硼/氮原子共掺入金刚石的晶格损伤及其退火过程的计算机模拟

Computer simulation of damage in diamond due to boron-nitrogen co-doping and its annealing

借助于Tersoff势函数和分子动力学模拟技术研究了室温下500eV的能量粒子硼(4个)和氮(8个)共掺入金刚石晶体中所引起的损伤区域内晶体微细观结构的变化特征以及后续加热退火晶体结构的演变特征.结果表明:随着掺入原子数目的增加,受影响的区域范围渐渐增大,12个粒子全部注入金刚石晶体后局部影响区域的半径达0.68nm,损伤区域中心的三配位原子数增加而四配位数原子数量减少.加热退火过程中损伤中心区域的原子发生扩散,部分原子的扩散距离达到4个晶格间距.加热退火使损伤区域中心原子间的平均键长趋于金刚石结构的键长.退火后薄膜中注入的杂质原子向表面扩散引起应力分布产生变化,杂质原子经过一系列的扩散过程能够到达空位的位置,减少薄膜中空位数量,减小晶格畸变程度,原子向表面扩散引起应力产生重新分布,薄膜中应力峰值的峰位向薄膜表面发生移动,局部应力集中程度降低.通过不同退火温度的比较发现低温下退火(800℃)更有利于空位的运动和晶格损伤的恢复从而提高晶格质量.

We report the structural characterization and lattice damage induced by the energetic boron （four atoms in all） and nitrogen atoms （eight atoms in all ） with the energy of 500 eV co-doped into diamond film and subsequent annealing by computer simulation based on Tersoff empirical potential. With the increasing number of implanted atoms, the affected volume is enlarged, the radius of the disrupted region reaches to 0.68 nm for twelve implanting atoms. As a result of annealing, the atoms of the disrupted core can move for rather long distances up to several lattice sites. The mean bond length after annealing approaches the diamond bond length, as obtained from the pair distribution function. Since it is rich in vacancies on the near surface layer, after annealing the interstitial-vacancy recombination could take place, leading to the redistribution of the stress. Annealing at 800℃ is adequate for the recovery of the implanted diamond lattice.