单根氧化锌纳米线力电性能及其服役行为的原位研究

发布时间：2018-04-24 06:39

  本文选题：ZnO纳米线 + 电致损伤　； 参考：《北京科技大学》2015年博士论文

【摘要】：ZnO是一种具有压电特性的半导体材料,一维ZnO纳米材料在构建应变传感器、纳米发电机等纳米器件中发挥了重要作用。但相关的电学、力学、力电耦合服役行为研究与服役过程中的损伤、断裂机理研究还不够深入。本文利用CVD法制备了ZnO纳米线,利用纳米操控、TEM、C-AFM研究了ZnO纳米线的电学、力学和力电耦合性能,研究了ZnO纳米线分别在电场、力场及力电耦合场下的服役行为,深入分析了ZnO纳米线在服役过程中的损伤、断裂机理。 利用扫描电镜中的纳米操控系统研究了ZnO纳米线的电学性能与服役行为。直径为103-807nm的ZnO纳米线电致损伤的阈值电压为15-60V,且随直径的增大呈线性增大；临界电流密度在107Am-2量级,且随直径的增大而呈指数减小。利用热核-壳模型解释了ZnO纳米线电致损伤和断裂的机理。纳米线电致损伤和断裂主要归因于产生在金属-半导体结处的焦耳热,当温度超过ZnO纳米线的熔点,纳米线就会发生熔化。 利用原位TEM系统研究了ZnO纳米线在单轴拉伸与压缩过程中的力学性能与服役行为。直径为199.45nm的ZnO纳米线在拉伸与压缩变形直至损伤断裂过程中存在应变梯度效应。断口处应变最大,随着远离断口,应变逐渐减小。ZnO纳米线的拉伸和压缩断裂都是韧性断裂。根据ZnO纳米线力学损伤断裂前后体积不变的特点验证了ZnO纳米线变形过程中的应变梯度效应。 利用原位TEM机械共振系统研究了ZnO线在高周应变下的疲劳性能与服役行为。ZnO纳米线经过高达108-109周次的共振,没有损伤产生；而遭受电子束辐照的ZnO纳米线在共振几秒后即发生断裂。直径小于100nm的ZnO纳米线的弹性模量接近或超过块体ZnO的模量140GPa,当直径大于100nm时,ZnO线的弹性模量远低于140GPa。 利用AFM研究了不同扫描角下ZnO纳米线的力学性能与服役行为。在14.8μm/s的扫描速率下,确定了施加在ZnO纳米线上的实际外力和扫描角关系的力学校准方程和阈值力方程。扫描角的存在,增强了施加在ZnO纳米线表面的实际外力。ZnO纳米线力学损伤断裂时的实际阈值力与扫描角无关,与纳米线的直径呈线性增加关系。利用阈值力方程和力学校准方程建立了ZnO纳米线的安全服役评价方程。研究中得到的ZnO纳米线的弹性模量要远低于文献中利用三点弯曲测得的数值,而断裂强度则相差不大。 利用C-AFM系统研究了ZnO纳米线的力电耦合性能与服役行为。均一直径的ZnO纳米线力电耦合损伤断裂的阈值电压随着外力的增大呈线性减小；在恒定外力作用下,不同直径的ZnO纳米线力电耦合损伤断裂的阈值电压与纳米线的直径呈线性增大。应力集中效应增强了ZnO纳米线与AFM针尖接触表面的电子聚集,导致产生更多的焦耳热,降低了导致ZnO纳米线熔断的阈值电压值。
[Abstract]:ZnO is a kind of semiconductor material with piezoelectric properties. One-dimensional ZnO nanomaterials play an important role in the construction of strain sensors, nano-generators and other nano-devices. However, the related studies of electrical, mechanical and mechanical coupled service behavior and damage and fracture mechanism during service are not enough. In this paper, ZnO nanowires were prepared by CVD method. The electrical, mechanical and electromechanical coupling properties of ZnO nanowires were studied by using nano-manipulation Tem C-AFM. The service behavior of ZnO nanowires in electric field, force field and electromechanical coupling field were studied respectively. The damage and fracture mechanism of ZnO nanowires in service were analyzed. The electrical properties and service behavior of ZnO nanowires were studied by using the nano manipulation system of scanning electron microscope (SEM). The threshold voltage of electrically induced damage of ZnO nanowires with diameter of 103-807nm is 15-60V, and increases linearly with the increase of diameter, and the critical current density is in the order of 107Am-2, and decreases exponentially with the increase of diameter. The mechanism of electrical damage and fracture of ZnO nanowires was explained by the thermo-core-shell model. The electrical damage and fracture of nanowires are mainly attributed to the Joule heat produced at metal-semiconductor junctions. When the temperature exceeds the melting point of ZnO nanowires the nanowires will melt. The mechanical properties and service behavior of ZnO nanowires during uniaxial tension and compression were studied by in situ TEM system. ZnO nanowires with diameter of 199.45nm have strain gradient effect during tensile and compression deformation to damage and fracture. The strain at the fracture surface is the largest and the strain decreases gradually with the distance from the fracture surface. The tensile and compressive fracture of ZnO nanowires are both ductile fracture. The strain gradient effect of ZnO nanowires during deformation was verified according to the invariant volume before and after mechanical damage of ZnO nanowires. In situ TEM mechanical resonance system was used to study the fatigue performance and service behavior of ZnO nanowires under high cycle strain. The ZnO nanowires irradiated by electron beam break after resonance for a few seconds. The elastic modulus of ZnO nanowires whose diameter is smaller than 100nm is close to or greater than that of bulk ZnO. When the diameter is larger than 100nm, the elastic modulus of ZnO nanowires is much lower than 140 GPa. The mechanical properties and service behavior of ZnO nanowires at different scanning angles were studied by AFM. At the scanning rate of 14. 8 渭 m / s, the mechanical calibration equation and the threshold force equation of the relationship between the actual external force and the scanning angle applied on the ZnO nanowires are determined. The existence of scanning angle enhances the actual external force applied on the surface of ZnO nanowires. The actual threshold force applied on the surface of ZnO nanowires is independent of the scanning angle and linearly increases with the diameter of nanowires. The safety service evaluation equation of ZnO nanowires is established by using threshold force equation and mechanical calibration equation. The elastic modulus of the ZnO nanowires obtained in the study is much lower than that measured by three-point bending in the literature, but the fracture strength is not different. The electromechanical coupling performance and service behavior of ZnO nanowires were studied by C-AFM system. The threshold voltage of ZnO nanowires with uniform diameter decreases linearly with the increase of external force, and under the constant external force, the threshold voltage decreases linearly with the increase of external force. The threshold voltage of electromechanical coupling damage fracture of ZnO nanowires with different diameters increases linearly with the diameter of nanowires. The stress concentration effect enhances the electron aggregation on the contact surface between ZnO nanowires and AFM tips, resulting in more Joule heat, and decreases the threshold voltage of ZnO nanowires.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1;O614.241

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相关期刊论文 前1条

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