  In the modern electronics overheating is one of the major reasons for device
failure. Overheating causes irreversible damage to circuit components and can
also lead to fire, explosions, and injuries. Accordingly, in the advent of 2D
material-based electronics, an understanding of their thermal properties in
addition to their electric ones is crucial to enable efficient transfer of
excess heat away from the electronic components. In this work we propose
structures based on free-standing, few-layer, nanopatterned MoS2 that insulate
and guide heat in the in-plane direction. We arrive at these designs via a
thorough study of the in-plane thermal conductivity as a function of thickness,
porosity, and temperature in both pristine and nanopatterned MoS2 membranes.
Two-laser Raman thermometry was employed to measure the thermal conductivities
of a set of free-standing MoS2 flakes with diameters greater than 20 um and
thicknesses from 5 to 40 nm, resulting in values from 30 to 85 W/mK,
respectively. After nanopatterning a square lattice of 100-nm diameter holes
with a focused ion beam we have obtained a greater than 10-fold reduction of
the thermal conductivities for the period of 500 nm and values below 1 W/mK for
the period of 300 nm. The results were supported by equilibrium molecular
dynamic simulations for both pristine and nanopatterned MoS2. The selective
patterning of certain areas results in extremely large difference in thermal
conductivities within the same material. Exploitation of this effect enabled
for the first time thermal insulation and heat guiding in the few-layer MoS2.
The patterned regions act as high thermal resistors: we obtained a thermal
resistance of 4x10-6 m2K/W with only four patterned lattice periods of 300 nm,
highlighting the significant potential of MoS2 for thermal management
applications.
