Research On Mechanical Problems In Self-assembly Of Superlattice Nanowire

The superlattice nanowire structure has extremely high potential application in the fields of semiconductors,photoelectric,thermoelectricity and so on.Experimen-tal studies have found that this kind of structure can be formed by self-assembly,but it is difficult to observe the whole self-assembly process by situ experiments due to its fast forming speed,so the process and mechanism of self-assembly of this struc-ture are still unclear now.Meanwhile,the superlattice structure can be regarded as one-dimensional nano-inclusion structure,studying the elastic interaction between in-clusions in nanowire is of great significance for regulating the self-assembly of super-lattice nanowire.This paper studies the self-assembly process and mechanism of Te-Ag2Te superlattice nanowire structure,and studies the elastic interaction law between inclusions in nanowire and its influencing factors,futhermore,We find that applying ex-ternal stress can modulate the elastic interaction between inclusions in nanowire.The specific works are as follows:We simulate the self-assembly process of Te-Ag2Te superlattice nanowire by the phase field model of stress coupling concentration.We introduce a static order parame-ter to characterize the shape of superlattice nanowire and another order parameter to dis-tinguish Te phase and Ag2Te phase inside the nanowire.The phase transaction process of the system is simulated by Cahn-Hilliard equation combined with smooth-boundary method,and the distribution and evolution process of stress are solved by phase field microelasticity theory.By calculating the elastic energy of the system,we find that the elastic interaction between Te or Ag2Te segments in the nanowire is near attraction and far repulsion.For segmented structures,the periodic superlattice structure has the low-est elastic energy,thus revealing the self-assembly mechanism of Te-Ag2Te superlattice nanowire.We regard superlattice nanowire as isotropic infinite cylindrical rod with homoge-neous inclusions structure.First,we obtain the analytical solution of stress distribution.and elastic energy for an infinite cylindrical rod containing two arbitrary size inclu-sions.Then,by phase field method,we can obtain the numerical solution of stress and elastic energy,which is verified and compared with the analytical solution.According to the variation curve of elastic energy with spacing,we find that there is a near at-traction far repulsion elastic interaction between inclusions in nanowire,and the length and Poisson's ratio of inclusions can affect the elastic interaction between inclusions.Then we prove that applying local radial stress on the nano wire surface can adjust the elastic interaction between inclusions in nanowire,thus changing the periodicity of the superlattice structure.Finally,we also study the elastic interaction between inclusions in nanowires with different cross-sectional shapes.