David Brunel - Academia.edu (original) (raw)
Papers by David Brunel
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
2016 IEEE 62nd Holm Conference on Electrical Contacts (Holm), 2016
Developing low friction and high conduction layers for electrical contacts has been a challenge f... more Developing low friction and high conduction layers for electrical contacts has been a challenge for many years. Graphene is known to display outstanding friction and electrical behaviors; lately much work has been conducted both in the applied and fundamental fields of friction in order to understand the mechanisms involved. In the past years we have done experimental work on the tribological behavior of galvanic gold surfaces coated with various types of graphene-like coatings deposited by spraying liquid phase exfoliated graphite. The results showed that the unevenly distributed graphene-like flakes on the surface could bring strong friction reduction. However such coatings are difficult to control and a more controllable deposition technique such as CVD is considered here. The aim of this work is to start investigating the effect of friction on the properties of graphene layers at a microscopic scale and at a macroscopic scale. The first aspect is presented here. In order to assess the effect of friction and wear on graphene films, an atomic force microscope (AFM) is used. The effects of friction of the cantilever tip on the graphene coated plane are investigated. Topographic and electrical properties of the wear scars are recorded as well as the structure of the coating, thanks to a new customized system consisting of a Conducting Probe-AFM (CP-AFM) fitted confocal Raman microscope. Simultaneous topographic maps, electrical maps and Raman maps can be recorded on the friction tracks produced on the graphene coated surfaces. Electrical maps are built from the local values of tip/surface resistance while structure maps are built from the intensity of chosen representative peaks of the Raman spectra. Preliminary results were acquired on CVD graphene transferred to a silicon substrate. This involves a special technique that can induce defects in the graphene film and leave some insulating contamination on the surface. Friction behavior is investigated for different numbers of cycles and for different normal loads. Both parameters seem to govern the behavior of the graphene film. The quantity of defects in the film structure and its wear off are correlated. From the understanding of the mechanisms involved in controlled samples such as CVD graphene on silicon, we aim at bringing insight in the behavior of graphene coatings deposited on gold for an electrical contact application. Such knowledge is necessary to assess the durability of the coatings in various situations such as wear and atmospheric ageing.
HAL (Le Centre pour la Communication Scientifique Directe), Oct 28, 2018
International audienc
Un nanotube de carbone est une molecule tubulaire dont les proprietes electroniques et quantiques... more Un nanotube de carbone est une molecule tubulaire dont les proprietes electroniques et quantiques sont tout a fait remarquables. Lorsqu'il est utilise en tant que canal de conduction d'un transistor a effet de champ, il est possible de detecter electriquement la presence de charges stockees a proximite de celui-ci, permettant ainsi la creation d'une memoire non-volatile ultime. Dans cette these, nous presentons les travaux realises sur des transistors a nanotubes (CNTFETs) utilises pour la detection de charges, le tout image par microscopie a force de Kelvin (KFM). Le calibrage de la sonde KFM sur des CNTFETs y est egalement presente. Les mesures de transport sont ainsi couplees a la cartographie des potentiels de surface du nanodispositif. Les charges electriques sont injectees a proximite d'un nanotube de carbone a l'aide d'une pointe metalisee d'un microscope a force atomique (AFM) et directement stockees dans la surface de SiO2. Les mesures electrique...
Monolayers of transition metal dichalcogenides are very appealing for electronics, optoelectronic... more Monolayers of transition metal dichalcogenides are very appealing for electronics, optoelectronics and photo/electro-catalysis. Despite the rapid progresses of synthesis methods, device performances remain very sensitive to defects and inhomogeneities (edges, second-layer islands, grain boundaries). Global characterization techniques such as mobility measurements in FETs or catalytic activity measurements by voltammetry cannot assess the impact of inhomogeneities. Local techniques (spectroscopy mapping, scanning probes...) are thus particularly important in the field of 2D materials. In the group, we synthesize TMDCs monolayers by CVD and integrate them in devices, notably FETs with thin and robust molecular layers as efficient gate-dielectrics able to preserve mobility. In this presentation, I will first present our device-oriented motivations, our synthesis results and their characterization by conventional means. I will then present the development of other local techniques with ...
