Research On Thermal Transport In Phosphorene By Strain Modulation

Heat transport at the nanoscale is not only of a fundamental issue in physics but also crucial to engineering applications.A plenty of novel phenomena and mechanisms have emerged,which are closely related to strain modulation.Phosphorene,a new two-dimensional semiconductor material with direct band gap,has drawn growing attention in recent years owing to its superior physical properties of significant utility.In this study,the thermal conductivity of phosphorene under various strains is explored systematically by molecular dynamics methods.Firstly,the thermal conductivity of intrinsic phosphorene versus size and temperature is discussed.At 300 K,the thermal conductivity of phosphorene along the armchair and zigzag directions is 18.57 and 52.52 Wm^-1K^-1,respectively,whose anisotropy ratio is 2.83.The mechanical properties of the tensile,compressive,and shear deformation of phosphorene are calculated,which verifies the rationality and reliability of the strain’s simulation.The results show that under the tensile and shear deformation,the phosphorene are brittle fractured,while the phosphorene’s change of shape is plastic under the compressive deformation.The tensile,compressive,and shear modulus of phosphorene in the armchair and zigzag directions are 20.6 and 95.6 GPa,20.86 and 102.01 GPa,22.20 and 22.34 GPa,respectively.The tensile and compressive mechanical properties of phosphorene exhibit significant anisotropy,but the shear mechanical properties not.Besides the softening of materials that induced by temperature can significantly weaken the tensile and shear resistance of phosphorene.Secondly,the strained phosphorene’s thermal conductivity along the armchair direction is lower than it without strain,which is different from the thermal conductivity along the zigzag direction’s effect of strain.In addition,the high-frequency phonons of phosphorene exhibit a significant redshift under small strain,which results in a decrease in phonon group velocity and thermal conductivity.As the strain increase continuously,the phonon vibration mode of phosphorene with the increase of compressive strain shows unapparent change.However,the high-frequency phonon vibration mode is affected crucially by tensile and shear strains.Therefore,the high-frequency phonon of phosphorene plays a dominant role in heat transport under strain.Meanwhile,mechanical deformation can alter the inharmonic vibration of the lattice seriously,which has a significant impact on the scattering of phonons in different degree.In conclusion,the thermal conductivity of phosphorene under different strain is determined both the changes in high-frequency phonon vibration and phonon scattering channels caused by mechanical deformation.Findings in this paper provide help insights for the understanding of the physical mechanisms of thermal transport in phosphorene,further promote the development of thermal regulation technology of phosphorene by means of strain modulation,and have significance for the future applications in phosphorene-based novel devices.