Chemical Stabilization and Improved Thermal Resilience of Molecular Arrangements: Possible Formation of a Surface Network of Bonds by Multiple Pulse Atomic Layer Deposition
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- 作者：Muriel de Pauli ; Matheus J. S. Matos ; Pablo F. Siles ; Mariana C. Prado ; Bernardo R. A. Neves ; Sukarno O. Ferreira ; M谩rio S. C. Mazzoni ; Angelo Malachias
- 刊名：Journal of Physical Chemistry B
- 出版年：2014
- 出版时间：August 14, 2014
- 年：2014
- 卷：118
- 期：32
- 页码：9792-9799
- 全文大小：440K
- ISSN：1520-5207
文摘
In this work, we make use of an atomic layer deposition (ALD) surface reaction based on trimethyl-aluminum (TMA) and water to modify O鈥揌 terminated self-assembled layers of octadecylphosphonic acid (OPA). The structural modifications were investigated by X-ray reflectivity, X-ray diffraction, and atomic force microscopy. We observed a significant improvement in the thermal stability of ALD-modified molecules, with the existence of a supramolecular packing structure up to 500 掳C. Following the experimental observations, density functional theory (DFT) calculations indicate the possibility of formation of a covalent network with aluminum atoms connecting OPA molecules at terrace surfaces. Chemical stability is also achieved on top of such a composite surface, inhibiting further ALD oxide deposition. On the other hand, in the terrace edges, where the covalent array is discontinued, the chemical conditions allow for oxide growth. Analysis of the DFT results on band structure and density of states of modified OPA molecules suggests that besides the observed thermal resilience, the dielectric character of OPA layers is preserved. This new ALD-modified OPA composite is potentially suitable for applications such as dielectric layers in organic devices, where better thermal performance is required.