102 research outputs found
Persistent enhancement of the carrier density in electron irradiated InAs nanowires
We report a significant and persistent enhancement of the conductivity in
free-standing non intentionnaly doped InAs nanowires upon irradiation in ultra
high vacuum. Combining four-point probe transport measurements performed on
nanowires with different surface chemistries, field-effect based measurements
and numerical simulations of the electron density, the change of the
conductivity is found to be caused by the increase of the surface free carrier
concentration. Although an electron beam of a few keV, typically used for the
inspection and the processing of materials, propagates through the entire
nanowire cross-section, we demonstrate that the nanowire electrical properties
are predominantly affected by radiation-induced defects occuring at the
nanowire surface and not in the bulk.Comment: 18 pages, 5 figure
Switching behaviors of graphene-boron nitride nanotube heterojunctions
High electron mobility of graphene has enabled their application in high-frequency analogue devices but their gapless nature has hindered their use in digital switches. In contrast, the structural analogous, h-BN sheets and BN nanotubes (BNNTs) are wide band gap insulators. Here we show that the growth of electrically insulating BNNTs on graphene can enable the use of graphene as effective digital switches. These graphene-BNNT heterojunctions were characterized at room temperature by four-probe scanning tunneling microscopy (4-probe STM) under real-time monitoring of scanning electron microscopy (SEM). A switching ratio as high as 105 at a turn-on voltage as low as 0.5âV were recorded. Simulation by density functional theory (DFT) suggests that mismatch of the density of states (DOS) is responsible for these novel switching behaviors
Design and Characterization of an Electrically Powered Single Molecule on Gold
The surface diffusion of individual molecules is of paramount importance in self-assembly processes and catalytic processes. However, the fundamental understanding of molecule diffusion peculiarities considering conformations and adsorption sites remain poorly known at the atomic scale. Here, we probe the 4âČ-(4-tolyl)-2,2âČ:6âČ,2âł-terpyridine adsorbed on the Au(111) herringbone structure combining scanning tunneling microscopy and atomic force microscopy. Molecules are controllably translated by electrons excitations over the reconstruction, except at elbows acting as pinning centers. Experimental data supported by theoretical calculations show the formation of coordination bonds between the molecule and Au atoms of the surface. Using force spectroscopy, we quantify local variation of the surface potential and the lateral force required to move the molecule. We found an elevation of the diffusion barrier at elbows of the reconstruction of âŒ100 meV compared to the rest of the surface
Transport phenomena in semiconductor nanostructures studied by multi-tip scanning tunneling microscopy
Le dĂ©veloppement des nanotechnologies passe par la mise au point de nouveaux instruments adaptĂ©s Ă la caractĂ©risation de la matiĂšre Ă l'Ă©chelle nanomĂ©trique. Le Nanoprobe acquis par l'IEMN au dĂ©but de ma thĂšse rĂ©pond Ă cet enjeu. Cet instrument constituĂ© d'une plateforme de Microscopie Ă Effet Tunnel Ă Quatre-Pointes (4T-STM) et surmontĂ©e d'un Microscope Ălectronique Ă Balayage (MEB) a pour vocation d'effectuer des analyses, contrĂŽles et tests de nanomatĂ©riaux et composants Ă©lectroniques.AprĂšs une description dĂ©taillĂ©e du fonctionnement de cet appareil (chapitre 2), une premiĂšre Ă©tude a Ă©tĂ© rĂ©alisĂ©e pour dĂ©terminer l'influence de l'irradiation Ă©lectronique sur des nanostructures semi-conductrices, Ă savoir ici des nanofils d'InAs (chapitre 3). Sous irradiation, les fils deviennent quasi-mĂ©talliques. GrĂące Ă des mesures originales du transport dans des nanofils semi-suspendus, ce changement des propriĂ©tĂ©s Ă©lectriques est attribuĂ© Ă la formation de dĂ©fauts chargĂ©s Ă la surface des fils. L'ionisation par impact est un phĂ©nomĂšne responsable de la multiplication des porteurs dans les cellules photovoltaĂŻques. Le quatriĂšme chapitre dĂ©montre l'intĂ©rĂȘt du Nanoprobe Ă caractĂ©riser ce phĂ©nomĂšne sur un systĂšme modĂšle, une jonction p-n de silicium. Alors que deux pointes en contact polarisent la diode, une troisiĂšme injecte localement par effet tunnel des Ă©lectrons possĂ©dant une Ă©nergie bien dĂ©finie. La mesure de porteurs supplĂ©mentaires