Ralph Krupke
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View article: On the mechanism of piezoresistance in nanocrystalline graphite
On the mechanism of piezoresistance in nanocrystalline graphite Open
Strain sensors are sensitive to mechanical deformations and enable the detection of strain also within integrated electronics. For flexible displays, the use of a seamlessly integrated strain sensor would be beneficial, and graphene is alr…
View article: Enhanced Broadband Photodetection with Geometry and Interface Engineered Nanocrystalline Graphite
Enhanced Broadband Photodetection with Geometry and Interface Engineered Nanocrystalline Graphite Open
Photodetection across the near‐infrared (NIR) to short‐wavelength infrared (SWIR) spectrum is important for many applications. This study explores photodetection using nanocrystalline graphite (NCG) in a suspended, narrow constriction conf…
View article: Sensitive Detection of a Gaseous Analyte with Low‐Power Metal–Organic Framework Functionalized Carbon Nanotube Transistors
Sensitive Detection of a Gaseous Analyte with Low‐Power Metal–Organic Framework Functionalized Carbon Nanotube Transistors Open
A highly sensitive and low‐power sensing platform for detecting ethanol molecules by interfacing high‐purity, large‐diameter semiconducting carbon nanotube transistors with a metal–organic framework layer is presented. The new devices outp…
View article: Graphitizability of Polymer Thin Films: An In Situ TEM Study of Thickness Effects on Nanocrystalline Graphene/Glassy Carbon Formation
Graphitizability of Polymer Thin Films: An In Situ TEM Study of Thickness Effects on Nanocrystalline Graphene/Glassy Carbon Formation Open
Polymer pyrolysis has emerged as a versatile method to synthesize graphenoid (graphene like) materials with varying thickness and properties. The morphology of the thin film, especially the thickness, greatly affects the graphitizability a…
View article: An electroluminescent and tunable cavity-enhanced carbon-nanotube-emitter in the telecom band
An electroluminescent and tunable cavity-enhanced carbon-nanotube-emitter in the telecom band Open
View article: Electroluminescence from Single-Walled Carbon Nanotubes with Quantum Defects
Electroluminescence from Single-Walled Carbon Nanotubes with Quantum Defects Open
Individual single-walled carbon nanotubes with covalent sidewall defects have emerged as a class of photon sources whose photoluminescence spectra can be tailored by the carbon nanotube chirality and the attached functional group/molecule.…
View article: Light Control over Chirality Selective Functionalization of Substrate Supported Carbon Nanotubes
Light Control over Chirality Selective Functionalization of Substrate Supported Carbon Nanotubes Open
Diazonium reactions with carbon nanotubes form optical sp3 defects that can be used in optical and electrical circuits. We investigate a direct on-device reaction supported by confined laser irradiation and present a technique where an arb…
View article: Light Control over Chirality Selective Functionalization of Substrate Supported Carbon Nanotubes
Light Control over Chirality Selective Functionalization of Substrate Supported Carbon Nanotubes Open
Diazonium reactions with carbon nanotubes form optical $sp^3$ defects that can be used in optical and electrical circuits. We investigate a direct on-device reaction supported by confined laser irradiation and present a technique where an …
View article: Physics and applications of nanotubes
Physics and applications of nanotubes Open
Nanotubes have been pursued aggressively over the last three decades. Significant progress has been made in the selective growth and post-synthetic sorting of highly monodisperse carbon nanotubes, in understanding their physics, and in ass…
View article: Electrically-Driven Light Emitter in Tailor-Made Photonic Crystal Cavity
Electrically-Driven Light Emitter in Tailor-Made Photonic Crystal Cavity Open
We for the first-time developed telecom hybrid graphene photonic crystal cavity device with an integrated carbon nanotube ensuring high enhancement of its electroluminescent signal and demonstrating the supervision of its intensity.
View article: Contact spacing controls the on-current for all-carbon field effect transistors
Contact spacing controls the on-current for all-carbon field effect transistors Open
View article: Sensing Molecules with Metal–Organic Framework Functionalized Graphene Transistors
Sensing Molecules with Metal–Organic Framework Functionalized Graphene Transistors Open
Graphene is inherently sensitive to vicinal dielectrics and local charge distributions, a property that can be probed by the position of the Dirac point in graphene field‐effect transistors. Exploiting this as a useful sensing principle re…
View article: Erratum to: Principles of carbon nanotube dielectrophoresis
Erratum to: Principles of carbon nanotube dielectrophoresis Open
The original article has been corrected.
