Temperature dependent optical properties of pentacene films on zinc oxide
Temperature dependent optical properties of pentacene films on zinc oxide
复制标题
DOI：
10.1063/1.3663863
复制
发表时间：
2011-11-21
影响因子：
4
通讯作者：
Heimbrodt, W.
中科院分区：
文献类型：
--
作者：
Helzel, J.;Jankowski, S.;Heimbrodt, W.
用吸收光谱法研究了ZnO衬底上并五苯薄膜在室温至10 K温度范围内的光学跃迁。采用分子束沉积法在ZnO-O（000-1）表面制备了厚度分别为10 nm、20 nm和100 nm的并五苯薄膜。已观察到一个独特的温度依赖性的两个Davydov组件的激子不同的膜厚度。在室温下，各个吸收带的能量位置是相同的所有的膜，而位置不同超过20毫电子伏，在10 K所造成的非常不同的膨胀系数的并五苯和ZnO。虽然并五苯只是通过货车德瓦尔斯相互作用键合到ZnO衬底上，但第一个并五苯单层（吸附层）被迫保持在ZnO表面上的初始位置，并因此遭受显著的拉伸应变。对于所有随后的并五苯单层，应变逐步减少，导致电子在界面处的强电位梯度。(C)2011年美国物理学会。[doi：10.1063/1.3663863]
The optical transitions of pentacene films deposited on ZnO have been studied by absorption spectroscopy as a function of temperature in the range of room temperature down to 10 K. The pentacene films were prepared with thicknesses of 10 nm, 20 nm, and 100 nm on the ZnO-O(000-1) surface by molecular beam deposition. A unique temperature dependence has been observed for the two Davydov components of the excitons for different film thicknesses. At room temperature, the energetic positions of the respective absorption bands are the same for all films, whereas the positions differ more than 20 meV at 10K caused by the very different expansion coefficients of pentacene and ZnO. Although the pentacene is just bonded via van der Waals interaction to the ZnO substrate, the very first pentacene monolayer (adlayer) is forced to keep the initial position on the ZnO surface and suffering, therefore, a substantial tensile strain. For all the subsequent pentacene monolayers, the strain is reduced step by step resulting electronically in a strong potential gradient at the interface. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3663863]