Effects of Surface Roughness and Oxide Layer on the Thermal Boundary Conductance at Aluminum/Silicon Interfaces

Abstract

Thermal boundary resistance dominates the thermal resistance in nanosystems since material length scales are comparable to material mean free paths. The primary scattering mechanism in nanosystems is interface scattering, and the structure and composition around these interfaces can affect scattering rates and, therefore, device thermal resistances. In this work, the thermal boundary conductance (the inverse of the thermal boundary resistance) is measured using a pump-probe thermoreflectance technique on aluminum films grown on silicon substrates that are subjected to various pre-Al-deposition surface treatments. The Si surfaces are characterized with Atomic Force Microscopy (AFM) to determine mean surface roughness. The measured thermal boundary conductance decreases as Si surface roughness increases. In addition, stripping the native oxide layer on the surface of the Si substrate immediately prior to Al film deposition causes the thermal boundary conductance to increase. The measured data are then compared to an extension of the diffuse mismatch model that accounts for interfacial mixing and structure around the interface.

Thermal Transport across Solid Interfaces with Nanoscale Imperfections: Effects of Roughness, Disorder, Dislocations, and Bonding on Thermal Boundary Conductance

“…However, it is apparent that the presence of this compositionally mixed interfacial region will decrease the interfacial thermal transport from one material to another. In a recent series of papers [19][20][21], we explored the extent of manipulation of phonon thermal boundary conductance through either chemical roughening of the Si [20,21] or creating roughness by synthesizing Si 1− Ge quantum dots on an Si surface. In both situations, the samples were exposed to ambient atmosphere to allow the formation of a silica or germania native oxide layer aer surface modi�cation to serve as a diffusion barrier to the Al transducer, as mentioned above; this was con�rmed with cross-sectional transmission electron microscopy [21].…”

“…As an example, consider a "perfect" interface and an atomically disordered, "imperfect" interface, depicted in Figure 1. e imperfect interface introduces roughness along with atomic imperfections that cause additional thermal scattering which can change ℎ K , as I have discussed in previous works [19][20][21][22][23][24] and will detail throughout this paper. e properties of this interface dictate the additional scattering mechanisms.…”

A Modified Theoretical Model to Accurately Account for Interfacial Roughness in Predicting the Interfacial Thermal Conductance

“…It is worth noting that in experiments, the oxidation of interface is a very common issue (Hopkins et al, 2010(Hopkins et al, , 2012Lee et al, 2016), which will affect phonon transport. Generally, the native oxides will increase the interfacial roughness and induce more scattering, thus decrease the transmission coefficient (Hopkins et al, 2010;Mu et al, 2016). While if the oxidation strengthens the chemical bond of the interface, this effect will be much stronger than the induced roughness scattering, the transmission coefficient will increase, and the ITC will increase (Hopkins et al, 2012).…”

Thermal conductivity and interface thermal conductance of thin films in Li ion batteries

“…The error in the results of analysis that arises from thickness measurements and heat capacity is estimated to be ~10%, as shown in table I.The heat capacity of LiNiMnO is determined from Neumann-Kopp approximation [25] and found to be 3.0 MWm -3 K -1 while that of LIPON is found to be 2. is a low value. The lower value could be due to several reasons but it is primarily associated with the roughness of the film surface as a result of laser generated particulates [26][27][28]. The thermal resistance at an interface is strongly dependent on the interface roughness as it reduces the thermal contact [28].In addition, thermal conductivity is electron mediated in Au while it is predominantly phonon mediated in LiNiMnO.…”