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Artykuły w czasopismach na temat "MoS2 graphene heterostructures"
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Dong, Haocong, Junzhu Li, Mingguang Chen, Hongwei Wang, Xiaochuan Jiang, Yongguang Xiao, Bo Tian i Xixiang Zhang. "High-throughput Production of ZnO-MoS2-Graphene Heterostructures for Highly Efficient Photocatalytic Hydrogen Evolution". Materials 12, nr 14 (11.07.2019): 2233. http://dx.doi.org/10.3390/ma12142233.
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High-throughput production of highly efficient photocatalysts for hydrogen evolution remains a considerable challenge for materials scientists. Here, we produced extremely uniform high-quality graphene and molybdenum disulfide (MoS2) nanoplatelets through the electrochemical-assisted liquid-phase exfoliation, out of which we subsequently fabricated MoS2/graphene van der Waals heterostructures. Ultimately, zinc oxide (ZnO) nanoparticles were deposited into these two-dimensional heterostructures to produce an artificial ZnO/MoS2/graphene nanocomposite. This new composite experimentally exhibited an excellent photocatalytic efficiency in hydrogen evolution under the sunlight illumination ( λ > 400 n m ), owing to the extremely high electron mobilities in graphene nanoplatelets and the significant visible-light absorptions of MoS2. Moreover, due to the synergistic effects in MoS2 and graphene, the lifetime of excited carriers increased dramatically, which considerably improved the photocatalytic efficiency of the ZnO/MoS2/graphene heterostructure. We conclude that the novel artificial heterostructure presented here shows great potential for the high-efficient photocatalytic hydrogen generation and the high throughput production of visible-light photocatalysts for industrial applications.
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Xiao, Haodong, Lin Lin, Jia Zhu, Junxiong Guo, Yizhen Ke, Linna Mao, Tianxun Gong, Huanyu Cheng, Wen Huang i Xiaosheng Zhang. "Highly sensitive and broadband photodetectors based on WSe2/MoS2 heterostructures with van der Waals contact electrodes". Applied Physics Letters 121, nr 2 (11.07.2022): 023504. http://dx.doi.org/10.1063/5.0100191.
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A nanoscale photodetector is a crucial part of intelligent imaging and wireless communication devices. Building van der Waals (vdWs) heterostructures based on two-dimensional transition metal dichalcogenides is thought to be a smart approach for achieving nanoscale photodetectors. However, the pinning effect induced by surface states, defects, and metal-induced gap states during the fabrication process of vdWs heterostructures and contacting electrodes leads to a large Schottky barrier and consequently limits the photoresponse of vdWs heterostructures. In this study, a photodetector based on the WSe2/MoS2 heterostructure with graphene (Gr)/indium tin oxide (ITO) hybrid electrodes has been fabricated. The vdWs contacts established between the exfoliated graphene layers and WSe2/MoS2 heterostructure are able to get rid of lattice damages caused by atom bombardment during the deposition of metal electrodes. In addition, the reduced Schottky barrier at graphene/heterostructure interfaces facilitates the transport of carriers. Experimental results show that the photodetector based on WSe2/MoS2 heterostructures with Gr/ITO hybrid electrodes exhibits a high responsivity of up to 1236.5 A W−1, a detectivity of up to 1.23 × 1013 Jones, and a fast response of 270/130 μs to light from the ultraviolet to near-infrared range.
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Cheng, Beitong, Yong Zhou, Ruomei Jiang, Xule Wang, Shuai Huang, Xingyong Huang, Wei Zhang i in. "Structural, Electronic and Optical Properties of Some New Trilayer Van de Waals Heterostructures". Nanomaterials 13, nr 9 (8.05.2023): 1574. http://dx.doi.org/10.3390/nano13091574.
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Constructing two-dimensional (2D) van der Waals (vdW) heterostructures is an effective strategy for tuning and improving the characters of 2D-material-based devices. Four trilayer vdW heterostructures, BP/BP/MoS2, BlueP/BlueP/MoS2, BP/graphene/MoS2 and BlueP/graphene/MoS2, were designed and simulated using the first-principles calculation. Structural stabilities were confirmed for all these heterostructures, indicating their feasibility in fabrication. BP/BP/MoS2 and BlueP/BlueP/MoS2 lowered the bandgaps further, making them suitable for a greater range of applications, with respect to the bilayers BP/MoS2 and BlueP/MoS2, respectively. Their absorption coefficients were remarkably improved in a wide spectrum, suggesting the better performance of photodetectors working in a wide spectrum from mid-wave (short-wave) infrared to violet. In contrast, the bandgaps in BP/graphene/MoS2 and BlueP/graphene/MoS2 were mostly enlarged, with a specific opening of the graphene bandgap in BP/graphene/MoS2, 0.051 eV, which is much larger than usual and beneficial for optoelectronic applications. Accompanying these bandgap increases, BP/graphene/MoS2 and BlueP/graphene/MoS2 exhibit absorption enhancement in the whole infrared, visible to deep ultraviolet or solar blind ultraviolet ranges, implying that these asymmetrically graphene-sandwiched heterostructures are more suitable as graphene-based 2D optoelectronic devices. The proposed 2D trilayer vdW heterostructures are prospective new optoelectronic devices, possessing higher performance than currently available devices.
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Wu, Shuang, Jifen Wang, Huaqing Xie i Zhixiong Guo. "Interfacial Thermal Conductance across Graphene/MoS2 van der Waals Heterostructures". Energies 13, nr 21 (9.11.2020): 5851. http://dx.doi.org/10.3390/en13215851.
