Th. doct.-ing.--Génie électronique--Toulouse--I.N.P., 1982. N°: 226.

Th. doct.-ing.--Toulouse, I.N.P., 1978. N°: 38.

Neste trabalho foram investigadas estruturas de diodos Schottky de carbeto de silício (SiC) com potencial uso em detectores de energia de partículas carregadas. Para tanto, foram fabricados diodos Schottky de SiC do tipo Metal-Isolador-Semicondutor (MIS). Uma estrutura MIS é considerada uma vez que o SiC sempre forma em sua superfície uma fina camada de oxicarbeto de silício (SiCxOy) nativo, de difícil remoção por ataques químicos. Foi desenvolvido um modelo modificado da teoria de Emissão Termiônica (TE), de modo a levar em conta o óxido nativo e/ou finas camadas dielétricas inseridas entre metal e semicondutor nas estruturas de diodos Schottky. Foram fabricadas estruturas alumínio/dielétrico/silício para caracterização dos dielétricos utilizados. Foram depositados os dielétricos de SiO2, TiO2, HfO2 e Al2O3 entre o metal Ni e o semicondutor de SiC, variando as espessuras de 1 a 8 nm. As espessuras depositadas foram confirmadas por Elipsometria espectral e Reflectometria de raio X, anteriormente à deposição por sputtering do contato Schottky de Ni. Após a deposição e o tratamento térmico do Ni, as estruturas de diodos Schottky foram caracterizadas eletricamente por meio de medidas de Corrente-Tensão (I-V) e Capacitância-Tensão (C-V), variando a temperatura de medida. Foi observado que a presença de uma fina camada dielétrica entre metal e semicondutor aumenta artificialmente a Altura da Barreira Schottky (SBH), diminuindo a corrente reversa quando o diodo é polarizado reversamente. Por meio do modelo modificado da TE, foi calculada uma espessura variando de 0.18 – 0.20 nm para o oxicarbeto de silício presente nos diodos estudados. As SBH reais foram extraídas por meio das medidas de I-V, variando-se a temperatura. Foram obtidos os valores da SBH de 1.39, 1.32 e 1.26 V, para os dielétricos TiO2, Al2O3, HfO2 e com 1 nm de espessura nominal cada, respectivamente. Para esses, o fator de idealidade calculado ficou próximo de 1. Espessuras de dielétricos acima de 4 nm começam a apresentar características de capacitores Metal-Óxido-Semicondutor e não de diodos Schottky. Por fim, reportamos as estruturas de Ni/Al2O3/4H-SiC/Ni e Ni/HfO2/4H-SiC/Ni, com 1 nm de dielétrico depositado, para uso como detector de partículas alfa no experimento de Espectrometria de Retroespalhamento Rutherford (RBS). Ambos os detectores apresentaram corrente reversa menor que 70 nA.cm-2 e resolução em energia de 76 keV, para polarização reversa de 40 V. / In the present work, silicon carbide (SiC) Schottky diodes with potential use in energy particle detectors were investigated. Metal-Insulator-Semiconductor (MIS) SiC Schottky diodes were fabricated. The MIS structures are considered because SiC always forms a thin native silicon oxycarbide (SiCxOy) layer in its surface that is difficult to remove by chemical means. A modified Thermionic Emission theory (TE) was developed to take into account the native oxide and/or thin dielectric layers present between metal and semiconductor in Schottky diodes. Aluminum/dielectric/silicon structures were fabricated for the dielectric characterization. SiO2, TiO2, HfO2 and Al2O3 dielectrics were deposited between Ni and SiC, with thicknesses varying from 1 to 8 nm. The deposited dielectrics layers thicknesses were confirmed by Ellipsometry spectra and X ray reflectometry before deposition of Ni Schottky contacts by sputtering. After Ni deposition and annealing, the Schottky diodes were electrically characterized by Current-Voltage (I-V) and Capacitance-Voltage measurements, varying the temperature. A thin dielectric layer present between metal and semiconductor artificially augments the Schottky Barrier Height (SBH) and lowers the reverse current when the diodes are reverse biased. A 0.18 – 0.20 nm of SiCxOy layer was inferred for the diodes using the modified TE. The real SBH was extracted from the I-V measurements and presented values of 1.39, 1.32 and 1.26 V for the diodes with 1 nm of TiO2, Al2O3 and HfO2, respectively. For these, an ideality factor close to 1 was calculated. Diodes with thicker (>4 nm) dielectrics layers shows Metal-Oxide-Semiconductor capacitors behavior. Ni/Al2O3/4H-SiC/Ni and Ni/HfO2/4H-SiC/Ni structures with 1 nm of dielectric layer thickness were used in Rutherford Backscattering Spectrometry experiments. Both detectors presented reverse current lower than 70 nA.cm-2 and energy resolution of 76 keV, when applied 40 V reverse bias.

