The Investigation Of Substrate And Tip Effects In Nanoindenter Technology

Nanoindentation is applied in many research fields for its advantages such as convenient sample preparation,easy operation,and highly repeatable results.Up to now,nanoindentation has become one of the main and the most important methods to measure the material mechanical properties in micro/nano-metrology,material science and surface science.This dissertation is supported by National Natural Science Fund of China (No.50335050)and State 863 Projects(No.2006AA04Z311).To enhance the reliable analysis of the measured results by nanoindentation,two important issues on substrate and tip radius effects in nanoindentaion applications are discussed here.The main research contents of this dissertation are summarized in following aspects:Firstly,the influence of materials mechanical properties in film/substrate systems in the nanoindentation results is investigated by finite element method(FEM).For soft film on hard substrate and hard film on soft substrate systems,the elastic and plastic deformation and the deformation evolvement process in films and substrates are analyzed respectively.Also the effects of mechanical properties of the film and the substrate in different systems on the hardness measurements are analyzed,as well as the film thickness.Further more,the mechanism of this kind of substrate effect is discussed.All these results have important meaning in measurement,evaluation and reliability analysis of the mechanical properties of film structure materials by nanoindentaion.Secondly,the effects of tip radius of the blunt indenter on the nanoindentation results are investigated by theoretical analysis and FEM method.The results show that the measurement values of hardness by nanoindentation have different and obvious depth size effects for the blunt indenters with different tip radii.Based on the results,we also analyzed and explained the mechanism of the tip radius size effects.A semi-empirical relation,which depicts hardness with tip radius and indentation depth is derived by theoretical analysis.And also,the elastic and plastic deformation and the deformation evolvement process in materials under different tip radius indenters are simulated by FEM.The simulation results indicate that the tip size effect in nanoindentaion is caused mainly by the underestimate of the contact area due to the indenter bluntness.And this kind of tip radius size effect becomes more and more obvious as the tip radius increases.For the elastic and plastic deformation distributions in materials under the indenters with different tip radii are different,the physical dissimilarity due to geometrical dissimilarity will also influence the tip size effect,although it is a factor with minor influence.Thirdly,the mechanical properties of radio frequency(RF)magnetron sputtering zinc oxide(ZnO)thin film on different substrates are investigated by nanoindentation, atomic force microscopy(AFM),and X-ray diffraction(XRD)technology.The mechanical properties and the nanostructures of RF magnetron sputtering ZnO film under different annealing temperatures are also discussed.Results show that proper anneal treatment can improve the crystal quality and enhance the mechanical properties of ZnO film.The film has a maximum hardness and elastic modulus value at 450℃annealing temperature in air.Finally,the research contents and the main innovations in this dissertation are summarized,and the future research directions of the nanoindentation application are discussed.