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The thermal conductivity and interface thermal conductance of graphene stacked MoS2 (graphene/MoS2) van der Waals heterostructure were studied by the first principles and molecular dynamics (MD) simulations. Firstly, two different heterostructures were established and optimized by VASP. Subsequently, we obtained the thermal conductivity (K) and interfacial thermal conductance (G) via MD simulations. The predicted Κ of monolayer graphene and monolayer MoS2 reached 1458.7 W/m K and 55.27 W/m K, respectively. The thermal conductance across the graphene/MoS2 interface was calculated to be 8.95 MW/m2 K at 300 K. The G increases with temperature and the interface coupling strength. Finally, the phonon spectra and phonon density of state were obtained to analyze the changing mechanism of thermal conductivity and thermal conductance.
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Thompson, Jesse E., Brandon T. Blue, Darian Smalley, Fernand Torres-Davila, Laurene Tetard, Jeremy T. Robinson i Masahiro Ishigami. "STM Tip-Induced Switching in Molybdenum Disulfide-Based Atomristors". MRS Advances 4, nr 48 (2019): 2609–17. http://dx.doi.org/10.1557/adv.2019.322.
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ABSTRACTScanning tunneling microscopy and spectroscopy (STM/STS) are used to electronically switch atomically-thin memristors, referred to as “atomristors”, based on a graphene/molybdenum disulfide (MoS2)/Au heterostructure. A gold-assisted exfoliation method was used to produce near-millimeter (mm) scale MoS2 on Au thin-film substrates, followed by transfer of a separately exfoliated graphene top layer. Our results reveal that it is possible to switch the conductivity of a graphene/MoS2/Au memristor stack using an STM tip. These results provide a path to further studies of atomically-thin memristors fabricated from heterostructures of two-dimensional materials such as graphene and transition metal dichalcogenides (TMDs).
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Wu, Feng, Zijin Wang, Jiaqi He, Zhenzhe Li, Lijuan Meng i Xiuyun Zhang. "Effect of 3d Transition Metal Atom Intercalation Concentration on the Electronic and Magnetic Properties of Graphene/MoS2 Heterostructure: A First-Principles Study". Molecules 28, nr 2 (4.01.2023): 509. http://dx.doi.org/10.3390/molecules28020509.
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The electronic and magnetic properties of graphene/MoS2 heterostructures intercalated with 3d transition metal (TM) atoms at different concentrations have been systematically investigated by first principles calculations. The results showed that all the studied systems are thermodynamically stable with large binding energies of about 3.72 eV–6.86 eV. Interestingly, all the TM-intercalated graphene/MoS2 heterostructures are ferromagnetic and their total magnetic moments increase with TM concentration. Furthermore, TM concentration-dependent spin polarization is obtained for the graphene layer and MoS2 layer due to the charge transfer between TM atoms and the layers. A significant band gap is opened for graphene in these TM-intercalated graphene/MoS2 heterostructures (around 0.094 eV–0.37 eV). With the TM concentration increasing, the band gap of graphene is reduced due to the enhanced spin polarization of graphene. Our study suggests a research direction for the manipulation of the properties of 2D materials through control of the intercalation concentration of TM atoms.
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Han, Tao, Hongxia Liu, Shulong Wang, Shupeng Chen, Kun Yang i Zhandong Li. "Synthesis and Spectral Characteristics Investigation of the 2D-2D vdWs Heterostructure Materials". International Journal of Molecular Sciences 22, nr 3 (27.01.2021): 1246. http://dx.doi.org/10.3390/ijms22031246.
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Due to the attractive optical and electrical properties, van der Waals (vdWs) heterostructures constructed from the different two-dimensional materials have received widespread attention. Here, MoS2/h-BN, MoS2/graphene, WS2/h-BN, and WS2/graphene vdWs heterostructures are successfully prepared by the CVD and wet transfer methods. The distribution, Raman and photoluminescence (PL) spectra of the above prepared heterostructure samples can be respectively observed and tested by optical microscopy and Raman spectrometry, which can be used to study their growth mechanisms and optical properties. Meanwhile, the uniformity and composition distribution of heterostructure films can also be analyzed by the Raman and PL spectra. The internal mechanism of Raman and PL spectral changes can be explained by comparing and analyzing the PL and Raman spectra of the junction and non-junction regions between 2D-2D vdWs heterostructure materials, and the effect of laser power on the optical properties of heterostructure materials can also be analyzed. These heterostructure materials exhibit novel and unique optical characteristics at the stacking or junction, which can provide a reliable experimental basis for the preparation of suitable TMDs heterostructure materials with excellent performance.
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Grundmann, Annika, Clifford McAleese, Ben Richard Conran, Andrew Pakes, Dominik Andrzejewski, Tilmar Kümmell, Gerd Bacher i in. "MOVPE of Large-Scale MoS2/WS2, WS2/MoS2, WS2/Graphene and MoS2/Graphene 2D-2D Heterostructures for Optoelectronic Applications". MRS Advances 5, nr 31-32 (2020): 1625–33. http://dx.doi.org/10.1557/adv.2020.104.
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ABSTRACTMost publications on (opto)electronic devices based on 2D materials rely on single monolayers embedded in classical 3D semiconductors, dielectrics and metals. However, heterostructures of different 2D materials can be employed to tailor the performance of the 2D components by reduced defect densities, carrier or exciton transfer processes and improved stability. This translates to additional and unique degrees of freedom for novel device design. The nearly infinite number of potential combinations of 2D layers allows for many fascinating applications. Unlike mechanical stacking, metal-organic vapour phase epitaxy (MOVPE) can potentially provide large-scale highly homogeneous 2D layer stacks with clean and sharp interfaces. Here, we demonstrate the direct successive MOVPE of MoS2/WS2 and WS2/MoS2 heterostructures on 2” sapphire (0001) substrates. Furthermore, the first deposition of large-scale MoS2/graphene and WS2/graphene heterostructures using only MOVPE is presented and the influence of growth time on nucleation of WS2 on graphene is analysed.
