D. Convertino - Academia.edu (original) (raw)
Papers by D. Convertino
Nanoscale Advances, 2021
The employment of 2D materials, as growth substrates or buffer layers, enables the epitaxial grow... more The employment of 2D materials, as growth substrates or buffer layers, enables the epitaxial growth of layered materials with different crystalline symmetries with a preferential crystalline orientation and the synthesis of heterostructures with a large lattice constant mismatch.
Epitaxial growth of graphene by thermal decomposition of silicon carbide (SiC) is a classical app... more Epitaxial growth of graphene by thermal decomposition of silicon carbide (SiC) is a classical approach to obtain large-area continuous films directly on a semi-conducting substrate [1, 2]. The two different basal planes of the hexagonal SiC polytypes, i.e., SiC(0001) (Si-face) and SiC (000-1) (C-face), show significantly different growth modes for graphene. In particular, the graphene layers obtained on the Cface lack a defined azimuthal orientation (i.e., turbostratic graphene) so that each layer behaves as an isolated layer and is electronically decoupled from the neighboring ones. For this reason, on this type of graphene, remarkable carrier mobilities have been measured [3]. Thickness control for graphene grown by means of thermal decomposition of SiC(000-1) is quite difficult to achieve. Recently, we have developed a chemical vapor deposition (CVD) approach that allows to synthesize graphene on SiC(0001) while finely controlling the number of grown layers [4].
Epitaxial growth of graphene by thermal decomposition of silicon carbide (SiC) is a classical and... more Epitaxial growth of graphene by thermal decomposition of silicon carbide (SiC) is a classical and successful approach to obtain large-area continuous films directly on a semi-insulating substrate [1,2]. In this process the SiC crystal acts as precursor: the heating of the substrate at temperatures around 1350°-1450°C in Argon atmosphere causes Si sublimation, and the C atoms left behind rearrange in a honeycomb structure forming one or more layers of graphene [2]. Notably, the two different crystal basal planes of the hexagonal polytypes of SiC, indicated as SiC(0001) (Si-face) and SiC(000-1) (C-face), show significantly different growth modes for graphene. In particular, the graphene layers obtained on the C-face lack a defined azimuthal orientation (i.e., turbostratic graphene) so that each layer behaves as an isolated graphene layer and is electronically decoupled from the neighboring ones. For this reason, on this type of graphene, remarkable carrier mobilties have been measured...
The great interest in fast room-temperature detectors for the far infrared (or terahertz THz) par... more The great interest in fast room-temperature detectors for the far infrared (or terahertz THz) part of the electromagnetic spectrum is strongly encouraged by the large variety of THz applications in biomedical and security imaging. In particular, many efforts are currently dedicated to develop compact, portable, sensitive, very fast imagers. Recently, a novel type of fast devices employing graphene sheets have been reported to efficiently detect THz light at room temperature thanks to a plasma-wave-assisted mechanism [1-3]. These detectors consist of field effect transistors whose channel is composed by graphene (GFET). Thanks to GFETs high quality electronics properties, graphene-based THz detectors are highly promising for fabricating focal plane sensing devices with high responsivity and ultrafast response time. In order to fabricate an array of GFET-detectors, large area graphene is strictly needed. For this reason, epitaxial graphene (EG) is an interesting solution, as high qual...
Several works reported increased differentiation of neuronal cells grown on graphene; however, th... more Several works reported increased differentiation of neuronal cells grown on graphene; however, the molecular mechanism driving axon elongation on this material has remained elusive. Here, we study the axonal transport of nerve growth factor (NGF), the neurotrophin supporting development of peripheral neurons, as a key player in the time course of axonal elongation of dorsal root ganglion neurons on graphene. We find that graphene drastically reduces the number of retrogradely transported NGF vesicles in favor of a stalled population in the first 2 days of culture, in which the boost of axon elongation is observed. This correlates with a mutual charge redistribution, observed via Raman spectroscopy and electrophysiological recordings. Furthermore, ultrastructural analysis indicates a reduced microtubule distance and an elongated axonal topology. Thus, both electrophysiological and structural effects can account for graphene action on neuron development. Unraveling the molecular players underneath this interplay may open new avenues for axon regeneration applications.
