Silke Christiansen | Helmholtz Zentrum Berlin (original) (raw)

Papers by Silke Christiansen

Research paper thumbnail of Index matching at the nanoscale: light scattering by core–shell Si/SiOxnanowires

Nanotechnology, Sep 22, 2016

Silicon nanowires (SiNWs) show strong resonant wavelength enhancement in terms of absorption as w... more Silicon nanowires (SiNWs) show strong resonant wavelength enhancement in terms of absorption as well as scattering of light. However, in most optoelectronic device concepts the SiNWs should be surrounded by a contact layer. Ideally, such a layer can also act as an index matching layer which could nearly halve the strong reflectance of light by silicon. Our results show that this reduction can be overcome at the nanometer scale, i.e. SiNWs embedded in a silica (SiO x ) layer can not only maintain their high scattering cross sections but also their strong polarization dependent scattering. Such effects can be useful for light harvesting or optoelectronic applications. Moreover, we show that it is possible to optically determine the diameters of the embedded nanoscale silicon (Si) cores.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Optical and structural characterization of Si/SiGe heterostructures grown by RTCVD

Thin Solid Films, Jul 1, 2000

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Chemokine/Cytokine Levels Correlate with Organ Involvement in PR3-ANCA-Associated Vasculitis

Journal of Clinical Medicine

Background: ANCA-associated vasculitis (AAV) is a rare small vessel disease characterized by mult... more Background: ANCA-associated vasculitis (AAV) is a rare small vessel disease characterized by multi-organ involvement. Biomarkers that can measure specific organ involvement are missing. Here, we ask whether certain circulating cytokines and chemokines correlate with renal involvement and if distinct cytokine/chemokine patterns can differentiate between renal, ear/nose/throat, joints, and lung involvement of AAV. Methods: Thirty-two sets of Birmingham vasculitis activity score (BVAS), PR3-ANCA titers, laboratory marker, and different cytokines were obtained from 17 different patients with AAV. BVAS, PR3-ANCA titers, laboratory marker, and cytokine concentrations were correlated to different organ involvements in active AAV. Results: Among patients with active PR3-AAV (BVAS > 0) and kidney involvement we found significant higher concentrations of chemokine ligand (CCL)-1, interleukin (IL)-6, IL21, IL23, IL-28A, IL33, monocyte chemoattractant protein 2 (MCP2), stem cell factor (SCF)...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Towards In-Vivo X-Ray Nanoscopy

Informatik aktuell, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of MO015ANALYZING the Effect of Microplastic Particles on Human Podocytes

Nephrology Dialysis Transplantation, 2021

Background and Aims Despite increasing use of plastic based products and their potential health r... more Background and Aims Despite increasing use of plastic based products and their potential health risks on the humans, very little is known about their possible accumulation in the food chain and their further long-term effect on the human health. Recently, there are increasing reports related to the potential risk of polystyrene microplastics to the human respiratory system and human intestinal epithelia cell line. In this study, we assayed the primary effect of microplastic particles on the human kidney cells. To that aim, we used human podocytes cells and four different types of plastic particles including; polyvinyl chloride (PVC), polypropylene (PP), polyamide (PA) and tyre wear particles to evaluate the effects of microplastics on the viability and morphology of human podocytes in vitro. Method In this study, we applied different biological methods such as, cell viability test and phalloidin staining, to assay the toxicity of particles and their further effects on the actin cyto...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Mechanical and Electrical Failure of Silver Nanowire Electrodes: A Scale Bridging In Situ Electron Microscopy Study

Microscopy and Microanalysis, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A network of trans-cortical capillaries as mainstay for blood circulation in long bones

