Effective Theory of Non-Adiabatic Quantum Evolution Based on the Quantum Geometric Tensor

International audienceWe study the role of the quantum geometric tensor (QGT) in the evolution of quantum systems. We show that all its components play an important role on the extra phase acquired by a spinor and on the trajectory of an accelerated wavepacket in any realistic finite-duration experiment. While the adiabatic phase is determined by the Berry curvature (the imaginary part of the tensor), the non-adiabaticity is determined by the quantum metric (the real part of the tensor) and allows to determine corrections in the regimes where Landau-Zener approach is inapplicable. The particular case of a planar microcavity in the strong coupling regime allows to extract the QGT components by direct light polarization measurements and to check their effects on the quantum evolution

Comparative Raman study of graphene growth from solid carbon source on Si(100) and SiO2 substrates by combining pulsed laser deposition and rapid thermal annealing

International audienceThis study reports the comparative investigation of graphene films prepared on Si (100) and SiO2 by combining pulsed laser deposition and rapid thermal annealing using Ni catalyst. The effect of substrate and growth temperatures (600-1000°C) on the formation of graphene films was investigated by Raman spectroscopy, mapping and scanning electron microscopy (SEM). It was found that graphene films formed on Si (100) is multilayered with the formation of various nickel silicides depending on the growth temperature, while graphene films prepared on SiO2 are predominant bi- and trilayered graphene with no nickel silicide formation. The analysis of the Raman D, G and 2D peaks intensities and positions as a function of the growth temperature showed a complete opposite evolution between Si (100) and SiO2 substrates. These findings contribute to a better understanding of the combination between the nature of the substrate and the growth temperature, when growing graphene films from solid carbon source with nickel catalyst on both Si(100) and SiO2 substrates. Such a good comprehension of the substrate impact is vital for potential applications and device fabrication of graphene

2D reproduction of the face on the Turin Shroud by infrared femtosecond pulse laser processing

International audienceFemtosecond pulse laser processing concentrates a huge quantity of light energy in extremely short pulses of a few tens to hundreds of femtoseconds, enabling superficial laser machining or marking of any kind of materials, with a reduced or insignificant heat affected area. A digitized paper printed image of the face on the Turin Shroud was used to monitor a scan head intercalated between a femtosecond pulsed laser source and a linen fabric sample, enabling the direct 2D reproduction of the image of the face with a laser beam size corresponding to one pixel of the digitized image. The contrast in the marked image was controlled by adjusting the energy density, the number of superimposed pulses per pixel, and the distance between successive impacts. The visual aspect of the laser-induced image is very similar, at naked eye, to the source image. The negative photograph of the marked linen fabric reveals a face remarkably close to the well-known negative picture of the face on the Turin Shroud. Analyses by infrared spectroscopy, Raman spectroscopy, and scanning electron microscopy were performed to characterize the laser marked areas

Boron-doped Graphene Synthesis by Pulsed Laser Co-Deposition of Carbon and Boron

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Pulsed laser co-deposition of carbon and boron for boron-doped graphene synthesis

International audienceThe introduction of dopants, such as boron, into the graphene network, is essential for many applications (electrochemistry, sensors, photovoltaics, catalysis, etc.). Many preparation routes have been investigated for B-doped graphene (BG) films: CVD, chemical reactions between graphene or graphene oxide with boron precursors, hydrothermal and solvothermal processes, arc discharge, high temperature sublimation of highly B-doped SiC and B4C thermal decomposition. Another way consists in pulsed laser co-ablation of C and B solid sources followed by rapid thermal heating of the B-doped carbon film deposited on a metal catalyst, to obtain BG layers. The objective is to achieve a better control of boron concentration in the films.Here, we use for the first time pulsed laser co-ablation for the synthesis of B-doped graphene layers. Amorphous a-C:B films, containing 2%at. boron, 10 nm thick, are synthetized by nanosecond pulsed laser deposition on a Ni thin film (60 nm thick) previously deposited on a SiO2 substrate. Rapid Thermal Annealing is performed at 1100°C during 2’ with a heating rate of 15°C/s and a cooling rate of 1°C/s. Raman, XPS, FEG-SEM and AFM characterizations allow to determine the nature, composition and morphology of the BG films. The results confirm the fabrication of bi-trilayers boron doped graphene films with the same boron doping level (2%at) as the starting material. Our results pave a new way for boron doped graphene synthesis using laser processing