Neste trabalho foram investigadas estruturas de diodos Schottky de carbeto de silício (SiC) com potencial uso em detectores de energia de partículas carregadas. Para tanto, foram fabricados diodos Schottky de SiC do tipo Metal-Isolador-Semicondutor (MIS). Uma estrutura MIS é considerada uma vez que o SiC sempre forma em sua superfície uma fina camada de oxicarbeto de silício (SiCxOy) nativo, de difícil remoção por ataques químicos. Foi desenvolvido um modelo modificado da teoria de Emissão Termiônica (TE), de modo a levar em conta o óxido nativo e/ou finas camadas dielétricas inseridas entre metal e semicondutor nas estruturas de diodos Schottky. Foram fabricadas estruturas alumínio/dielétrico/silício para caracterização dos dielétricos utilizados. Foram depositados os dielétricos de SiO2, TiO2, HfO2 e Al2O3 entre o metal Ni e o semicondutor de SiC, variando as espessuras de 1 a 8 nm. As espessuras depositadas foram confirmadas por Elipsometria espectral e Reflectometria de raio X, anteriormente à deposição por sputtering do contato Schottky de Ni. Após a deposição e o tratamento térmico do Ni, as estruturas de diodos Schottky foram caracterizadas eletricamente por meio de medidas de Corrente-Tensão (I-V) e Capacitância-Tensão (C-V), variando a temperatura de medida. Foi observado que a presença de uma fina camada dielétrica entre metal e semicondutor aumenta artificialmente a Altura da Barreira Schottky (SBH), diminuindo a corrente reversa quando o diodo é polarizado reversamente. Por meio do modelo modificado da TE, foi calculada uma espessura variando de 0.18 – 0.20 nm para o oxicarbeto de silício presente nos diodos estudados. As SBH reais foram extraídas por meio das medidas de I-V, variando-se a temperatura. Foram obtidos os valores da SBH de 1.39, 1.32 e 1.26 V, para os dielétricos TiO2, Al2O3, HfO2 e com 1 nm de espessura nominal cada, respectivamente. Para esses, o fator de idealidade calculado ficou próximo de 1. Espessuras de dielétricos acima de 4 nm começam a apresentar características de capacitores Metal-Óxido-Semicondutor e não de diodos Schottky. Por fim, reportamos as estruturas de Ni/Al2O3/4H-SiC/Ni e Ni/HfO2/4H-SiC/Ni, com 1 nm de dielétrico depositado, para uso como detector de partículas alfa no experimento de Espectrometria de Retroespalhamento Rutherford (RBS). Ambos os detectores apresentaram corrente reversa menor que 70 nA.cm-2 e resolução em energia de 76 keV, para polarização reversa de 40 V. / In the present work, silicon carbide (SiC) Schottky diodes with potential use in energy particle detectors were investigated. Metal-Insulator-Semiconductor (MIS) SiC Schottky diodes were fabricated. The MIS structures are considered because SiC always forms a thin native silicon oxycarbide (SiCxOy) layer in its surface that is difficult to remove by chemical means. A modified Thermionic Emission theory (TE) was developed to take into account the native oxide and/or thin dielectric layers present between metal and semiconductor in Schottky diodes. Aluminum/dielectric/silicon structures were fabricated for the dielectric characterization. SiO2, TiO2, HfO2 and Al2O3 dielectrics were deposited between Ni and SiC, with thicknesses varying from 1 to 8 nm. The deposited dielectrics layers thicknesses were confirmed by Ellipsometry spectra and X ray reflectometry before deposition of Ni Schottky contacts by sputtering. After Ni deposition and annealing, the Schottky diodes were electrically characterized by Current-Voltage (I-V) and Capacitance-Voltage measurements, varying the temperature. A thin dielectric layer present between metal and semiconductor artificially augments the Schottky Barrier Height (SBH) and lowers the reverse current when the diodes are reverse biased. A 0.18 – 0.20 nm of SiCxOy layer was inferred for the diodes using the modified TE. The real SBH was extracted from the I-V measurements and presented values of 1.39, 1.32 and 1.26 V for the diodes with 1 nm of TiO2, Al2O3 and HfO2, respectively. For these, an ideality factor close to 1 was calculated. Diodes with thicker (>4 nm) dielectrics layers shows Metal-Oxide-Semiconductor capacitors behavior. Ni/Al2O3/4H-SiC/Ni and Ni/HfO2/4H-SiC/Ni structures with 1 nm of dielectric layer thickness were used in Rutherford Backscattering Spectrometry experiments. Both detectors presented reverse current lower than 70 nA.cm-2 and energy resolution of 76 keV, when applied 40 V reverse bias.

