Effects of surface roughness and oxide layer on the thermal boundary conductance at aluminum/silicon interfaces

Abstract

In nanosystems, the primary scattering mechanisms occur at the interfaces between the material layers. As such, the structure and composition around these interfaces can affect scattering rates and, therefore, thermal resistances. In this work, we measure the room-temperature thermal boundary conductance of aluminum films grown on silicon substrates subjected to various pre-Al-deposition surface treatments with a pump-probe thermoreflectance technique. The Si surfaces are characterized with atomic force microscopy to determine mean surface roughness. The measured thermal boundary conductances decrease as Si surface roughness increases. In addition, stripping of the native oxide layer from the surface of the Si substrate immediately prior to Al film deposition causes the thermal boundary conductance to increase. The measured data are compared to an extension of the diffuse mismatch model that accounts for interfacial mixing and structure around the interface in order to better elucidate the thermal scattering processes affecting thermal boundary conductance at rough interfaces.

Influence of diamond surface termination on thermal boundary conductance between Al and diamond

“…Treatment with a hydrogen plasma cleans the substrate but induces only a moderate increase in TBC as compared to the other three treatments. The fact that our value for H plasma treated diamond is higher than that of Collins et al may be due to traces of Al and Si coming from the machine used, or to the lower roughness of our substrates 44,45 . The roughness would also explain why the sample treated at 900 • C has a higher TBC than the one at 700 • C since hydrogen treatment has been shown to smoothen < 100 > faces of diamond 46,47 .…”

“…This might be owed to the use of different ways of oxidizing the surface since acid and plasma treatment was used, not heating in an oxygen-rich atmosphere 48 . It could also be due to a difference in substrate roughness: Collins reports a roughness of 20 nm and such a roughness was shown to reduce the TBC in an Al/Si system by a factor of 2 as compared to a roughness of 0.6 nm and less 44,45 . Direct comparison of XPS spectra would be necessary to know if the first hypothesis has a significant impact or if the difference is only related to roughness.…”

A review on the role of interface in mechanical, thermal, and electrical properties of polymer composites

“…Therefore, the interfacial zones predominantly affect the thermal conductivity of the composite [245,246]. As a result, anything that can affect the interfacial regions (e.g., geometry of particles [247][248][249][250][251][252][253], aggregation [254][255][256], interfacial pressure [257], roughness [258][259][260], and the strength of interactions at the interfaces [261][262][263][264][265]) in the composites would influence their thermal conductivity. In this section, we will review the parameters affecting the interfacial interactions and their subsequent impact on the thermal conductivity of the composites.…”

Relationship of thermal boundary conductance to structure from an analytical model plus molecular dynamics simulations

“…These structural details become more important on a nanoscale because when the characteristic dimensions are comparable to or less than the phonon mean-free-paths, the interfacial scattering increases 6 . Unfortunately, interfacial thermal transport experiments are extremely challenging, and only recently have experimental studies begun to address some relationships between Kapitza conductance and microstructural features of interfaces 5,10,11,[13][14][15] . Due to the lack of understanding of dependence of Kapitza conductance on structural details, the design of devices has typically relied on a trial-and-error approach rather than a science-based optimization.…”

“…Atomic-scale engineering of interfaces for specific thermal applications has been an elusive goal because Kapitza conductance is extremely sensitive to many structural details at the interface, including crystallinity, crystallographic orientation, roughness, interdiffusion, and chemical reaction 5,[5][6][7][8][9][10][11][12] . These structural details become more important on a nanoscale because when the characteristic dimensions are comparable to or less than the phonon mean-free-paths, the interfacial scattering increases 6 .…”