The Study Of Structural Design And Interfacial Energy Transport Properties Of Heterojunctions

Heterojunction general structure is composed of two or more layers of different materials,each with a different band gap.The formation of heterojunction is accompanied by the formation of interfacial thermal resistance and resistance which affect the application of heterojunction in electronic devices.In this paper,molecular dynamics simulation and first-principles calculation methods were used to study the effects of interfacial structure on interfacial thermal,electrical transport and mechanical stability of two heterostructures,namely,carbon nanotubs-graphene nanoribbons and silicon-magnesium silicate,respectively,starting from the application of microelectronic system and segmented thermoelectric materials.The main work can be divided into the following two parts1.By classical molecular dynamics method,we study the non-planar junction,where the material mismatch at the material junction leads to the change of the local or overall properties of the material.The change in mechanical stability and thermal transport properties in longitudinally drawn carbon nanotubes is investigated by varying the sharpness of the carbon nanotube draw-off,i.e.,the size of the opening angle of the transition from carbon nanotubes to graphene nanoribbons.The computational study shows that the more drastic the transition from carbon nanotubes to graphene nanoribbons,the larger the opening angle of the junction,the higher the local thermal conductivity and the lower the thermal resistance per unit length.Moreover,the maximum opening angle at the junction is constant at 16.3°for different diameters of carbon nanotubes.This finding is important for the study of the structure and properties of the junction transition in the 1D-2D system,and provides relevant information for the preparation of heterojunctions in this system.2.In this paper,Si-Mg₂Si with excellent thermoelectric properties was selected as the research object based on the advantages of non-toxicity,non-pollution,wide source of raw materials and economy.The effect of interfacial structure along different crystal orientation composition on its contact conductivity,thermal resistance and mechanical stability is investigated.By means of molecular dynamics simulations based on Newton's second law and first-principles calculation methods of density generalized theory,we computationally studied we constructed six different crystallographic orientations of Si-Mg₂Si structures and discussed the Si-Mg₂Si interfacial stability and investigated its interfacial transport properties.The results show that the segmented thermoelectric material composed of(001)Si interface and(001)Mg₂Si?terminal Si has an interfacial thermal resistance of 63.26×10^-8 Km²W^-1 and an interfacial conductance of 0.6166 e²h^-1,which is the best in terms of mechanical stability and thermal and electrical transport properties,indicating that this structure has a high conversion efficiency in energy conversion.This indicates that the structure has high conversion efficiency in energy conversion.The relationship between interfacial structure and mechanical stability,contact thermal resistance,electrical resistance and their physical mechanisms is revealed,and the problems addressed involve various scientific fields such as physics,chemistry,surface science and nanoscience.It plays a key role not only in the design of segmented thermoelectric materials,but also guides the development of areas where material interfaces play an important role,such as thermal interface materials,complexes,and surface coatings.