ABSTRACT Nano-objects such as carbon nanotubes are of great interest for the development of new g... more ABSTRACT Nano-objects such as carbon nanotubes are of great interest for the development of new generation of circuits the functionality of which could advantageously complement CMOS. However, conventional circuit architectures are not suited for nano-devices as they can barely cope with defects and variability. Conversely, neural networks represent a challenging approach which could take advantage of the rich functionality of nano-objects and at the same time handle variability. In this context, we showed that optically-gated carbon nanotube field effect transistors (OG-CNTFETs) [1,2] have all the required characteristics of artificial synapses, the basic building block for adaptive circuits [3]. They can be operated as 2-terminal devices with memory capabilities, large dynamics, high programming speed [4] and tolerance to variability. In this work, we use nanotube network-based OG-CNTFETs the resistivity of which can be adjusted at a constant gate bias (using a combination of light and source-drain electrical pulses) and then maintained in a non volatile way. We first present a way to implement these devices in circuits with parallel addressing and CMOS compatibility [5]. We discuss the physical implementation of the proposed crossbar architecture based on the use of silicon wires as shared gate electrodes and show preliminary evidences of the independent programmability of the crossbar nodes (Figure 1). A strategy to define the circuit function through a post-fabrication learning step has been proposed by J-O. Klein's group at IEF-Orsay [6]. It consists in operating pairs of OG-CNTFETs as signed synapses. We currently work in close collaboration to implement the proposed learning rule. We hence discuss our recent progress in this second direction. [5] Zhao et al, Nanotechnology 21 (2010) 175202. [6] Liao et al, "Design and modeling of a neuro-inspired learning circuit using nanotube-based memory devices", submitted to IEEE Trans. on Circ. and Sys.
Parylene C (PC) has attracted tremendous attention throughout the past few years due to its extra... more Parylene C (PC) has attracted tremendous attention throughout the past few years due to its extraordinary properties such as high mechanical strength and biocompatibility. When used as a flexible substrate and combined with high-κ dielectrics such as aluminum oxide (Al 2 O 3 ), the Al 2 O 3 /PC stack becomes very compelling for various applications in fields such as biomedical microsystems and microelectronics. For the latter, the atomic layer deposition of oxides is particularly needed as it allows the deposition of high-quality and nanometer-scale oxide thicknesses. In this work, atomic layer deposition (ALD) and electron beam physical vapor deposition (EBPVD) of Al 2 O 3 on a 15 μm-thick PC layer are realized and their effects on the Al 2 O 3 /PC resulting stack are investigated via X-ray photoelectron spectroscopy combined with atomic force microscopy. An ALD-based Al 2 O 3 /PC stack is found to result in a nanopillar-shaped surface, while an EBPVD-based Al 2 O 3 / PC stack yields an expected smooth surface. In both cases, the Al 2 O 3 /PC stack can be easily peeled off from the reusable SiO 2 substrate, resulting in a flexible Al 2 O 3 /PC film. These fabrication processes are economic, high yielding, and suitable for mass production. Although ALD is particularly appreciated in the semiconducting industry, EBPVD is here found to be better for the realization of the Al 2 O 3 /PC flexible substrate for micro-and nanoelectronics.