L'étude des interglaciaires passés qui sont des périodes chaudes avec un volume de glace réduit comme l’interglaciaire actuel, l'Holocène, est cruciale pour comprendre le climat futur. Ce travail apporte de nouvelles informations sur le climat des interglaciaires clés, les stades isotopiques marins (MIS) 11 et 31, considérés comme des analogues au réchauffement global projeté. Une analyse pollinique des sédiments du Site IODP U1385 (marge sud-ouest ibérique) a été effectuée à haute résolution, ce qui permet de comparer directement les variations de la végétation (atmosphère) avec celles de la température des eaux de surface océaniques. Nos données montrent qu’à l’échelle orbitale, la forêt du sud-ouest de l’Europe pendant le MIS 11 est principalement influencée par la précession alors que pendant le MIS 31, malgré des valeurs de précession extrêmes, le forçage dominant est l’obliquité, favorisant une végétation moins méditerranéenne et un régime climatique tempéré. De plus, la variabilité millénaire apparaît comme une caractéristique persistante mais les épisodes de refroidissement varient en intensité et durée en fonction des conditions limites qui favorisent un forçage prédominant des hautes ou basses latitudes. Enfin, nous examinons l'expression régionale de l'Holocène et de ses analogues orbitaux, les MIS 11c et 19c dans le sud-ouest de l’Europe. Ceci révèle que l'optimum Holocène se distingue par un plus fort développement forestier et donc que les MIS 11c et 19cne sont pas des analogues à l’Holocène pour notre zone d’étude. Grâce à une comparaison modèle-données, nous montrons aussi que la forêt interglaciaire dans cette région est principalement contrôlée par la précession en influençant les précipitations hivernales, facteur critique pour le développement de la forêt méditerranéenne, tandis que le CO2 joue un rôle négligeable. / The study of past interglacials, periods of reduced ice volume like our present interglacial, the Holocene, is crucial for understanding the future climate. This work provides new insights into the intensity and climate variability of key interglacials, namely Marine Isotopic Stages (MIS) 11 and 31, considered as analogues for the projected global warming. A highresolution pollen analysis at IODP Site U1385 off SW Iberia was performed, which enables adirect comparison between atmospheric-driven vegetation changes and sea surface temperature variability. At orbital time scale, this thesis shows that the dominant orbital forcing on the SW European forest was different between the interglacials of the 100-ky (MIS 11) and 41-ky (MIS31) worlds. While during MIS 11 its weak precessional forcing predominates, during MIS 31 itsextreme precession forcing is dwarfed by the prevailing influence of obliquity leading to a temperate climate regime as shown by a less Mediterranean character of the vegetation. This work also shows that millennial-scale variability was a pervasive feature and suggests that the different intensity and duration of the cooling events in SW Iberia was related to different atmospheric and oceanic configurations modulated by high or low-latitude forcing depending on the baseline climate states. Finally, this study examines the dominant forcing underlying the regional expression of the Holocene and its orbital analogues, MIS 11c and 19c, over SW Iberia using a data-model comparison approach. This comparison reveals that the Holocene optimum stands out for its higher forest development and therefore these interglacials cannot be considered as analogues for the Holocene vegetation and climate changes in Iberia. Additionally,it shows that the SW Iberian forest dynamics during these interglacials were primarily controlled by precession through its influence on winter precipitation, which is critical for the Mediterranean forest development whereas CO2 played a negligible role.

