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Étude et réalisation d'une matrice de détecteurs bolométriques de très haute résolution. Intérêt d'une conception en couches minces

Abstract : There has been considerable development in the field of bolometric detectors in the last decade, which is evidence of the power and the sensitivity of the thermal measurement of a deposited energy. Our study is aimed at a search for the ultimate resolution in energy and position. We have developed an ultrahigh vacuum system that makes possible the optimisation of the deposition conditions, the adhesion and the thermal treatment of the detectors, due to the ability to transfer the substrate between the different chambers of the system, without leaving the ultrahigh vacuum environment. This system has enabled us to develop an all thin film bolometer, centred on a 10 nm thick thermometric film, of very low heat capacity and very high sensitivity, due to the metal-insulator transition properties. The volume and the shape of each bolometer element are defined by mechanical masking and ionic etching, which enables us to define the heat capacity, the thermal response time and the electrical impedance of each element by controlling the film thickness and shape factor. Two bolometer prototypes have been fabricated using this method. One is dedicated to space astrophysics, and the other one for calorimetric measurements of atomic monolayers. We show that a limit on the size reduction of active volume of the thermometric material appears at low temperature, and that this limit is linked to the rapid decrease of the electron-phonon coupling with temperature. We give a theoretical evaluation of this for a 10µm by 11µm microbolometer. This leads us to show that the reduction of the operating temperature does not give the optimum working conditions in the case of a microbolometer.
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Karim Djotni. Étude et réalisation d'une matrice de détecteurs bolométriques de très haute résolution. Intérêt d'une conception en couches minces. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 1995. Français. ⟨tel-00002735⟩

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