Stephan Hofmann
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View article: Achieving 100% amplitude modulation depth in the terahertz range with graphene-based tuneable capacitance metamaterials
Achieving 100% amplitude modulation depth in the terahertz range with graphene-based tuneable capacitance metamaterials Open
Effective control of terahertz radiation requires fast and efficient modulators with a large modulation depth—a challenge that is often tackled by using metamaterials. Metamaterial-based active modulators can be created by placing graphene…
View article: High‐Throughput Ellipsometric Contrast Microscopy of Lateral 2D Heterostructures for Optoelectronics
High‐Throughput Ellipsometric Contrast Microscopy of Lateral 2D Heterostructures for Optoelectronics Open
Covalently‐bonded lateral 2D heterostructures offer unique (opto)electronic functionalities and can be deposited during a single growth process. However, the position of lateral junctions is typically uncontrolled due to random nucleation …
View article: Selective Synthesis of Large-Area Monolayer Tin Sulfide from Simple Substances
Selective Synthesis of Large-Area Monolayer Tin Sulfide from Simple Substances Open
Both tin monosulfide (SnS) and tin disulfide (SnS2) are thermodynamically stable layered materials with the potential for spin-valleytronic devices and photodetectors. Notably, SnS, owing to its low symmetry, exhibits interesting propertie…
View article: Understanding Volatile Electrical Switching in hBN Nanodevices by Fully Optical Operando Investigation
Understanding Volatile Electrical Switching in hBN Nanodevices by Fully Optical Operando Investigation Open
Memristors based on 2D materials have emerged as promising candidates for use in artificial synaptic devices and energy‐efficient neuromorphic computing. Limited understanding of the fundamental switching mechanisms hinders device optimiza…
View article: Properties of quantum emitters in different hBN sample types particularly suited for nanophotonic integration
Properties of quantum emitters in different hBN sample types particularly suited for nanophotonic integration Open
Single photon emitters in two-dimensional hexagonal boron nitride (hBN) are promising solid-state quantum emitters for photonic applications and quantum networks. Despite their favorable properties, much is still unknown about their charac…
View article: The role of non-equilibrium populations in dark exciton formation
The role of non-equilibrium populations in dark exciton formation Open
In two-dimensional transition metal dichalcogenide structures, the optical excitation of a bright exciton may be followed by the formation of a plethora of lower energy dark states. In these formation and relaxation processes between diffe…
View article: Terahertz harmonic generation and nonlinear spectroscopy of metamaterial-gated/graphene resonators
Terahertz harmonic generation and nonlinear spectroscopy of metamaterial-gated/graphene resonators Open
We report on the terahertz (THz) harmonic generation in an active graphene/metamaterial device by using powerful ultrafast table-top THz time-domain spectroscopic systems. Complex nonlinear transmission spectra, comprising even and odd har…
View article: Se Nanowire Crystal Formation via Oxidation of 2D HfSe<sub>2</sub>: A Solid-State, In Situ Reaction Coupling for Heterogeneous Integration Technologies
Se Nanowire Crystal Formation via Oxidation of 2D HfSe<sub>2</sub>: A Solid-State, In Situ Reaction Coupling for Heterogeneous Integration Technologies Open
Effective heterogeneous integration of low-dimensional nanomaterials in applications ranging from quantum electronics to biomedical devices requires a detailed understanding of different formation and interfacing reactions and the ability …
View article: The 2D Materials Roadmap
The 2D Materials Roadmap Open
Over the past two decades, 2D materials have rapidly evolved into a diverse and expanding family of material platforms. Many members of this materials class have demonstrated their potential to deliver transformative impact on fundamental …
View article: Localisation of hexagonal boron nitride colour centres using patterned dielectric layers on graphene
Localisation of hexagonal boron nitride colour centres using patterned dielectric layers on graphene Open
One of the most promising building blocks for the development of spin qubits, single-photon sources, and quantum sensors at room temperature, as well as 2D ultraviolet light-emitting diodes, are defect colour centres in 2D hexagonal boron …
View article: Operando Scanning Electron Microscopy Study of Support Interactions and Mechanisms of Salt-Assisted WS<sub>2</sub> Growth
Operando Scanning Electron Microscopy Study of Support Interactions and Mechanisms of Salt-Assisted WS<sub>2</sub> Growth Open
Salt enhanced chemical vapor deposition of WS2 and related 2D materials is widespread, and while many mechanisms including vapor-liquid-solid (VLS) mediated growth have been suggested, gaining a more detailed understanding remains challeng…
View article: Ultrafast nano-imaging of dark excitons
Ultrafast nano-imaging of dark excitons Open
Saudi Arabian Ministry of Higher Education
View article: Fast crystallographic texture mapping of atomically thin hBN films on Ni(111) using secondary electron contrast
Fast crystallographic texture mapping of atomically thin hBN films on Ni(111) using secondary electron contrast Open
Fast crystallographic texture mapping of monolayer films with conventional scanning electron microscopy, including the nature of the resulting domain boundaries, adlayers and overlapping bilayer regions.
