Thermal Conductivity Reduction at Inorganic-Organic Interfaces: From Regular Superlattices to Irregular Gradient Layer Sequences

Nanoscale superlattice structures are known to significantly suppress the thermal conductivity in thin films due to phonon scattering at the interfaces of the mutually different layers. Here it is demonstrated that in addition to the number of interfaces, their spacing within the film can lead to a reduction in thermal conductivity. The proof-of-concept data are for ZnO/benzene thin films fabricated through sequential gas-surface reactions in atomic/molecular layer precision using the atomic/molecular layer deposition technique. In comparison to similarly constructed regular superlattice thin films, thermal conductivity values that are of the same magnitude, or even lower, are achieved for hybrid ZnO/benzene thin films in which the inorganic and organic layers are arranged in a more irregular manner to form various gradient patterns.