Готові списки джерел за темами / Van der Waals (vdW) heterostructures

Добірка наукової літератури з теми "Van der Waals (vdW) heterostructures"

Автор: Grafiati
Опубліковано: 6 вересня 2023

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Статті в журналах з теми "Van der Waals (vdW) heterostructures"

1

Albarakati, Sultan, Cheng Tan, Zhong-Jia Chen, James G. Partridge, Guolin Zheng, Lawrence Farrar, Edwin L. H. Mayes, et al. "Antisymmetric magnetoresistance in van der Waals Fe3GeTe2/graphite/Fe3GeTe2 trilayer heterostructures." Science Advances 5, no. 7 (July 2019): eaaw0409. http://dx.doi.org/10.1126/sciadv.aaw0409.

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With no requirements for lattice matching, van der Waals (vdW) ferromagnetic materials are rapidly establishing themselves as effective building blocks for next-generation spintronic devices. We report a hitherto rarely seen antisymmetric magnetoresistance (MR) effect in vdW heterostructured Fe3GeTe2 (FGT)/graphite/FGT devices. Unlike conventional giant MR (GMR), which is characterized by two resistance states, the MR in these vdW heterostructures features distinct high-, intermediate-, and low-resistance states. This unique characteristic is suggestive of underlying physical mechanisms that differ from those observed before. After theoretical calculations, the three-resistance behavior was attributed to a spin momentum locking induced spin-polarized current at the graphite/FGT interface. Our work reveals that ferromagnetic heterostructures assembled from vdW materials can exhibit substantially different properties to those exhibited by similar heterostructures grown in vacuum. Hence, it highlights the potential for new physics and new spintronic applications to be discovered using vdW heterostructures.
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2

Rakib, Tawfiqur, Pascal Pochet, Elif Ertekin, and Harley T. Johnson. "Moiré engineering in van der Waals heterostructures." Journal of Applied Physics 132, no. 12 (September 28, 2022): 120901. http://dx.doi.org/10.1063/5.0105405.

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Isolated atomic planes can be assembled into a multilayer van der Waals (vdW) heterostructure in a precisely chosen sequence. These heterostructures feature moiré patterns if the constituent 2D material layers are stacked in an incommensurable way, due to a lattice mismatch or twist. This design-by-stacking has opened up the promising area of moiré engineering, a term that can be understood in two different perspectives, namely, (i) structural—engineering a moiré pattern by introducing twist, relative strain, or defects that affect the commensurability of the layers and (ii) functional—exploiting a moiré pattern to find and tune resulting physical properties of a vdW heterostructure. The latter meaning, referring to the application of a moiré pattern, is seen in the literature in the specific context of the observation of correlated electronic states and unconventional superconductivity in twisted bilayer graphene. The former meaning, referring to the design of the moiré pattern itself, is present in the literature but less commonly discussed or less understood. The underlying link between these two perspectives lies in the deformation field of the moiré superlattice. In this Perspective, we describe a path from designing a moiré pattern to employing the moiré pattern to tune physical properties of a vdW heterostructure. We also discuss the concept of moiré engineering in the context of twistronics, strain engineering, and defect engineering in vdW heterostructures. Although twistronics is always associated with moiré superlattices, strain and defect engineering are often not. Here, we demonstrate how strain and defect engineering can be understood within the context of moiré engineering. Adopting this perspective, we note that moiré engineering creates a compelling opportunity to design and develop multiscale electronic devices.
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3

Ma, Zechen, Ruifeng Li, Rui Xiong, Yinggan Zhang, Chao Xu, Cuilian Wen, and Baisheng Sa. "InSe/Te van der Waals Heterostructure as a High-Efficiency Solar Cell from Computational Screening." Materials 14, no. 14 (July 6, 2021): 3768. http://dx.doi.org/10.3390/ma14143768.

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Designing the electronic structures of the van der Waals (vdW) heterostructures to obtain high-efficiency solar cells showed a fascinating prospect. In this work, we screened the potential of vdW heterostructures for solar cell application by combining the group III–VI MXA (M = Al, Ga, In and XA = S, Se, Te) and elementary group VI XB (XB = Se, Te) monolayers based on first-principle calculations. The results highlight that InSe/Te vdW heterostructure presents type-II electronic band structure feature with a band gap of 0.88 eV, where tellurene and InSe monolayer are as absorber and window layer, respectively. Interestingly, tellurene has a 1.14 eV direct band gap to produce the photoexcited electron easily. Furthermore, InSe/Te vdW heterostructure shows remarkably light absorption capacities and distinguished maximum power conversion efficiency (PCE) up to 13.39%. Our present study will inspire researchers to design vdW heterostructures for solar cell application in a purposeful way.
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4

He, Junshan, Cong Wang, Bo Zhou, Yu Zhao, Lili Tao, and Han Zhang. "2D van der Waals heterostructures: processing, optical properties and applications in ultrafast photonics." Materials Horizons 7, no. 11 (2020): 2903–21. http://dx.doi.org/10.1039/d0mh00340a.

