In situ studies of morphology, strain, and growth modes of a molecular organic thin film
In situ studies of morphology, strain, and growth modes of a molecular organic thin film
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DOI：
10.1103/physrevb.56.3046
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发表时间：
1997-08
影响因子：
3.7
通讯作者：
P. Fenter;F. Schreiber;L. Zhou;P. Eisenberger;S. Forrest
中科院分区：
文献类型：
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作者：
P. Fenter;F. Schreiber;L. Zhou;P. Eisenberger;S. Forrest
利用掠入射X射线散射研究了3，4，9，10-二萘嵌苯四甲酸二酐（PTCDA）在Au（111）表面上的结晶薄膜（{lt}70 ML）的分子结构和形貌随薄膜厚度、衬底温度和生长速率的变化。尽管前两个PTCDA单层以逐层方式生长，但是超过第二单层的膜演变强烈地取决于导致低温[即，非平衡（NEQ）]和高温[平衡（EQ）]生长机制。在NEQ制度中，膜随着膜厚度的增加而单调地粗糙化，但保持良好限定的膜厚度。此外，我们发现这些薄膜具有晶格应变，这是独立的膜厚度。在EQ制度中，膜获得厚度为{gt}2 ML的三维形态，并且晶格应变随着厚度的增加而迅速减小。我们还表明，NEQ和EQ制度之间的过渡是尖锐的，并取决于生长速率和衬底温度之间的平衡。这些结果表明，PTCDA/Au（111）体系是由不完全润湿描述的，应变和动力学在决定分子有机膜特性方面起着重要作用。{版权} {美国物理学会}
We use grazing incidence x-ray scattering to study the molecular structure and morphology of thin ({lt}70 ML) crystalline films of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) on Au(111) surfaces as a function of film thickness, substrate temperature, and growth rate. Although the first two PTCDA monolayers grow in a layer-by-layer fashion, the film evolution beyond the second monolayer depends strongly upon the growth conditions resulting in low-temperature [i.e., nonequilibrium (NEQ)] and high-temperature [equilibrium (EQ)] growth regimes. In the NEQ regime, the films roughen monotonically with increasing film thickness, but retain a well-defined film thickness. Furthermore, we find that these films have a lattice strain which is independent of film thickness. In the EQ regime, the film acquires a three-dimensional morphology for thicknesses {gt}2 ML, and the lattice strain decreases rapidly with increasing thickness. We also show that the transition between the NEQ and EQ regimes is sharp and depends upon the balance between the growth rate and substrate temperature. These results suggest that the PTCDA/Au(111) system is thermodynamically described by incomplete wetting, and that strain and kinetics play an important role in determining molecular organic film characteristics. {copyright} {ital 1997} {ital The American Physical Society}