المؤلفون: Gong, Ze^{Aff1, Aff2}, van den Dries, Koen, Migueles-Ramírez, Rodrigo A.^{Aff4, Aff5, Aff6}, Wiseman, Paul W., Cambi, Alessandra, Shenoy, Vivek B.^{Aff1, Aff7, IDs4146702338598z_cor6}

المصدر: Nature Communications. 14(1)

المؤلفون: Heo, Su-Jin^{Aff1, Aff2, Aff3, Aff4}, Thakur, Shreyasi, Chen, Xingyu^{Aff3, Aff6}, Loebel, Claudia^{Aff2, Aff3}, Xia, Boao^{Aff1, Aff2}, McBeath, Rowena, Burdick, Jason A.^{Aff2, Aff3, Aff8}, Shenoy, Vivek B.^{Aff2, Aff3, Aff6}, Mauck, Robert L.^{Aff1, Aff2, Aff3, Aff4, IDs41551022009105_cor9}, Lakadamyali, Melike^{Aff3, Aff5, Aff9, IDs41551022009105_cor10}

المصدر: Nature Biomedical Engineering. 7(2):177-191

المؤلفون: Jo, Kiyoung, Kumar, Pawan, Orr, Joseph, Anantharaman, Surendra B., Miao, Jinshui, Motala, Michael, Bandyopadhyay, Arkamita, Kisslinger, Kim, Muratore, Christopher, Shenoy, Vivek B., Stach, Eric, Glavin, Nicholas, Jariwala, Deep

المصدر: ACS Nano 2021

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Physics - Applied Physics, Physics - Optics

الوصف: The semiconductor-metal junction is one of the most critical factors for high performance electronic devices. In two-dimensional (2D) semiconductor devices, minimizing the voltage drop at this junction is particularly challenging and important. Despite numerous studies concerning contact resistance in 2D semiconductors, the exact nature of the buried interface under a three-dimensional (3D) metal remains unclear. Herein, we report the direct measurement of electrical and optical responses of 2D semiconductor-metal buried interfaces using a recently developed metal-assisted transfer technique to expose the buried interface which is then directly investigated using scanning probe techniques. We characterize the spatially varying electronic and optical properties of this buried interface with < 20 nm resolution. To be specific, potential, conductance and photoluminescence at the buried metal/MoS$_2$ interface are correlated as a function of a variety of metal deposition conditions as well as the type of metal contacts. We observe that direct evaporation of Au on MoS$_2$ induces a large strain of ~5% in the MoS$_2$ which, coupled with charge transfer, leads to degenerate doping of the MoS$_2$ underneath the contact. These factors lead to improvement of contact resistance to record values of 138 kohm-um, as measured using local conductance probes. This approach was adopted to characterize MoS$_2$-In/Au alloy interfaces, demonstrating contact resistance as low as 63 kohm-um. Our results highlight that the MoS$_2$/Metal interface is sensitive to device fabrication methods, and provides a universal strategy to characterize buried contact interfaces involving 2D semiconductors.
Comment: 6 figures + supplement

URL الوصول: http://arxiv.org/abs/2101.12203

المؤلفون: Frey, Nathan C., Horton, Matthew K., Munro, Jason M., Griffin, Sinéad M., Persson, Kristin A., Shenoy, Vivek B.

المصدر: Science Advances 09 Dec 2020: Vol. 6, no. 50, eabd1076

مصطلحات موضوعية: Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons, Physics - Computational Physics

الوصف: The discovery of intrinsic magnetic topological order in $\rm MnBi_2Te_4$ has invigorated the search for materials with coexisting magnetic and topological phases. These multi-order quantum materials are expected to exhibit new topological phases that can be tuned with magnetic fields, but the search for such materials is stymied by difficulties in predicting magnetic structure and stability. Here, we compute over 27,000 unique magnetic orderings for over 3,000 transition metal oxides in the Materials Project database to determine their magnetic ground states and estimate their effective exchange parameters and critical temperatures. We perform a high-throughput band topology analysis of centrosymmetric magnetic materials, calculate topological invariants, and identify 18 new candidate ferromagnetic topological semimetals, axion insulators, and antiferromagnetic topological insulators. To accelerate future efforts, machine learning classifiers are trained to predict both magnetic ground states and magnetic topological order without requiring first-principles calculations.
Comment: 9 pages, 6 figures

URL الوصول: http://arxiv.org/abs/2006.01075

المؤلفون: Kumar, Pawan, Horwath, James P., Foucher, Alexandre C., Price, Christopher C., Acero, Natalia, Shenoy, Vivek B., Stach, Eric A., Jariwala, Deep

مصطلحات موضوعية: Condensed Matter - Materials Science, Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Applied Physics

الوصف: Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been the subject of sustained research interest due to their extraordinary electronic and optical properties. They also exhibit a wide range of structural phases because of the different orientations that the atoms can have within a single layer, or due to the ways that different layers can stack. Here we report the first study of direct-visualization of structural transformations in atomically-thin layers under highly non-equilibrium thermodynamic conditions. We probe these transformations at the atomic scale using real-time, aberration corrected scanning transmission electron microscopy and observe strong dependence of the resulting structures and phases on both heating rate and temperature. A fast heating rate (25 C/sec) yields highly ordered crystalline hexagonal islands of sizes of less than 20 nm which are composed of a mixture of 2H and 3R phases. However, a slow heating rate (25 C/min) yields nanocrystalline and sub-stoichiometric amorphous regions. These differences are explained by different rates of sulfur evaporation and redeposition. The use of non-equilibrium heating rates to achieve highly crystalline and quantum-confined features from 2D atomic layers present a new route to synthesize atomically-thin, laterally confined nanostrucutres and opens new avenues for investigating fundamental electronic phenomena in confined dimensions.

