In-situ Study Of Interfacial Phase Transformation Of Nano Materials Induced By Field At Atomic Scale

With the improvement of chip integration,the size of the device is gradually reduced to nanometer scale,and the proportion of interface in the device increases.The phase structure at the interface of nanomaterials has an important impact on the performance of the device.It is of great significance to study the evolution of interfacical phase structure of nanomaterials from atomic scale,realize the precise control of interface phase,and the corresponding relationship between phase structure and performance.It can improve the performance of electronic devices.In situ transmission electron microscope(TEM)with high resolution and various external stimuli can dynamically characterize and manipulate materials at the atomic scale.In this paper,the in situ TEM is used as the main research tool.TEM sample preparation method is optimized.The interfacial structure of nanomaterials is manipulated by in situ TEM.The relationship between the interfacial structure and the performance of nanomaterials is established,and the mechanism of interfacial phase transition is analyzed.The main contents include:(1)Study on phase transition behavior on the surface of bismuth nanowires induced by e-beam.The manipulation of the morphology and structure on the surface of bismuth nanowires is realized.The thermal effect of the e-beam is used to induce a solid-liquid phase transition on the surface of the bismuth nanowire to form bismuth nanoparticles.By site-specific irradiation,the manipulation of crystal orientation inside a single nanoparticle is realized.The phase transition process,including nucleation,growth,and coalescence of bismuth nanoparticles,was studied in situ at the atomic scale.The results show that the nucleation occurred at the edge of the bismuth nanodroplet,the crystal orientation is adjustable and not affected by the substrate.The metastable state in the coalesced area introduced the additional interfacial states,determining the phase transition behavior inside the nanoparticle.(2)Study on phase transition behavior on the surface of Zn₂Ge O₄(ZGO)nanowires induced by in situ thermal field.The manipulation of microstructure on the surface of ZGO nanowires is realized.The in situ thermal field is used to induce the sublimation phase transition on the surface of the ZGO nanowires,and the complete sublimation process of the nanowires is analyzed.The results show that the sublimation of the ZGO nanowires is related to size,which is caused by the competition between the surface energy and the crystal structure.When the size of the nanowire is larger than the critical size,the nanowire sublimates along a certain crystal plane with a minimum energy barrier.When the size of the nanowire is close to the critical size,the surface energy should be taken into consideration.The atoms at the surface rearrange and form a curved surface,and the nanostructure behaves as a quasi-liquid.When the size of the nanowire is far smaller than the critical size,the sublimation of the nanoparticle is mainly affected by the surface energy,showing an isotropic sublimation behavior.(3)Study on interfacial phase transition behavior of Ag₂Se grains induced by in situ thermal field.The manipulation of the phase transition rate of Ag₂Se grains is realized.In situ thermal transmission electron microscopy is used to study the dynamic phase transition of Ag₂Se.The phase transition of Ag₂Se nanoparticles with different sizes is characterized at atomic scale under heating,constant temperature,cooling,and e-beam irradiation.The results show that Ag₂Se has two kinds of phase transition growth behaviors:longitudinal and transverse.Through statistical analysis of the relationship between grain boundary size and growth rate of different sizes of nanoparticles during phase transition,it is found that the grain boundary of Ag₂Se nanoparticles has a uniform and variable growth behavior.In this paper,in situ TEM is used to manipulate the atomic configuration,electronic structure,and phase transition behavior at the interface by applying external stimuli such as e-beam irradiation and thermal field.It reveals the influence of interfacial phase transition on the properties of materials and devices,and provides new ideas for the improvement of nano-manufacturing technology and device performance in the future.