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Rocha Robledo, Ana K., Mario Flores Salazar, Bárbara A. Muñiz Martínez, Ángel A. Torres-Rosales, Héctor F. Lara-Alfaro, Osvaldo Del Pozo-Zamudio, Edgar A. Cerda-Méndez, Sergio Jiménez-Sandoval i Andres De Luna Bugallo. "Interlayer charge transfer in supported and suspended MoS2/Graphene/MoS2 vertical heterostructures". PLOS ONE 18, nr 7 (25.07.2023): e0283834. http://dx.doi.org/10.1371/journal.pone.0283834.
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In this letter, we report on the optical and structural properties of supported and suspended MoS2/Graphene/MoS2 vertical heterostructures using Raman and photoluminescence (PL) spectroscopies. Vertical heterostructures (VH) are formed by multiple wet transfers on micro-sized holes in SiO2/Si substrates, resulting in VH with different configurations. The strong interlayer coupling is confirmed by Raman spectroscopy. Additionally, we observe an enhancement of the PL emission in the three-layer VH (either support or suspended) compared with bare MoS2 or MoS2/Graphene. This suggests the formation of a spatial type-II band alignment assisted by the graphene layer and thus, the operation of the VH as a n++/metal/n junction.
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Luu, Thi Ha Thu, Quang Trung Do, Manh Trung Tran, Tu Nguyen, Duy Hung Nguyen i Thanh Huy Pham. "Optical Properties of 1D ZnO/MoS\(_2\) Heterostructures Synthesized by Thermal Evaporation Method". Communications in Physics 32, nr 3 (22.06.2022): 319. http://dx.doi.org/10.15625/0868-3166/16867.
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MoS2 material attracts a great attention from researchers due to its graphene-like structure and the bandgap difference between its hexagonal monolayer and bulks. Recently, ZnO/MoS2 heterostructures have been received significant interest due to their distinguished properties. In this study, one-dimensional ZnO and ZnO/MoS2 heterostructures were successfully synthesized by a thermal co-evaporation method. Compare with ZnO, the band-to-band emission of ZnO/MoS2 heterostructures establishes a “blueshift” towards a shorter wavelength. It could be explained by the lattice strain in ZnO/MoS2 heterostructures due to the difference of primitive cell of ZnO and MoS2. Additionally, the quench in the visible region of the PL spectrum of ZnO/MoS2 heterostructures also explains the reduction of the defect in ZnO due to the presence of MoS2.
Rozprawy doktorskie na temat "MoS2 graphene heterostructures"
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Nasseri, Mohsen. "NANOSCALE DEVICES CONSISTING OF HETEROSTRUCTURES OF CARBON NANOTUBES AND TWO-DIMENSIONAL LAYERED MATERIALS". UKnowledge, 2018. https://uknowledge.uky.edu/physastron_etds/59.
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One dimensional carbon nanotubes (CNTs) and two-dimensional layered materials like graphene, MoS2, hexagonal boron nitride (hBN), etc. with different electrical and mechanical properties are great candidates for many applications in the future. In this study the synthesis and growth of carbon nanotubes on both conducting graphene and graphite substrates as well as insulating hBN substrate with precise crystallographic orientation is achieved. We show that the nanotubes have a clear preference to align to specific crystal directions of the underlying graphene or hBN substrate. On thicker flakes of graphite, the edges of these 2D materials can control the orientation of these carbon nanotubes. This integrated aligned growth of materials with similar lattices provides a promising route to achieving intricate nanoscale electrical circuits. Furthermore, short channel nanoscale devices consisting of the heterostructure of 1D and 2D materials are fabricated. In these nanoscale devices the nanogap is created due to etching of few layer graphene flake through hydrogenation and the channel is either carbon nanotubes or 2D materials like graphene and MoS2. Finally the transport properties of these nanoscale devices is studied.
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Chen, Zhesheng. "Novel two dimensional material devices : from fabrication to photo-detection". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066595/document.