Nature Metabolism, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Axial p–n Junctions in GaN Microrods

physica status solidi (b), 2018

GaN microrods with an axial p–n junction are grown by metal‐organic vapor phase epitaxy (MOVPE). ... more GaN microrods with an axial p–n junction are grown by metal‐organic vapor phase epitaxy (MOVPE). Scanning electron microscopy in combination with cathodoluminescence measurements have been performed to visualize the microrod sections consisting of n‐ and p‐type GaN and the p–n junction. Current–voltage measurements are carried out between different microrod sections to prove the successful formation of a p–n junction. Photovoltaic and photodetecting properties have been determined by illumination of the p–n junction with a UV laser. The shorter p‐type sections in axial microrods and the presence of large diameter rods suggest a growth mode change from vertical to lateral growth during p‐type deposition.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Understanding GaN/InGaN core–shell growth towards high quality factor whispering gallery modes from non-polar InGaN quantum wells on GaN rods

Nanotechnology, 2017

GaN microrods are used as a basis for subsequent InGaN quantum well (QW) and quantum dot depositi... more GaN microrods are used as a basis for subsequent InGaN quantum well (QW) and quantum dot deposition by metal-organic vapor phase epitaxy. The coverage of the shell along the sidewall of rods is dependent on the rod growth time and a complete coverage is obtained for shorter rod growth times. Transmission electron microscopy measurements are performed to reveal the structural properties of the InGaN layer on the sidewall facet and on the top facet. The presence of layers in the microrod and on the microrod surface will be discussed with respect to GaN and InGaN growth. A detailed model will be presented explaining the formation of multiple SiN layers and the partial and full coverage of the shell around the core. Cathodoluminescence measurements are performed to analyze the InGaN emission properties along the microrod and to study the microresonator properties of such hexagonal core-shell structures. High quality factor whispering gallery modes with [Formula: see text] are reported for the first time in a GaN microrod/InGaN non-polar QW core-shell geometry. The GaN/InGaN core-shell microrods are expected to be promising building blocks for low-threshold laser diodes and ultra-sensitive optical sensors.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Mode Matching for Optical Antennas

Physical Review Letters, 2017

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Free charges versus excitons: photoluminescence investigation of InGaN/GaN multiple quantum well nanorods and their planar counterparts

Nanoscale, Jan 15, 2018

InGaN/GaN multiple quantum well (MQW) nanorods have demonstrated significantly improved optical a... more InGaN/GaN multiple quantum well (MQW) nanorods have demonstrated significantly improved optical and electronic properties compared to their planar counterparts. However, the exact nature of the processes whereby nanorod structures impact the optical properties of quantum wells is not well understood, even though a variety of mechanisms have been proposed. We performed nanoscale spatially resolved, steady-state, and time-resolved photoluminescence (PL) experiments confirming that photoexcited electrons and holes are strongly bound by Coulomb interactions (i.e., excitons) in planar MQWs due to the large exciton binding energy in InGaN quantum wells. In contrast, free electron-hole recombination becomes the dominant mechanism in nanorods, which is ascribed to efficient exciton dissociation. The nanorod sidewall provides an effective pathway for exciton dissociation that significantly improves the optical performance of InGaN/GaN MQWs. We also confirm that surface treatment of nanorod s...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Microstructure of silicon nanorods for novel solar cells

Resolution and Discovery, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of In-Situ Characterization of Individual Building Blocks for Nanophotonic Solar Cells by Correlative Microscopy

Microscopy and Microanalysis, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Carrier-induced refractive index change observed by a whispering gallery mode shift in GaN microrods

New Journal of Physics, 2015

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Self-Catalyzed Growth of Vertically Aligned InN Nanorods by Metal–Organic Vapor Phase Epitaxy

Nano Letters, 2016

Vertically aligned hexagonal InN nanorods were grown mask-free by conventional metal-organic vapo... more Vertically aligned hexagonal InN nanorods were grown mask-free by conventional metal-organic vapor phase epitaxy without any foreign catalyst. The In droplets on top of the nanorods indicate a self-catalytic vapor-liquid-solid growth mode. A systematic study on important growth parameters has been carried out for the optimization of nanorod morphology. The nanorod N-polarity, induced by high temperature nitridation of the sapphire substrate, is necessary to achieve vertical growth. Hydrogen, usually inapplicable during InN growth due to formation of metallic indium, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the sapphire surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temperature is similar. Transmission electron microscopy, spatially resolved energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy have been performed to analyze the structural properties. Spatially resolved cathodoluminescence investigations are carried out to verify the optical activity of the InN nanorods. The InN nanorods are expected to be the material of choice for high-efficiency hot carrier solar cells.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Inorganic photovoltaics – Planar and nanostructured devices

