Eres Gyula, Tischler J Z, Rouleau C M, Lee Ho Nyung, Christen H M, Zschack P, Larson B C
Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 61801, USA.
Phys Rev Lett. 2016 Nov 11;117(20):206102. doi: 10.1103/PhysRevLett.117.206102.
We use real-time diffuse surface x-ray diffraction to probe the evolution of island size distributions and its effects on surface smoothing in pulsed laser deposition (PLD) of SrTiO_{3}. We show that the island size evolution obeys dynamic scaling and two distinct regimes of island growth kinetics. Our data show that PLD film growth can persist without roughening despite thermally driven Ostwald ripening, the main mechanism for surface smoothing, being shut down. The absence of roughening is concomitant with decreasing island density, contradicting the prevailing view that increasing island density is the key to surface smoothing in PLD. We also report a previously unobserved crossover from diffusion-limited to attachment-limited island growth that reveals the influence of nonequilibrium atomic level surface transport processes on the growth modes in PLD. We show by direct measurements that attachment-limited island growth is the dominant process in PLD that creates step flowlike behavior or quasistep flow as PLD "self-organizes" local step flow on a length scale consistent with the substrate temperature and PLD parameters.
我们使用实时漫反射表面X射线衍射来探究在脉冲激光沉积(PLD)制备SrTiO₃过程中岛尺寸分布的演变及其对表面平滑化的影响。我们表明,岛尺寸的演变遵循动态标度律以及岛生长动力学的两种不同模式。我们的数据表明,尽管作为表面平滑化主要机制的热驱动奥斯特瓦尔德熟化过程被关闭,但PLD薄膜生长仍可在不发生粗糙度增加的情况下持续进行。粗糙度不增加的同时岛密度降低,这与普遍认为的增加岛密度是PLD中表面平滑化关键的观点相矛盾。我们还报告了一种此前未观察到的从扩散限制型到附着限制型岛生长的转变,这揭示了非平衡原子级表面输运过程对PLD中生长模式的影响。我们通过直接测量表明,附着限制型岛生长是PLD中的主导过程,它在与衬底温度和PLD参数一致的长度尺度上产生台阶流状行为或准台阶流,即PLD“自组织”局部台阶流。