  The development of electronic devices, especially those that involve
heterogeneous integration of materials, has led to increased challenges in
addressing their thermal operational-temperature demands. The heat flow in
these systems is significantly influenced or even dominated by thermal boundary
resistance at interface between dissimilar materials. However, controlling and
tuning heat transport across an interface and in the adjacent materials has so
far drawn limited attention. In this work, we grow chemical-vapor-deposited
(CVD) diamond on silicon substrates by graphoepitaxy and experimentally
demonstrate tunable thermal transport across diamond membranes and
diamond-silicon interfaces. We observed the highest diamond-silicon thermal
boundary conductance (TBC) measured to date and increased diamond thermal
conductivity due to strong grain texturing in the diamond near the interface.
Additionally, non-equilibrium molecular-dynamics (NEMD) simulations and a
Landauer approach are used to understand the diamond-silicon TBC. These
findings pave the way for tuning or increasing thermal conductance in
heterogeneously integrated electronics that involve polycrystalline materials
and will impact applications including electronics thermal management and
diamond growth.