Graphene and doped-graphene synthesis by Pulse Laser Deposition: a review

International audienceGraphene is a remarkable two-dimensional (2D) material that is of great interest to both academia and industry. Several methods are used to produce either pristine graphene or doped graphene. Among these methods, Pulse Laser Deposition (PLD) has proved to be an alternative route for producing graphene layers from amorphous carbon thin films, due to many advantages including the controlled film thickness and dopant compositions in the films [1]. The present talk will review the ability of PLD to produce graphene and doped graphene films, mainly with nitrogen or boron atoms [2]. The growth mechanism will be highlighted on the basis of XPS investigations in situ during graphene growth. The film characteristics depending on the synthesis process are discussed mainly on the basis of Raman and XPS/AES investigations. Exploration of some electrical conduction properties are emphasized. In particular, electroanalytical experiments show that functionalized electrodes with nitrogen-doped graphene from PLD exhibits excellent reversibility, close to the theoretical value of 59 mV, and very high sensitivity to hydrogen peroxide oxidation [3]. The electroanalytical results were correlated with the composition and nanoarchitecture of the N-doped graphene film identified as a few-layer defected and textured graphene film containing a balanced mixture of graphitic-N and pyrrolic-N chemical functions. The present talk will help researchers to have an overview of the interest of PLD for graphene and doped-graphene synthesis

Elaboration of Graphene and doped-graphene by Pulsed Laser Deposition

International audienceIn recent years, the research on graphene has received a lot of interest to both academia and industry due to its outstanding physical and chemical properties, and its potential for various applications. Due to this, several methods are used to produce either pristine graphene or doped graphene. Among these methods, Pulsed Laser Deposition (PLD) has proved to be an alternative route for producing graphene layers from amorphous carbon thin films, due to many advantages including the controlled film thickness and dopant compositions in the films [1]. The present talk will give an overview of the ability of PLD to fabricate graphene and doped graphene films, mainly with nitrogen or boron atoms [2]. The growth mechanism will be highlighted based on XPS investigations in situ during graphene growth. The graphene films characteristics depending on the substrates and the influence of synthesis process parameters such as initial amorphous carbon (a-C) thickness, laser energy and annealing temperature on the growth of graphene are discussed mainly based on Raman analysis. Investigations of electrochemistry properties of nitrogen-doped graphene synthesized by PLD are emphasized. The results show that functionalized electrodes with nitrogen-doped graphene exhibit excellent reversibility, close to the theoretical value of 59 mV, and very high sensitivity to hydrogen peroxide oxidation [3]. The present talk will help researchers to get an overview of the interest of PLD for graphene and doped-graphene synthesis.References1.Y. Bleu, F. Bourquard, T. Tite, A.-S. Loir, C. Maddi, C. Donnet, F. Garrelie, Frontier in Chemistry, 2018, 6, 572.2.C. Maddi, F. Bourquard, V. Barnier, J. Avila, M.-C. Asensio, T. Tite, C Donnet, F. Garrelie, Scientific Reports, 2018, 8, 3247.3.F. Bourquard, Y. Bleu, A.-S. Loir, B. Caja-Munoz, J. Avila, M.-C. Asensio, G. Raimondi, M. Shokouhi, I. Rassas, C. Farre, C. Chaix, V. Barnier, N. Jaffrezic-Renault, F. Garrelie, C. Donnet, Materials, 2019, 12, 666

Mechanism of formation of nitrogenated doped graphene films, investigated by in situ XPS during thermal annealing in vacuum