Les semiconducteurs basés sur les nitrures III - N à large bande interdite présentent un intérêt croissant pour la recherche et le monde industriel. Parmi eux, les composants de puissance à base de nitrure de gallium constituent un domaine de recherche majeur de l'électronique à l'état solide pour les applications hyperfréquences. Les travaux décrits dans cette thèse correspondent à la conception et à la réalisation de transistors de puissance à haute mobilité pour l'amplification en bandes X et Ku (8-18 GHz). L'évolution continue des hétérostructures demande de constantes rétroactions avec le procédé technologique. Dans ce but, l'approche utilisée a consisté au développement et à l'optimisation des briques technologiques de base, associée à l'analyse physique indispensable à l'optimisation des choix technologiques. Une étude fine des contacts ohmique et Schottky a été entreprise. Une optimisation des conditions de réalisation des fossés de grille, du contact ohmique, des métallisations, du prétraitement de surface et de la nature du diélectrique de passivation a été nécessaire. L'ajout d'une électrode de champ a été étudiée afin d'améliorer davantage la tenue en tension des composants et minimiser l'impact des pièges de surface. Dans ce cadre, nous avons conçu et développé différentes topologies de plaque de champ. Plusieurs diélectriques innovants comme le nitrure de bore ont été testés afin d'établir les potentialités de ces transistors HEMTs à grille isolée. L'ensemble de cette technologie optimisée a été appliquée sur une couche HEMT AlGaN/GaN sur substrat Si (001) et a permis d'établir un état de l'art en puissance à 10GHz pour cette nouvelle filière bas coût. / III-N based semiconductors due to their wide bandgap properties present more and more interest in research and industry. ln this frame, the microwave power devices based on gallium nitride constitute a major research field in electronics regarding solid state for microwave applications. The work described in this thesis is the design and the fabrication of high mobility power transistors for amplification in X and Ku band (8-18 GHz). The constantly improvement of epitaxies is correlated to a constant feedback with the technology. ln this way, the approach used in the development and optimization of base modules is associated to the physical analysis necessary to optimize the technological choices. A detailed study of Schottky and ohmic contacts is undertaken. An optimization of technological process conditions for gate recess, ohmic contact, the metallization, the surface pretreatment and the nature of the dielectric passivation was necessary. Fieldplate structure are also studied to further improve the withstanding voltage of components and minimize the impact of surface traps. ln this context, different fieldplate topologies are designed and developed. Several innovative dielectric material as boron nitride are tested to determine the capabilities of these insulated gate HEMTs transistors. The optimized process is applied to AlGaN/GaN HEMT on Si substrate (100) demonstrating a microwave power state-of-the-art at 10GHz for low-cost applications.

Quantifier les variations de température océanique du passé est nécessaire pour comprendre les mécanismes qui régissent l’évolution climatique. Les méthodes de paléo-thermométrie classiques peuvent souffrir de limitation inhérente à l’écologie des organismes et/ou à cause de l’influence d'effets physico-chimiques (salinité, acidité de l’eau de mer…). Ce travail se focalise sur la technique de paléothermométrie Δ47, qui repose sur la mesure du « clumping isotopique » dans les carbonates. Il vise d’abord à établir une calibration appliquée aux foraminifères et ensuite à mettre en œuvre cette calibration pour l’étude des variations climatiques au cours de la transition du Pléistocène moyen (MPT). Notre calibration Δ47-température des foraminifères planctoniques et benthiques, prélevés dans des sédiments modernes, couvre une gamme de température de -2 à 25°C. Les valeurs de Δ47 sur 9 espèces de foraminifères présentent une excellente corrélation avec la température de calcification des organismes, estimée à partir des mesures isotopiques de l’oxygène. Les résultats obtenus confirment l’absence d’effets liés à l’écologie des foraminifères (effets vitaux et de taille des organismes) et démontrent que la salinité n’affecte pas les mesures de Δ47. Cette étude constitue une avancée méthodologique importante pour les futures études paléocéanographiques sur les foraminifères. La MPT correspond à une transition climatique marquée par un changement de fréquence des cycles glaciaires-interglaciaires (de 41 000 à 100 000 ans). La compréhension de cette période est un enjeu scientifique majeur pour appréhender la mise en place du climat actuel. Notre calibration Δ47-température a permis de quantifier les variations de températures au cours de la MPT en mer méditerranée (Section de Montalbano Jonico, sud de l’Italie) et particulièrement des stades isotopiques marins 31 et 19, considérés comme des analogues à l’Holocène. Les résultats indiquent que (i) les températures (Δ47) obtenues sont en adéquation avec les températures obtenues