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Анотація:
The investigation of van der Waals (vdW) heterostructures has been becoming an attractive research topic. This review aims to present a thorough summarization of the research progress of vdW heterostructures in ultrafast photonics.
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5

Degaga, Gemechis D., Sumandeep Kaur, Ravindra Pandey, and John A. Jaszczak. "First-Principles Study of a MoS2-PbS van der Waals Heterostructure Inspired by Naturally Occurring Merelaniite." Materials 14, no. 7 (March 27, 2021): 1649. http://dx.doi.org/10.3390/ma14071649.

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Анотація:
Vertically stacked, layered van der Waals (vdW) heterostructures offer the possibility to design materials, within a range of chemistries and structures, to possess tailored properties. Inspired by the naturally occurring mineral merelaniite, this paper studies a vdW heterostructure composed of a MoS2 monolayer and a PbS bilayer, using density functional theory. A commensurate 2D heterostructure film and the corresponding 3D periodic bulk structure are compared. The results find such a heterostructure to be stable and possess p-type semiconducting characteristics. Due to the heterostructure’s weak interlayer bonding, its carrier mobility is essentially governed by the constituent layers; the hole mobility is governed by the PbS bilayer, whereas the electron mobility is governed by the MoS2 monolayer. Furthermore, we estimate the hole mobility to be relatively high (~106 cm2V−1s−1), which can be useful for ultra-fast devices at the nanoscale.
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6

Liu, Zixiang, and Zhiguo Wang. "Electronic Properties of MTe2/AsI3(M=Mo and W) Van der Waals Heterostructures." MATEC Web of Conferences 380 (2023): 01011. http://dx.doi.org/10.1051/matecconf/202338001011.

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Two dimensional (2D) materials with unique physical or chemical prperties has triggered worldwide interest in the fields of material science, condensed matter physics, and devices physics. Vertically stacking different 2D materials enables the creation of a large variety of van der Waals heterostructures. The van der Waals heterostructures robust the merits of the 2D materials electronic prperties. Using density functional theory calculations, the electronic structure of MTe2/AsI3(M=Mo and W) Van der Waals heterostructures are investigated in this work. The results show by stacking MTe2(M=Mo and W) and AsI3 vertically, a strongly binding vdW heterostructure with a type-II band alignment can be formed, which gives expectation of high multifunctional electronic performance. This theoretical study provides vital insights of 2D materials and their heterostructures which could be potential candidates for future nanoelectronic applications.
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7

You, Siwen, Xiao Guo, Junjie Jiang, Dingbang Yang, Mingjun Li, Fangping Ouyang, Haipeng Xie, Han Huang, and Yongli Gao. "Temperature−Dependent Raman Scattering Investigation on vdW Epitaxial PbI2/CrOCl Heterostructure." Crystals 13, no. 1 (January 6, 2023): 104. http://dx.doi.org/10.3390/cryst13010104.

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Van der Waals (vdW) epitaxial growth provides an efficient strategy to prepare heterostructures with atomically and electronically sharp interfaces. Herein, PbI2 was in situ thermally deposited onto exfoliated thin−layered CrOCl nanoflakes in high vacuum to fabricate vdW PbI2/CrOCl heterostructures. Optical microscopy, atomic force microscopy, X−ray diffraction, and temperature−dependent Raman spectroscopy were used to investigate the structural properties and phonon behaviors of the heterostructures. The morphology of PbI2 films on the CrOCl substrate obviously depended on the substrate temperature, changing from hemispherical granules to 2D nanoflakes with flat top surfaces. In addition, anomalous blueshift of the Ag1 and Au2 modes as the temperature increased in PbI2/CrOCl heterostructure was observed for the first time. Our results provide a novel material platform for the vdW heterostructure and a possible method for optimizing heterostructure growth behaviors.
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8

Sun, Cuicui, and Meili Qi. "Hybrid van der Waals heterojunction based on two-dimensional materials." Journal of Physics: Conference Series 2109, no. 1 (November 1, 2021): 012012. http://dx.doi.org/10.1088/1742-6596/2109/1/012012.

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Abstract Since the discovery of graphene, two-dimensional (2D) layered materials have always been the focus of material research. The layers of 2D materials are covalent bonds, and the layers are weakly bonded to adjacent layers through van der Waals (vdW) interactions. Since any dangling-bond-free surface could be combined with another material through vdW forces, the concept can be extended. This can refer to the integration of 2D materials with any other non-2D materials through non-covalent interactions. The emerging mixed-dimensional (2D+nD, where n is 0, 1 or 3) heterostructure devices has been studied and represents a wider range of vdW heterostructures. New electronic devices and optoelectronic devices based on such heterojunctions have unique functions. Therefore, this article depicts the research progress of (2D+nD, where n is 0, 1 or 3) vdW heterojunctions based on 2D materials.
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9

Li, Xufan, Ming-Wei Lin, Junhao Lin, Bing Huang, Alexander A. Puretzky, Cheng Ma, Kai Wang, et al. "Two-dimensional GaSe/MoSe2misfit bilayer heterojunctions by van der Waals epitaxy." Science Advances 2, no. 4 (April 2016): e1501882. http://dx.doi.org/10.1126/sciadv.1501882.

