Department of Mathematical Sciences, Loughborough University, Loughborough, Leicestershire, UK.
J Phys Condens Matter. 2013 Apr 3;25(13):135002. doi: 10.1088/0953-8984/25/13/135002. Epub 2013 Mar 1.
Results are presented for modelling of the evaporation and magnetron sputter deposition of Zn(x)O(y) onto an O-terminated ZnO (0001¯) wurtzite surface. Growth was simulated through a combination of molecular dynamics (MD) and an on-the-fly kinetic Monte Carlo (otf-KMC) method, which finds diffusion pathways and barriers without prior knowledge of transitions. We examine the effects of varying experimental parameters, such as substrate bias, distribution of the deposition species and annealing temperature. It was found when comparing evaporation and sputtering growth that the latter process results in a denser and more crystalline structure, due to the higher deposition energy of the arriving species. The evaporation growth also exhibits more stacking faults than the sputtered growth. Post-annealing at 770 K did not allow complete recrystallization, resulting in films which still had stacking faults where monolayers formed in the zinc blende phase, whereas annealing at 920 K enabled the complete recrystallization of some films to the wurtzite structure. At the latter temperature atoms could also sometimes be locked in the zinc blende phase after annealing. When full recrystallization did not take place, both wurtzite and zinc blende phases were seen in the same layer, resulting in a phase boundary. Investigation of the various distributions of deposition species showed that, during evaporation, the best quality film resulted from a stoichiometric distribution where only ZnO clusters were deposited. During sputtering, however, the best quality film resulted from a slightly O rich distribution. Two stoichiometric distributions, one involving mainly ZnO clusters and the other involving mainly single species, showed that the distribution of deposition species makes a huge impact on the grown film. The deposition of predominantly single species causes many more O atoms at the surface to be sputtered or reflected, resulting in an O deficiency of up to 18% in the deposited film and therefore resulting in more stacking faults and phase boundaries. The methods used allow analysis of key mechanisms that occur during the growth process and give hints as to the optimum conditions under which complete crystalline layers can form.
呈现了用于建模 Zn(x)O(y)在 O 终止 ZnO(0001¯)纤锌矿表面上的蒸发和磁控溅射沉积的结果。通过分子动力学 (MD) 和即时动力学蒙特卡罗 (otf-KMC) 方法的组合进行了生长模拟，该方法在没有事先了解跃迁的情况下找到了扩散途径和势垒。我们研究了改变实验参数（例如基底偏压、沉积物种的分布和退火温度）的影响。通过比较蒸发和溅射生长发现，由于到达物种的沉积能量较高，后者过程导致更致密和更结晶的结构。蒸发生长还表现出比溅射生长更多的层错。在 770 K 退火后，不完全的再结晶导致薄膜仍存在堆叠层错，其中在闪锌矿相中形成单层的地方，而在 920 K 退火则使一些薄膜完全再结晶到纤锌矿结构。在后者温度下，原子有时也可以在退火后锁定在闪锌矿相中。当不完全发生再结晶时，同一层中会看到纤锌矿和闪锌矿相，从而形成相界。对各种沉积物种分布的研究表明，在蒸发过程中，质量最好的薄膜来自仅沉积 ZnO 团簇的化学计量分布。然而，在溅射过程中，质量最好的薄膜来自稍微富氧的分布。两种化学计量分布，一种主要涉及 ZnO 团簇，另一种主要涉及单个物种，表明沉积物种的分布对生长的薄膜有巨大影响。主要沉积单一种类会导致更多的表面 O 原子被溅射或反射，从而导致沉积薄膜中的 O 缺乏高达 18%，因此导致更多的层错和相界。所使用的方法允许分析生长过程中发生的关键机制，并为形成完全结晶层的最佳条件提供线索。
