Dependence of transport property of sol-gel derived La0.7Ca0.3MnO3 thin films on their thicknesses

La0.7Ca0.3MnO3 thin films with various thicknesses were successfully fabricated on SrTiO3 single crystal substrates via sol-gel method.X-Ray diffraction manifests that all the films have highly preferential orientation.Electrical transport measurement shows a strong impact of film thickness on the physical properties of La0.7Ca0.3MnO3 thin films,which can be attributed to the change of lattice structure of the films substrate induced by strain.Further study indicates that in the films with small film thicknesses,variable range hopping of small polarons is the dominant transport process at high temperatures,and in those films with larger thicknesses small polarons are the predominant charge carriers even at very low temperatures.利用溶膠-凝膠工藝在SrTiO3單晶襯底上制備了一系列不同厚度的La0.7Ca0.3MnO3薄膜.X射線衍射表明這些薄膜均具有高度的擇優取向性和結晶學質量.電學輸運性質的研究結果凸顯了膜厚的重要作用,主要歸因于襯底施加的應力引起的薄膜晶格參數的改變.進一步的分析揭示,在厚度較小的膜中,小極化子的變程躍遷是高溫下La0.7Ca0.3MnO3薄膜的主要導電機制,而在較厚的膜中,即使在低溫下小極化子也是主要的載流子