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Two-dimensional (2D) heterostructures hold the promise for future atomically thin electronics and optoelectronics because of their diverse functionalities. Although heterostructures consisting of different 2D materials with well-matched lattices and novel physical properties have been successfully fabricated via van der Waals (vdW) epitaxy, constructing heterostructures from layered semiconductors with large lattice misfits remains challenging. We report the growth of 2D GaSe/MoSe2heterostructures with a large lattice misfit using two-step chemical vapor deposition (CVD). Both vertically stacked and lateral heterostructures are demonstrated. The vertically stacked GaSe/MoSe2heterostructures exhibit vdW epitaxy with well-aligned lattice orientation between the two layers, forming a periodic superlattice. However, the lateral heterostructures exhibit no lateral epitaxial alignment at the interface between GaSe and MoSe2crystalline domains. Instead of a direct lateral connection at the boundary region where the same lattice orientation is observed between GaSe and MoSe2monolayer domains in lateral GaSe/MoSe2heterostructures, GaSe monolayers are found to overgrow MoSe2during CVD, forming a stripe of vertically stacked vdW heterostructures at the crystal interface. Such vertically stacked vdW GaSe/MoSe2heterostructures are shown to formp-njunctions with effective transport and separation of photogenerated charge carriers between layers, resulting in a gate-tunable photovoltaic response. These GaSe/MoSe2vdW heterostructures should have applications as gate-tunable field-effect transistors, photodetectors, and solar cells.
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10

Song, Tiancheng, Xinghan Cai, Matisse Wei-Yuan Tu, Xiaoou Zhang, Bevin Huang, Nathan P. Wilson, Kyle L. Seyler, et al. "Giant tunneling magnetoresistance in spin-filter van der Waals heterostructures." Science 360, no. 6394 (May 3, 2018): 1214–18. http://dx.doi.org/10.1126/science.aar4851.

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Magnetic multilayer devices that exploit magnetoresistance are the backbone of magnetic sensing and data storage technologies. Here, we report multiple-spin-filter magnetic tunnel junctions (sf-MTJs) based on van der Waals (vdW) heterostructures in which atomically thin chromium triiodide (CrI3) acts as a spin-filter tunnel barrier sandwiched between graphene contacts. We demonstrate tunneling magnetoresistance that is drastically enhanced with increasing CrI3 layer thickness, reaching a record 19,000% for magnetic multilayer structures using four-layer sf-MTJs at low temperatures. Using magnetic circular dichroism measurements, we attribute these effects to the intrinsic layer-by-layer antiferromagnetic ordering of the atomically thin CrI3. Our work reveals the possibility to push magnetic information storage to the atomically thin limit and highlights CrI3 as a superlative magnetic tunnel barrier for vdW heterostructure spintronic devices.
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Більше джерел

Дисертації з теми "Van der Waals (vdW) heterostructures"

1

Menon, Vaidehi. "Stiffness and Strain Sensitivity of Graphene-CNT van der Waals Heterostructures: Molecular Dynamics Study." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1595938261814484.

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2

Boddison-Chouinard, Justin. "Fabricating van der Waals Heterostructures." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38511.

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The isolation of single layer graphene in 2004 by Geim and Novoselov introduced a method that researchers could extend to other van der Waals materials. Interesting and new properties arise when we reduce a crystal to two dimensions where they are often different from their bulk counterpart. Due to the van der Waals bonding between layers, these single sheets of crystal can be combined and stacked with diferent sheets to create novel materials. With the goal to study the interesting physics associated to these stacks, the focus of this work is on the fabrication and characterization of van der Waals heterostructures. In this work, we first present a brief history of 2D materials, the fabrication of heterostructures, and the various tools used to characterize these materials. We then give a description of the custom-built instrument that was used to assemble various 2D heterostructures followed by the findings associated with the optimization of the cleanliness of the stack's interface and surface. Finally, we discuss the results related to the twisting of adjacent layers of stacked MoS2 and its relation to the interlayer coupling between said layers.
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3

Mauro, Diego. "Electronic properties of Van der Waals heterostructures." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10565/.

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L’interazione spin-orbita (SOI) nel grafene è attualmente oggetto di intensa ricerca grazie alla recente scoperta di una nuova classe di materiali chiamati isolanti topologici. Questi materiali, la cui esistenza è strettamente legata alla presenza di una forte SOI, sono caratterizzati dall’interessante proprietà di avere un bulk isolante ed allo stesso tempo superfici conduttrici. La scoperta teorica degli isolanti topologici la si deve ad un lavoro nato con l’intento di studiare l’influenza dell’interazione spin-orbita sulle proprietà del grafene. Poichè questa interazione nel grafene è però intrinsecamente troppo piccola, non è mai stato possibile effettuare verifiche sperimentali. Per questa ragione, vari lavori di ricerca hanno recentemente proposto tecniche volte ad aumentare questa interazione. Sebbene alcuni di questi studi abbiano mostrato un effettivo aumento dell’interazione spin-orbita rispetto al piccolo valore intrinseco, sfortunatamente hanno anche evidenziato una consistente riduzione della qualità del grafene. L’obbiettivo che ci si pone in questa tesi è di determinare se sia possibile aumentare l’interazione spin-orbita nel grafene preservandone allo stesso tempo le qualità. La soluzione proposta in questo lavoro si basa sull’utilizzo di due materiali semiconduttori, diselenio di tungsteno WSe2 e solfuro di molibdeno MoS2, utilizzati da substrato su cui sopra verrà posizionato il grafene formando così un’eterostruttura -nota anche di “van der Waal” (vdW)-. Il motivo di questa scelta è dovuto al fatto che questi materiali, appartenenti alla famiglia dei metalli di transizione dicalcogenuri (TMDS), mostrano una struttura reticolare simile a quella del grafene, rendendoli ideali per formare eterostrutture e ancora più importante, presentano una SOI estremamente grande. Sostanzialmente l’idea è quindi di sfruttare questa grande interazione spin-orbita del substrato per indurla nel grafene aumentandone così il suo piccolo valore intrinseco.
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4

