose a novel GNR device concept, enabling the control of both charge and spin signals, integrated within the simplest three-terminal device configuration. In a conventional FET device, a gate electrode is employed to tune the Fermi level of the system in and out of a static bandgap. By contrast, in the switching mechanism proposed here, the applied gate voltage can dynamically open and close an interaction gap, with only a minor shift of the Fermi level. Furthermore, the strong interplay of the band structure and edge spin configuration in zigzag ribbons enables such transistors to carry spin polarized current without employing an external magnetic field or ferromagnetic contacts. Using an experimentally validated theoretical model, we show that such transistors can switch at low voltages and high speed, and the spin polarization of the current can be tuned from 0% to 50% by using the same back gate electrode. Furthermore, such devices are expected to be robust against edge irregularities and can operate at room temperature. Controlling both charge and spin signal within the simplest FET device configuration could open up new routes in data processing with graphene based devices.}, year = {2017}, eissn = {2053-1583}, orcid-numbers = {Vancsó, Péter/0000-0003-4333-9787; Tapasztó, Levente/0000-0002-9377-8465} } @article{MTMT:3122457, title = {The intrinsic defect structure of exfoliated MoS2 single layers revealed by Scanning Tunneling Microscopy}, url = {https://m2.mtmt.hu/api/publication/3122457}, author = {Vancsó, Péter and Magda, Gábor Zsolt and Pető, János and Noh, JY and Kim, YS and Hwang, C and Biró, László Péter and Tapasztó, Levente}, doi = {10.1038/srep29726}, journal-iso = {SCI REP}, journal = {SCIENTIFIC REPORTS}, volume = {6}, unique-id = {3122457}, issn = {2045-2322}, abstract = {MoS2 single layers have recently emerged as strong competitors of graphene in electronic and optoelectronic device applications due to their intrinsic direct bandgap. However, transport measurements reveal the crucial role of defect-induced electronic states, pointing out the fundamental importance of characterizing their intrinsic defect structure. Transmission Electron Microscopy (TEM) is able to image atomic scale defects in MoS2 single layers, but the imaged defect structure is far from the one probed in the electronic devices, as the defect density and distribution are substantially altered during the TEM imaging. Here, we report that under special imaging conditions, STM measurements can fully resolve the native atomic scale defect structure of MoS2 single layers. Our STM investigations clearly resolve a high intrinsic concentration of individual sulfur atom vacancies, and experimentally identify the nature of the defect induced electronic mid-gap states, by combining topographic STM images with ab intio calculations. Experimental data on the intrinsic defect structure and the associated defect-bound electronic states that can be directly used for the interpretation of transport measurements are essential to fully understand the operation, reliability and performance limitations of realistic electronic devices based on MoS2 single layers.}, year = {2016}, eissn = {2045-2322}, orcid-numbers = {Vancsó, Péter/0000-0003-4333-9787; Biró, László Péter/0000-0001-7261-0420; Tapasztó, Levente/0000-0002-9377-8465} } @article{MTMT:2984284, title = {Exfoliation of large-area transition metal chalcogenide single layers}, url = {https://m2.mtmt.hu/api/publication/2984284}, author = {Magda, Gábor Zsolt and Pető, János and Dobrik, Gergely and Hwang, C and Biró, László Péter and Tapasztó, Levente}, doi = {10.1038/srep14714}, journal-iso = {SCI REP}, journal = {SCIENTIFIC REPORTS}, volume = {5}, unique-id = {2984284}, issn = {2045-2322}, abstract = {Isolating large-areas of atomically thin transition metal chalcogenide crystals is an important but challenging task. The mechanical exfoliation technique can provide single layers of the highest structural quality, enabling to study their pristine properties and ultimate device performance. However, a major drawback of the technique is the low yield and small (typically <10 um) lateral size of the produced single layers. Here, we report a novel mechanical exfoliation technique, based on chemically enhanced adhesion, yielding MoS2single layers with typical lateral sizes of several hundreds of microns. The idea is to exploit the chemical affinity of the sulfur atoms that can bind more strongly to a gold surface than the neighboring layers of the bulk MoS2 crystal. Moreover, we found that our exfoliation process is not specific to MoS2, but can be generally applied for various layered chalcogenides including selenites and tellurides, providing an easy access to large-area 2D crystals for the whole class of layered transition metal chalcogenides.}, year = {2015}, eissn = {2045-2322}, orcid-numbers = {Dobrik, Gergely/0000-0002-6690-274X; Biró, László Péter/0000-0001-7261-0420; Tapasztó, Levente/0000-0002-9377-8465} }