本文選題：ZnO納米線 + 電致?lián)p傷　； 參考：《北京科技大學》2015年博士論文

【摘要】：ZnO是一種具有壓電特性的半導體材料,一維ZnO納米材料在構建應變傳感器、納米發(fā)電機等納米器件中發(fā)揮了重要作用。但相關的電學、力學、力電耦合服役行為研究與服役過程中的損傷、斷裂機理研究還不夠深入。本文利用CVD法制備了ZnO納米線,利用納米操控、TEM、C-AFM研究了ZnO納米線的電學、力學和力電耦合性能,研究了ZnO納米線分別在電場、力場及力電耦合場下的服役行為,深入分析了ZnO納米線在服役過程中的損傷、斷裂機理。 利用掃描電鏡中的納米操控系統(tǒng)研究了ZnO納米線的電學性能與服役行為。直徑為103-807nm的ZnO納米線電致?lián)p傷的閾值電壓為15-60V,且隨直徑的增大呈線性增大；臨界電流密度在107Am-2量級,且隨直徑的增大而呈指數(shù)減小。利用熱核-殼模型解釋了ZnO納米線電致?lián)p傷和斷裂的機理。納米線電致?lián)p傷和斷裂主要歸因于產生在金屬-半導體結處的焦耳熱,當溫度超過ZnO納米線的熔點,納米線就會發(fā)生熔化。 利用原位TEM系統(tǒng)研究了ZnO納米線在單軸拉伸與壓縮過程中的力學性能與服役行為。直徑為199.45nm的ZnO納米線在拉伸與壓縮變形直至損傷斷裂過程中存在應變梯度效應。斷口處應變最大,隨著遠離斷口,應變逐漸減小。ZnO納米線的拉伸和壓縮斷裂都是韌性斷裂。根據(jù)ZnO納米線力學損傷斷裂前后體積不變的特點驗證了ZnO納米線變形過程中的應變梯度效應。 利用原位TEM機械共振系統(tǒng)研究了ZnO線在高周應變下的疲勞性能與服役行為。ZnO納米線經過高達108-109周次的共振,沒有損傷產生；而遭受電子束輻照的ZnO納米線在共振幾秒后即發(fā)生斷裂。直徑小于100nm的ZnO納米線的彈性模量接近或超過塊體ZnO的模量140GPa,當直徑大于100nm時,ZnO線的彈性模量遠低于140GPa。 利用AFM研究了不同掃描角下ZnO納米線的力學性能與服役行為。在14.8μm/s的掃描速率下,確定了施加在ZnO納米線上的實際外力和掃描角關系的力學校準方程和閾值力方程。掃描角的存在,增強了施加在ZnO納米線表面的實際外力。ZnO納米線力學損傷斷裂時的實際閾值力與掃描角無關,與納米線的直徑呈線性增加關系。利用閾值力方程和力學校準方程建立了ZnO納米線的安全服役評價方程。研究中得到的ZnO納米線的彈性模量要遠低于文獻中利用三點彎曲測得的數(shù)值,而斷裂強度則相差不大。 利用C-AFM系統(tǒng)研究了ZnO納米線的力電耦合性能與服役行為。均一直徑的ZnO納米線力電耦合損傷斷裂的閾值電壓隨著外力的增大呈線性減��；在恒定外力作用下,不同直徑的ZnO納米線力電耦合損傷斷裂的閾值電壓與納米線的直徑呈線性增大。應力集中效應增強了ZnO納米線與AFM針尖接觸表面的電子聚集,導致產生更多的焦耳熱,降低了導致ZnO納米線熔斷的閾值電壓值。
[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.
【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TB383.1;O614.241

【參考文獻】

相關期刊論文 前1條

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本文編號：1795552