The surface structure of Few-Layer Graphene (FLG) epitaxially grown on the C-face of SiC has been... more The surface structure of Few-Layer Graphene (FLG) epitaxially grown on the C-face of SiC has been investigated by TM-AFM in ambient air and upon interaction with diluted aqueous solutions of bio-organic molecules (dimethyl sulfoxide, DMSO, and L-Methionine). On pristine FLG we observe nicely ordered, three-fold oriented rippled domains, with a 4.7+/-0.2 nm periodicity (small periodicity, SP) and a peak-to-valley distance in the range 0.1-0.2 nm. Upon mild interaction of the FLG surface with the molecular solution, the ripple periodicity relaxes to 6.2+/-0.2 nm (large periodicity, LP), while the peak-to-valley height increases to 0.2-0.3 nm. When additional energy is transferred to the system through sonication in solution, graphene planes are peeled off from FLG, as shown by quantitative analysis of XPS and Raman spectroscopy data which indicate a neat reduction of thickness. Upon sonication rippled domains are no longer observed. Regarding HOPG, we could not observe ripples on clea...
Physical Chemistry Chemical Physics
The surface structure of Few-Layer Graphene (FLG) epitaxially grown on the C-face of SiC has been... more The surface structure of Few-Layer Graphene (FLG) epitaxially grown on the C-face of SiC has been investigated by TM-AFM in ambient air and upon interaction with dilute aqueous solutions of bio-organic molecules (l-methionine and dimethyl sulfoxide, DMSO).
MRS Advances
This work presents a comparison of the structural, chemical and electronic properties of multi-la... more This work presents a comparison of the structural, chemical and electronic properties of multi-layer graphene grown on SiC(000-1) by using two different growth approaches: thermal decomposition and chemical vapor deposition (CVD). The topography of the samples was investigated by using atomic force microscopy (AFM), and scanning electron microscopy (SEM) was performed to examine the sample on a large scale. Raman spectroscopy was used to assess the crystallinity and electronic behavior of the multi-layer graphene and to estimate its thickness in a non-invasive way. While the crystallinity of the samples obtained with the two different approaches is comparable, our results indicate that the CVD method allows for a better thickness control of the grown graphene.
![Research paper thumbnail of Erratum: “Coherent absorption of light by graphene and other optically conducting surfaces in realistic on-substrate configurations,” [APL Photonics 2, 016101 (2017)]](https://attachments.academia-assets.com/69507055/thumbnails/1.jpg)
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Applied Physics Letters, 2015
Beilstein journal of nanotechnology, 2015
Graphene-based electrodes are very promising for molecular electronics and spintronics. Here we r... more Graphene-based electrodes are very promising for molecular electronics and spintronics. Here we report a systematic characterization of the electroburning (EB) process, leading to the formation of nanometer-spaced gaps, on different types of few-layer graphene (namely mechanically exfoliated graphene on SiO2, graphene epitaxially grown on the C-face of SiC and turbostratic graphene discs deposited on SiO2) under air and vacuum conditions. The EB process is found to depend on both the graphene type and on the ambient conditions. For the mechanically exfoliated graphene, performing EB under vacuum leads to a higher yield of nanometer-gap formation than working in air. Conversely, for graphene on SiC the EB process is not successful under vacuum. Finally, the EB is possible with turbostratic graphene discs only after the creation of a constriction in the sample using lithographic patterning.
Applied Physics Letters, 2015
Titanium-island formation on graphene as a function of defect density is investigated. When depos... more Titanium-island formation on graphene as a function of defect density is investigated. When depositing titanium on pristine graphene, titanium atoms cluster and form islands with an average diameter of about 10 nm and an average height of a few atomic layers. We show that if defects are introduced in the graphene by ion bombardment, the mobility of the deposited titanium atoms is reduced and the average diameter of the islands decreases to 5 nm with monoatomic height. This results in an optimized coverage for hydrogen storage applications since the actual titanium surface available per unit graphene area is significantly increased.
2D Materials, 2015
In this work we present a simple pathway to obtain large single-crystal graphene on copper (Cu) f... more In this work we present a simple pathway to obtain large single-crystal graphene on copper (Cu) foils with high growth rates using a commercially available cold-wall chemical vapour deposition (CVD) reactor. We show that graphene nucleation density is drastically reduced and crystal growth is accelerated when: i) using ex-situ oxidised foils; ii) performing annealing in an inert atmosphere prior to growth; iii) enclosing the foils to lower the precursor impingement lux during growth. Growth rates as high as 14.7 and 17.5 µm per minute are obtained on lat and folded foils, respectively. Thus, single-crystal grains with lateral size of about one millimetre can be obtained in just one hour. The samples are characterised by optical microscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy as well as selected area electron difraction (SAED) and low-energy electron difraction (LEED), which conirm the high quality and homogeneity of the ilms. The development of a process for the quick production of large grain graphene in a commonly used commercial CVD reactor is a signiicant step towards an increased accessibility to millimetre-sized graphene crystals.