View article: A close-space sublimation approach to tungsten oxide and sulfide nanostructure formation
A close-space sublimation approach to tungsten oxide and sulfide nanostructure formation Open
A highly resource-efficient Close-Space Sublimation (CSS) approach is presented, along with versatile one-step and two-step process designs, for the controlled synthesis of a wide range of tungsten (sub)oxide and tungsten disulfide nanostr…
View article: Forming and compliance-free operation of low-energy, fast-switching HfO<sub><i>x</i></sub>S<sub><i>y</i></sub>/HfS<sub>2</sub> memristors
Forming and compliance-free operation of low-energy, fast-switching HfO<sub><i>x</i></sub>S<sub><i>y</i></sub>/HfS<sub>2</sub> memristors Open
Memristors based on partially oxidised layered semiconductors show sub-nJ resistance switching between several states with no need for electroforming or compliance, making them promising candidates for future neuromorphic computing hardwar…
View article: Selective synthesis of large-area monolayer tin sulfide from simple substances
Selective synthesis of large-area monolayer tin sulfide from simple substances Open
Both tin monosulfide (SnS) and tin disulfide (SnS2) are thermodynamically stable layered materials with potential for spin-valleytronic devices and photodetectors. Notably, monolayer SnS, owing to its low symmetry, exhibits interesting pro…
View article: Graphene Microelectrode Arrays, 4D Structured Illumination Microscopy, and a Machine Learning Spike Sorting Algorithm Permit the Analysis of Ultrastructural Neuronal Changes During Neuronal Signaling in a Model of Niemann–Pick Disease Type C
Graphene Microelectrode Arrays, 4D Structured Illumination Microscopy, and a Machine Learning Spike Sorting Algorithm Permit the Analysis of Ultrastructural Neuronal Changes During Neuronal Signaling in a Model of Niemann–Pick Disease Type C Open
Simultaneously recording network activity and ultrastructural changes of the synapse is essential for advancing understanding of the basis of neuronal functions. However, the rapid millisecond‐scale fluctuations in neuronal activity and th…
View article: Recommendations and tools to enable reproducibility in 2D materials research
Recommendations and tools to enable reproducibility in 2D materials research Open
Research on 2D materials has achieved significant milestones and fuelled a rapidly growing industrial sector. This progress, however, is accompanied by challenges in reproducibility, arising from the atomic thinness, fragility, and environ…
View article: Controlled Fabrication of Native Ultra‐Thin Amorphous Gallium Oxide From 2D Gallium Sulfide for Emerging Electronic Applications
Controlled Fabrication of Native Ultra‐Thin Amorphous Gallium Oxide From 2D Gallium Sulfide for Emerging Electronic Applications Open
Oxidation of 2D layered materials has proven advantageous in creating oxide/2D material heterostructures, opening the door for a new paradigm of low‐power electronic devices. Gallium (II) sulfide (β‐GaS), a hexagonal phase group III monoch…
View article: Highly Sensitive Glucose Sensors Based on Gated Graphene Microwave Waveguides
Highly Sensitive Glucose Sensors Based on Gated Graphene Microwave Waveguides Open
A novel approach is demonstrated to identify glucose concentration in aqueous solutions based on the combined effect of its frequency‐dependent interaction with microwaves propagating in graphene channels and the modification of graphene r…
View article: Forming and Compliance-free Operation of Low-energy, Fast-switching HfO$_x$S$_y$/HfS$_2$ Memristors
Forming and Compliance-free Operation of Low-energy, Fast-switching HfO$_x$S$_y$/HfS$_2$ Memristors Open
