Molekulare Festkörperphysik, Philipps-Universität Marburg, D-35032 Marburg, Germany.
J Chem Phys. 2013 Mar 21;138(11):114901. doi: 10.1063/1.4795004.
Using thermal desorption spectroscopy (TDS) the thermal stability of binary pentacene/perfluoropentacene (PEN/PFP) thin films has been investigated for various preparation protocols. Variation of stoichiometry ratio reveals a significantly enhanced thermal stability in comparison to the single compounds only for films with equimolar stoichiometry. The stabilization also depends on the preparation method and was found for co-deposition as well as for multi-stacks and subsequently grown PEN/PFP-stacks but not for stacks grown in the reversed order. By systemically varying the substrate temperature during deposition, we prove that the resulting intermixture is caused by a thermally activated diffusion during film growth and not due to post-deposition diffusion induced upon heating during TDS measurements. The different extents of thermal stabilization are discussed in the context of the film morphology studied by means of atomic force microscopy (AFM). For complementary information, optical absorption spectra of the heterostructures are analyzed, where the arisal of new absorption bands and the extinction of excitonic bands existing in the pure compounds are identified as decisive criteria to judge the efficiency of intermixture.
使用热解吸光谱（TDS），我们研究了不同制备方案下二元并五苯/全氟并五苯（PEN/PFP）薄膜的热稳定性。化学计量比的变化表明，与仅由单一化合物组成的薄膜相比，具有等摩尔化学计量比的薄膜具有显著增强的热稳定性。这种稳定化还取决于制备方法，我们发现对于共沉积以及多堆叠和随后生长的 PEN/PFP 堆叠都是如此，但对于相反顺序生长的堆叠则不是。通过在沉积过程中系统地改变衬底温度，我们证明所得混合物是由于薄膜生长过程中热激活扩散引起的，而不是由于 TDS 测量过程中加热引起的沉积后扩散所致。在原子力显微镜（AFM）研究的薄膜形貌的背景下，讨论了不同程度的热稳定化。为了获得补充信息，还分析了异质结构的光吸收光谱，其中新吸收带的出现和纯化合物中存在的激子带的消光被确定为判断混合物效率的决定性标准。
