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4D-STEM Nanoscale Strain Analysis in van der Waals Materials: Advancing beyond Planar Configurations

Bolhuis, M. (author), van Heijst, S.E. (author), Sangers, J.J.M. (author), Conesa Boj, S. (author)

Achieving nanoscale strain fields mapping in intricate van der Waals (vdW) nanostructures, like twisted flakes and nanorods, presents several challenges due to their complex geometry, small size, and sensitivity limitations. Understanding these strain fields is pivotal as they significantly influence the optoelectronic properties of vdW...

journal article 2024

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Magnetotransport properties of CrO₂ nanowires fabricated by selective area growth

Prateek, K. (author), Bolhuis, M. (author), Ben Hamida, A. (author), Scholma, D. (author), Conesa Boj, S. (author), Aarts, Jan (author)

Chromium dioxide (CrO₂) nanowires with their half-metallic ferromagnetic properties have shown great promise in spintronics applications. However, growth of such wires remains challenging. We used the Selective Area growth method to fabricate high quality epitaxial CrO₂ wires on a TiO₂ substrate, using...

journal article 2023

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Heterostrain-Driven Bandgap Increase in Twisted WS₂: A Nanoscale Study

van Heijst, S.E. (author), Bolhuis, M. (author), Brokkelkamp, A.R. (author), Sangers, Jeroen J.M. (author), Conesa Boj, S. (author)

Twisted 2D materials present an enticing platform for exploring diverse electronic properties owning to the tunability of their bandgap energy. However, the intricate relationship between local heterostrain fields, thickness, and bandgap energy remains insufficiently understood, particularly at the nanoscale. Here, it presents a comprehensive...

journal article 2023

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Localized Exciton Anatomy and BandGap Energy Modulation in 1D MoS₂ Nanostructures

van der Lippe, Stijn (author), Brokkelkamp, A.R. (author), Rojo, Juan (author), Conesa Boj, S. (author)

This study presents an in-depth investigation of the electronic properties and bandgap energy distribution in 1D molybdenum disulfide (1D-MoS₂) nanostructures. Through a combination of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and electron energy-loss spectroscopy (EELS), it reveals...

journal article 2023

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Edge-induced excitations in Bi₂Te₃ from spatially-resolved electron energy-gain spectroscopy

La, H.L. (author), Brokkelkamp, A.R. (author), van der Lippe, Stijn (author), ter Hoeve, Jaco (author), Rojo, Juan (author), Conesa Boj, S. (author)

Among the many potential applications of topological insulator materials, their broad potential for the development of novel tunable plasmonics at THz and mid-infrared frequencies for quantum computing, terahertz detectors, and spintronic devices is particularly attractive. The required understanding of the intricate relationship between...

journal article 2023

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First-Principles Calculation of Optoelectronic Properties in 2D Materials: The Polytypic WS₂ Case

Maduro, L.A. (author), van Heijst, S.E. (author), Conesa Boj, S. (author)

The phenomenon of polytypism, namely unconventional crystal phases displaying a mixture of stacking sequences, represents a powerful handle to design and engineer novel physical properties in two-dimensional (2D) materials. In this work, we characterize from first-principles the optoelectronic properties associated with the 2H/3R polytypism...

journal article 2022

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Revealing the nanogeometry of WS2 nanoflowersby polarization-resolved Raman spectroscopy

Komen, I. (author), van Heijst, S.E. (author), Caldarola, M. (author), Conesa Boj, S. (author), Kuipers, L. (author)

Recent studies of transition metal dichalcogenides (TMDs) have revealed exciting optical properties, such as stable excitons and chiral light–matter interactions. Chemical vapor deposition techniques provide a platform for the fabrication of nanostructures with diverse geometries, ranging from horizontal flakes to flower-like structures. Raman...

journal article 2022

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Spatially Resolved Band Gap and Dielectric Function in Two-Dimensional Materials from Electron Energy Loss Spectroscopy

