【作者】 倪牟翠；

【导师】 张喜和； 陈亚孚；

【作者基本信息】 长春理工大学 ， 光学， 2010， 博士

【摘要】 集成光学和光电子技术产业的发展依赖于优质、多功能薄膜材料的获得和器件的制备,脉冲激光沉积（Pulsed laser deposition,PLD）方法是目前最先进的薄膜制备方法之一。本文利用PLD方法研究钙钛矿型氧化物钛酸锶（SrTiO₃）薄膜、异质结的制备及其电学和光学性质。首先,深入探讨了在PLD过程中脉冲激光与靶物质及激光产生的等离子体间的相互作用的物理机制,系统研究了沉积参数如激光功率密度、激光重复频率、反应室氧分压、衬底温度、衬底类型对SrTiO₃薄膜生长的影响。然后,采用优化的沉积参数在两种不同的铌掺杂浓度的掺铌钛酸锶（Nb:SrTiO₃）衬底上进行PLD镀膜,制备了SrTiO₃/Nb:SrTiO₃异质结,利用X射线衍射（XRD）、透射电子显微镜（TEM）、拉曼光谱（Raman spectrum）、厚度测试仪对薄膜和异质结进行了表征。结果表明所得到的SrTiO₃薄膜为单相外延生长,SrTiO₃/Nb:SrTiO₃异质结的性质受到衬底掺杂浓度的调制。进一步地,系统研究了SrTiO₃/Nb:SrTiO₃异质结的界面电子传输性质和光电性质,首次发现了这种异质结中的受界面控制的电流回滞及电阻开关、多电阻态现象并对其进行了合理解释;测量了异质结在紫外光作用下的光电导和光生伏特效应,发现SrTiO₃/Nb:SrTiO₃异质结的光电性质受到其衬底掺杂浓度的调制,衬底掺杂浓度较高的结中光电导更加明显,并且其光生伏特效应与其被置于哪个电阻态密切相关。研究认为,高浓度的Nb掺杂改变了SrTiO₃/Nb:SrTiO₃异质结的界面电子结构,使界面产生较多的缺陷能级并可作为电子的束缚（trap）中心。当外加电场或光照时,束缚中心对电子的俘获或释放使其产生独特的电阻开关、多电阻态及依赖于电阻态的光电效应现象。这一研究工作有助于深入理解激光与物质相互作用的物理机制,且对于新型氧化物光电子材料和器件的开发制备具有启发性的意义。更多还原

【Abstract】 Fabrication of high quality and multifunction thin films and devices plays an important role in the development of integrated optics and photoelectric technology. Pulsed laser deposition （PLD） is one of the most advanced methods for film growth. In this thesis, SrTiO₃ films and its heterostructures SrTiO₃/Nb:SrTiO₃ have been fabricated using PLD method and the electrical and photoelectrical characteristics of the junctions have been investigated.The fundamental physics involving laser-material interaction and laser-plasma interaction during PLD process has been studied thoroughly. The impacts of deposition parameters such as the pulse energy density, the laser pulse frequency, the oxygen pressure, the substrate temperature and the substrate species on film growth have been investigated systematically.SrTiO₃ thin films were deposited on Nb: SrTiO₃ substrates with different Nb doping levels using PLD method. Optimized deposition parameters were employed to achieve smooth epitaxial films with high crystalline perfection. X-ray diffractometer （XRD）, transmission electron microscope （TEM） and confocal Raman micro-spectroscopy were used for the microstructure analysis. The characteristics of SrTiO₃/Nb:SrTiO₃ heterojunctions were found to be modulated by the Nb doping levels of substrates.The electrical transport and photoelectrical properties of SrTiO₃/Nb:SrTiO₃ heterojunctions have been investigated. The hysteretic current-voltage curves, remarkable resistance switching phenomena and multi-resistance states were observed and the results have been discussed by considering the role of defects in the interfacial depletion region of the heterojunctions. The photoconductivity and photovoltaic effects of SrTiO₃/Nb:SrTiO₃ heterojunctions under ultraviolet light irradiation have been measured. These behaviors depend on the Nb doping levels of substrates and the junction with higher Nb concentration in the substrate shows larger photoconductivity. Furthermore, photovoltaic effects in the junction with multi-resistance states have been found to correlate with its resistance states. In the junction with high Nb doping level, defects with high concentration create a considerable number of defect energy levels, which act as "traps" of electrons, in the electrical band structure of interface. When external electrical field or light are applied, trapping or detrapping of electrons by these defects result in the resistance switching, multi-resistance states and particular photovoltaic phenomena. This work is helpful for understanding fundamental physics of light-matter interaction and is useful for fabrication of novel photoelectric devices.更多还原