Nanoscale Advances, 2021
The employment of 2D materials, as growth substrates or buffer layers, enables the epitaxial grow... more The employment of 2D materials, as growth substrates or buffer layers, enables the epitaxial growth of layered materials with different crystalline symmetries with a preferential crystalline orientation and the synthesis of heterostructures with a large lattice constant mismatch.
Epitaxial growth of graphene by thermal decomposition of silicon carbide (SiC) is a classical app... more Epitaxial growth of graphene by thermal decomposition of silicon carbide (SiC) is a classical approach to obtain large-area continuous films directly on a semi-conducting substrate [1, 2]. The two different basal planes of the hexagonal SiC polytypes, i.e., SiC(0001) (Si-face) and SiC (000-1) (C-face), show significantly different growth modes for graphene. In particular, the graphene layers obtained on the Cface lack a defined azimuthal orientation (i.e., turbostratic graphene) so that each layer behaves as an isolated layer and is electronically decoupled from the neighboring ones. For this reason, on this type of graphene, remarkable carrier mobilities have been measured [3]. Thickness control for graphene grown by means of thermal decomposition of SiC(000-1) is quite difficult to achieve. Recently, we have developed a chemical vapor deposition (CVD) approach that allows to synthesize graphene on SiC(0001) while finely controlling the number of grown layers [4].
Epitaxial growth of graphene by thermal decomposition of silicon carbide (SiC) is a classical and... more Epitaxial growth of graphene by thermal decomposition of silicon carbide (SiC) is a classical and successful approach to obtain large-area continuous films directly on a semi-insulating substrate [1,2]. In this process the SiC crystal acts as precursor: the heating of the substrate at temperatures around 1350°-1450°C in Argon atmosphere causes Si sublimation, and the C atoms left behind rearrange in a honeycomb structure forming one or more layers of graphene [2]. Notably, the two different crystal basal planes of the hexagonal polytypes of SiC, indicated as SiC(0001) (Si-face) and SiC(000-1) (C-face), show significantly different growth modes for graphene. In particular, the graphene layers obtained on the C-face lack a defined azimuthal orientation (i.e., turbostratic graphene) so that each layer behaves as an isolated graphene layer and is electronically decoupled from the neighboring ones. For this reason, on this type of graphene, remarkable carrier mobilties have been measured...
The great interest in fast room-temperature detectors for the far infrared (or terahertz THz) par... more The great interest in fast room-temperature detectors for the far infrared (or terahertz THz) part of the electromagnetic spectrum is strongly encouraged by the large variety of THz applications in biomedical and security imaging. In particular, many efforts are currently dedicated to develop compact, portable, sensitive, very fast imagers. Recently, a novel type of fast devices employing graphene sheets have been reported to efficiently detect THz light at room temperature thanks to a plasma-wave-assisted mechanism [1-3]. These detectors consist of field effect transistors whose channel is composed by graphene (GFET). Thanks to GFETs high quality electronics properties, graphene-based THz detectors are highly promising for fabricating focal plane sensing devices with high responsivity and ultrafast response time. In order to fabricate an array of GFET-detectors, large area graphene is strictly needed. For this reason, epitaxial graphene (EG) is an interesting solution, as high qual...
Several works reported increased differentiation of neuronal cells grown on graphene; however, th... more Several works reported increased differentiation of neuronal cells grown on graphene; however, the molecular mechanism driving axon elongation on this material has remained elusive. Here, we study the axonal transport of nerve growth factor (NGF), the neurotrophin supporting development of peripheral neurons, as a key player in the time course of axonal elongation of dorsal root ganglion neurons on graphene. We find that graphene drastically reduces the number of retrogradely transported NGF vesicles in favor of a stalled population in the first 2 days of culture, in which the boost of axon elongation is observed. This correlates with a mutual charge redistribution, observed via Raman spectroscopy and electrophysiological recordings. Furthermore, ultrastructural analysis indicates a reduced microtubule distance and an elongated axonal topology. Thus, both electrophysiological and structural effects can account for graphene action on neuron development. Unraveling the molecular players underneath this interplay may open new avenues for axon regeneration applications.