Progress in Materials Science, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of New insights into colloidal gold flakes: structural investigation, micro-ellipsometry and thinning procedure towards ultrathin monocrystalline layers

Nanoscale, Jan 18, 2016

High-quality fabrication of plasmonic devices often relies on wet-chemically grown ultraflat, pre... more High-quality fabrication of plasmonic devices often relies on wet-chemically grown ultraflat, presumably single-crystalline gold flakes due to their superior materials properties. However, important details about their intrinsic structure and their optical properties are not well understood yet. In this study, we present a synthesis routine for large flakes with diameters of up to 70 μm and an in-depth investigation of their structural and optical properties. The flakes are precisely analyzed by transmission electron microscopy, electron backscatter diffraction and micro-ellipsometry. We found new evidence for the existence of twins extending parallel to the Au flake {111} surfaces which have been found to not interfere with the presented nanopatterning. Micro-Ellipsometry was carried out to determine the complex dielectric function and to compare it to previous measurements of bulk single crystalline gold. Finally, we used focused ion beam milling to prepare smooth crystalline laye...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Optical and structural characterization of silicon‐carbon‐nitride thin films for optoelectronics

physica status solidi c, 2010

Amorphous a‐SiCN:H films were deposited by radio frequency Plasma Enhanced Chemical Vapour Deposi... more Amorphous a‐SiCN:H films were deposited by radio frequency Plasma Enhanced Chemical Vapour Deposition (PECVD) at 13.56 MHz from silane‐methane‐ammonia (SiH4+CH4+NH3) gaseous mixture. Morphological, structural and optical characterization of a‐SiCN:H in correlation with process parameters was done. High growth rate of films was influenced mainly by presence of ammonia and silane in technological process. FTIR spectra analysis of films revealed the influence of gaseous mixture content in PECVD process on their structure. The refractive index and optical gap depended on elemental composition of films. The total reflectivity of a‐SiCN:H on monocrystalline silicon revealed increase with the decrease in carbon and nitrogen content. The a‐SiCN:H films are smooth, homogeneous, chemically inert and wear resistive and also hydrogen rich, which is important from the application point of view (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Bookmarks Related papers MentionsView impact

Research paper thumbnail of GaN‐Based Nanorods/Graphene Heterostructures for Optoelectronic Applications

physica status solidi (b), 2019

The insulating character of sapphire, meltback etching of Si, bulk and surface defects prevented ... more The insulating character of sapphire, meltback etching of Si, bulk and surface defects prevented the efficient integration of GaN nanostructures in optoelectronic devices. Here, it is demonstrated that graphene can simultaneously serve as an electrical bottom contact, a chemically inert buffer layer, and a superior lattice and thermal matched growth substrate. Vertically aligned, high crystal quality GaN nanorods (NRs) without bulk defects such as threading dislocations and with only a mild strain at the NRs’ base are grown by metal‐organic vapor‐phase epitaxy on defect‐free graphene using nanometer‐sized AlxGa1−xN nucleation islands. Here no influence of the supporting substrate on the GaN epitaxy is observed. However, at defects in graphene the effects of dangling bonds and the underlying substrate, presumably through nanoholes in graphene, on the properties of GaN NRs are visible. It is also shown that surface defects in InxGa1−xN/GaN NRs from planar films produced by etching of ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Efficient Nitrogen Doping of Single-Layer Graphene Accompanied by Negligible Defect Generation for Integration into Hybrid Semiconductor Heterostructures

ACS Applied Materials & Interfaces, 2017

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Index matching at the nanoscale: light scattering by core–shell Si/SiOxnanowires