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Au delà du graphène, de nouveaux semiconducteurs 2D tels que MoS2, GaS, GaSe et InSe deviennent pertinents pour les applications et dispositifs émergents. Dans cette thèse, nous fabriquons des échantillons de quelques feuillets atomiques de ces matériaux pour des dispositifs de photo-détecteurs et les caractérisons par microscopie optique, AFM et TEM. L'interaction de la lumière avec le substrat et le dispositif ultra-mince étant critique pour son fonctionnement, nous calculons et mesurons le contraste et l'intensité de la lumière diffusée par le dispositif. Nous caractérisons également la réponse Raman et la photoluminescence en fonction du nombre de couches pour étudier les propriétés vibrationnelles et électroniques. Plusieurs dispositifs ont été fabriqués et analysés. Nous examinons d'abord les dispositifs homogènes basés sur MoS2, GaSe ou InSe, et trouvons une excellente photosensibilité pour notre photo-détecteur MoS2. Nous examinons ensuite plusieurs hétéro-structures pour combiner les propriétés de chaque matériau et atteindre de meilleures performances. Le premier exemple est un photo-détecteur graphène/InSe dont la photosensibilité augmente de quatre ordres de grandeur par rapport à un dispositif basés sur InSe seul. Nous montrons également que la couche supérieure de graphène prévient la dégradation de couches atomiques ultra-minces dans l'air. Des hétéro-structures plus complexes graphène/InSe/graphène et graphène/InSe/Au montrent un effet photovoltaïque. Enfin, nous combinons InSe avec MoS2 et obtenons un dispositifs avec photo-réponse rapide, un comportement de type photo-diode, une distribution de photo-courant uniforme et un fort effet photovoltaïqueNovel two dimensional (2D) semiconductors beyond graphene such as MoS2, GaS, GaSe and InSe are increasingly relevant for emergent applications and devices. In this thesis, we fabricate these 2D samples for photo-detector applications and characterize them with optical microscopy, atomic force microscopy, Raman and photoluminescence (PL) spectroscopy and transmission electron microscopy. Since the interaction of light with the substrate and the ultra-thin photodetector device is critical for its functioning we calculate and measure optical contrast and intensity of light scattered from the device. We also characterize the Raman and PL response as a function of number of layers to study both vibrational properties and the band gap transition. For the device application, we first examine homogenous devices based on few-layer MoS2, GaSe and InSe respectively and find an excellent photoresponsivity in our few-layer MoS2 photo-detector. We then examine several geometries for heterostructure devices, which have the advantage of combining favorable properties of each material to reach better performances. The first example is a graphene/InSe photo-detector where the photoresponsivity increases by four orders of magnitude with respect to a few-layer InSe device while the top graphene layer is also shown to prevent degradation of ultra-thin atomic layers in air. Still more complex graphene/InSe/graphene and graphene/InSe/Au heterostructures show a photovoltaic effect. Finally for the first time, we combine InSe with MoS2 and obtain a high performance device with fast photo-response, photodiode like behavior, uniform photocurrent distribution and high photovoltaic effect
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MONSHI, MD Monirojjaman. "Band Gap Engineering of 2D Nanomaterials and Graphene Based Heterostructure Devices". FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3354.
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Two-Dimensional (2D) materials often exhibit distinguished properties as compared to their 3D counterparts and offer great potential to advance technology. However, even graphene, the first synthesized 2D material, still faces several challenges, despite its high mobility and high thermal conductivity. Similarly, germanene and silicene face challenges due to readily available semiconducting properties to be used in electronics, photonics or photocatalysis applications. Here, we propose two approaches to tune the band gap: One is by forming nanoribbon and edge functionalization and another by doping using inorganic nanoparticle’s interaction with 2D nanomaterials.
Edge functionalization of armchair germanene nanoribbons (AGeNRs) has the potential to achieve a range of band gaps. The edge atoms of AGeNRs are passivated with hydrogen (-H and -2H) or halogen (-F, -Cl,-OH, -2F,-2Cl) atoms. Using density functional theory calculations, we found that edge-functionalized AGeNRs had band gaps as small as 0.012 eV when functionalized by -2H and as high as 0.84 eV with -2F.
Doping can change the semiconducting behavior of AGeNRs to metal due to the half-filled band making it useful for negative differential resistance (NDR) devices. In the case of zigzag germanene nanoribbons (ZGeNRs), single N or B doping transformed them from anti-ferromagnetic (AFM) semiconducting to ferromagnetic (FM) semiconductor or half-metal. Lastly, formation and edge free energy studies revealed the feasibility of chemical synthetization of edge-functionalized and doped germanene.
Electronic, optical and transport properties of the graphene/ZnO heterostructure have been explored using first-principles density functional theory. The results show that Zn12O12 can open a band gap of 14.5 meV in graphene, increase its optical absorption by 1.67 times, covering the visible spectrum and extended to the infra-red (IR) range, and create slight nonlinear I-V characteristics depending on the applied bias. This agrees well with collaborative experimental measurement of a similar system.
In conclusion, we have successfully studied the potential use of edge functionalization, band gap periodicity in nanoribbon width, and doping in germanene nanoribbons. Structural stability was also studied to investigate the feasibility for experimental synthesization. Inorganic nanoparticle’s interaction with graphene envisages the possibility of fabricating photo-electronic device covering visible spectrum and beyond. Finally, graphene complexes were merged with naturally available direct band gap of monolayer MoS2 to build efficient energy harvesting and photo detecting devices.
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Kvashnin, D. G., P. B. Sorokin, G. Seifert i L. A. Chernozatonskii. "MoS₂ decoration by Mo-atoms and the MoS₂– Mo–graphene heterostructure: a theoretical study". Royal Society of Chemistry, 2015. https://tud.qucosa.de/id/qucosa%3A36376.
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Here we propose a completely new covalent heterostructure based on graphene and self-decorated MoS₂ monolayers. Detailed investigation of the decoration process of the MoS₂ surface by Mo adatoms was performed using first principles DFT methods. Comparison between valence-only and semicore pseudopotentials was performed to correctly describe the interaction between Mo adatoms and the MoS₂ surface. It was found that self-decoration by Mo atoms is favorable from an energetic point of view. We studied in detail various decoration paths of Mo atoms on the MoS₂ surface. The strong variation of electronic properties after the decoration of MoS₂ was found. The impact of the presence of Mo adatoms on the electronic properties of the graphene/MoS₂ heterostructure was shown.
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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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Di, Felice Daniela. "Electronic structure and transport in the graphene/MoS₂ heterostructure for the conception of a field effect transistor". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS267/document.
