Enhancement of Interfacial Thermal Transport between Metal and Organic Semiconductor Using Self-Assembled Monolayers with Different Terminal Groups

Abstract

Inferior heat transfer between metal and organic semiconductor is a challenge for the performance improvement of organic semiconductor devices. In this paper, we use nonequilibrium molecular dynamics to study the thermal energy transport between functionalized gold (Au) and pentacene interfaces. The functionalized modifications of the Au surface are implemented by inserting four different self-assembled monolayers (SAMs) at the interface of Au and pentacene. The four different SAMs includeand 6-mercaptohexanoic acid [HS(CH 2 ) 5 COOH]. The interfacial thermal conductance of the bare Au interface is 8.91 ± 2.45 MW m −2 K −1 . It is found that the interfacial thermal conductance can be enhanced by all four SAMs. The SAMs [HS(CH 2 ) 5 CH 3 and HS(CH 2 ) 6 NH 2 ] with a similar enhancement ability can improve the interfacial thermal conductance about six to seven times. Moreover, the SAMs with stronger polarization groups [HS(CH 2 ) 6 OH and HS(CH 2 ) 5 COOH] display larger enhancement ability. Especially, the interfacial thermal conductance of the SAM [HS(CH 2 ) 5 COOH]-functionalized Au interface is increased about 11 times. The enhancement of interfacial thermal transport is attributed to the better phonon vibrational coupling and the stronger interfacial interactions. SAMs can play the role of a "phonon bridge" to connect the phonon density of states of Au and pentacene, which leads to the increase in interfacial thermal conductance at the interface. The stronger polarization groups of SAMs bring about the higher adhesion energy and pull interfacial atoms closer to the interface, which leads to smaller temperature drops and higher interfacial thermal conductance. The existences of hydrogen bonds are also observed for SAMs [HS(CH 2 ) 6 OH and HS(CH 2 ) 5 COOH]-functionalized interfaces, which are beneficial to the energy transfer at the interface. This work can provide a significant insight into tuning thermal transport properties of organic electronic devices.

Molecular Structure Effect of a Self-Assembled Monolayer on Thermal Resistance across an Interface

“…These studies have investigated the effects of various characteristics of SAMs on the interfacial thermal conductance from two different points of view: (1) considering accurate information about SAM, including SAM coverage [4,9,10], length of SAMs [4,[11][12][13], distinct functional group [9,[13][14][15][16][17], heterogeneous fin structure [18], vibrational spectral overlapping [9], nanoscale roughness [19][20][21], and so on. Huang et al [16] investigated interfacial thermal conductance (ITC) across the interface of water and gold tailored with -CH 3 SAM, -OHSAM, and -COOHSAM.…”

Interfacial thermal transport of graphene/β-Ga2O3 heterojunctions: a molecular dynamics study with a self-consistent interatomic potential

“…The phonon density of states (PDOS) is an important indicator to reveal the phonon transport mechanism, 58,60 which can be calculated by taking a Fourier transform of the velocity autocorrelation function (VACF): 63–65 where v is the atomic velocity, ω represents the angular frequency, and the angle brackets denote the ensemble average. We calculate the PDOS of the three interfaces of the graphene/β-Ga 2 O 3 heterojunction (Fig.…”

A brief review of thermal transport in mesoscopic systems from nonequilibrium Green's function approach

“…Recently, interfacial phonon transports have been extensively studied across the interfaces based on various nanostructures such as single-molecule junctions [57][58][59] , self-assembled monolayer interfaces [60][61][62] , one-dimensional nanotube junctions 63,64 , and twodimensional heterojunctions [65][66][67][68][69] .…”