dĂ©montre le phĂ©nomĂšne d'ionisation par impact avec une rĂ©solution inĂ©galĂ©e jusqu'Ă prĂ©sent.The advent of nanotechnology involves the development of an instrumentation capable of investigating the matter at this scale. The Nanoprobe acquired by IEMN at the beginning of my thesis brings technical solutions to this issue. This instrument consisting of a Four-Tip Scanning Tunneling Microscopy platform (4T-STM) and topped with a Scanning Electron Microscope (SEM) is dedicated to perform analysis, inspections and tests on nanomaterials and electronic devices. After a detailed description of this instrument (Chapter 2), a first study was conducted to determine the influence of electron irradiation on semiconductor nanostructures, InAs nanowires are treated here. Under irradiation, the nanowires become quasi-metallic. Thanks to original transport measurements on freestanding nanowires, this change of the electrical properties is attributed to the formation of charged defects on the surface of nanowires. The impact ionization is a phenomenon responsible for carrier multiplication in solar cells. The fourth chapter shows the ability of the Nanoprobe to characterize this phenomenon in a typical model, a silicon p-n junction. While 2 tips in contact polarize the diode, a third one locally injects tunneling electrons that have a well defined energy. The measurement of supplementary carriers proves that impact ionization occurs and can be measured with a resolution never reached before
Espace carcĂ©ral et formats dâexpression : des communications sous contraintes
International audienceSi lâexpĂ©rience carcĂ©rale impose une cohabitation forcĂ©e entre dĂ©tenus, elle implique aussi une dĂ©pendance forte aux personnels pĂ©nitentiaires. Lâarticle montre quâaux limitations imposĂ©es aux corps et Ă la mobilitĂ© des dĂ©tenus sâajoutent des entraves et restrictions qui pĂšsent sur leurs possibilitĂ©s dâexpression, y compris dans la communication avec les personnels pĂ©nitentiaires
Engagements (et) publics. ĂlĂ©ments pour une sociologie publique de la prison
Quelle parole peut porter la recherche en sciences sociales auprĂšs des acteurs du champ pĂ©nitentiaire ? Lâarticle se propose dâaborder cette question classique depuis une perspective sous-exploitĂ©e : la diversitĂ© des publics des sciences sociales. Si les sciences sociales, par leur capacitĂ© Ă dĂ©crire, Ă comprendre et Ă expliquer, donnent des prises sur le monde social, la question critique centrale est de savoir Ă qui nous donnons ces prises, et sur quoi ou sur qui. Issue de dĂ©bats anglo-saxons qui se structurent depuis une dizaine dâannĂ©es autour des labels de public sociology et de public criminology, cette interrogation est susceptible de dessiner de nouveaux chantiers de recherche, de discussion et de diffusion des sciences sociales et, se faisant, de moduler les implications sociales et politiques de nos travaux dans le champ pĂ©nitentiaire. Le propos sâattache Ă prĂ©senter les termes de ce dĂ©fi que la sociologie publique adresse aux recherches en sciences sociales, et Ă en mesurer la portĂ©e pour la pratique scientifique dans le champ de la sociologie carcĂ©rale et pĂ©nitentiaire.What is the role of social science research in the penitentiary or carceral field? The article proposes to address this classic question from the under-studied perspective of the diversity of the publics of the social sciences. If social sciences, through their ability to describe, to understand and to explain, provide grasps on the social world, it becomes critical to wonder who we are providing with these grasps to, and on what or on whom. In the light of Anglo-Saxon debates that have been structured over the last decade around the labels of public sociology and public criminology, this question is likely to stir new research, discussion and dissemination of the social sciences, as well as to question the social and political implications of our work in the penitentiary or carceral field
A la découverte des archives Reinach
Un silence Ă©tourdissant... voilĂ ce quâon ressentait Ă chaque instant. Chaque mouvement, dans cette ambiance sombre et Ă©touffante, Ă©tait une prise de risque. DĂšs quâun nouveau document Ă©tait dĂ©couvert, nous soulevions lâimmĂ©moriale poussiĂšre qui le recouvrait. Elle attaquait nos voies respiratoires, noircissait nos mains, nos visages et les lieux. Lâobjet Ă©tait examinĂ©, ouvert, puis il Ă©tait enregistrĂ©... Non, je nâai pas participĂ© Ă la dĂ©couverte du potentiel tombeau de NĂ©fertiti. CâĂ©tait..