View article: Ionic liquid gating of single-walled carbon nanotube devices with ultra-short channel length down to 10 nm
Ionic liquid gating of single-walled carbon nanotube devices with ultra-short channel length down to 10 nm Open
Ionic liquids enable efficient gating of materials with nanoscale morphology due to the formation of a nanoscale double layer that can also follow strongly vaulted surfaces. On carbon nanotubes, this can lead to the formation of a cylindri…
View article: Principles of carbon nanotube dielectrophoresis
Principles of carbon nanotube dielectrophoresis Open
Dielectrophoresis (DEP) describes the motion of suspended objects when exposed to an inhomogeneous electric field. It has been successful as a method for parallel and site-selective assembling of nanotubes from a dispersion into a sophisti…
View article: Anomalous Cyclotron Motion in Graphene Superlattice Cavities
Anomalous Cyclotron Motion in Graphene Superlattice Cavities Open
We consider graphene superlattice miniband fermions probed by electronic interferometry in magnetotransport experiments. By decoding the observed Fabry-Pérot interference patterns together with our corresponding quantum transport simulatio…
View article: Vanishing Hysteresis in Carbon Nanotube Transistors Embedded in Boron Nitride/Polytetrafluoroethylene Heterolayers
Vanishing Hysteresis in Carbon Nanotube Transistors Embedded in Boron Nitride/Polytetrafluoroethylene Heterolayers Open
Carbon nanotube field‐effect transistors fabricated on silicon wafers with thermal oxide often suffer from large gate‐voltage hysteresis, induced by charge trapping sites in oxides, surface hydroxyl groups, and the presence of water molecu…
View article: Raman Fingerprints of Graphene Produced by Anodic Electrochemical Exfoliation
Raman Fingerprints of Graphene Produced by Anodic Electrochemical Exfoliation Open
Electrochemical exfoliation is one of the most promising methods for scalable production of graphene. However, limited understanding of its Raman spectrum as well as lack of measurement standards for graphene strongly limit its industrial …
View article: Low-Temperature Electroluminescence Excitation Mapping of Excitons and Trions in Short-Channel Monochiral Carbon Nanotube Devices
Low-Temperature Electroluminescence Excitation Mapping of Excitons and Trions in Short-Channel Monochiral Carbon Nanotube Devices Open
Single-walled carbon nanotubes as emerging quantum-light sources may fill a technological gap in silicon photonics due to their potential use as near-infrared, electrically driven, classical or nonclassical emitters. Unlike in photolumines…
View article: Separation of Specific Single-Enantiomer Single-Wall Carbon Nanotubes in the Large-Diameter Regime
Separation of Specific Single-Enantiomer Single-Wall Carbon Nanotubes in the Large-Diameter Regime Open
The enantiomer-level isolation of single-walled carbon nanotubes (SWCNTs) in high concentration and with high purity for nanotubes greater than 1.1 nm in diameter is demonstrated using a two-stage aqueous two-phase extraction (ATPE) techni…
View article: Andreev reflection in ballistic normal metal/graphene/superconductor junctions
Andreev reflection in ballistic normal metal/graphene/superconductor junctions Open
We report the study of ballistic transport in normal metal/graphene/superconductor junctions in edge-contactgeometry. While in the normal state, we have observed Fabry-Pérot resonances suggesting that charge carrierstravel ballistically, t…
View article: Low-temperature electroluminescence excitation mapping of excitons and\n trions in short channel monochiral carbon nanotube device
Low-temperature electroluminescence excitation mapping of excitons and\n trions in short channel monochiral carbon nanotube device Open
Single walled carbon nanotubes as emerging quantum-light sources may fill a\ntechnological gap in silicon photonics due to their potential use as near\ninfrared, electrically driven, classical or non-classical emitters. Unlike in\nphotolum…
View article: Low-temperature electroluminescence excitation mapping of excitons and trions in short channel monochiral carbon nanotube device
Low-temperature electroluminescence excitation mapping of excitons and trions in short channel monochiral carbon nanotube device Open
Single walled carbon nanotubes as emerging quantum-light sources may fill a technological gap in silicon photonics due to their potential use as near infrared, electrically driven, classical or non-classical emitters. Unlike in photolumine…
View article: Author Correction: Carbon nanotubes as emerging quantum-light sources
Author Correction: Carbon nanotubes as emerging quantum-light sources Open
View article: Graphene Field-Effect Transistors Employing Different Thin Oxide Films: A Comparative Study
Graphene Field-Effect Transistors Employing Different Thin Oxide Films: A Comparative Study Open
In this work, we report on a comparison among graphene field-effect transistors (GFETs) employing different dielectrics as gate layers to evaluate their microwave response. In particular, aluminum oxide (Al$_{2}$O$_{3}$), titanium oxide (T…
View article: Asymmetry of resonance Raman profiles in semiconducting single-walled carbon nanotubes at the first excitonic transition
Asymmetry of resonance Raman profiles in semiconducting single-walled carbon nanotubes at the first excitonic transition Open
Carbon nanotubes are one-dimensional nanoscale systems with strongly pronounced chirality-dependent optical properties with multiple excitonic transitions. We investigate the high-energy G mode of semiconducting single-walled nanotubes of …
View article: Nanocrystalline graphene at high temperatures: insight into nanoscale processes
Nanocrystalline graphene at high temperatures: insight into nanoscale processes Open
In contrast to pristine graphene, nanocrystalline graphene shows a fundamentally different high-temperature behavior due to its reactive nature.
View article: Valley Subband Splitting in Bilayer Graphene Quantum Point Contacts
Valley Subband Splitting in Bilayer Graphene Quantum Point Contacts Open
We report a study of one-dimensional subband splitting in a bilayer graphene quantum point contact in which quantized conductance in steps of 4e$^{2}$/h is clearly defined down to the lowest subband. While our source-drain bias spectroscop…
View article: Tuning Anti-Klein to Klein Tunneling in Bilayer Graphene
Tuning Anti-Klein to Klein Tunneling in Bilayer Graphene Open
We show that in gapped bilayer graphene, quasiparticle tunneling and the corresponding Berry phase can be controlled such that they exhibit features of single-layer graphene such as Klein tunneling. The Berry phase is detected by a high-qu…
View article: Photocurrent study of all-printed photodetectors on paper made of different transition metal dichalcogenide nanosheets
Photocurrent study of all-printed photodetectors on paper made of different transition metal dichalcogenide nanosheets Open
We have inkjet-printed in-plane ‘metal–semiconductor–metal’ type photodetectors on paper, one of the cheapest flexible substrates, which is also recyclable and foldable, in contrast to traditional plastic substrates. The photodetectors are…