The Effects Of Size,temperature And Pressure On The Band Gap And Elastic Modulus In Layered Semiconductor Materials

The effects of size,temperature and pressure on the band gap and elastic modulus in the layered semiconductor materials have attracted much attention in the field of materials science.It is hard to explain the special behaviors of band gap and elastic modulus by existing theoretical models.It is need to develop a new theoretical model to reveal the physical mechanism and key factors behind them.This paper have from physical content to establish the function of the band gap and elastic modulus with parameters of chemical bond,it is based on the bond-order-length-strength theory and local bond average approach.The function use to research the effects of size,temperature and pressure on the band gap and elastic modulus in layered semiconductor materials(such as MoS2,WS2,ReSe2,BN,etc.).The research results of this paper are summarized as follows:(1)There have function between the band gap and the chemical bond parameters in materials.Reveals a relation between the band gap and crystal potential,the band gap is proportional to energy of the single bond in layered semiconductor materials.It is pointed out that the absence of atomic coordination induces surface relaxation and bond energy enhancement on the surface in nanometer layered semiconductor materials,which caused wider band gap has compared with bulk.The surface to volume ratio is the influence factors of the relative amplitude of the band gap.When high temperature or low pressure,the bond became weaker and the crystal potential reduced,which cause the band gap decreases.(2)The relationship between the elastic modulus and the chemical bond parameters is constructed in the layered semiconductor materials.It is clarified that the elastic modulus is proportional to the average density in the layered semiconductor materials.The change of atomic bond in the surface of materials that caused the enhance of energy density,which is the main reason for the increase of the elastic modulus with size in layered semiconductor materials.The surface to volume ratio is the main factor affecting the relative variation of elastic modulus.Due to the bond become longer and weaker under the high temperature or low pressure,the energy density decreases,which lead to the decrease of the elastic modulus.