par d’autres paléothermomètres, (2) les températures permettent de retracer les changements de régime océanographique et hydrologique, et (3) la mesure du Δ47 est complément prometteur pour les études multi-méthodes en paléocéanographie. / The quantification of past oceanic temperature changes is a critical requirement for understanding the mechanisms which regulate climate variations. Classical methods of paleothermometry could suffer from well-known limitations related to ecology and/or to physico-chemical biases (sea water salinity, acidity…). This work focuses on clumped-isotope carbonate thermometry (Δ47). It aims to establish a calibration of Δ47 foraminifera and use it to study past climatic variations through the Mid-Pleistocene Transition (MPT). Our Δ47 calibration in planktonic and benthic foraminifera collected from modern marine sediment covers a temperature range of -2 to 25 °C. The clumped-isotope compositions of 9 species of foraminifera show a robust correlation with the calcification temperature, estimated from the measurements of oxygen-18. These results confirm the absence of bias linked to foraminifer ecology (species-specific and foraminifer size effects) and provide evidence that salinity does not affect the Δ47 thermometer. This study constitutes significant methodological progress for future paleoceanographic applications in foraminifera.The MPT is a climatic transition characterized by a shift in the frequencies of glacial-interglacial cycles (from 41 000 to 100 000 years). Understanding the MPT is a major scientific objective, which underlies our effort to study the establishment of our present climate. Our Δ47 calibration was used to quantify temperature changes through the MPT in the Mediterranea Sea (Montalbano Jonico section, south of Italy), and in particular the marine isotopic stages 31 and 19, which may be described as Holocene analogues. We find that (1) Δ47 temperatures are in good agreement with temperatures reconstructed from other paleothermometers, (2) these results allow reconstructing changes in past oceanographic and hydrologic regime, and (3) Δ47 measurement are a promising component of multi-proxy paleoceanographic studies.

Ferroelectric non-volatile memories have gained momentous importance in the recent years. Significant research is being done on different device structures with several ferroelectric films for better data retention, lower power dissipation and higher density of integration. Metal - ferroelectric insulator – semiconductor (MIS) capacitor structures with Poly Vinylidene Fluoride(80%) - trifluoroethylene (20%) (PVDF – TrFE) copolymer are observed to demonstrate consistent dielectric properties and retainable memory action under selected operating conditions. Prior research was done on devices with MFeOS structure with an oxide buffer layer. The presence of a buffer oxide reduces the field acting on the film for memory state switching, which in effect requires the devices to be operated at higher voltages. In this work, MFeS devices with lower ferroelectric film thickness; with, and without a very thin buffer oxide have been studied. The dielectric behavior of PVDF thin film, when deposited directly on Si, is observed to exhibit reliable memory properties without significant charge injection under certain operating conditions. Electrical characteristics such as capacitance-voltage(C-V) and polarization-electric field (P-E) hysteresis with the direction of measurement and conduction properties through the junction have been comprehensively studied to establish the behavior of the MIS device for possible use in MIS FETs for high density ferroelectric memories.

The correct number of chromosomes is important for the maintenance of healthy cells and organisms. Maintenance of a correct chromosome number depends on the accurate distribution of chromosomes to the daughter cells during cell division, and errors in chromosome segregation result in abnormal chromosome numbers, or aneuploidy. Aneuploidy is typically associated with deleterious effects on organismal and cellular fitness; however, aneuploidy has also been associated with enhanced cellular growth in certain contexts, such as cancer. Another type of deviation from the normal chromosome number can occur when entire sets of chromosomes are added to the normal (diploid) chromosome number, resulting in polyploidy. Whereas polyploidy is found in certain normal tissues and organisms, tetraploidy (four sets of chromosomes) is associated with a number of precancerous lesions and is believed to promote aneuploidy and tumorigenesis. While it is clear that chromosome mis-segregation causes aneuploidy, the effect of aneuploidy on chromosome segregation is less clear. Similarly, it is unclear whether and how tetraploidy may affect chromosome segregation. The work described here shows that aneuploidy can cause chromosome mis-segregation and induces chromosome-specific phenotypic effects. In contrast, tetraploidy does not per se induce chromosome mis-segregation, but enables the accumulation of aneuploidy thanks to a "genetic buffer" effect that allows tetraploid cells to tolerate aneuploidy better than diploid cells. / Ph. D.

