Design And Application Of In-situ Liquid And Electrical TEM Chips Based On MEMS Technology

Transmission electron microscope(TEM)utilize the signals coming from the interaction between the incident energetic electron beam and the sample to provide the structural and compositional information of materials at atomic level,hence it serves an effective tool for revealing the structure-property relationship of the target materials,are finds wide applications in scientific research.Traditional electron microscope requires a high-vacuum working environment to ensure its best performance,while the cost is that this condition often deviate the real working environment and conditions of materials in practice service,as they usually work in liquid,gaseous and under mechanical loading,electrical biasing etc.In this way,it is necessary to develop new techniques and methodology to address these challenges and create similar environments and conditions inside the microscope.Amongst various approaches for in situ TEM,deployment of TEM sample holders with special functionality is an effective way to introduce external excitations such as light,electricity,heat and atmosphere into the microscope.Hence we can simulate the real service environment of materials and characterize the dynamic evolution of the material structures and properties in real time.A key technology is the development and fabrication of MEMS chips with the designed functionalities that meets the requests of in situ TEM measurements.In this paper,I proposed a modified fabrication process to prepare two types of in situ TEM chips.The first one is liquid-cell TEM chips.It typically consists of a spacer chip and a blank chip made of silicon and decorated with silicon nitride thin film,which was used as the imaging window,as well as for the purpose of liquid encapsulation and vacuum isolation with the TEM column.To test the reliability and applicability,this chip was used for in situ LCTEM study of the growth of silver nanocrystals in solution.The second one is the four-electrode electrical biasing chip.Again thin SiNx film was used as the window layer,and Cr/Au was used as the electrode material.To fulfill the purpose of TEM observations,additional holes were drilled on these as-formed chips via focused ion beam.Taking the two-dimensional molybdenum disulfide material as a model system,I further test the capability of this chip on measuring the current-voltage characteristics under different annealing conditions.