Study On Mechanical Property Of Zinc Oxide Nanowire At Atmosphere

Due to the extremely outstanding piezoelectric property and photoelectric property of one-dimensional(1D)zinc oxide(ZnO)nanowire,it has a great prospect in the application of nano-devices such as nanogenerator,LED,photodetector and so on.At the same time,1D ZnO nanowire is always applied in the nano-mechanics researches for its rich nanostructure and developed preparation.The study on the mechanical property of 1D ZnO nanowire at atmosphere is not only valuable for its application in the nano-electro-mechanical systems(NEMS),but also significant for the research on the measurement environment how to influence the 1D ZnO nanowire mechanical property.Based on the smallest resonator array,this paper measures the resonant frequency of high-quality 1D ZnO nanowire with [0001]orientation by utilizing the atomic force microscope(AFM)resonance,the Young's modulus of the corresponding 1D ZnO nanowire can be calculated by Euler-Bernoulli cantilever model.On the measurement results,this paper build a “shell-shell-core” model to study the size-dependent Young's modulus of 1D ZnO nanowire in ambient air.This paper prepares high-quality 1D ZnO nanowire by utilizing gold catalyzed chemical vapor deposition(CVD),and the 1D ZnO nanowire vibration is induced by cross electrode applied with alternating electric field.The amplitude-frequency response of 1D ZnO nanowire is detected by AFM resonance,the amplitude value is highest when the 1D ZnO nanowire resonance occurs.Additionally,to improve the measurement resolution,three methods are taken in this paper: the used AFM cantilever selected stiffness with 0.3N/m,the distance between cantilever tip and sample is selected as 5nm and voltage of alternative electric field take 0.4V.The resonance frequencies of 1D ZnO nanowires with different diameter are measured and corresponding Young's modulus are calculated.The diameters of 1D ZnO nanowires in this paper are range from 48 nm to 239 nm,these results show that the Young's modulus of 1D ZnO nanowires at atmosphere has obvious size-dependence,it decreases with diameter increase and tend to the Young's modulus value 140 GPa of bulk ZnO.Based on the “shell-core” model built on measurement in vacuum,by adding a “outer shell” area,a “shell-shell-core” model is proposed in this paper to study the influence of measure environment in air on the 1D ZnO nanowires Young's modulus size dependence.By reasonably take some values of “shell-shell-core” and fitting with measured results at atmosphere,the Young's modulus of “outer shell” area takes 345.4GPa.The size-dependent Young's modulus of 1D ZnO nanowires is more obvious corresponding to measurementresult in vacuum,that mainly due to the surface-effect of 1D ZnO nanowires strengthen at atmosphere for the activity of oxygen.