异质扩散过程中ES势垒的计算

Computation of the Ehrlich-Schwoebel barrier to adatom diffusion in heteroepitaxial systems

利用分子动力学中的静态结构计算方法对Pd,Ag及Cu原子在面心立方铜的台阶表面扩散过程中的Ehrlich-Schwoebel(ES)势垒进行了模拟计算,研究了各种台阶表面情况下增原子扩散过程中的ES势垒;讨论了与衬底互溶的金属和与衬底不互溶的金属增原子扩散的ES势垒的异同,并将模拟结果与同质情况的研究结果进行了对比.结果表明:1)在同质和异质扩散过程中ES势垒随着台阶高度的变化关系是相似的,即随着台阶高度的增加,ES势垒逐渐增加;当台阶高度达到某一高度时ES势垒将趋于定值.2)在跳跃机理下,与Cu互溶的金属(Pd)在Cu表面台阶上扩散的ES势垒最大,其次是Cu,最小的是与Cu不互溶的金属(Ag);而在交换机理下,与Cu不互溶的金属(Ag)在Cu表面台阶上扩散的ES势垒最大,其次是Cu,最小的是与Cu互溶的金属(Pd).3)对大多数台阶的情况,交换机理支配着原子在台阶边缘的扩散行为;且表面台阶高度对交换扩散过程影响较大.

The Ehrlich-Schwoebel （ES） barriers to the diffusion of adatoms （Pd,Ag and Cu） on different bench terraces of fcc Cu are compared by molecular dynamics computation. The computation reveals that： 1 ） For both heteroepitaxial and homoepitaxial systems, the ES barriers increase similarly with the increase of bench terrace height until a certain height is reached. 2） The ES barrier of adatom Pd is the biggest, the second one is that of adatom Cu, and the smallest one is that of adatom Ag for the hopping diffusion mechanism, while the ES barrier of adatom Ag is the biggest, the second one is that of adatom Cu, and the smallest one is that of adatom Pd for the exchange diffusion mechanism. 3）The ES barrier of exchange is lower than that of hopping mechanism in most cases of bench terraces.