International audienceapplications such as nanoelectronics, nanophotonics, sensor devices and green energy technology. One way consists in thermal heating of a doped solid carbon source, such as an amorphous a-C:N film, in the presence of a metal catalyst, to obtain nitrogenated graphene (NG) layers. The control of such a process requires to investigate diffusion and segregation mechanisms of the graphene precursor through the metal catalyst.In the present study, the mechanism of atomic diffusion and NG film growth through a nickel catalyst thin film was investigated using in situ X-ray photoelectron spectroscopy (XPS) performed during thermal heating responsible for NG synthesis. Amorphous a-C:N films, containing 16%at. nitrogen, 10 nm thick, were synthetized by femtosecond pulsed laser ablation on fused silica substrates. A 150 nm thick nickel film was subsequently deposited by thermal evaporation on the a-C:N films. Thermal annealing at various temperatures (200, 300, 500 and 650°C), with different time durations, were performed in ultra-high vacuum during in situ XPS analysis, to carry out the top surface genesis of the NG film onto the nickel catalyst. FEG-SEM, Raman and X-ray absorption (XAS) spectroscopies were also performed to elucidate the nature and chemical composition of NG films. The diffusion of carbon and nitrogen through the nickel film towards the surface from 300°C was observed, without any graphene signature. Graphene films are formed at the highest temperatures, with a final 3%at. nitrogen content, in both pyrrolic and pyridinic configurations. The solid-state transformation mechanism responsible for the formation of few-layer NG films is thus investigated. The kinetics of carbon surface enrichment observed using in-situ XPS is discussed in the frame of the interface segregation theory and modelled using the du Plessis approach

Dynamics of carbon diffusion and segregation through nickel catalyst, investigated by in-situ XPS, during the growth of nitrogen-doped graphene

International audienceThe mechanisms of diffusion and segregation of carbon from a solid carbon-based film, through a nickel film catalyst, was investigated using in situ, time- and depth-resolved X-ray photoelectron spectroscopy. The graphene precursor was a carbon nitride amorphous film obtained by pulse laser deposition. Changes in both surface and bulk sensitive carbon components versus annealing time was investigated at temperatures between 200 °C and 500 °C. A model of carbon diffusion/segregation through the nickel film was implemented, enabling the quantitative description of the graphene growth. Carbon diffusion through the nickel film was shown to occur at low temperatures (200–300 °C) and to induce the growth of graphene domains. The fine microstructure and high density of defects in the nickel catalyst film accelerated the transport of carbon, faster than conventional bulk diffusion. At 500 °C, bulk diffusion of carbon occurred, due to the recovering of the nickel grain microstructure. The diffusion/segregation model developed in this study can be used as a support to a better control of the growth and quality of the graphene. Our interpretations are discussed in relation to similar approaches related to graphene growth by chemical vapor deposition

Innovative process to obtain thin films and micro-nanostructured ZrN films from a photo-structurable ZrO2 sol-gel using rapid thermal nitridation

International audienceZirconium nitride (ZrN) is widely used in many industrial sectors for its outstanding performances including its mechanical properties, high chemical and thermal stability. Associated with its plasmonic behavior, these properties make ZrN a suitable candidate for optical applications at high temperature or in extreme environments. The authors present an innovative, easy-to-use and rapid process for producing ZrN thin films from a photo-structurable ZrO 2 sol-gel using a rapid thermal nitridation (RTN) process. In this process, a ZrO 2 sol-gel layer is converted into a ZrN thin film in a few minutes by rapid thermal annealing (RTA) under ammonia gas. Compared to physical or chemical vapor deposition, usually used to produce ZrN thin films, the advantages of the sol-gel method include suitability for non-planar and large substrates and the possibility of nanotexturing of crystallized ZrN surfaces in considerably less time, at a larger scale and at a lower cost. The ZrO 2 and ZrN thin films were characterized by Raman spectroscopy, X-ray diffraction and Transmission Electron Microscopy, to confirm complete nitridation. The optical, electrical and tribological properties were also investigated. Finally, the nitridation method was also used on structured ZrO 2 layers and showed the versatility of the process e.g. enabling the production of micro-nanostructured ZrN films without using any etching techniques