镧锶钴氧薄膜的脉冲激光沉积法制备及电性能测试

【作者】 李丽萍；

【导师】 张鹏翔；

【作者基本信息】 昆明理工大学 ， 材料学， 2004， 硕士

【摘要】 铁电薄膜集成器件是当代信息科学技术的重要前沿之一，而钙钛矿结构的铁电薄膜与导电薄膜的异质结构是集成铁电器件的核心。为了使铁电薄膜能更好地应用于集成器件，选用合适的方法制备制备合适的电极是非常重要的，电极层的性能直接决定了铁电薄膜材料性能的优劣。本论文的主要任务就是用脉冲激光法在不同的衬底上沉积导电钙钛矿结构氧化物La_0.5Sr_0.5CoO₃薄膜，并对生长出薄膜的结晶程度、表面形貌及导电性能进行了测试及分析。以实现应用于集成铁电器件，达到电极与铁电薄膜界面的结构匹配，延长铁电集成器件的寿命。 本文用脉冲激光沉积法在Si衬底、SiO₂／Si衬底、Pt／Ti／SiO₂／Si衬底、LaAlO₃衬底四种衬底上制备了La_0.5Sr_0.5CoO₃薄膜。结晶程度及表面形貌测试结果显示LaAlO₃衬底上生长的薄膜晶化程度和生长情况最好，其次为Pt／Ti／SiO₂／Si衬底上生长的薄膜，在镀膜温度为600℃，镀膜氧压为50Pa条件下，Si衬底和SiO₂／Si衬底上的薄膜晶化程度也已很好。而Si衬底、SiO₂／Si衬底及Pt／Ti／SiO₂／Si衬底上生长的薄膜都有不同程度的微裂纹产生。经过炉内退火（in-situ）处理的薄膜样品产生微裂纹的程度有所减轻，层层蒸镀，并经过in-situ处理的薄膜样品表面形貌显著改善。而炉外后退火（ex-situ）处理对薄膜没有改善。晶格匹配、热膨胀系数的匹配是获得生长良好薄膜的关键因素。 La_0.5Sr_0.5CoO₃薄膜电性能的测试显示电阻率与结晶程度、表面形貌密切相关。但Pt／Ti／SiO₂／Si衬底上生长的薄膜虽然也存在微裂纹，电阻率却最低，其原因可能在于薄膜厚度薄，在进行薄膜表面电阻测量时，电子穿透La_0.5Sr_0.5CoO₃薄膜从Pt膜上传输走了。 本文还研究了倾斜衬底上La_0.5Sr_0.5CoO₃薄膜和另外一种钙钛矿结构氧化物La_0.67Ca_0.33MnO₃薄膜的电阻各向异性效应，结果显示，倾斜衬底上生长的La_0.5Sr_0.5CoO₃薄膜和La_0.67Ca_0.33MnO₃薄膜都有电阻各向异性效应，并且随着衬底的倾斜角度的增大，各向异性越明显，这与倾斜衬底上薄膜的各向异性生长有关。此外，我们还发现了倾斜衬底上La_0.5Sr_0.5CoO₃薄膜的激光感生电压（LITV）效应，以及La_0.5Sr_0.5CoO₃薄膜的气敏效应。更多还原

【Abstract】 The research topic of the integrated devices of ferroelectric thin films has gained much attention in recent years, which is an important branch of modern information science and technology. The core of the integrated ferroelectric devices is the heterostructure of perovskite ferroelectric and conducting thin film. In order to apply ferroelectric thin films in integrated devices, it is very important to prepare suitable electrode using suitable method, as the performance of electrode has determined the performance of ferroelectric thin films. The main topic of this thesis is to deposit the thin film of the conductive perovskite oxides using the pulsed laser deposition (PLD) technique and to study the influence of crystallization surface profile lattice mismatchonthe resistances of the films. The aim of the research is to apply the integrated ferroelectric devices and attain the structural matching of the interface of the electrode and the ferroelectric thin film and prolong lifetime of the integrated ferroelectric devices.La0.5Sr0.5CoO3 thin films have been prepared by pulsed laser deposition (PLD) on Si?SiO2/Si?Pt/Ti/ SiO2/Si and LaAlO3 substrates. The result of the measure of the degree of crystallization and surface profile of the films reveal that the degree of crystallization of film on LaAlO3 substrate is best; it on Pt/Ti/ SiO2/Si substrate is subsequent; and it on Si and SiO2/Si substrates with the condition of 600癈 and 50Pa is well. The films on Si?SiO2/Si and Pt/Ti/ SiO2/Si substrates have microcrazes in different degree. The degree of microcrazes of the films with in-situ is lightened, the surface profile of the film deposited in multiple layers with in-situ is improved signlly. But the films with ex-situ treatment have no apparent improvement.The resistance of La0.5Sr0.5CoO3 thin film has affinity with the degree of crystallization and surface profile of the films. The films on Pt/Ti/ SiO2/Si substrates have microcrazes too, but they have the least resistance, the reason perhaps is the electrons penetrate the La0.5Sr0.5CoO3 film and transmit on Pt film when the resistance of La0.5Sr0.5CoO3 thin film ismeasured, for the thickness of La0.5Sr0.5CoO3 thin film is light.In addition, the resistance anisotropy of La0.5Sr0.5CoO3 and La0.67Ca0.33MnO3 thin films on tilted LaAlO3 substrates have studied in this thesis. The result reveal that the La0.5Sr0.5CoO3 and La0.67Ca0.33MnO3 thin films grown on tilted substrates demonstrate resistance anisotropy, and the film on the substrate with the bigger tilting angle has the larger resistance anisotropy, it is agreeable to theoretical explanation. Otherwise, in the experiments we have discovered the laser induced thermoelectric voltage (LITV) of La0.5Sr0.5CoO3 thin films on tilted substrate and the gas sensitivity of La0.5Sr0.5CoO3 thin film, and their application foregrounds are quite extensive.更多还原