Journal of physics. Condensed matter : an Institute of Physics journal, Jan 2, 2015
We report on electron cooling power measurements in few-layer graphene excited by Joule heating b... more We report on electron cooling power measurements in few-layer graphene excited by Joule heating by means of a new setup combining electrical and optical probes of the electron and phonon baths temperatures. At low bias, noise thermometry allows us to retrieve the well known acoustic phonon cooling regimes below and above the Bloch-Grüneisen temperature, with additional control over the phonon bath temperature. At high electrical bias, we show the relevance of direct optical investigation of the electronic temperature by means of black-body radiation measurements. In this regime, the onset of new efficient relaxation pathways involving optical modes is observed.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
2016 IEEE 62nd Holm Conference on Electrical Contacts (Holm), 2016
Developing low friction and high conduction layers for electrical contacts has been a challenge f... more Developing low friction and high conduction layers for electrical contacts has been a challenge for many years. Graphene is known to display outstanding friction and electrical behaviors; lately much work has been conducted both in the applied and fundamental fields of friction in order to understand the mechanisms involved. In the past years we have done experimental work on the tribological behavior of galvanic gold surfaces coated with various types of graphene-like coatings deposited by spraying liquid phase exfoliated graphite. The results showed that the unevenly distributed graphene-like flakes on the surface could bring strong friction reduction. However such coatings are difficult to control and a more controllable deposition technique such as CVD is considered here. The aim of this work is to start investigating the effect of friction on the properties of graphene layers at a microscopic scale and at a macroscopic scale. The first aspect is presented here. In order to assess the effect of friction and wear on graphene films, an atomic force microscope (AFM) is used. The effects of friction of the cantilever tip on the graphene coated plane are investigated. Topographic and electrical properties of the wear scars are recorded as well as the structure of the coating, thanks to a new customized system consisting of a Conducting Probe-AFM (CP-AFM) fitted confocal Raman microscope. Simultaneous topographic maps, electrical maps and Raman maps can be recorded on the friction tracks produced on the graphene coated surfaces. Electrical maps are built from the local values of tip/surface resistance while structure maps are built from the intensity of chosen representative peaks of the Raman spectra. Preliminary results were acquired on CVD graphene transferred to a silicon substrate. This involves a special technique that can induce defects in the graphene film and leave some insulating contamination on the surface. Friction behavior is investigated for different numbers of cycles and for different normal loads. Both parameters seem to govern the behavior of the graphene film. The quantity of defects in the film structure and its wear off are correlated. From the understanding of the mechanisms involved in controlled samples such as CVD graphene on silicon, we aim at bringing insight in the behavior of graphene coatings deposited on gold for an electrical contact application. Such knowledge is necessary to assess the durability of the coatings in various situations such as wear and atmospheric ageing.
HAL (Le Centre pour la Communication Scientifique Directe), Oct 28, 2018
International audienc
Un nanotube de carbone est une molecule tubulaire dont les proprietes electroniques et quantiques... more Un nanotube de carbone est une molecule tubulaire dont les proprietes electroniques et quantiques sont tout a fait remarquables. Lorsqu'il est utilise en tant que canal de conduction d'un transistor a effet de champ, il est possible de detecter electriquement la presence de charges stockees a proximite de celui-ci, permettant ainsi la creation d'une memoire non-volatile ultime. Dans cette these, nous presentons les travaux realises sur des transistors a nanotubes (CNTFETs) utilises pour la detection de charges, le tout image par microscopie a force de Kelvin (KFM). Le calibrage de la sonde KFM sur des CNTFETs y est egalement presente. Les mesures de transport sont ainsi couplees a la cartographie des potentiels de surface du nanodispositif. Les charges electriques sont injectees a proximite d'un nanotube de carbone a l'aide d'une pointe metalisee d'un microscope a force atomique (AFM) et directement stockees dans la surface de SiO2. Les mesures electrique...
Monolayers of transition metal dichalcogenides are very appealing for electronics, optoelectronic... more Monolayers of transition metal dichalcogenides are very appealing for electronics, optoelectronics and photo/electro-catalysis. Despite the rapid progresses of synthesis methods, device performances remain very sensitive to defects and inhomogeneities (edges, second-layer islands, grain boundaries). Global characterization techniques such as mobility measurements in FETs or catalytic activity measurements by voltammetry cannot assess the impact of inhomogeneities. Local techniques (spectroscopy mapping, scanning probes...) are thus particularly important in the field of 2D materials. In the group, we synthesize TMDCs monolayers by CVD and integrate them in devices, notably FETs with thin and robust molecular layers as efficient gate-dielectrics able to preserve mobility. In this presentation, I will first present our device-oriented motivations, our synthesis results and their characterization by conventional means. I will then present the development of other local techniques with ...
