Variations of acoustic and diffuse mismatch models in predicting thermal-boundary resistance

Solid solid thermal-boundary resistance plays an important role in determin ing heat flow, in both cryogenic and room-temperature applications. The aco ustic mismatch model (AMM) and the diffuse mismatch model (DMM) have tradit ionally been used to predict the thermal boundary resistance R-b across the interface of two adjoining materials at temperatures well below the Debye temperatures of the materials in question. Both the AMM and DMM use the Deb ye density of states (DOS) in bath contacting solids. Here, the use of a me asured DOS is made in conjunction with the DMM. This shows an improvement i n the prediction of R-b relative to that based on the Debye DOS. Another ap proach considered is to predict R-b from measured specific heat per unit vo lume C data. The measured C automatically includes the effect of temperatur e an the DOS. This leads to a marginal improvement in R-b above that predic ted when using the measured DOS. The AMM describes the thermal transport at a solid-solid interface below a few Kelvin quite accurately. The DMM, theo retically more suitable for interfacial transport above a few Kelvin, is no better than AMM for predicting the thermal-boundary resistance at a solid- solid interface. This raises the possibility that both diffuse and specular reflections are taking place at the interface. This kind of mired reflecti on is very common in radiative transport. Offing to the similarity in phono n transport and radiative transport a mixed model, considering bath specula r and diffuse reflection, is developed, which is able to predict R-b values between those of the AMM and DMM. Further, a regime map is developed which delineates three predominant regimes describing the dominance of the R-b p redictions made by the AMM, DMM, and mixed models.