The Cmr Thin Films And Bolometer Application Of Study

One of the most important directions in the study of colossal magnetoresistance materials is to fabricate the bolometer, which can work near the room temperature and shows an excellent performance, if the films can be prepared with the metal-insulator transition temperature (TMI) reaching to the room temperature. The main topic of this thesis is to deposit the LaCaMnO3 films using the pulsed laser deposition (PLD) technique, and to improve the properties of the films through a serials of processes including the post annealing treatments. At last, the relation between the physical properties and the film making processes of the materials are discussed and some possible applications explored.LaCaMnO3 films were prepared on two different substrates (SrTiO3 and LaAlO3) by excimer pulsed laser deposition method using the LaCaMnO3 polycrystalline materials doped with 4wt% Ag, which exhibits an excellent properties. A reliable process is obtained through repeated experiments and summaries. The films have a smooth and glossy surface. The result of XRD shows that the film demonstrates good properties of integrity, epitaxial-like grown and no other impure phase. The metal-insulator transition temperature (TMI) varies from 190K to 240K commonly for the as-grown samples.The properties of LaCaMnO3 films were enhanced dramatically with a post annealing treatment in high temperature and high oxygen pressure. The films show the highest so far TMI, which reaches the 300K, the transition of resistivity is kept in a narrow temperature range and the temperature coefficient of resistance (TCR) is about 5-8%. This is the best result abtained hi the compounds of LaCaMnO3. The resistivity of the films drops compared with the as-grown films, but the temperature of maximum magnetoresistance reaches 287K, very close to the room temperature. Therefore it is not only an important improvement to fabricate the CMR bolometer which can work near room temperature, but also a prospective research for otherapplications such as magnetic-sensors, spintronics devices and infrared detectors.As one of the most important applications, CMR bolometer is fabricated using the LaCaMnO3 films, which has a metal-insulator transition temperature at 300K. The archetypal bolometer is fabricated after the film is photolithographed, evaporated Au electrodes and fixed. An initial measurement is carried out and the result shows that the bolometer is still sensitive to the infrared signal even the intensity of the signal source is very weak, if the bolometer is in a proper temperature. So it is a good beginning to do more minute measurements and achieve an excellent result and provide such a probability to develop infrared detection and infrared photography.The CMR materials have complex physical properties. Some phenomena of the LaCaMnO3 films are discussed, such as the effects of mismatch between the substrates and the films, the variation of the resistance of films under different bias currents. And the effects and improvements are discussed with details after the films are annealed in high temperature and high oxygen pressure. All of the results are very helpful because we can get more information of the materials and explore more applications in future.