van Enckevort Willem J P, Noorduin Wim L, Graswinckel Sander, Verwer Paul, Vlieg Elias
Radboud University, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 ED Nijmegen, The Netherlands.
Akzo Nobel Industrial Chemicals, Salt and Crystallization, Deventer, The Netherlands.
Cryst Growth Des. 2018 Sep 5;18(9):5099-5107. doi: 10.1021/acs.cgd.8b00546. Epub 2018 Jul 23.
A growth cell suitable for microscopic in situ observation of well-controlled crystal growth from the vapor phase is used to study the heteroepitaxial growth of anthraquinone crystals on a (100) NaCl substrate. In this, the morphology, orientation, nucleation, and growth rate of the crystals is studied as a function of driving force, Δμ/. At the lowest Δμ/, the crystals are block-shaped and show no preferential orientation with respect to the substrate. Increasing the driving force leads to the growth of oriented block- and needle-shaped crystals, which nucleate from macrosteps on the substrate. At the highest Δμ/, crystals nucleate on the flat surface areas or at monatomic steps on the substrate, resulting in a dramatic increase in epitaxial needle density. Growth rate measurements show an exponential behavior as a function of Δμ/. In all cases, the supply of growth units proceeds via surface diffusion over the NaCl substrate surface toward the anthraquinone crystals. At the lowest Δμ/, growth is partly limited by integration of the growth units at the crystal surfaces. At intermediate driving force, kinetic roughening sets in, leading to rounded needle tips. At the highest supersaturation, growth is completely governed by the supply of growth units via surface diffusion, leading to tip splitting as a consequence of morphological instability.
一种适用于从气相进行可控晶体生长的微观原位观察的生长池，被用于研究蒽醌晶体在(100) NaCl衬底上的异质外延生长。在此过程中，研究了晶体的形态、取向、成核和生长速率与驱动力Δμ/的函数关系。在最低的Δμ/时，晶体呈块状，相对于衬底没有择优取向。增加驱动力会导致取向的块状和针状晶体生长，这些晶体从衬底上的宏观台阶处成核。在最高的Δμ/时，晶体在衬底的平坦表面区域或单原子台阶处成核，导致外延针密度急剧增加。生长速率测量显示出作为Δμ/函数的指数行为。在所有情况下，生长单元的供应通过NaCl衬底表面的表面扩散朝着蒽醌晶体进行。在最低的Δμ/时，生长部分受到晶体表面生长单元整合的限制。在中等驱动力下，动力学粗糙化开始出现，导致针尖变圆。在最高过饱和度下，生长完全由通过表面扩散的生长单元供应控制，导致由于形态不稳定性而出现尖端分裂。