O que hoje se denomina Mon coeur mis à nu é um conjunto de notas, aforismos bombásticos, ideias de capítulos por vir, agrupados e encadernados por Poulet-Malassis após a morte de Charles Baudelaire. Em 1887, Eugène Crépet publica a obra pela primeira vez, sob o título factício Journaux intimes. Os gestos editoriais pelos quais passou desde então tendem a conter seus inacabamentos, seja recorrendo à denominação diário íntimo, seja apagando editorialmente marcas da materialidade manuscrita e da provisoriedade de toda proposta de ordenação das notas. Mais recentemente, dois marcos começam a apontar para a dimensão inacabada de Mon coeur mis à nu, ainda que circunscritos a certa concepção filológica do processual: a noção de poética do rascunho, cunhada por Béatrice Didier ao tratar dos escritos póstumos de Baudelaire, e a edição diplomática de 2001, realizada por Claude Pichois para a editora suíça Droz. Tomando a retradução como estratégia de tradução, propõem-se nesta tese duas traduções simultâneas de Mon coeur mis à nu: uma tradução manuscrítica (voltada para a materialidade do manuscrito e sua transcrição-tradução) e um comentário do original como possibilidade de escrita tradutória (voltado para a necessidade de traçar linhas de força que rompam com a ordenação arbitrária de Malassis e desenhem outras relações possíveis, sem cair, em contrapartida, na falsa solução da desordenação absoluta e primordial). Mon coeur mis à nu apresenta uma escrita de cólera, que tem relação, por sua vez, com a teatralidade (a encenação de certa postura encolerizada, desagradável e chocante) e com a fusée (o aforismo incendiário, o processo de escrita que, atravessado pela cólera, faz-se projeto inacabado, promessa de explosão, projetos-projéteis lançados sobre a página contra a França, a modernidade, a canaille littéraire). Por fim, propomos a noção de contínuo do rascunho, que nos permite construir estratégias de edição e tradução que levem em consideração os inacabamentos de Mon coeur mis à nu, seu aspecto manuscrito, sua dispersão, seu efeito processual, sua cólera que, no limite, se volta contra a própria possibilidade de obra acabada. / The todays so-called Mon coeur mis à nu is a compound of notes, bombastic aphorisms, ideas for chapters to come, combined and bound by Poulet-Malassis after Charles Baudelaires death. In 1887, Eugène Crépet publishes the work for the first time under the sham title of Journaux intimes. The editorial gestures by which the work has passed ever since tend to contain its unfinishments, by means of denominating it intimal journal or by editorially erasing marks of the handwritten materiality and of the fugacity of any suggested organization of the notes. More recently, two milestones begin to highlight Mon coeur mis à nus unfinished dimension, albeit limited to a certain philological conception of the processual: the notion of draft poetics, initiated by Béatrice Didier approaching Baudelaires posthumous writings, and the 2001 diplomatic edition prepared by Claude Pichois for Droz, a Belgian publishing house. Understanding retranslation as a translation strategy, this thesis proposes two simultaneous translations for Mon coeur mis à nu: a manuscriptical translation (aiming the handwritten materiality and its transcription-translation) and a commentary of the original as a possibility of translational writing (aiming the necessity of tracing lines of force that break Malassis arbitrary ordering and redraw other possible relations, without succumbing, in return, to the false solution of the absolute and primeval disorder). Mon coeur mis à nu presents a wrathful writing related to, on the other hand, the theatricality (the mis-en-scène of a certain rabid, unpleasant, shocking posture) and the fusée (the incendiary aphorism, the writing process that, traversed by cholera, produces itself as an unfinished project, a promise of explosion, projects-projectiles launched over the page against France, the modernity, the canaille littéraire). Finally, we offer the notion of draft continuum, that allows us to build strategies of edition and translation that consider Mon coeur mis à nus unfinishments, its handwritten aspect, its dispersion, its processual effect, its cholera that, to the limit, turns against the possibility itself of being a finished work.