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L'isolement du graphène, une monocouche de graphite composée d'un plan d’atomes de carbone, a démontré qu'il est possible de séparer un seul plan d'épaisseur atomique, que l'on appelle matériau bidimensionnel (2D), à partir des solides de Van de Waals (vdW). Grâce à leur stabilité, différents matériaux 2D peuvent être empilés pour former les hétérostructures de vdW. L'interaction vdW à l'interface étant suffisamment faible, les propriétés spécifiques de chaque matériau demeurent globalement inchangées dans l’empilement. En utilisant une démarche théorique et computationnelle basée sur la théorie de la fonctionnelle de la densité (DFT) et le formalisme de Keldysh-Green, nous avons étudié l'hétérostructure graphène/MoS₂ . Le principal intérêt des propriétés spécifiques du graphène et du MoS₂ pour la conception d'un transistor à effet de champ réside dans la mobilité du graphène, à la base d'un transistor haute performance et dans le gap électronique du MoS₂, à la base de la commutation du dispositif. Tout d'abord, nous avons étudié les effets de la rotation entre les deux couches sur les propriétés électroniques à l'interface, en démontrant que les propriétés électroniques globales ne sont pas affectées par l'orientation. En revanche, les images STM (microscope à effet tunnel) sont différentes pour chaque orientation, en raison d'un changement de densité de charge locale. Dans un deuxième temps, nous avons utilisé l’interface graphène/MoS₂ en tant que modèle très simple de Transistor à Effet de Champ. Nous avons analysé le rôle des hétérostructures de vdW sur la performance du transistor, en ajoutant des couches alternées de graphène et MoS₂ sur l'interface graphène/MoS₂. Il a ainsi été démontré que la forme de la DOS au bord du gap est le paramètre le plus important pour la vitesse de commutation du transistor, alors que si l’on ajoute des couches, il n’y aura pas d’amélioration du comportement du transistor, en raison de l'indépendance des interfaces dans les hétérostructures de vdW. Cependant, cela démontre que, dans le cadre de la DFT, on peut étudier les propriétés de transport des hétérostructures de vdW plus complexes en séparant chaque interface et en réduisant le temps de calcul. Les matériaux 2D sont également étudiés ici en tant que pointe pour STM et AFM (microscope à force atomique) : une pointe de graphène testée sur MoS₂ avec défauts a été comparée aux résultats correspondants pour une pointe en cuivre. La résolution atomique a été obtenue et grâce à l'interaction de vdW entre la pointe et l’échantillon, il est possible d’éviter les effets de contact responsables du transfert d'atomes entre la pointe et l'échantillon. En outre, l'analyse des défauts est très utile du fait de la présence de nouveaux pics dans le gap du MoS₂ : ils peuvent ainsi être utilisés pour récupérer un pic de courant et donner des perspectives pour améliorer la performance des transistorsThe isolation of graphene, a single stable layer of graphite, composed by a plane of carbon atoms, demonstrated the possibility to separate a single layer of atomic thickness, called bidimensional (2D) material, from the van der Waals (vdW) solids. Thanks to their stability, 2D materials can be used to form vdW heterostructures, a vertical stack of different 2D crystals maintained together by the vdW forces. In principle, due to the weakness of the vdW interaction, each layer keeps its own global electronic properties. Using a theoretical and computational approach based on the Density Functional Theory (DFT) and Keldish-Green formalism, we have studied graphene/MoS₂ heterostructure. In this work, we are interested in the specific electronic properties of graphene and MoS₂ for the conception of field effect transistor: the high mobility of graphene as a basis for high performance transistor and the gap of MoS₂ able to switch the device. First, the graphene/MoS₂ interface is electronically characterized by analyzing the effects of different orientations between the layers on the electronic properties. We demonstrated that the global electronic properties as bandstructure and Density of State (DOS) are not affected by the orientation, whereas, by mean of Scanning Tunneling Microscope (STM) images, we found that different orientations leads to different local DOS. In the second part, graphene/MoS₂ is used as a very simple and efficient model for Field Effect Transistor. The role of the vdW heterostructure in the transistor operation is analyzed by stacking additional and alternate graphene and MoS₂ layers on the simple graphene/MoS₂ interface. We demonstrated that the shape of the DOS at the gap band edge is the fundamental parameter in the switch velocity of the transistor, whereas the additional layers do not improve the transistor behavior, because of the independence of the interfaces in the vdW heterostructures. However, this demonstrates the possibility to study, in the framework of DFT, the transport properties of more complex vdW heterostructures, separating the single interfaces and reducing drastically the calculation time. The 2D materials are also studied in the role of a tip for STM and Atomic Force Microscopy (AFM). A graphene-like tip, tested on defected MoS₂, is compared with a standard copper tip, and it is found to provide atomic resolution in STM images. In addition, due to vdW interaction with the sample, this tip avoids the contact effect responsible for the transfer of atoms between the tip and the sample. Furthermore, the analysis of defects can be very useful since they induce new peaks in the gap of MoS₂: hence, they can be used to get a peak of current representing an interesting perspective to improve the transistor operation
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Paul, Tathagata. "Physics and application of charge transfer in van der Waals heterostructures". Thesis, 2019. https://etd.iisc.ac.in/handle/2005/4503.
