Prospects of Room-Temperature Microbolometer Based on CMR Thin Films
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PROSPECTS OF ROOM-TEMPERATURE MICROBOLOMETER BASED ON CMR THIN FILMS A. Verevkin Applied Physics Department, Yale University, New Haven, CT06520 N. Noginova and E.S. Gillman Centerfor MaterialsResearch Norfolk State University, Norfolk, VA 23504 ABSTRACT We discuss performance of CMR-based bolometers for pulse and modulated electromagnetic radiation detection. Ultimate characteristics of CMR thin film-based bolometers are considered based of current experimental studies of photoresponse. INTRODUCTION During past few years, much attention has been paid to investigation of interrelated processes of magnetic and charge ordering in the manganites of doped rare earth elements with perovskite crystal structure. The manganites demonstrate "colossal" magnetoresistance (CMR) at temperatures near the Curie point T, [1]. Most of the application research works are devoted to magnetic properties as determining the usage of those compounds in magnetic sensing applications. Other possible directions are study and design of CMR thin film-based microbolometers ([2],[3]). In particular, a sharp temperature dependence of the resistance of CMR materials can be utilized for possible microbolometer application. Temperature variations of fast photoresponse to intensive pulsed laser radiation [4-5] as well as slow bolometric response [6-7] in CMR films have been studied recently. Why may CMR films be attractive for microbolometer applications? In this paper we discuss two types of microbolometers, slow response and fast response CMR-based detectors. Slow CMR-based detectors. Here we discuss possible advantages of the slow quasi equilibrium heating in CMR-based thin film bolometers, when the electron subsystem temperature Te is equal to the phonon subsystem temperature TP, or the time dependence of Te(t) is close to the time dependence Tph(t). Note, that in the CMR materials, at the temperatures below T,, the electron temperature Te is related to the electron spin system temperature for more correct description (see below). The effective times of the "slow" bolometric response observed in CMR films are typically in the range of milliseconds. These times are determined mainly by slow phonon cooling of both of the film and the substrate. Temperature dependence of the response observed in this regime is strictly proportional to dR/dT at 50
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