Simulation And Calculation Of Thermal Conductivity Of Nano-ZnO Thin Films

As the rapid development of science and technology,micro/nano science and technology have become the bottlenecks and breakthroughs in materials,energy,aerospace,electronics and medical fields,and their development degree and progress have restricted the development of various fields.The study found that nanomaterials have different thermal transport properties compared to traditional coarse-grained materials,and now they have become a research hotspot for scientific researchers.For example,when the feature size of a material is reduced to the nanometer level,the thermal conductivity of the material will show a size effect as the feature size changes.At the same time,lattice defects,doping,etc.increase the carrier scatter,which further reduces the thermal conductivity.Due to the complex relationship between the thermal conductivity of nanomaterials and their microstructures,the research on thermal conductivity of nanomaterials is still in its preliminary stage.In order to further study the thermal transport properties of nano-materials,this article will take nano-ZnO films as the research object,and conduct research through computer simulation and theoretical calculation.The paper uses Atomsk software to establish nano-ZnO thin film models with different thicknesses and different grain sizes.The thermal conductivity of the corresponding model is obtained by LAMMPS simulation calculation.The results show that as the film thickness and grain size continue to decrease,the thermal conductivity also continues to decrease,showing a significant size effect,which is consistent with the theoretical calculations obtained in the paper.The paper attributed the above phenomenon to the decrease in film thickness and grain size,which increased the specific surface area of the material's micro-nanostructures,increased interface density,and enhanced interface scattering.In this paper,the probability density of phonons is solved according to the diffusion mismatch model.The mean free path of phonons under the influence of grain boundaries is solved by Mathisson's rule.Then the relationship between the thermal conductivity in the crystal and the grain size is calculated according to molecular dynamics theory,and finally establish a theoretical mathematical model of effective thermal conductivity.According to the impedance model and quantum mechanics theory,the electron transmittance is approximated,and the electronic thermal conductivity is further obtained.The phonon thermal conductivity is compared with the electronic thermal conductivity,and the experimental values in the literature are compared with the theoretical model we derived.The results show that as the grain size decreases,the phonon thermal conductivity and electronic thermal conductivity also decrease,which is consistent with the experimental results.At the same time,the paper concludes that the phonon thermal conductivity is 5 to 6 orders of magnitude greater than the electronic thermal conductivity,and the size effect increases with decreasing grain size;the experimental value of the effective thermal conductivity is different from the theoretical calculated value,less than 15%,and that verifying the correctness of the theoretical calculation.This study has promoted the research progress of thermal conductivity of nano-ZnO films to a certain extent.