Criteria for Cross-Plane Dominated Thermal Transport in Multilayer Thin Film Systems During Modulated Laser Heating

Abstract

Pump-probe transient thermoreflectance (TTR) techniques are powerful tools for measuring the thermophysical properties of thin films, such as thermal conductivity, Λ, or thermal boundary conductance, G. This paper examines the assumption of one-dimensional heating on, Λ and G, determination in nanostructures using a pump-probe transient thermoreflectance technique. The traditionally used one-dimensional and axially symmetric cylindrical conduction models for thermal transport are reviewed. To test the assumptions of the thermal models, experimental data from Al films on bulk substrates (Si and glass) are taken with the TTR technique. This analysis is extended to thin film multilayer structures. The results show that at 11 MHz modulation frequency, thermal transport is indeed one dimensional. Error among the various models arises due to pulse accumulation and not accounting for residual heating.

Thermal boundary conductance of transition metals on diamond

“…The sensitivity parameter is the same as described in (Costescu et al, 2003;Hopkins et al, 2010b), namely: with i the parameter to be investigated. A value close to zero means that a parameter has a low in uence and conversely, a value far from zero, no matter its sign, means that the parameter has a high in uence.…”

Experimental estimates of in-plane thermal conductivity in FePt-C granular thin film heat assisted magnetic recording media using a model layered system

“…Likewise, the k th values of Au were calculated from the Au sheet resistance as measured by 4-point probe measurements for separate Au films deposited on 1 lm-thick thermally grown SiO 2 films on Si substrates following the Weidemann Franz Law. The k th value of n-type Si substrates were found to be 95 6 10 W/m-K, which appears low relative to the bulk value (143 W/m-K) for Si, but is reasonably attributed to the known suppression in k th observed by high frequency FDTR measurements 17,18 paired with effects of added phonon scattering due to phosphorous dopant concentration of about 10 15 Table I. These values were averaged over 3 measurements at 3 locations on the samples.…”

“…Measurement of in-plane thermal conductivity, on the other hand, is extremely challenging, when it is low, as it is in these films, because cross-plane thermal conduction paths into the underlayers or substrate dominate the measurement. 14,15 In this paper, we present an experimental approach that allows us to estimate the in-plane thermal conductivity in FePt granular thin films, by making a measurement on an experimental model system that avoids parallel thermal conduction pathways.…”

Interfacial electron and phonon scattering processes in high-powered nanoscale applications.

“…We measure the thermal boundary conductance with timedomain thermoreflectance (TDTR). 36,48 The trends in thermal boundary conductance show that the effect of the QDs on h K are more apparent at elevated temperatures, where at low temperatures, the QD patterning does not drastically affect h K . The functional dependence of h K with RMS surface roughness reveals a trend that suggests that both vibrational mismatch and phonon attenuation near the interface contribute to the reduction in h K .…”

“…Specifically, we metalize plasma functionalized graphene and then measure h K at Al/SLG/SiO 2 contacts with time domain thermoreflectance (TDTR) techniques. 36,48 Through these measurements, adsorbates on the SLG surfaces are shown to influence the cross plane thermal conductance. These influences are attributed to changes in the bonding between the metal and the SLG that itself is affected by increased disorder within the SLG.…”