Nanotechnology, Sep 22, 2016

Silicon nanowires (SiNWs) show strong resonant wavelength enhancement in terms of absorption as w... more Silicon nanowires (SiNWs) show strong resonant wavelength enhancement in terms of absorption as well as scattering of light. However, in most optoelectronic device concepts the SiNWs should be surrounded by a contact layer. Ideally, such a layer can also act as an index matching layer which could nearly halve the strong reflectance of light by silicon. Our results show that this reduction can be overcome at the nanometer scale, i.e. SiNWs embedded in a silica (SiO x ) layer can not only maintain their high scattering cross sections but also their strong polarization dependent scattering. Such effects can be useful for light harvesting or optoelectronic applications. Moreover, we show that it is possible to optically determine the diameters of the embedded nanoscale silicon (Si) cores.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Optical and structural characterization of Si/SiGe heterostructures grown by RTCVD

Thin Solid Films, Jul 1, 2000

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Chemokine/Cytokine Levels Correlate with Organ Involvement in PR3-ANCA-Associated Vasculitis

Journal of Clinical Medicine

Background: ANCA-associated vasculitis (AAV) is a rare small vessel disease characterized by mult... more Background: ANCA-associated vasculitis (AAV) is a rare small vessel disease characterized by multi-organ involvement. Biomarkers that can measure specific organ involvement are missing. Here, we ask whether certain circulating cytokines and chemokines correlate with renal involvement and if distinct cytokine/chemokine patterns can differentiate between renal, ear/nose/throat, joints, and lung involvement of AAV. Methods: Thirty-two sets of Birmingham vasculitis activity score (BVAS), PR3-ANCA titers, laboratory marker, and different cytokines were obtained from 17 different patients with AAV. BVAS, PR3-ANCA titers, laboratory marker, and cytokine concentrations were correlated to different organ involvements in active AAV. Results: Among patients with active PR3-AAV (BVAS > 0) and kidney involvement we found significant higher concentrations of chemokine ligand (CCL)-1, interleukin (IL)-6, IL21, IL23, IL-28A, IL33, monocyte chemoattractant protein 2 (MCP2), stem cell factor (SCF)...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Towards In-Vivo X-Ray Nanoscopy

Informatik aktuell, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of MO015ANALYZING the Effect of Microplastic Particles on Human Podocytes

Nephrology Dialysis Transplantation, 2021

Background and Aims Despite increasing use of plastic based products and their potential health r... more Background and Aims Despite increasing use of plastic based products and their potential health risks on the humans, very little is known about their possible accumulation in the food chain and their further long-term effect on the human health. Recently, there are increasing reports related to the potential risk of polystyrene microplastics to the human respiratory system and human intestinal epithelia cell line. In this study, we assayed the primary effect of microplastic particles on the human kidney cells. To that aim, we used human podocytes cells and four different types of plastic particles including; polyvinyl chloride (PVC), polypropylene (PP), polyamide (PA) and tyre wear particles to evaluate the effects of microplastics on the viability and morphology of human podocytes in vitro. Method In this study, we applied different biological methods such as, cell viability test and phalloidin staining, to assay the toxicity of particles and their further effects on the actin cyto...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Mechanical and Electrical Failure of Silver Nanowire Electrodes: A Scale Bridging In Situ Electron Microscopy Study

Microscopy and Microanalysis, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A network of trans-cortical capillaries as mainstay for blood circulation in long bones

Nature Metabolism, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Axial p–n Junctions in GaN Microrods

physica status solidi (b), 2018

GaN microrods with an axial p–n junction are grown by metal‐organic vapor phase epitaxy (MOVPE). ... more GaN microrods with an axial p–n junction are grown by metal‐organic vapor phase epitaxy (MOVPE). Scanning electron microscopy in combination with cathodoluminescence measurements have been performed to visualize the microrod sections consisting of n‐ and p‐type GaN and the p–n junction. Current–voltage measurements are carried out between different microrod sections to prove the successful formation of a p–n junction. Photovoltaic and photodetecting properties have been determined by illumination of the p–n junction with a UV laser. The shorter p‐type sections in axial microrods and the presence of large diameter rods suggest a growth mode change from vertical to lateral growth during p‐type deposition.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Understanding GaN/InGaN core–shell growth towards high quality factor whispering gallery modes from non-polar InGaN quantum wells on GaN rods