Marsden, Alexander J. "Van der Waals epitaxy in graphene heterostructures." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/77193/.

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Анотація:
Graphene — a two-dimensional sheet of carbon atoms — has surged into recent interest with its host of remarkable properties and its ultimate thinness. However, graphene combined with other materials is starting to attract more attention. These heterostructures can be important for production routes, incorporating graphene into existing technologies, or for modifying its intrinsic properties. This thesis aims to examine the role of van der Waals epitaxy within these heterostructures. First, the graphene-copper interaction during chemical vapour deposition of graphene is investigated. Graphene is found to grow with a mismatch epitaxy of 8 relative to the [001] direction of the Cu(100) surface, despite a mismatch in symmetry and lattice parameter between two. Further, the electronic structure of both graphene and copper is unchanged by the interaction. This highlights the weak interaction between the two, owing to its van der Waals nature. Functionalised graphene is another important heterostructure, and is intensively studied for both graphene production routes and for altering graphene’s properties. Here, it is the change to the homogeneous graphene surface that makes it interesting for van der Waals epitaxy. The effect of functionalisation of graphene with atomic oxygen and nitrogen is presented next. In both cases, only small amounts of functionalisation ( 5 at%) is sufficient to significantly deteriorate the -band structure of the graphene through localisation. For small amounts of nitrogen functionalisation, and greater amounts of oxygen functionalisation, extended topological defects are formed in the graphene lattice. Unlike epoxide oxygen groups, these disruptions to the pristine graphene are found to be irreversible by annealing. Next, the interaction between graphene and the organic semiconducting molecule vanadyl-phthalocyanine (VOPc) is presented. As a result of the van der Waals nature of the graphene surface, VOPc molecules can form crystals microns in size when deposited onto a substrate with an elevated temperature of 155 C; at ambient temperatures, the crystals are only tens of nanometres across. In contrast, the functionalised graphene oxide surface prevents large crystal growth, even at elevated temperatures, because surface functionalities inhibit molecule diffusion. This highlights the importance of graphene as a substrate for molecular crystal growth, even when the growth is not epitaxial. Finally, the supramolecular assembly of trimesic acid (TMA) and terephthalic acid (TPA) is presented. Despite their chemical similarity they display different behaviour as they transition from monolayers to three-dimensional structures: for TMA, the epitaxial chicken wire structure seen at a monolayer templates up through the layers as molecules stack, until a thickness of 20 nm, when random in-plane orientations appear; on the other hand, TPA forms a brickwork structure at the monolayer, which quickly transitions to fibre-like crystals with a bulk structure for the thin films. However, the TPA orientation is still determined by the epitaxy with the graphene substrate, although this is significantly weaker than for TMA.
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5

Coy, Diaz Horacio. "Preparation and Characterization of Van der Waals Heterostructures." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6212.

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In this dissertation different van der Waals heterostructures such as graphene-MoS2 and MoTe2-MoS2 were prepared and characterized. In the first heterostructure, polycrystalline graphene was synthesized by chemical vapor deposition and transferred on top of MoS2 single crystal. In the second heterostructure, MoTe2 monolayers were deposited on MoS2 by molecular beam epitaxy. Characterization of graphene-MoS2 heterostructures was conducted by spin and angle resolve spectroscopy which showed that the electronic structure of the bulk MoS2 and graphene in this van der Waals heterostructures is modified. For MoS2 underneath the graphene, a band structure renormalization and spin polarization are observed. The band structure of MoS2 is modified because the graphene induces screening which shifts the Г-point ~150 meV to lower binding compared to the sample without graphene. The spin polarization is explained by the dipole arising from band bending which breaks the symmetry at the MoS2 surface. For graphene, the band structure at lower binding energy shows that the Dirac cone remains intact with no significant doping. Instead, away from the Fermi level the formation of several gaps in the pi-band due to hybridization with states from the MoS2 is observed. For the heterostructures made depositing monolayer of MoTe2 on MoS2, the morphology, structure and electronic structure were studied. Two dimensional growth is observed under tellurium rich growth conditions and a substrate temperature of 200 °C but formation of a complete monolayer was not achieved. The obtained MoTe2 monolayer shows a high density of the mirror-twins grain boundaries arranged in a pseudo periodic wagon wheel pattern with a periodicity of ~2.6 nm. These grain boundary are formed due to Te-deficiency during the growth. The defect states from these domain boundary pin the Fermi level in MoTe2 and thus determine the band alignment in the MoTe2-MoS2 heterostructures.
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6

Ma, Qiong Ph D. Massachusetts Institute of Technology. "Optoelectronics of graphene-based Van der Waals heterostructures." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104523.