We demonstrate low energy, forming and compliance-free operation of a resistive memory obtained by the partial oxidation of a two-dimensional layered van-der-Waals semiconductor: hafnium disulfide (HfS$_2$). Semiconductor - oxide heterostr…
View article: Close-space sublimation of single-crystal metal films
Close-space sublimation of single-crystal metal films Open
Cost-effective, versatile, and rapid deposition of single-crystal metal films is crucial to a wide spectrum of applications ranging from catalysis, plasmonics, electrochemistry, and optoelectronics to templating, epitaxial substrates, and …
View article: Versatile fitting approach for operando spectroscopic imaging ellipsometry of HfS<sub>2</sub> oxidation
Versatile fitting approach for operando spectroscopic imaging ellipsometry of HfS<sub>2</sub> oxidation Open
Facile mapping of 2D heterostructures and resolving anisotropic formation kinetics down to the monolayer level are critical to developing scalable interfacing solutions and unlocking their application potential in emerging nano-optoelectro…
View article: Correction to: Imaging Light‐Induced Migration of Dislocations in Halide Perovskites with 3D Nanoscale Strain Mapping
Correction to: Imaging Light‐Induced Migration of Dislocations in Halide Perovskites with 3D Nanoscale Strain Mapping Open
Owing to an error in properly normalizing the reconstruction phase data into atomic displacements, the strain values that we used to calculate the root mean squared local strain, εrms, and to calculate the fraction of the crystals more str…
View article: Stability of Plasmonic Mg-MgO Core–Shell Nanoparticles in Gas-Phase Oxidative Environments
Stability of Plasmonic Mg-MgO Core–Shell Nanoparticles in Gas-Phase Oxidative Environments Open
Magnesium is a recent addition to the plasmonic toolbox: nanomaterials that efficiently utilize photons' energy due to their ability to sustain localized surface plasmon resonances. Magnesium nanoparticles protected by a native oxide shell…
View article: Controlled Fabrication of Native Ultra-Thin Amorphous Gallium Oxide from 2D Gallium Sulfide for Emerging Electronic Applications
Controlled Fabrication of Native Ultra-Thin Amorphous Gallium Oxide from 2D Gallium Sulfide for Emerging Electronic Applications Open
Oxidation of two-dimensional (2D) layered materials has proven advantageous in creating oxide/2D material heterostructures, opening the door for a new paradigm of low-power electronic devices. Gallium (II) sulfide ($β$-GaS), a hexagonal ph…
View article: Graphene microelectrode arrays, 4D structured illumination microscopy, and a machine learning-based spike sorting algorithm permit the analysis of ultrastructural neuronal changes during neuronal signalling in a model of Niemann-Pick disease type C
Graphene microelectrode arrays, 4D structured illumination microscopy, and a machine learning-based spike sorting algorithm permit the analysis of ultrastructural neuronal changes during neuronal signalling in a model of Niemann-Pick disease type C Open
Simultaneously recording network activity and ultrastructural changes of the synapse is essential for advancing our understanding of the basis of neuronal functions. However, the rapid millisecond-scale fluctuations in neuronal activity an…
View article: Hexagonal Boron Nitride Spacers for Fluorescence Imaging of Biomolecules
Hexagonal Boron Nitride Spacers for Fluorescence Imaging of Biomolecules Open
Fluorescence imaging is an invaluable tool to investigate biomolecular dynamics, mechanics, and interactions in aqueous environments. Two‐dimensional materials offer large‐area, atomically smooth surfaces for wide‐field biomolecule imaging…