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Since the discovery of graphene, the field of 2D materials has garnered massive interest from a materials science, basic physics and device application point of view. This
results from the diverse range of electronic and transport properties observed in these
systems. For example, graphene, which has a gapless Dirac fermionic band structure with
extremely high carrier mobility, shows low photoresponse due to the absence of a band
gap. However, layered transition metal dichalcogenides (TMDCs) such as MoS2, which
possess a semiconducting band structure with disorder dominated hopping like transport
mechanism and low carrier mobility, demonstrates high photoresponse due to the presence
of a band gap. One of the major benefits of 2D materials is the possibility of stacking
together isolated atomic planes of different materials in a layer by layer manner forming an atomic Lego or a van der Waals heterostructure. Proximity induced interaction
between two or more 2D crystals with varied crystal structure and electronic properties leads to a plethora of possibilities for the emergence of new physics and/or device
functionality. Consequently, van der Waals heterostructures have been utilized to design
devices for a wide variety of applications such as electronic, piezoelectric, thermoelectric,
optoelectronic and non-volatile information storage to name a few. For optoelectronic
and memory-based applications, charge transfer between the constituent layers of the van
der Waals heterostructure has proven to be of immense importance. There are reports
of excellent photodetectors based on MoS2 graphene heterostructures where a transfer of
photogenerated carriers from the MoS2 to graphene layer leads to high responsivity figures
of ∼ 5 × 108 AW−1 at room temperature. In this thesis, we study the effect of vertical
charge transfer in TMDC based van der Waals heterostructures aimed at non-volatile
memory, memristor and bio-inspired synaptic applications.
For this purpose, we use a trilayer stack of MoS2, hBN and graphene. Here hBN acts
as a tunnel barrier separating the MoS2 channel from the graphene floating gate (FG).
This design is motivated by our investigations into the ON/OFF switching mechanism in
back gated TMDC FETs where we observed clear signatures of percolative switching in
a disordered channel with low subthreshold slopes. An improvement in the subthreshold
slope is brought about by capacitance engineering via extension of the FG, leading tohigh quality MoS2 FETs with near-ideal subthreshold slope (≈ 80 mV/decade) maintained for almost four decades of change in conductance. The device also demonstrates a
large anti-hysteresis in the transfer characteristics due to the transfer of charges from the
channel to the FG. This, coupled with a low OFF state current makes the MoS2 FG device
ideal for energy efficient memory applications. The charge transfer process also leads to a
hysteresis in the output characteristics which is indicative of a memristor like behaviour.
Furthermore, the quanta of charge transferred can be controlled using short time period
pulses at the gate and drain terminal. This leads to a multi-state memory device with repeated increase and decrease of the channel conductance resulting from the accumulation
or depletion of electronic charges on the graphene FG. Pulsed charge transfer mediated
changes in device conductance is analogous to the pulsed potentiation and depression of a
biological synapse which is mediated via controlled release of neurotransmitters into the
synaptic cleft. In addition to pulsed potentiation and depression, the device successfully
replicates other synaptic properties such as paired pulse facilitation (PPF) and spike time
dependent plasticity (STDP) while maintaining a low power dissipation (∼5 fJ per pulse),
making it ideal for future neuromorphic applications.
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Roy, Kallol. "Optoelectronic Properties of Graphene Based Van-der-Waals Hybrids". Thesis, 2017. http://etd.iisc.ac.in/handle/2005/4142.
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Light matter interactions in atomically thin van der Waals materials have attracted significant attention in recent day [1–6]. Although the thickness does not exceed few nano-meters, such an atomically thin materials alone or in combination with other nanostructures show exciting and unexpected photodetection properties [7–16].
Fabrication of atomically sharp junctions can be achieved with 2D van der Waals heterostructures, which significantly enhances the scope to design new type of physical systems, where novel phenomena can be studied [15, 17, 18]. Heterostructures combine properties of dissimilar materials resulting improved device performances and hence, can be applied to multiple fields [19–21].
This thesis encompasses photo-response study of various atomically thin heterostructures made of graphene, bilayer-graphene (BLG) and MoS2. A graphene-on-MoS2 heterostructure, made of monolayer graphene and few atomic layers of MoS2, combine superior electronic transport properties of graphene with the optical properties of MoS2. Such hybrids exhibit enormous photo-responsivity, with values as high as ∼ 1010 A W−1 at ∼ 130 K and ∼ 108 A W−1 at room temperature, which make these the most photo-responsive material available till date. Presence of tunable persistent photo-response allows these to function as optoelectronic memory devices; where the persistent state shows near perfect charge retention within the experimental time scale of operation (∼ 12 hrs).
Noise-free large gain (109 − 1010) mechanism is one of the salient features of graphene-MoS2 hybrids. Devices made from BLG-on-MoS2 hybrids further help in improving the photoresponsive gain in these devices, and a large photoresponsivity (∼ 109 A W−1) is maintained even when operating these devices at low channel bias (VDS < 50 mV), or at a low range of channel current (IDS < 10 nA). In an optimized operating condition, where circuit noise is lower than the signal from a single photoelectron, BLG-on-MoS2 devices function as a number resolved single photon detector. High specific detectivity and low noise equivalent power of these devices, allow investigation of photon noise present in an optical source.
Along with the optoelectronic property study, various optical and electrical character-izations are adapted that explain the interface properties of graphene-MoS2 heterostructures. For example, Raman spectroscopy and photoluminicence study at the interface suggest strong interlayer coupling and efficient dissociation of excitons respectively, which play a key role in attaining large photoresponse. Interfacial barrier characteristics are also investigated in a vertical graphene-MoS2 geometry, which shows that the barrier height can be tuned by applying an electrostatic field.
Various experimental techniques and instruments, such as heterostructure fabrication technique and setup, optical cryostat etc., were developed in house to accomplish experimental investigation, which are discussed in details.
Results of photo-response study in van der Waals materials have opened up the possibility of designing a new class of photosensitive devices which can be utilized in various optoelectronic applications such as in biomedical sensing, astronomical sensing, optical communications, optical quantum information processing and in applications where low intensity photodetection and number resolved single photon detection attracts tremendous interest.
