Interfacial thermal conductance of ZnO/hBN vdW heterostructures

As electronic devices miniaturize yet with more functions, internal heat accumulation becomes a critical issue, adversely affecting the lifespan and efficiency of the devices. Owing to its high thermal conductivity (TC), mechanical strength and electrical insulation properties, the two-dimensional hexagonal boron nitride (hBN) can be used in electronic devices for efficient thermal management and most importantly provide short-circuit protection. The heat dissipation efficiency of hBN is largely hindered by interfacial thermal resistance (ITR) between hBN layers. Till now, the available strategies reduce ITR and correspondingly enhance interfacial thermal conductance (ITC) of hBN at the expense of mechanical strength. Motivated by reports that zinc oxide (ZnO) interlayers can reduce the ITR in multilayer hBN sheets, this work investigates the ZnO/hBN interface at the atomic scale and elucidates the underlying mechanisms behind the ITC of ZnO/hBN heterostructures. The variation of ITC under high temperatures, size effect and lattice mismatch are systematically investigated via nonequilibrium molecular dynamics (NEMD) simulation. NEMD simulations reveal that the ITC increases by up to 50 % and 87.6 % with increasing temperature and hBN layer number, respectively, but it decreases with increasing lattice mismatch at the interface induced by rotation of the hBN layer. The mechanisms behind the ITC variation are closely examined using phonon-based analyses, including phonon density of states (PDOS) and spectral transmission function (STF). This heterostructure is also insensitive to heat flow direction, enabling predictable bidirectional heat dissipation under various operating conditions. Our work confirms that this ZnO/hBN heterostructures are promising thermal interface materials with excellent, controllable heat dissipation performance and high strength.