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Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Research on van der Waals (vdW) materials (homo- or hetero-) is a rapidly emerging field in condensed matter physics. They are layered structures with strong chemical bonding within layers and relatively weak van der Waals force to combine layers together. This unique layer-bylayer nature makes it easy to exfoliate layers out and at the same time to re-assemble in arbitrary sequences with different combinations. The versatility, flexibility, and relatively low cost of production make the scientific community enthusiastic about their future. In this thesis, I investigate the fundamental physical processes of light-matter interactions in these layered structures, including graphene, boron nitride, transition metal dichalcogenides and heterostructures formed from these materials. My research involves state-of-the-art nanoscale fabrication and microscale photocurrent spectroscopy and imaging. In Chapter 1, 1 will briefly discuss basic physical properties of the vdW materials involved in this thesis and introduce the main nanofabrication and measurement techniques. Chapter 2-4 are about hot electron dynamics and electron-phonon coupling in intrinsic graphene systems, among which Chapter 2 is focusing on the generation mechanism of the photocurrent at the p-n interface, which is demonstrated to have a photothermoelectric origin. This indicates a weak electron-phonon coupling strength in graphene. Chapter 3 is a direct experimental follow-up of the work in Chapter 2 and reveals the dominant electron-phonon coupling mechanism at different temperature and doping regimes. In Chapter 4, I present the observation of anomalous geometric photocurrent patterns in various devices at the charge neutral point. The spatial pattern can be understood as a local photo-generated current near edges being collected by remote electrodes. The anomalous behavior as functions of change density and temperature indicates an interesting regime of energy and charge dynamics. In Chapter 5 and 6, 1 will show the photoresponse of graphene-BN heterostuctures. In graphene-BN stack directly on SiO₂, we observed strong photo-induced doping phenomenon, which can be understood as charge transfer from graphene across BN and eventually trapped at the interface between BN and SiO₂. By inserting another layer of graphene between BN and SiO₂ , we can measure an electrical current after photoexcitation due to such charge transfer. We further studied the competition between this vertical charge transfer and in-plane carrier-carrier scattering in different regimes. In Chapter 7, I will briefly summarize collaborated work with Prof. Dimitri Basov's group on near-field imaging of surface polariton in two-dimensional materials. This technique provides a complementary tool to examine the intriguing light-matter interaction (for large momentum excitations) in low-dimensional materials. Chapter 8 is the outlook, from my own point of view, what more can be done following this thesis.
by Qiong Ma.
Ph. D.
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7

Khestanova, Ekaterina. "Van der Waals heterostructures : fabrication, mechanical and electronic properties." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/van-der-waals-heterostructures-fabrication-mechanical-and-electronic-properties(047ce24b-7a58-4192-845d-54c7506f179f).html.

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The fast progress in the exploration of 2D materials such as graphene became possible due to development of fabrication techniques that allowed these materials to be protected from e.g. undesirable doping and gave rise to new functionalities realized within van der Waals heterostructures. Attracted by van der Waals interaction the constituent layers of such heterostructures preserve their exceptional electronic quality and for example in graphene allow for high electron mobility to be achieved. However, the studies of atomically thin layers such as NbSe2 that exhibit metallic behavior have been impeded by their reactivity and hence oxidation during exposure to ambient or oxidizing agents such as solvents. In this thesis, the existing heterostructure assembly technique was improved by the introduction of exfoliation and re-stacking by a fully motorized system placed in an inert atmosphere. This approach allowed us to overcome the problem of environmental degradation and create Hall bars and planar tunnel junctions from atomically thin superconducting NbSe2. Furthermore, this versatile approach allowed us to study the thickness dependence of the normal and superconducting state transport properties of NbSe2, uncovering the reduction of the superconducting energy gap and transition temperature in the thinnest samples. On the other hand, 2D materials being just 1-3 atoms thick represent an ultimate example of a membrane - thin but laterally extended object. Consisting of such atomically thin membranes the van der Waals heterostructures can be used for purposes other than the studies of electronic transport. In this work, ubiquitous bubbles occurring during van der Waals heterostructure assembly are employed as a tool to explore 2D materials' mechanical properties and mutual adhesion. This allowed us to measure Young's modulus of graphene and other 2D materials under 1-2% strain and deduce the internal pressure that can reach up to 1 GPa in sub-nanometer size bubbles.
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8

Yu, Geliang. "Transport properties of graphene based van der Waals heterostructures." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/transport-properties-of-graphene-based-van-der-waals-heterostructures(5cbb782f-4d49-42da-a05e-15b26606e263).html.