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Sahoo, Anindita. "Electrical Transport in the Hybrid Structures of 2D Van Der Waals Materials and Perovskite Oxide". Thesis, 2016. http://etd.iisc.ac.in/handle/2005/2948.
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Perovskite oxides have provided a wide variety of exotic functionalities based on their unique physical and chemical properties. By combining different perovskite oxides, interesting physical phenomena have been observed at the interfaces of perovskite heterostructures. The most interesting among these phenomena is the formation of two dimensional electron gas at the interface of two perovskite materials SrTiO3 and LaAlO3 which led to a number of fascinating physical properties such as metal-insulator transition, super-conductivity, large negative magnetoresistance and so on. This has raised the interest in exploiting the interface of various hybrids structures built on the perovskite oxide backbone. On the other hand, the two dimensional (2D) van der Waals materials such as graphene, MoS2, boron nitride etc. represent a new paradigm in the 2D electron-ics. The functionalities of these individual materials have been combined to obtain new enriched functionalities by stacking different materials together forming van der Waals heterostructures. In this work, we present a detailed study of the interface in hybrid structures made of vander Waals materials (graphene and MoS2) and their hybrids with a perovskite material namely, SrTiO3 which is known as the building block of complex oxide heterostructures.
In graphene-MoS2 vertical heterostructure, we have carried out a detailed set of investigations on the modulation of the Schottky barrier at the graphene-MoS2 interface with varying external electric field. By using different stacking sequences and device structures, we obtained high mobility at large current on-off ratio at room temperature along with a tunable Schottky barrier which can be varied as high as ∼ 0.4 eV by applying electric field. We also explored the interface of graphene and SrTiO3 as well as MoS2 and SrTiO3 by electrical transport and low frequency 1/f noise measurements. We observed a hysteretic feature in the transfer characteristics of dual gated graphene and MoS2 field effect transistors on SrTiO3. The dual gated geometry enabled us to measure the effective capacitance of SrTiO3 interface which showed an enhancement indicating the possible existence of negative capacitance developed by the surface dipoles at the interface of SrTiO3 and the graphene or MoS2 channel. Our 1/f noise study and the analysis of higher order statistics of noise also support the possibility of electric field-driven reorient able surface dipoles at the interface.
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Sahoo, Anindita. "Electrical Transport in the Hybrid Structures of 2D Van Der Waals Materials and Perovskite Oxide". Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2948.
Pełny tekst źródłaStreszczenie:
Perovskite oxides have provided a wide variety of exotic functionalities based on their unique physical and chemical properties. By combining different perovskite oxides, interesting physical phenomena have been observed at the interfaces of perovskite heterostructures. The most interesting among these phenomena is the formation of two dimensional electron gas at the interface of two perovskite materials SrTiO3 and LaAlO3 which led to a number of fascinating physical properties such as metal-insulator transition, super-conductivity, large negative magnetoresistance and so on. This has raised the interest in exploiting the interface of various hybrids structures built on the perovskite oxide backbone. On the other hand, the two dimensional (2D) van der Waals materials such as graphene, MoS2, boron nitride etc. represent a new paradigm in the 2D electron-ics. The functionalities of these individual materials have been combined to obtain new enriched functionalities by stacking different materials together forming van der Waals heterostructures. In this work, we present a detailed study of the interface in hybrid structures made of vander Waals materials (graphene and MoS2) and their hybrids with a perovskite material namely, SrTiO3 which is known as the building block of complex oxide heterostructures.
In graphene-MoS2 vertical heterostructure, we have carried out a detailed set of investigations on the modulation of the Schottky barrier at the graphene-MoS2 interface with varying external electric field. By using different stacking sequences and device structures, we obtained high mobility at large current on-off ratio at room temperature along with a tunable Schottky barrier which can be varied as high as ∼ 0.4 eV by applying electric field. We also explored the interface of graphene and SrTiO3 as well as MoS2 and SrTiO3 by electrical transport and low frequency 1/f noise measurements. We observed a hysteretic feature in the transfer characteristics of dual gated graphene and MoS2 field effect transistors on SrTiO3. The dual gated geometry enabled us to measure the effective capacitance of SrTiO3 interface which showed an enhancement indicating the possible existence of negative capacitance developed by the surface dipoles at the interface of SrTiO3 and the graphene or MoS2 channel. Our 1/f noise study and the analysis of higher order statistics of noise also support the possibility of electric field-driven reorient able surface dipoles at the interface.
Części książek na temat "MoS2 graphene heterostructures"
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Giannazzo, Filippo, Gabriele Fisichella, Giuseppe Greco, Patrick Fiorenza i Fabrizio Roccaforte. "Conductive Atomic Force Microscopy of Two-Dimensional Electron Systems: From AlGaN/GaN Heterostructures to Graphene and MoS2". W Conductive Atomic Force Microscopy, 163–85. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2017. http://dx.doi.org/10.1002/9783527699773.ch7.
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Roy, Kallol. "Photoresponse in Graphene-on-MoS$$_2$$ Heterostructures". W 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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Roy, Kallol. "Switching Operation with Graphene-on-MoS$$_2$$ Heterostructures". W Optoelectronic Properties of Graphene-Based van der Waals Hybrids, 157–70. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-59627-9_7.
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Roy, Kallol. "Bilayer-Graphene-on-MoS$$_2$$ Heterostructures: Channel Bandgap, Transconductance, and Noise". W Optoelectronic Properties of Graphene-Based van der Waals Hybrids, 171–89. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-59627-9_8.
