Study On Bond Relaxation Kinetics Of Thermal Properties Of Transition Metal Dichalcogenides

The two-dimensional layered semiconductor material with atomic layer thickness shows great application potential in nanoelectronics and optoelectronic devices.However,it detection and diagnosis of the thermal properties of the two-dimensional layered semiconductor material are still a huge challenge.Experience shows that from the perspective of chemical bond relaxation theory and vibration,the core-shell structure model,and local bond average?LBA?approach can be used to explore the thermal properties of low-dimensional materials and thus bring new insights.In this paper,based on bond order-length-strength?BOLS?theory and the core-shell structure model,the functional expressions of the thermal parameters of the transition metal dichalcogenides?Mo Se₂,WSe₂?at different temperatures and sizes are established,which reveals the physical causes behind them and quantitatively obtains the relevant thermal parameters,as follows:?1?Temperature effect of Mo Se₂ and WSe₂ thermal parameters.Starting from the definition of the thermal expansion coefficient,a quantitative function relationship between the thermal expansion coefficient,lattice constant,thermal strain and temperature is established.The physical mechanism of the temperature effect of the thermal parameters of the transition metal dichalcogenide semiconductor materials is revealed:the coefficient of thermal expansion is proportional to the debye specific heat;it is inversely proportional to the atomic binding energy.When the temperature is higher than one-third of the Debye temperature of the material,the lattice constant and thermal strain are linearly related to the temperature.Debye temperature 276K and 260K of bulk Mo Se₂ and WSe₂ were obtained.?2?Size effect of Mo Se₂ and WSe₂ thermal parameters.According to bond order-length-strength?BOLS?theory and the core-shell structure model,the relationship between the thermal expansion coefficient and the debye temperature size effect function is established.Quantitatively obtained the binding energy,debye temperature and thermal expansion coefficient of Mo Se₂ and WSe₂ in different sizes.The correlation of the size effect of the thermal parameter of the two-dimensional layered material is revealed:the binding energy and debye temperature decrease as the size decreases,and the thermal expansion coefficient increases as the size decreases.At the same time,the temperature effect of thermal strain of single-layer Mo Se₂ and WSe₂ semiconductor materials is obtained.In summary,from the perspective of bond order-length-strength theory,this paper analyzes the physical causes of changes in thermal parameters of the two-dimensional layered semiconductor material at different temperatures and sizes,and obtains the corresponding thermal parameters.It provides a theoretical basis for the application of the two-dimensional layered semiconductor material in optoelectronic devices.