Brokkelkamp, A.R. (author), Ter Hoeve, Jaco (author), Postmes, Isabel (author), van Heijst, S.E. (author), Maduro, L.A. (author), Davydov, Albert V. (author), Krylyuk, Sergiy (author), Rojo, Juan (author), Conesa Boj, S. (author)

The electronic properties of two-dimensional (2D) materials depend sensitively on the underlying atomic arrangement down to the monolayer level. Here we present a novel strategy for the determination of the band gap and complex dielectric function in 2D materials achieving a spatial resolution down to a few nanometers. This approach is based...

journal article 2022

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Molybdenum nanopillar arrays: Fabrication and engineering

Maduro, L.A. (author), de Boer, Charles (author), Zuiddam, M.R. (author), Memisevic, E. (author), Conesa Boj, S. (author)

We report on the fabrication of molybdenum (Mo) nanopillar (NP) arrays with NP diameters down to 75 nm by means of deep-reactive ion etching at cryogenic temperatures. A variable-thickness Mo metal layer sputtered onto a Si₃N₄/Si substrate makes possible NPs with different lengths in a controllable manner. We demonstrate...

journal article 2021

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Morphology-induced spectral modification of self-assembled WS₂pyramids

Komen, I. (author), van Heijst, S.E. (author), Conesa Boj, S. (author), Kuipers, L. (author)

Due to their intriguing optical properties, including stable and chiral excitons, two-dimensional transition metal dichalcogenides (2D-TMDs) hold the promise of applications in nanophotonics. Chemical vapor deposition (CVD) techniques offer a platform to fabricate and design nanostructures with diverse geometries. However, the more exotic the...

journal article 2021

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Position-Controlled Fabrication of Vertically Aligned Mo/MoS₂ Core–Shell Nanopillar Arrays

Maduro, L.A. (author), Noordam, M.L. (author), Bolhuis, M. (author), Kuipers, L. (author), Conesa Boj, S. (author)

The fabrication of 2D materials, such as transition metal dichalcogenides (TMDs), in geometries beyond the standard platelet-like configuration exhibits significant challenges which severely limit the range of available morphologies. These challenges arise due to the anisotropic character of their bonding van der Waals out-of-plane while...

journal article 2021

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Charting the low-loss region in electron energy loss spectroscopy with machine learning

Roest, Laurien I. (author), van Heijst, S.E. (author), Maduro, L.A. (author), Rojo, Juan (author), Conesa Boj, S. (author)

Exploiting the information provided by electron energy-loss spectroscopy (EELS) requires reliable access to the low-loss region where the zero-loss peak (ZLP) often overwhelms the contributions associated to inelastic scatterings off the specimen. Here we deploy machine learning techniques developed in particle physics to realise a model...

journal article 2021

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Illuminating the Electronic Properties of WS₂ Polytypism with Electron Microscopy

van Heijst, S.E. (author), Mukai, Masaki (author), Okunishi, Eiji (author), Hashiguchi, Hiroki (author), Roest, Laurien I. (author), Maduro, L.A. (author), Rojo, Juan (author), Conesa Boj, S. (author)

Tailoring the specific stacking sequence (polytypes) of layered materials represents a powerful strategy to identify and design novel physical properties. While nanostructures built upon transition-metal dichalcogenides (TMDs) with either the 2H or 3R crystalline phases have been routinely studied, knowledge of TMD nanomaterials based on...

journal article 2021

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Robust Sample Preparation of Large-Area In- and Out-of-Plane Cross Sections of Layered Materials with Ultramicrotomy

Cichocka, M.O. (author), Bolhuis, M. (author), van Heijst, S.E. (author), Conesa Boj, S. (author)

Layered materials (LMs) such as graphene or MoS2 have attracted a great deal of interest recently. These materials offer unique functionalities due to their structural anisotropy characterized by weak van der Waals bonds along the out-of-plane axis and covalent bonds in the in-plane direction. A central requirement to access the structural...