ABSTRACT Nano-objects such as carbon nanotubes are of great interest for the development of new g... more ABSTRACT Nano-objects such as carbon nanotubes are of great interest for the development of new generation of circuits the functionality of which could advantageously complement CMOS. However, conventional circuit architectures are not suited for nano-devices as they can barely cope with defects and variability. Conversely, neural networks represent a challenging approach which could take advantage of the rich functionality of nano-objects and at the same time handle variability. In this context, we showed that optically-gated carbon nanotube field effect transistors (OG-CNTFETs) [1,2] have all the required characteristics of artificial synapses, the basic building block for adaptive circuits [3]. They can be operated as 2-terminal devices with memory capabilities, large dynamics, high programming speed [4] and tolerance to variability. In this work, we use nanotube network-based OG-CNTFETs the resistivity of which can be adjusted at a constant gate bias (using a combination of light and source-drain electrical pulses) and then maintained in a non volatile way. We first present a way to implement these devices in circuits with parallel addressing and CMOS compatibility [5]. We discuss the physical implementation of the proposed crossbar architecture based on the use of silicon wires as shared gate electrodes and show preliminary evidences of the independent programmability of the crossbar nodes (Figure 1). A strategy to define the circuit function through a post-fabrication learning step has been proposed by J-O. Klein's group at IEF-Orsay [6]. It consists in operating pairs of OG-CNTFETs as signed synapses. We currently work in close collaboration to implement the proposed learning rule. We hence discuss our recent progress in this second direction. [5] Zhao et al, Nanotechnology 21 (2010) 175202. [6] Liao et al, "Design and modeling of a neuro-inspired learning circuit using nanotube-based memory devices", submitted to IEEE Trans. on Circ. and Sys.
Parylene C (PC) has attracted tremendous attention throughout the past few years due to its extra... more Parylene C (PC) has attracted tremendous attention throughout the past few years due to its extraordinary properties such as high mechanical strength and biocompatibility. When used as a flexible substrate and combined with high-κ dielectrics such as aluminum oxide (Al 2 O 3 ), the Al 2 O 3 /PC stack becomes very compelling for various applications in fields such as biomedical microsystems and microelectronics. For the latter, the atomic layer deposition of oxides is particularly needed as it allows the deposition of high-quality and nanometer-scale oxide thicknesses. In this work, atomic layer deposition (ALD) and electron beam physical vapor deposition (EBPVD) of Al 2 O 3 on a 15 μm-thick PC layer are realized and their effects on the Al 2 O 3 /PC resulting stack are investigated via X-ray photoelectron spectroscopy combined with atomic force microscopy. An ALD-based Al 2 O 3 /PC stack is found to result in a nanopillar-shaped surface, while an EBPVD-based Al 2 O 3 / PC stack yields an expected smooth surface. In both cases, the Al 2 O 3 /PC stack can be easily peeled off from the reusable SiO 2 substrate, resulting in a flexible Al 2 O 3 /PC film. These fabrication processes are economic, high yielding, and suitable for mass production. Although ALD is particularly appreciated in the semiconducting industry, EBPVD is here found to be better for the realization of the Al 2 O 3 /PC flexible substrate for micro-and nanoelectronics.
Journal of physics. Condensed matter : an Institute of Physics journal, Jan 2, 2015
We report on electron cooling power measurements in few-layer graphene excited by Joule heating b... more We report on electron cooling power measurements in few-layer graphene excited by Joule heating by means of a new setup combining electrical and optical probes of the electron and phonon baths temperatures. At low bias, noise thermometry allows us to retrieve the well known acoustic phonon cooling regimes below and above the Bloch-Grüneisen temperature, with additional control over the phonon bath temperature. At high electrical bias, we show the relevance of direct optical investigation of the electronic temperature by means of black-body radiation measurements. In this regime, the onset of new efficient relaxation pathways involving optical modes is observed.