Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 22904, USA.
J Chem Phys. 2011 Mar 7;134(9):094704. doi: 10.1063/1.3557823.
Self-assembled monolayers (SAMs) have recently garnered much interest due to their unique electrical, chemical, and thermal properties. Several studies have focused on thermal transport across solid-SAM junctions, demonstrating that interface conductance is largely insensitive to changes in SAM length. In the present study, we have investigated the vibrational spectra of alkanedithiol-based SAMs as a function of the number of methylene groups forming the molecular backbone via Hartree-Fock methods. In the case of Au-alkanedithiol junctions, it is found that despite the addition of nine new vibrational modes per added methylene group, only one of these modes falls below the maximum phonon frequency of Au. In addition, the alkanedithiol one-dimensional density of normal modes (modes per unit energy per unit length) is nearly constant regardless of chain length, explaining the observed insensitivity. Furthermore, we developed a diffusive transport model intended to predict interface conductance at solid-SAM junctions. It is shown that this predictive model is in an excellent agreement with prior experimental data available in the literature.
自组装单分子层 (SAMs) 由于其独特的电学、化学和热学性质，最近引起了广泛关注。许多研究都集中在固体-SAM 结处的热传输上，表明界面电导率对 SAM 长度的变化基本不敏感。在本研究中，我们通过 Hartree-Fock 方法研究了基于烷二硫醇的 SAM 的振动光谱，作为形成分子主链的亚甲基数量的函数。对于 Au-烷二硫醇结，尽管每个添加的亚甲基基团增加了九个新的振动模式，但只有一个模式低于 Au 的最大声子频率。此外，烷二硫醇的一维正则模式密度（单位能量每单位长度的模式数）几乎保持不变，与链长无关，解释了观察到的不敏感性。此外，我们开发了一种扩散输运模型，旨在预测固体-SAM 结的界面电导率。结果表明，该预测模型与文献中可用的先前实验数据非常吻合。
