Drummy Lawrence F, Miska Paul K, Alberts David, Lee Nuram, Martin David C
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136, USA.
J Phys Chem B. 2006 Mar 30;110(12):6066-71. doi: 10.1021/jp054951g.
We have investigated the crystal growth of the organic semiconductor pentacene by complementing molecular simulations of surface energies with experimental images of pentacene films. Pentacene thin films having variations in thickness and grain size were produced by vacuum sublimation. Large (approximately 20 microm) faceted crystals grew on top of the underlying polycrystalline thin film. The films were characterized using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Single crystals most commonly grew in a truncated diamond shape with the largest crystal face, (001), growing parallel to the substrate. Crystal morphologies and surface energies were calculated using force field-based molecular simulations. The (001) surface was found to have the lowest energy, at 76 mJ/m(2), which was consistent with experimental observations of crystal face size. It was demonstrated that the morphology of the large faceted crystals approached the equilibrium growth shape of pentacene. From contact angle measurements, the critical surface tension of textured pentacene thin films in air was determined to be 34 mJ/m(2).
我们通过用并五苯薄膜的实验图像补充表面能的分子模拟，研究了有机半导体并五苯的晶体生长。通过真空升华制备了厚度和晶粒尺寸不同的并五苯薄膜。大的（约20微米）多面晶体生长在下层多晶薄膜之上。使用光学显微镜（OM）、X射线衍射（XRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）对薄膜进行了表征。单晶最常见的生长形状是截顶菱形，最大的晶面（001）与衬底平行生长。使用基于力场的分子模拟计算了晶体形态和表面能。发现（001）表面的能量最低，为76 mJ/m²，这与晶面尺寸的实验观察结果一致。结果表明，大的多面晶体的形态接近并五苯的平衡生长形状。通过接触角测量，确定了空气中织构化并五苯薄膜的临界表面张力为34 mJ/m²。
