Heat conduction across thin films calculated with AlmaBTE

AlmaBTE has been used to predict the cross plane thermal conductivity of technologically relevant crystalline and solid solution thin films, including SiGe, InGaAs, AlGaN, and the highly anisotropic SnSe. The calculation unveils the existence of a clearly distinct regime of sub-ballistic thermal conduction with a fractional exponent in the film’s thickness dependence, occurring only on alloys but not on ordered materials. Such regime manifests itself already at alloy concentrations as small as 1%, and it persists for a very large range of thicknesses, from tens of nm to micrometers. Furthermore, the associated fractional exponent is material dependent, and it bears a deeper relationship with the fractal dimension of superdiffusive heat conduction recently demonstrated in transient heat dynamics. (Preprint available at arXiv.)