Un bureau derriÚre les barreaux. Travail relationnel et pouvoir discrétionnaire dans les audiences pénitentiaires
La sociologie carcĂ©rale a documentĂ© la place centrale des nĂ©gociations informelles et interpersonnelles entre prisonniers et surveillants pĂ©nitentiaires, dans une institution de contrainte largement bureaucratisĂ©e. Cet article entend enrichir la comprĂ©hension de la place de la communication en prison en rendant compte des Ă©changes entre prisonniers et une catĂ©gorie peu Ă©tudiĂ©e des professionnels, lâencadrement pĂ©nitentiaire de proximitĂ©. Contrairement aux agents de premiĂšre ligne, ces « gradĂ©s » pĂ©nitentiaires dĂ©tiennent un pouvoir largement discrĂ©tionnaire sur les enjeux quotidiens de la vie en dĂ©tention. En Ă©tudiant plus particuliĂšrement les « audiences », entretiens interpersonnels en face Ă face, lâanalyse souligne le travail relationnel rĂ©ciproque qui sây dĂ©ploie. Au-delĂ de simples transactions ponctuelles, lâaudience autorise lâinstauration dâune coopĂ©ration fragile et asymĂ©trique entre acteurs a priori antagonistes. Elle stabilise ainsi des attentes relationnelles qui contribuent Ă redĂ©finir la nature de la contrainte institutionnelle et des rĂ©pertoires dâaction des acteurs de la dĂ©tention. Par lâinvestissement relationnel du pouvoir discrĂ©tionnaire Ă lâaudience, le pouvoir carcĂ©ral sâhybride, articulant dĂ©pendance personnelle et normes bureaucratiques, obligations morales et formalisme lĂ©gal. LâĂ©tude des audiences pĂ©nitentiaires invite ainsi Ă penser la place et les modalitĂ©s dâun rĂ©investissement institutionnel du travail relationnel par les agents intermĂ©diaires, souvent rĂ©duits Ă leur rĂŽle dans la traduction entre la conception et lâapplication de rĂ©formes institutionnelles.The sociology of prisons has long documented the central role of informal and interpersonal negotiations between prisoners and prison officers within a highly bureaucratised custodial institution. This paper seeks to contribute to our understanding of the role of communication behind bars, as it focuses on the exchanges between prisoners and a professional group â prison middle management â that has received little scholarly attention. Unlike frontline guards, middle-ranking officers hold significant discretionary power in the day-to-day issues of prison life. In particular, this analysis underlines the relational work that takes place during prison hearings, which are formal face-to-face meetings between a prisoner and a middle-ranking prison officer. In addition to one-off transactions, hearings provide an opportunity for the construction of a fragile and asymmetrical cooperation between structurally antagonistic participants. Indeed, hearings may establish reciprocal relational expectations that help to redefine the nature of institutional restraint as well as the repertoires of action available to the actors of the prison system. Through the relational investment of discretionary power in the hearing, penal power becomes hybrid, combining personal dependence and bureaucratic norms, moral obligations and legal formalism. The study of prison hearings thus raises the question of the role of relational work and its reinvestment in formal settings within penal institutions. Often reduced to their role in the enforcement of public policies, middle-managers are instrumental in such back-office relational work
Les reconfigurations de la relation carcérale. Sociologie des espaces de communication entre prisonnier·e·s et autorités pénitentiaires
This research focuses on one of the transformations affecting contemporary French prisons: the opening and renewal of communication spaces between prisoners and prison authorities. The possibility for prisoners to express requests and to engage in legal remedies has become part of prison formal functioning. This change resulted from the introduction of new norms regulating prison life, the emergence of new institutions to enforce them, as well as the implementation of standardized procedures and the promotion of new security doctrines. To assess this evolution, the research investigates how discourses shape everyday life in prisons, with a focus on their thematic, relational and argumentative capacities. At the same time, it pays specific attention to how formats shape discourses, notably through technical, material and normative constraints. The thesis is organized in four chapters, which are dealing with one specific space of communication: the prison corridors where informal and daily communications