Research On La_1-xCa_xMnO₃:Ag_y Thin Film Laser Induced Voltage

Manganese oxides La_1-xCa_xMnO₃?LCMO?have attracted much attention,owing to their rich physical phenomenon and magnetic phase diagram.LCMO which have high metal-insulator transition temperature?T_p?,resistance temperature coefficient?TCR?and strong laser induced voltage?LIV?are the foundation of desiging high-performance optical detector,infrared detector and other instruments.In this thesis,we mainly study the La_1-xCa_xMnO₃:Ag materials which were prepared by sol-gel method and ultraviolet pulsed laser deposition technique,respectively.The structure,phase,morphology,electrical properties and LIV were investigated by X-ray diffraction?XRD?,scanning electron microscope?SEM?,atomic force microscope?AFM?,resistance-temperature?R-T?and LIV measurement.The La_1-x-x Ca_xMnO₃:Ag_0.2?x=0.33,0.3,0.33?polycrystalline materials were synthesized by sol-gel method.The XRD patterns indicate that the polycrystalline materials are crystallized in a single phase.The SEM pictures indicate that grains are compact without obvious flaws.La_0.67Ca_0.33MnO₃:Ag_0.2 polycrystalline materials have high T_p?270K?and La_0.72Ca_0.28MnO₃:Ag_0.2have high TCR(78.8%·K^-1),and both two materials have large grain size?67.24?m and 74.96?m respectively?.La_0.67Ca_0.33MnO₃:Ag_0.2 films with different thickness were deposited on different substrates.The mismatch of lattice constant between substrates and films and stress have great influence on the properties of films.The TCR of films growing on?LaAlO₃?_0.3-?Sr₂AlTaO₆?_0.7?LSAT?which have a very small mismatch are higher.The films influenced by compressive stress have a relatively high level of T_p and a higher LIV peak voltage?U_p?,and influenced by tensile stress show worse properties.The angle of substrate is also an influence factor.When the angle increases,response time???get longer and the U_p increase.The U_p is 1.74V when the angle is 15°.In all samples,the La_0.72Ca_0.28MnO₃:Ag_0.2.2 films grow on LAO substrates?10°?have the highest TCR(18.46%·K^-1).Within limits,U_p increase with the increase in laser energy.All series of films have an optimum thickness,which has the strongest LIV signal.The signal decay time constants are larger when the films are thin and show the tendency that decrease first and then increase with increase in thickness.