Nanotechnology, 2017

GaN microrods are used as a basis for subsequent InGaN quantum well (QW) and quantum dot depositi... more GaN microrods are used as a basis for subsequent InGaN quantum well (QW) and quantum dot deposition by metal-organic vapor phase epitaxy. The coverage of the shell along the sidewall of rods is dependent on the rod growth time and a complete coverage is obtained for shorter rod growth times. Transmission electron microscopy measurements are performed to reveal the structural properties of the InGaN layer on the sidewall facet and on the top facet. The presence of layers in the microrod and on the microrod surface will be discussed with respect to GaN and InGaN growth. A detailed model will be presented explaining the formation of multiple SiN layers and the partial and full coverage of the shell around the core. Cathodoluminescence measurements are performed to analyze the InGaN emission properties along the microrod and to study the microresonator properties of such hexagonal core-shell structures. High quality factor whispering gallery modes with [Formula: see text] are reported for the first time in a GaN microrod/InGaN non-polar QW core-shell geometry. The GaN/InGaN core-shell microrods are expected to be promising building blocks for low-threshold laser diodes and ultra-sensitive optical sensors.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Mode Matching for Optical Antennas

Physical Review Letters, 2017

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Free charges versus excitons: photoluminescence investigation of InGaN/GaN multiple quantum well nanorods and their planar counterparts

Nanoscale, Jan 15, 2018

InGaN/GaN multiple quantum well (MQW) nanorods have demonstrated significantly improved optical a... more InGaN/GaN multiple quantum well (MQW) nanorods have demonstrated significantly improved optical and electronic properties compared to their planar counterparts. However, the exact nature of the processes whereby nanorod structures impact the optical properties of quantum wells is not well understood, even though a variety of mechanisms have been proposed. We performed nanoscale spatially resolved, steady-state, and time-resolved photoluminescence (PL) experiments confirming that photoexcited electrons and holes are strongly bound by Coulomb interactions (i.e., excitons) in planar MQWs due to the large exciton binding energy in InGaN quantum wells. In contrast, free electron-hole recombination becomes the dominant mechanism in nanorods, which is ascribed to efficient exciton dissociation. The nanorod sidewall provides an effective pathway for exciton dissociation that significantly improves the optical performance of InGaN/GaN MQWs. We also confirm that surface treatment of nanorod s...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Microstructure of silicon nanorods for novel solar cells

Resolution and Discovery, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of In-Situ Characterization of Individual Building Blocks for Nanophotonic Solar Cells by Correlative Microscopy

Microscopy and Microanalysis, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Carrier-induced refractive index change observed by a whispering gallery mode shift in GaN microrods

New Journal of Physics, 2015

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Self-Catalyzed Growth of Vertically Aligned InN Nanorods by Metal–Organic Vapor Phase Epitaxy

Nano Letters, 2016

Vertically aligned hexagonal InN nanorods were grown mask-free by conventional metal-organic vapo... more Vertically aligned hexagonal InN nanorods were grown mask-free by conventional metal-organic vapor phase epitaxy without any foreign catalyst. The In droplets on top of the nanorods indicate a self-catalytic vapor-liquid-solid growth mode. A systematic study on important growth parameters has been carried out for the optimization of nanorod morphology. The nanorod N-polarity, induced by high temperature nitridation of the sapphire substrate, is necessary to achieve vertical growth. Hydrogen, usually inapplicable during InN growth due to formation of metallic indium, and silane are needed to enhance the aspect ratio and to reduce parasitic deposition beside the nanorods on the sapphire surface. The results reveal many similarities between InN and GaN nanorod growth showing that the process despite the large difference in growth temperature is similar. Transmission electron microscopy, spatially resolved energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy have been performed to analyze the structural properties. Spatially resolved cathodoluminescence investigations are carried out to verify the optical activity of the InN nanorods. The InN nanorods are expected to be the material of choice for high-efficiency hot carrier solar cells.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Inorganic photovoltaics – Planar and nanostructured devices