between prisoners and supervisors take place, the written requests sent by prisoners to prison officials, the face-to-face audiences where one prisoner and one prison manager discuss prison-related grievances and, finally, the disciplinary hearings where communications are polarized by the almost inevitability of punishment. By adopting a bottom-up perspective, analyzing these communicational spaces makes it possible to describe a new and hybrid economy of power relations in prison. To do this, the research mainly draws from fieldwork conducted in two French prisons. It combines ethnographic observation of the expression and handling of grievances, interviews with prisoners and professionals, and analysis of bodies of written or oral communications between prisoners and prison officers.Cette recherche interroge lâune des transformations que connaissent les prisons françaises contemporaines : lâouverture et le renouvellement dâespaces de communication entre prisonnier·e·s et autoritĂ©s pĂ©nitentiaires. Sous lâeffet de la densification de lâenvironnement normatif, de la multiplication des organes de contrĂŽle, du dĂ©veloppement de procĂ©dures standardisĂ©es ou encore de la promotion de nouvelles doctrines sĂ©curitaires, la prison a en effet intĂ©grĂ© Ă son fonctionnement formel la possibilitĂ© pour les prisonnie·e·s dâexprimer des requĂȘtes et des recours. Prendre au sĂ©rieux cette Ă©volution suppose de sâintĂ©resser Ă ce que ces discours font au quotidien carcĂ©ral, et tout particuliĂšrement Ă leurs thĂ©matiques, relationnelles et argumentatives, mais aussi aux formats de ces communications entre prisonnier·e·s et autoritĂ©s pĂ©nitentiaires, et notamment Ă leurs contraintes techniques, matĂ©rielles et normatives. Lâarchitecture de cette thĂšse suit pour cela quatre espaces de communication : les coursives oĂč sâinscrivent les communications informelles et quotidiennes entre prisonnier·e·s et surveillant·e·s, les requĂȘtes Ă©crites par des prisonnier·e·s Ă des responsables pĂ©nitentiaires, les entretiens en face Ă face entre un·e prisonnier·e et un·e responsable et, enfin, les commissions de discipline oĂč est mis en jeu le pouvoir de sanction formel de lâinstitution. En adoptant un regard par le bas, lâanalyse distincte et globale de ces espaces permet alors de dĂ©crire une Ă©conomie hybride des relations de pouvoir en prison, oĂč cohabitent, se confrontent et se renforcent des formes relationnelles souvent dĂ©crites comme irrĂ©conciliables. Pour cela, cette recherche sâappuie Ă titre principal sur une enquĂȘte dans deux Ă©tablissements pĂ©nitentiaires français. On y a combinĂ© lâobservation ethnographique des situations dâexpression et de traitement des dolĂ©ances, la rĂ©alisation dâentretiens auprĂšs des diffĂ©rents acteurs de la dĂ©tention et lâanalyse de corpus de communication, oraux ou Ă©crits, entre prisonnier·e·s et agents pĂ©nitentiaires
Construire sa lĂ©gitimitĂ© Ă Ă©noncer le droit. Ătude de dolĂ©ances de prisonniers
International audienceThis paper accounts for modes of expression of legal references in petitions sent by prisoners to the French General-Controller of Places of Deprivation of Liberty. The diversity of the rhetorical operations stating and qualifying legal references offers a chance to outline some of the moral constraints faced by socially weakened actors to establish their own legitimacy to communicate about the law with an administrative entity. According to the way the law itself is characterized (the legal system, the law, my rights), prisonersâ rhetorical strategies change, drawing the contours of a twofold social unworthiness: unworthiness to state the law and unworthiness to present oneself as entitled.Cet article cherche Ă rendre compte des modes dâĂ©nonciation du droit dĂ©ployĂ©s dans les dolĂ©ances adressĂ©es par des personnes incarcĂ©rĂ©es au ContrĂŽleur gĂ©nĂ©ral des lieux de privation de libertĂ© (CGLPL). La diversitĂ© de ces opĂ©rations rhĂ©toriques de mobilisation et dâattĂ©nuation du droit permet en effet de mettre en Ă©vidence certaines contraintes morales Ă la tentative, pour des acteurs socialement affaiblis, de placer leur relation avec une autoritĂ© administrative sur le terrain du droit. Selon la maniĂšre dont le droit lui-mĂȘme est caractĂ©risĂ© (la justice, le droit, mes droits), les stratĂ©gies rhĂ©toriques dĂ©ployĂ©es se transforment, et dessinent en creux une double indignitĂ© sociale : indignitĂ© Ă Ă©noncer le droit et indignitĂ© Ă se prĂ©senter comme titulaire de droits
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