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Анотація:
In the past few years, led by graphene, a large variety of two dimensional (2D) materials have been discovered to exhibit astonishing properties. By assembling 2D materials with different designs, we are able to construct novel artificial van der Waals (vdW) heterostructures to explore new fundamental physics and potential applications for future technology. This thesis describes several novel vdW heterostructures and their fundamental properties. At the beginning, the basic properties of some 2D materials and assembled vdW heterostructures are introduced, together with the fabrication procedure and transport measurement setups. Then the graphene based capacitors on hBN (hexagonal Boron Nitride) substrate are studied, where quantum capacitance measurements are applied to determine the density of states and many body effects. Meanwhile, quantum capacitance measurement is also used to search for alternative substrates to hBN which allow graphene to exhibit micrometer-scale ballistic transport. We found that graphene placed on top of MoS2 and TaS2 show comparable mobilities up to 60,000cm2/Vs. After that, the graphene/hBN superlattices are studied. With a Hall bar structure based on the superlattices, we find that new Dirac minibands appear away from the main Dirac cone with pronounced peaks in the resistivity and are accompanied by reversal of the Hall effects. With the capacitive structure based on the superlattices, quantum capacitance measurement is used to directly probe the density states in the graphene/hBN superlattices, and we observe a clear replica spectrum, the Hofstadter-butterfly fan diagram, together with the suppression of quantum Hall Ferromagnetism. In the final part, we report on the existence of the valley current in the graphene/hBN superlattice structure. The topological current originating from graphene’s two valleys flows in opposite directions due to the broken inversion symmetry in the graphene/hBN superlattice, meaning an open band gap in graphene.
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9

Tomarken, Spencer Louis. "Thermodynamic and tunneling measurements of van der Waals heterostructures." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123567.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 201-212).
In certain electronic systems, strong Coulomb interactions between electrons can favor novel electronic phases that are difficult to anticipate theoretically. Accessing fundamental quantities such as the density of states in these platforms is crucial to their analysis. In this thesis, I explore the application of two measurement techniques towards this goal: capacitance measurements that probe the thermodynamic ground state of an electronic system and planar tunneling measurements that access its quasiparticle excitation spectrum. Both techniques were applied to van der Waals materials, a class of crystals composed of layered atomic sheets with weak interplane bonding which permits the isolation of single and few-layer sheets that can be manually assembled into heterostructures. Capacitance measurements were performed on a material system commonly known as magic-angle twisted bilayer graphene (MATBG).
When two monolayers of graphene, a single sheet of graphite, are stacked on top of one another with a relative twist between their crystal axes, the resultant band structure is substantially modified from the cases of both monolayer graphene and Bernal-stacked (non-twisted) bilayer graphene. At certain magic angles, the low energy bands become extremely flat, quenching the electronic kinetic energy and allowing strong electron-electron interactions to become relevant. Exotic insulating and superconducting phases have been observed using conventional transport measurements. By accessing the thermodynamic density of states of MATBG, we estimate its low energy bandwidth, Fermi velocity, and interaction-driven energy gaps. Time-domain planar tunneling was performed on a heterostructure that consisted of monolayer graphene and hexagonal boron nitride (serving as the dielectric and tunnel barrier) sandwiched between a graphite tunneling probe and metal gate.
Tunneling currents were induced by applying a sudden voltage pulse across the full parallel plate structure. The lack of in-plane charge motion allowed access to the tunneling density of states even when the heterostructure was electrically insulating in the quantum Hall regime. These measurements represent the first application of time-domain planar tunneling to the van der Waals class of materials, an important step in extending the technique to new material platforms.
by Spencer Louis Tomarken.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Physics
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10

Luo, Yuanhong Ph D. Massachusetts Institute of Technology. "Twist angle physics in graphene based van der Waals heterostructures." Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119050.

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Анотація:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2018.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged student-submitted from PDF version of thesis.
Includes bibliographical references (pages 121-131).
In this thesis, I present my experimental work on twisted bilayer graphene, a van der Waals heterostructure consisting of two graphene sheets stack on top of each other. In particular, the twist angle is a new degree of freedom in this system, and has an important effect in the determination of its transport properties. The work presented will explore the twist-dependent physics in two regimes: the large twist angle and small twist angle regimes. In the large-twist angle limit, the two sheets have little interlayer interactions and are strongly decoupled, allowing us to put independent quantum Hall edge modes in both layers. We study the edge state interactions in this system, culminating in the formation of a quantum spin Hall state in twisted bilayer graphene. In the small twist angle limit, interlayer interactions are strong and the layers are strongly hybridized. Additionally, a new long-range moiré phenomenon emerges, and we study the effects of the interplay between moiré physics and interlayer interactions on its transport properties.
by Yuanhong Luo.
Ph. D.
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Книги з теми "Van der Waals (vdW) heterostructures"

1

Holwill, Matthew. Nanomechanics in van der Waals Heterostructures. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18529-9.

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2

Finney, Nathan Robert. Symmetry engineering via angular control of layered van der Waals heterostructures. [New York, N.Y.?]: [publisher not identified], 2021.

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Holwill, Matthew. Nanomechanics in van der Waals Heterostructures. Springer, 2019.