The surface structure of Few-Layer Graphene (FLG) epitaxially grown on the C-face of SiC has been... more The surface structure of Few-Layer Graphene (FLG) epitaxially grown on the C-face of SiC has been investigated by TM-AFM in ambient air and upon interaction with diluted aqueous solutions of bio-organic molecules (dimethyl sulfoxide, DMSO, and L-Methionine). On pristine FLG we observe nicely ordered, three-fold oriented rippled domains, with a 4.7+/-0.2 nm periodicity (small periodicity, SP) and a peak-to-valley distance in the range 0.1-0.2 nm. Upon mild interaction of the FLG surface with the molecular solution, the ripple periodicity relaxes to 6.2+/-0.2 nm (large periodicity, LP), while the peak-to-valley height increases to 0.2-0.3 nm. When additional energy is transferred to the system through sonication in solution, graphene planes are peeled off from FLG, as shown by quantitative analysis of XPS and Raman spectroscopy data which indicate a neat reduction of thickness. Upon sonication rippled domains are no longer observed. Regarding HOPG, we could not observe ripples on clea...
Physical Chemistry Chemical Physics
The surface structure of Few-Layer Graphene (FLG) epitaxially grown on the C-face of SiC has been... more The surface structure of Few-Layer Graphene (FLG) epitaxially grown on the C-face of SiC has been investigated by TM-AFM in ambient air and upon interaction with dilute aqueous solutions of bio-organic molecules (l-methionine and dimethyl sulfoxide, DMSO).
MRS Advances
This work presents a comparison of the structural, chemical and electronic properties of multi-la... more This work presents a comparison of the structural, chemical and electronic properties of multi-layer graphene grown on SiC(000-1) by using two different growth approaches: thermal decomposition and chemical vapor deposition (CVD). The topography of the samples was investigated by using atomic force microscopy (AFM), and scanning electron microscopy (SEM) was performed to examine the sample on a large scale. Raman spectroscopy was used to assess the crystallinity and electronic behavior of the multi-layer graphene and to estimate its thickness in a non-invasive way. While the crystallinity of the samples obtained with the two different approaches is comparable, our results indicate that the CVD method allows for a better thickness control of the grown graphene.
Applied Physics Letters, 2015
Beilstein journal of nanotechnology, 2015
Graphene-based electrodes are very promising for molecular electronics and spintronics. Here we r... more Graphene-based electrodes are very promising for molecular electronics and spintronics. Here we report a systematic characterization of the electroburning (EB) process, leading to the formation of nanometer-spaced gaps, on different types of few-layer graphene (namely mechanically exfoliated graphene on SiO2, graphene epitaxially grown on the C-face of SiC and turbostratic graphene discs deposited on SiO2) under air and vacuum conditions. The EB process is found to depend on both the graphene type and on the ambient conditions. For the mechanically exfoliated graphene, performing EB under vacuum leads to a higher yield of nanometer-gap formation than working in air. Conversely, for graphene on SiC the EB process is not successful under vacuum. Finally, the EB is possible with turbostratic graphene discs only after the creation of a constriction in the sample using lithographic patterning.
Applied Physics Letters, 2015
Titanium-island formation on graphene as a function of defect density is investigated. When depos... more Titanium-island formation on graphene as a function of defect density is investigated. When depositing titanium on pristine graphene, titanium atoms cluster and form islands with an average diameter of about 10 nm and an average height of a few atomic layers. We show that if defects are introduced in the graphene by ion bombardment, the mobility of the deposited titanium atoms is reduced and the average diameter of the islands decreases to 5 nm with monoatomic height. This results in an optimized coverage for hydrogen storage applications since the actual titanium surface available per unit graphene area is significantly increased.
2D Materials, 2015
In this work we present a simple pathway to obtain large single-crystal graphene on copper (Cu) f... more In this work we present a simple pathway to obtain large single-crystal graphene on copper (Cu) foils with high growth rates using a commercially available cold-wall chemical vapour deposition (CVD) reactor. We show that graphene nucleation density is drastically reduced and crystal growth is accelerated when: i) using ex-situ oxidised foils; ii) performing annealing in an inert atmosphere prior to growth; iii) enclosing the foils to lower the precursor impingement lux during growth. Growth rates as high as 14.7 and 17.5 µm per minute are obtained on lat and folded foils, respectively. Thus, single-crystal grains with lateral size of about one millimetre can be obtained in just one hour. The samples are characterised by optical microscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy as well as selected area electron difraction (SAED) and low-energy electron difraction (LEED), which conirm the high quality and homogeneity of the ilms. The development of a process for the quick production of large grain graphene in a commonly used commercial CVD reactor is a signiicant step towards an increased accessibility to millimetre-sized graphene crystals.