Progress in Materials Science, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of New insights into colloidal gold flakes: structural investigation, micro-ellipsometry and thinning procedure towards ultrathin monocrystalline layers

Nanoscale, Jan 18, 2016

High-quality fabrication of plasmonic devices often relies on wet-chemically grown ultraflat, pre... more High-quality fabrication of plasmonic devices often relies on wet-chemically grown ultraflat, presumably single-crystalline gold flakes due to their superior materials properties. However, important details about their intrinsic structure and their optical properties are not well understood yet. In this study, we present a synthesis routine for large flakes with diameters of up to 70 μm and an in-depth investigation of their structural and optical properties. The flakes are precisely analyzed by transmission electron microscopy, electron backscatter diffraction and micro-ellipsometry. We found new evidence for the existence of twins extending parallel to the Au flake {111} surfaces which have been found to not interfere with the presented nanopatterning. Micro-Ellipsometry was carried out to determine the complex dielectric function and to compare it to previous measurements of bulk single crystalline gold. Finally, we used focused ion beam milling to prepare smooth crystalline laye...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Optical and structural characterization of silicon‐carbon‐nitride thin films for optoelectronics

physica status solidi c, 2010

Amorphous a‐SiCN:H films were deposited by radio frequency Plasma Enhanced Chemical Vapour Deposi... more Amorphous a‐SiCN:H films were deposited by radio frequency Plasma Enhanced Chemical Vapour Deposition (PECVD) at 13.56 MHz from silane‐methane‐ammonia (SiH4+CH4+NH3) gaseous mixture. Morphological, structural and optical characterization of a‐SiCN:H in correlation with process parameters was done. High growth rate of films was influenced mainly by presence of ammonia and silane in technological process. FTIR spectra analysis of films revealed the influence of gaseous mixture content in PECVD process on their structure. The refractive index and optical gap depended on elemental composition of films. The total reflectivity of a‐SiCN:H on monocrystalline silicon revealed increase with the decrease in carbon and nitrogen content. The a‐SiCN:H films are smooth, homogeneous, chemically inert and wear resistive and also hydrogen rich, which is important from the application point of view (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Bookmarks Related papers MentionsView impact

Research paper thumbnail of GaN‐Based Nanorods/Graphene Heterostructures for Optoelectronic Applications

physica status solidi (b), 2019

The insulating character of sapphire, meltback etching of Si, bulk and surface defects prevented ... more The insulating character of sapphire, meltback etching of Si, bulk and surface defects prevented the efficient integration of GaN nanostructures in optoelectronic devices. Here, it is demonstrated that graphene can simultaneously serve as an electrical bottom contact, a chemically inert buffer layer, and a superior lattice and thermal matched growth substrate. Vertically aligned, high crystal quality GaN nanorods (NRs) without bulk defects such as threading dislocations and with only a mild strain at the NRs’ base are grown by metal‐organic vapor‐phase epitaxy on defect‐free graphene using nanometer‐sized AlxGa1−xN nucleation islands. Here no influence of the supporting substrate on the GaN epitaxy is observed. However, at defects in graphene the effects of dangling bonds and the underlying substrate, presumably through nanoholes in graphene, on the properties of GaN NRs are visible. It is also shown that surface defects in InxGa1−xN/GaN NRs from planar films produced by etching of ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Efficient Nitrogen Doping of Single-Layer Graphene Accompanied by Negligible Defect Generation for Integration into Hybrid Semiconductor Heterostructures

ACS Applied Materials & Interfaces, 2017

Bookmarks Related papers MentionsView impact