Tuning Interfacial Thermal Conductance Across Metal–Organic Semiconductor Interfaces by Mixing Self-Assembled Monolayers

Interface engineering not only plays an important role in improving interfacial electronic properties but also is of great importance for interfacial thermal transport inside organic electronics. In this study, nonequilibrium molecular dynamics simulations are conducted to investigate the effect of mixing self-assembled monolayers (SAMs) on the interfacial thermal conductance between the SAM-modified gold (Au) and an organic semiconductor, pentacene. SAM molecules with terminal groups of carboxyl (−COOH) and methyl (−CH3) and with different molecular chain lengths are exploited to modify the Au surface. The dependent relationship between the interfacial thermal conductance value and the chain length of the SAM molecule is investigated first, and two different variation trends are observed at interfaces modified by SAMs with −COOH and −CH3 groups. SAMs with different chain lengths and different terminal groups are randomly mixed to study the influence of binary mixing modulation of SAMs on interfacial thermal transport. A nonmonotonic trend that interfacial thermal conductance is first decreased and then increased is observed at binary SAM-modified (with long and short molecular lengths) interfaces. Spectral analysis on interfacial thermal conductance indicates that mixing long and short SAMs would mainly suppress interfacial thermal transport through low-frequency and intermediate-frequency vibrational modes. Mixing SAMs with different terminal groups of −COOH and −CH3 can induce a linear variation trend because of the linear modulation of interfacial adhesion energy.