URL الوصول: http://arxiv.org/abs/2002.08845

المؤلفون: Guo, Zhenlin, Price, Christopher, Shenoy, Vivek B., Lowengrub, John

مصطلحات موضوعية: Physics - Computational Physics

الوصف: Vertically-stacked monolayers of graphene and other atomically-thin 2D materials have attracted considerable research interest because of their potential in fabricating materials with specifically-designed properties. Chemical vapor deposition has proved to be an efficient and scalable fabrication method. However, a lack of mechanistic understanding has hampered efforts to control the fabrication process beyond empirical trial-and-error approaches. In this paper, we develop a general multiscale Burton-Cabrera-Frank (BCF) type model of the vertical growth of 2D materials to predict the necessary growth conditions for vertical versus in-plane (monolayer) growth of arbitrarily-shaped layers. This extends previous work where we developed such a model assuming the layers were fully-faceted (Ye et al., ACS Nano, 11, 12780-12788, 2017). To solve the model numerically, we reformulate the system using the phase-field/diffuse domain method that enables the equations to be solved in a fixed regular domain. We use a second-order accurate, adaptive finite-difference/nonlinear multigrid algorithm to discretize and solve the discrete system. We investigate the effect of parameters, including the van der Waals interaction energies between the layers, the kinetic attachment rates, the edge-energies and the deposition flux, on layer growth and morphologies. While the conditions that favor vertical growth generally follow an analytic thermodynamic criterion we derived for circular layers, the layer boundaries may develop significant curvature during growth, consistent with experimental observations. Our approach provides a mechanistic framework for controlling and optimizing the growth multilayered 2D materials.

URL الوصول: http://arxiv.org/abs/1911.11135

المؤلفون: Mandyam, Srinivas V., Zhao, Meng Qiang, Das, Paul Masih, Zhang, Qicheng, Price, Christopher C., Gao, Zhaoli, Shenoy, Vivek B., Drndic, Marija, Johnson, Alan T. Charlie

مصطلحات موضوعية: Condensed Matter - Materials Science

الوصف: Bilayer two-dimensional (2D) van der Waals (vdW) materials are attracting increasing attention due to their predicted high quality electronic and optical properties. Here we demonstrate dense, selective growth of WSe2 bilayer flakes by chemical vapor deposition with the use of a 1:10 molar mixture of sodium cholate and sodium chloride as the growth promoter to control the local diffusion of W-containing species. A large fraction of the bilayer WSe2 flakes showed a 0 and 60o twist between the two layers, while moire 15 and 30o-twist angles were also observed. Well-defined monolayer-bilayer junctions were formed in the as-grown bilayer WSe2 flakes, and these interfaces exhibited p-n diode rectification and an ambipolar transport characteristic. This work provides an efficient method for the layer-controlled growth of 2D materials, in particular, 2D transition metal dichalcogenides and promotes their applications in next-generation electronic and optoelectronic devices.

URL الوصول: http://arxiv.org/abs/1908.09013

المؤلفون: Alisafaei, Farid^{Aff1, Aff2}, Mandal, Kalpana^{Aff1, Aff3}, Saldanha, Renita^{Aff4, Aff5}, Swoger, Maxx^{Aff4, Aff5}, Yang, Haiqian, Shi, Xuechen^{Aff1, Aff3}, Guo, Ming, Hehnly, Heidi, Castañeda, Carlos A.^{Aff8, Aff9}, Janmey, Paul A.^{Aff1, Aff3, Aff10}, Patteson, Alison E.^{Aff4, Aff5}, Shenoy, Vivek B.^{Aff1, Aff11, IDs42003024063664_cor12}

المصدر: Communications Biology. 7(1)

المؤلفون: Kant, Aayush^{Aff1, Aff2}, Guo, Zixian^{Aff1, Aff3}, Vinayak, Vinayak^{Aff1, Aff2}, Neguembor, Maria Victoria, Li, Wing Shun^{Aff5, Aff6}, Agrawal, Vasundhara^{Aff6, Aff7}, Pujadas, Emily, Almassalha, Luay^{Aff6, Aff8}, Backman, Vadim^{Aff6, Aff7}, Lakadamyali, Melike^{Aff1, Aff9}, Cosma, Maria Pia^{Aff4, Aff10, Aff11}, Shenoy, Vivek B.^{Aff1, Aff2, Aff3, IDs4146702448698z_cor12}

المصدر: Nature Communications. 15(1)

المؤلفون: Frey, Nathan C, Horton, Matthew K, Munro, Jason M, Griffin, Sinéad M, Persson, Kristin A, Shenoy, Vivek B

المصدر: Science Advances. 6(50)

مصطلحات موضوعية: Quantum Physics, Physical Sciences, Condensed Matter Physics

الوصف: The discovery of intrinsic magnetic topological order in MnBi2Te4 has invigorated the search for materials with coexisting magnetic and topological phases. These multiorder quantum materials are expected to exhibit new topological phases that can be tuned with magnetic fields, but the search for such materials is stymied by difficulties in predicting magnetic structure and stability. Here, we compute more than 27,000 unique magnetic orderings for more than 3000 transition metal oxides in the Materials Project database to determine their magnetic ground states and estimate their effective exchange parameters and critical temperatures. We perform a high-throughput band topology analysis of centrosymmetric magnetic materials, calculate topological invariants, and identify 18 new candidate ferromagnetic topological semimetals, axion insulators, and antiferromagnetic topological insulators. To accelerate future efforts, machine learning classifiers are trained to predict both magnetic ground states and magnetic topological order without requiring first-principles calculations.

وصف الملف: application/pdf

URL الوصول: https://escholarship.org/uc/item/02561982