IOP Publishing, Journal of Physics: Conference Series, 1(150), p. 012027, 2009
DOI: 10.1088/1742-6596/150/1/012027
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In order to measure the Cosmological Microwave Background (CMB), high performance "bolometric cameras" similar to CCDs are currently developed. They are made out of thousands of pixels, each of which is a bolometer on its own. In order to meet the requirements for future CMB experiments - notably the measurement of the CMB B-mode polarization - the sensitivity of each pixel should be improved by one or two orders of magnitude compared to what now exists. Taking advantage of the solid-state properties of amorphous NbxSi1-x thin films, we here present a proposal for a new bolometer structure that would increase the pixels' sensitivity, its response time and allow a simplification of the fabrication process. In this resistive detector (that can be either high impedance or TES) the three functions of a classical bolometer (wave absorption, temperature measurement and thermal decoupling) are achieved in a single NbxSi1-x film. The frequency properties of this material allow the merger of the two first functions. The natural thermal decoupling between electrons and phonons at low temperature then makes it possible to use this single object as bolometer. This new type of detector solely uses the electronic properties of the NbxSi1-x thin films and is free of any phononic mediation of the energy.