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4

2D Materials and Van der Waals Heterostructures. MDPI, 2020. http://dx.doi.org/10.3390/books978-3-03928-769-7.

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5

Zhang, Zheng, and Yue Zhang. Van der Waals Heterostructures: Fabrications, Properties and Applications. Wiley & Sons, Incorporated, John, 2022.

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6

Zhang, Zheng, and Yue Zhang. Van der Waals Heterostructures: Fabrications, Properties and Applications. Wiley & Sons, Limited, John, 2022.

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7

Zhang, Zheng, and Yue Zhang. Van der Waals Heterostructures: Fabrications, Properties and Applications. Wiley & Sons, Incorporated, John, 2022.

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8

Zhang, Zheng, and Yue Zhang. Van der Waals Heterostructures: Fabrications, Properties and Applications. Wiley & Sons, Incorporated, John, 2022.

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Частини книг з теми "Van der Waals (vdW) heterostructures"

1

Holwill, Matthew. "van der Waals Heterostructures." In Nanomechanics in van der Waals Heterostructures, 19–31. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18529-9_3.

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2

Lui, C. H. "Raman Spectroscopy of van der Waals Heterostructures." In Raman Spectroscopy of Two-Dimensional Materials, 81–98. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-1828-3_4.

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3

Holwill, Matthew. "Introduction." In Nanomechanics in van der Waals Heterostructures, 1–6. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18529-9_1.

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4

Holwill, Matthew. "Properties of Two-Dimensional Materials." In Nanomechanics in van der Waals Heterostructures, 7–17. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18529-9_2.

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5

Holwill, Matthew. "Fabrication and Characterisation Techniques." In Nanomechanics in van der Waals Heterostructures, 33–51. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18529-9_4.

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6

Holwill, Matthew. "Studying Superlattice Kinks via Electronic Transport." In Nanomechanics in van der Waals Heterostructures, 53–70. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18529-9_5.

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7

Holwill, Matthew. "Atomic Force Microscopy Studies of Superlattice Kinks." In Nanomechanics in van der Waals Heterostructures, 71–83. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18529-9_6.

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8

Holwill, Matthew. "Additional Work." In Nanomechanics in van der Waals Heterostructures, 85–91. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18529-9_7.

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9

Holwill, Matthew. "Conclusions and Future Work." In Nanomechanics in van der Waals Heterostructures, 93–94. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-18529-9_8.

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10

Roy, Kallol. "Photoresponse in Graphene-on-MoS$$_2$$ Heterostructures." In Optoelectronic Properties of Graphene-Based van der Waals Hybrids, 141–56. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-59627-9_6.

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Тези доповідей конференцій з теми "Van der Waals (vdW) heterostructures"

1

Okada, Mitsuhiro, Yusuke Kureishi, Alex Kutana, Kenji Watanabe, Takashi Taniguchi, Hisanori Shinohara, and Ryo Kitaura. "Identification of PL emissions from Interlayer Excitons in 2D van der Waals Heterostructures." In JSAP-OSA Joint Symposia. Washington, D.C.: Optica Publishing Group, 2017. http://dx.doi.org/10.1364/jsap.2017.7a_a404_3.

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Two-dimensional (2D) semiconductors, including MoS2, WS2, MoSe2, etc., have provided a fascinating opportunity to explore optical properties in 2 dimensions. In particular, van der Waals (vdW) heterostructures composed of these 2D semiconductors, such as WS2/MoS2, offer a novel platform for optical physics arising from interlayer excitons. It is, however, not straightforward to understand optical response from interlayer excitons because contributions from interlayer excitons with different transition energies overlap to a show broad peak in optical spectra. In this work, we have focused on the assignment of PL emission from interlayer excitons by using hBN-sandwiched high-quality samples.
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2

Ghanekar, Alok, Yi Zheng, Weixing Zhang, and Zongqin Zhang. "Selective Emission Properties and vdW Energy of Micro/Nano-Sized Spherical Shapes." In ASME 2016 Heat Transfer Summer Conference collocated with the ASME 2016 Fluids Engineering Division Summer Meeting and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/ht2016-7494.

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Near-field thermal radiation and van der Waal force between flat plates and curved surfaces have been probed in the past; however the peculiarities of radiative heat transfer and van der Waals stress due to fluctuations of electromagnetic fields for micro/nano-sized spherical objects have not been studied in great details. We demonstrate how fluctuational electrodynamics can be used to determine emissivity and van der Waals contribution to surface energy for various spherical shapes in a homogeneous and isotropic medium. The dyadic Green’s function formalism of radiative energy and fluctuation-induced van der Waals stress for different spherical configurations has been developed. We present the calculations for a single sphere, a bubble, a spherical shell and a coated sphere. We observe that emission spectrum ofmicro/nanoscale spheres displays several sharp peaks as the size of object reduces. Our calculations indicate that surface energy becomes size dependent (r-3) due to van der Waals phenomena for small radii.
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3

Heinz, Tony F. "Optical Properties of van der Waals Heterostructures." In Laser Science. Washington, D.C.: OSA, 2015. http://dx.doi.org/10.1364/ls.2015.lw4h.1.

