Si原子修饰空位缺陷石墨烯的结构与性能优化

Optimization of structures and properties of vacancy-defected graphene modified by Si atoms

本征石墨烯具有诸多优点,但因为其导电性不可控而难以直接应用.为了能够有效调节石墨烯的导电能力,使其变得可控,科学家不断地寻找石墨烯改性的方法.高能粒子轰击方法由于能够轻易实现异质粒子在石墨烯中的掺杂,因而引起了研究者的广泛关注.本文采用分子动力学方法模拟了具有一定能量的Si6团簇垂直轰击石墨烯的过程.通过可视化软件对体系的微观结构进行观察,同时记录石墨烯的结构变化.结果表明,在能量较低(0.875~55.9 eV)时,Si6并不能破坏石墨烯的结构,而能量较高(503.9 eV以上)时,Si6可以轻易破坏石墨烯结构并引入边缘规则的空位缺陷.在探明了不同能量范围下Si6轰击给石墨烯带来的影响之后,采用初始能量为0.146 eV的不同数量Si原子对轰击所得的空位缺陷石墨烯进行修补,并利用第一性原理方法对Si原子修补石墨烯所得构型进行结构优化和电子结构的计算.结果表明,Si原子的引入能够较好地饱和空位缺陷所带来的碳悬键.Si原子之间存在强烈的相互作用,且Si原子在空位缺陷处形成三维结构.Si原子的引入能成功打开石墨烯的带隙,同时会降低四空位缺陷石墨烯的导电性.该研究为石墨烯的改性提供了新思路.

Intrinsic graphene has so many advantages that it is regarded as an alternative material for silicon in the semiconductor industry;however,it is difficult to be directly applied into electronic devices because of its uncontrollable electrical conductivity.Therefore,it is urgent to modify the electrical properties of graphene to promote its application in practical production.Scientists have been looking for modified methods to make graphene controllable in order to effectively adjust its conductive ability.As one of the effective means to modify the properties of many materials,the bombardment with high-energy particles can regulate the electrical properties of graphene easily by doping the heterogeneous particles in graphene,and therefore attracts extensive attention of researchers.Si is the suitable choice as doped atoms in graphene because Si and C are congeners of chemical elements with some similar properties.Herein the processes of bombarding graphene with Si6clusters were simulated by the molecular dynamics method for investigating the structural evolution during bombardment.The microstructures of the system were observed by visualization software,and the detailed structural changes of graphene were recorded in the meantime.The results indicate that Si6is not able to cause damage to C–C bonds in graphene at the low energy range[0.875,55.9]eV but destroys the structures of graphene easily and introduces vacancy defects with the regular edge at the high energy range(above 503.9 eV).The bombarded graphene tends to form a variety of complex structures when the energy of Si6is in the range of(55.9,503.9]eV.The effects of different bombardment energy on graphene were investigated,which gives us a reference value(0.146 eV)for the initial energy that each Si atom used to repair the graphene needs.Then,the repairing processes of vacancy-defected graphene obtained by bombardment were performed with different numbers of Si atoms by the molecular dynamics methods.The first-principles methods are used to optimize the repaired geometric configurations left by molecular dynamics simulations to obtain the stable structures needed in the subsequent calculations of the electronic structures.The optimized configurations show that the carbon dangling bonds caused by vacancy defects can be saturated by the introduction of Si atoms.Moreover,the results calculated by first-principles methods differ from those by molecular dynamics methods and there is a strong interaction between Si atoms,which forms three-dimensional structures at the vacancy defects.The electronic structures of the three optimized configurations show that the band gaps of graphene are opened and the conductivity of graphene with four vacancies is reduced by the introduction of Si atoms.This study provides a new idea for the modification of graphene and will hopefully be valuable for designing modern gas sensing and electronic devices.