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Singh, Sachin, Pravin Kumar Singh, A. K. Sharma, Pooja Lohia i D. K. Dwivedi. "Sensitivity Enhancement of Graphene and Blue Phosphorene/Mos2 Heterostructure-Based SPR Biosensor Using Gold (Au) Metal Layer: Theoretical Insight". W Lecture Notes in Electrical Engineering, 481–87. Singapore: Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-0312-0_47.
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A. Kharadi, Mubashir, Gul Faroz A. Malik i Farooq A. Khanday. "Photo-Detectors Based on Two Dimensional Materials". W Photodetectors [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95559.
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2D materials like transition metal dichalcogenides, black phosphorous, silicene, graphene are at the forefront of being the most potent 2D materials for optoelectronic applications because of their exceptional properties. Several application-specific photodetectors based on 2D materials have been designed and manufactured due to a wide range and layer-dependent bandgaps. Different 2D materials stacked together give rise to many surprising electronic and optoelectronic phenomena of the junctions based on 2D materials. This has resulted in a lot of popularity of 2D heterostructures as compared to the original 2D materials. This chapter presents the progress of optoelectronic devices (photodetectors) based on 2D materials and their heterostructures.
Streszczenia konferencji na temat "MoS2 graphene heterostructures"
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Soavi, G., D. De Fazio, S. R. Tamalampudi, D. Yoon, E. Mostaani, A. R. Botello, S. Dal Conte, G. Cerullo, I. Goykhman i A. C. Ferrari. "Gate tuneable ultrafast charge transfer in graphene/MoS2 heterostructures". W 2017 Conference on Lasers and Electro-Optics Europe (CLEO/Europe) & European Quantum Electronics Conference (EQEC). IEEE, 2017. http://dx.doi.org/10.1109/cleoe-eqec.2017.8087707.
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Singh, Amit, Seunghan Lee, Hoonkyung Lee i Hiroshi Watanabe. "Dielectric Constant and van der Waals Interlayer Interaction of MoS2-Graphene Heterostructures". W 2020 IEEE 15th International Conference on Nano/Micro Engineered and Molecular System (NEMS). IEEE, 2020. http://dx.doi.org/10.1109/nems50311.2020.9265634.
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Jadriško, Valentino, Borna Radatović, Borna Pielić, Christoph Gadermaier, Marko Kralj i Nataša Vujičić. "Structural and optical characterization of nanometer sized MoS2/graphene heterostructures for potential use in optoelectronic devices". W CLEO: Applications and Technology. Washington, D.C.: Optica Publishing Group, 2023. http://dx.doi.org/10.1364/cleo_at.2023.jw2a.123.
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We show growth of heterostructures on Ir(111) crystal and subsequent transfer to a Si wafer. This remedies substrate constraints imposed by MBE and allows to harness its advantages for applications in (opto)electronics and quantum technology.
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P. S., Midhun, Anjala Jayaraj, Savitha Nalini, Asha A. S., Rajeev Kumar K. i Jayaraj M. K. "Synthesis of mono/ few layered MoS2 thin films and graphene: MoS2 van der Waal heterostructures using pulsed laser deposition". W Nanoengineering: Fabrication, Properties, Optics, Thin Films, and Devices XVI, redaktorzy André-Jean Attias i Balaji Panchapakesan. SPIE, 2019. http://dx.doi.org/10.1117/12.2529185.
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Luo, Duan, Jian Tang, Xiaozhe Shen, Fuhao Ji, Jie Yang, Stephen Weathersby, Michael E. Kozina i in. "Twist-angle-dependent photoresponse in MoS2-graphene van der Waals heterostructures probed by ultrafast electron diffraction". W International Conference on Ultrafast Phenomena. Washington, D.C.: OSA, 2020. http://dx.doi.org/10.1364/up.2020.tu1a.3.
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Ren, W. P., Q. J. Wang, Q. H. Tan i Y. K. Liu. "Graphene-MoS2 heterostructure transistor". W Fourteenth National Conference on Laser Technology and Optoelectronics, redaktorzy Huai-Liang Xu, Feng Chen, Lingfei Ji, Buhong Li, Xiaoping Xie, Yuxin Leng, Zhengming Sheng i in. SPIE, 2019. http://dx.doi.org/10.1117/12.2533593.
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Schneider, Daniel S., Eros Reato, Leonardo Lucchesi, Zhenyu Wang, Agata Piacetini, Jens Bolten, Damiano Marian i in. "MoS2/graphene Lateral Heterostructure Field Effect Transistors". W 2021 Device Research Conference (DRC). IEEE, 2021. http://dx.doi.org/10.1109/drc52342.2021.9467156.
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Song, Yingchao, i Zhihong Zhu. "Vertical graphene/MoS2 van der Waals heterostructure photodetector". W Nanophotonics. SPIE, 2023. http://dx.doi.org/10.1117/12.2651571.
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Aksimsek, Sinan, i Zhipei Sun. "Graphene-MoS2 heterostructure based surface plasmon resonance biosensor". W 2016 URSI International Symposium on Electromagnetic Theory (EMTS). IEEE, 2016. http://dx.doi.org/10.1109/ursi-emts.2016.7571346.
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Ghobadi, Nayereh. "Molecular dynamics simulation of elastic properties of multilayer MoS2 and graphene/MoS2 heterostructure". W 2017 Iranian Conference on Electrical Engineering (ICEE). IEEE, 2017. http://dx.doi.org/10.1109/iraniancee.2017.7985466.
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