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4

Roy, T., M. Tosun, M. Amani, D. H. Lien, D. Kiriya, P. Zhao, S. Desai, A. Sachid, S. R. Madhvapathy, and A. Javey. "Van der Waals heterostructures for tunnel transistors." In 2015 Fourth Berkeley Symposium on Energy Efficient Electronic Systems (E3S). IEEE, 2015. http://dx.doi.org/10.1109/e3s.2015.7336791.

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5

Pramanik, Nikhil, Sunchao Huang, Ruihuan Duan, Chris Boothroyd, Zheng Liu, and Liang Jie Wong. "Tunable Table-Top X-Rays from Tilted Van Der Waals Crystals." In CLEO: QELS_Fundamental Science. Washington, D.C.: Optica Publishing Group, 2022. http://dx.doi.org/10.1364/cleo_qels.2022.fth4a.3.

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We theoretically predict and experimentally demonstrate unprecedented versatility in free electron-driven X-ray sources based on van der Waals (vdW) materials. By controlling the crystal tilt, we broaden the accessible X-ray photon range by over 100%.
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6

Matsuoka, Hiroshige, Niki Kitahama, Teppei Tanaka, and Shigehisa Fukui. "Theoretical Study of van der Waals Dispersion Pressures Considering One-Dimensional Material Distributions in In-Plane Direction." In ASME 2013 Conference on Information Storage and Processing Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/isps2013-2845.

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The van der Waals (vdW) dispersion pressures between a half-space consisting of a uniform material and a half-space with one-dimensional material distribution in the in-plane direction have been theoretically derived. Two patterns of material distribution were considered here, i.e., a periodic distribution of materials (Pattern 1) and a distribution of two materials with single interface (Pattern 2). The vdW pressure for Pattern 1 was derived based on a Fourier series, while the vdW pressure for Pattern 2 was derived as elementary functions. The basic characteristics of these vdW pressures were clarified.
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7

Zheng, Yi, and Arvind Narayanaswamy. "A First-Principles Method of Determining Van Der Waals Forces in a Dissipative Media." In ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/mnhmt2012-75165.

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Lifshitz theory of van der Waals (vdW) force and energy is strictly valid when the location at which the stress tensor is calculated is in vacuum. Generalization of Lifshitz theory to the case when the stress tensor is to be calculated in a dissipative material, as opposed to vacuum, is a surprisingly difficult undertaking because there is no expression for the electromagnetic stress tensor in dissipative materials. Here, we derive the expression for vdW force in planar dissipative media by calculating the Maxwell stress tensor in a fictious layer of vacuum, that is eventually made to vanish, introduced in the structure, without employing the complicated quantum field theoretic method proposed by Dzyaloshinskii, Lifshitz, and Pitaevskii. Even though this work has proven to be a corroboration of Dzyaloshinskii et al., it has thrown new light on our understanding of vdW forces and suggests that it should be possible to achieve the similar result for objects with arbitrary shapes.
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8

Tsoukalas, Athanasios, and Anthony Tzes. "Modelling and Adaptive Control of Tendon-Driven Micromanipulators in the Presence of Van-der-Waals Forces." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59542.

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In this article, the design problem of an adaptive controller for a robotic micromanipulator, including the effects of the applied Van der Waals (VdW) forces is considered. The micro-manipulator’s dynamic model is appropriately modified in order to include the interaction of the attractive VdW-forces. Inhere, every link is decomposed into a series of elementary particles (e.g. spheres), each one interacting with the robot’s neighboring objects during its motion. This interaction induces nonlinear additive terms in the model, attributed to the overall effect of the VdW-forces. The actuation is achieved by a tendon-driven system. At each joint, a pair of tendons is attached and act in an almost passive antagonistic manner. The kinematic and dynamic analysis of the tendon-driven actuation mechanism is offered. Consequently, the microrobot’s model is shown to be linearly parameterizable. Subject to this observation, a globally stabilizable adaptive control scheme is derived, estimating the unknown parameters (masses, generalized VdW-forces) and compensating any variations of those. Simulation studies on a 2-DOF micro-manipulator are offered to highlight the effectiveness of the proposed scheme.
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9

Hashemi, Daniel, Stefan C. Badescu, Michael Snure, and Michael Snure. "Band Alignment in Van der Waals Phosphorous Heterostructures." In THE 3rd INTERNATIONAL CONFERENCE ON THEORETICAL AND APPLIED NANOSCIENCE AND NANOTECHNOLOGY. Avestia Publishing, 2019. http://dx.doi.org/10.11159/tann19.130.

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10

Plochocka, Paulina. "Excitons in MoS2/MoSe2 Van der Waals heterostructures." In nanoGe Fall Meeting 2019. València: Fundació Scito, 2019. http://dx.doi.org/10.29363/nanoge.ngfm.2019.443.

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Звіти організацій з теми "Van der Waals (vdW) heterostructures"

1

Kim, Philip. Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures. Fort Belvoir, VA: Defense Technical Information Center, March 2015. http://dx.doi.org/10.21236/ada616377.

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