Kinetics-driven anisotropic growth of pentacene thin films
Kinetics-driven anisotropic growth of pentacene thin films
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DOI：
10.1103/physrevb.77.035426
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发表时间：
2008-01-01
影响因子：
3.7
通讯作者：
Sakurai, Toshio
中科院分区：
文献类型：
--
作者：
Al-Mahboob, Abdullah;Sadowski, Jerzy T.;Sakurai, Toshio
本文对（001）取向并五烯（C22H14, Pn）薄膜在硅表面的非外延和外延结构的生长进行了广泛的研究，以阐明其固有的薄膜生长机制。晶体结构的各向异性显著地改变了并五苯薄膜的动力学驱动生长过程。在Si(111)-7x7和α根3-Bi-Si（111）表面上扩散限制生长的Pn岛的原位实时低能电镜研究显示其形状具有明确的各向异性。虽然这种各向异性与有机薄膜晶体结构有关，但不能从平衡晶体形状直接预测。研究发现，在动力学生长条件下，尽管沿a轴的阶长能量最低，但Pn岛总是沿着平面内晶胞的b轴方向拉长，这与晶体多晶型或外延关系无关，表明Pn薄膜生长具有内在的沿b轴方向的动力学偏好。利用这种动力学偏好，并在Pn沉积过程中限制惰性表面上可用通量的方向，使我们能够控制Pn畴的晶体取向。
The growth of nonepitaxial as well as epitaxial structures of (001)-oriented pentacene (C22H14, Pn) thin films on silicon surfaces has been extensively studied in order to elucidate the intrinsic thin-film growth mechanism. The kinetically driven growth processes in pentacene films were found to be modified significantly by the anisotropy of the crystal structure. In situ real-time low-energy electron microscopy studies of diffusion-limited growth of Pn islands on Si(111)-7x7 and alpha root 3-Bi-Si(111) surfaces reveal a definite anisotropy in their shapes. Although this anisotropy is associated with organic film crystal structure, it cannot be predicted directly from the equilibrium crystal shape. It has been found that under kinetic growth conditions the Pn islands are always elongated along the b axis of the in-plane unit cell, even though the step along the a axis has the lowest energy, regardless of crystalline polymorph or epitaxial relation, indicating that Pn thin-film growth has an intrinsic kinetic preference along the b-axis direction. Utilizing this kinetic preference and constraining the direction of available flux on inert surfaces during Pn deposition enabled us to control the crystal orientation of Pn domains.