  The role of interfacial nonidealities and disorder on thermal transport
across interfaces is traditionally assumed to add resistance to heat transfer,
decreasing the thermal boundary conductance (TBC).$^1$ However, recent
computational works have suggested that interfacial defects can enhance this
thermal boundary conductance through emergence of unique vibrations that are
intrinsic to the material interface and defect atoms,$^{2-6}$ a finding that
contradicts traditional theory and conventional understanding. By manipulating
the local heat flux of atomic vibrations that comprise these interfacial modes,
in principle, the TBC can be increased. In this work, we provide evidence that
interfacial defects can enhance the TBC across interfaces through the emergence
of unique high frequency vibrational modes that arise from atomic mass defects
at the interface with relatively small masses. We demonstrate ultrahigh TBC at
amorphous SiOC:H/SiC:H interfaces, approaching 1 GW m$^{-2}$ K$^{-1}$, that is
further increased through the introduction of nitrogen defects. The fact that
disordered interfaces can exhibit such high conductances, which can be further
increased with additional defects offers a unique direction in controlling
interfacial thermal transport that becomes important in manipulating heat
transfer across materials with high densities of interfaces.