journal article 2020

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Vertically-oriented MoS₂ nanosheets for nonlinear optical devices

Bolhuis, M. (author), Hernandez Rueda, F.J. (author), van Heijst, S.E. (author), Tinoco Rivas, M. (author), Kuipers, L. (author), Conesa Boj, S. (author)

Transition metal dichalcogenides such as MoS2 represent promising candidates for building blocks of ultra-thin nanophotonic devices. For such applications, vertically-oriented MoS2 (v-MoS2) nanosheets could be advantageous as compared to conventional horizontal MoS2 (h-MoS2) given that their inherent broken symmetry would favor an enhanced...

journal article 2020

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Lock-in Ultrafast Electron Microscopy Simultaneously Visualizes Carrier Recombination and Interface-Mediated Trapping

Garming, M.W.H. (author), Bolhuis, M. (author), Conesa Boj, S. (author), Kruit, P. (author), Hoogenboom, J.P. (author)

Visualizing charge carrier flow over interfaces or near surfaces meets great challenges concerning resolution and vastly different time scales of bulk and surface dynamics. Ultrafast or four-dimensional scanning electron microscopy (USEM) using a laser pump electron probe scheme circumvents the optical diffraction limit, but disentangling...

journal article 2020

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Metallic edge states in zig-zag vertically-oriented MoS₂ nanowalls

Tinoco, Miguel (author), Maduro, Louis (author), Conesa Boj, S. (author)

The remarkable properties of layered materials such as MoS₂ strongly depend on their dimensionality. Beyond manipulating their dimensions, it has been predicted that the electronic properties of MoS₂ can also be tailored by carefully selecting the type of edge sites exposed. However, achieving full control over the type...

journal article 2019

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Observation of Conductance Quantization in InSb Nanowire Networks

Fadaly, E.M.T. (author), Zhang, H. (author), Conesa Boj, S. (author), Car, D. (author), Gül, Önder (author), Plissard, Sébastien R. (author), op het Veld, R.L.M. (author), Kölling, Sebastian (author), Kouwenhoven, Leo P. (author), Bakkers, E.P.A.M. (author)

Majorana zero modes (MZMs) are prime candidates for robust topological quantum bits, holding a great promise for quantum computing. Semiconducting nanowires with strong spin orbit coupling offer a promising platform to harness one-dimensional electron transport for Majorana physics. Demonstrating the topological nature of MZMs relies on...

journal article 2017

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Strain-Dependent Edge Structures in MoS₂ Layers

Tinoco Rivas, M. (author), Maduro, L.A. (author), Masaki, Mukai (author), Okunishi, Eiji (author), Conesa Boj, S. (author)

Edge structures are low-dimensional defects unavoidable in layered materials of the transition metal dichalcogenides (TMD) family. Among the various types of such structures, the armchair (AC) and zigzag (ZZ) edge types are the most common. It has been predicted that the presence of intrinsic strain localized along these edges structures can...

journal article 2017

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Hard Superconducting Gap in InSb Nanowires

Gül, Önder (author), Zhang, H. (author), de Vries, F.K. (author), van Veen, J. (author), Zuo, K. (author), Mourik, V. (author), Conesa Boj, S. (author), Nowak, M.P. (author), van Woerkom, D.J. (author), Quintero Perez, M. (author), Cassidy, M.C. (author), Geresdi, A. (author), Koelling, Sebastian (author), Car, D. (author), Plissard, S.R. (author), Bakkers, E.P.A.M. (author), Kouwenhoven, Leo P. (author)

Topological superconductivity is a state of matter that can host Majorana modes, the building blocks of a topological quantum computer. Many experimental platforms predicted to show such a topological state rely on proximity-induced superconductivity. However, accessing the topological properties requires an induced hard superconducting gap,...

journal article 2017