  The thermal conductivity of suspended single-layer graphene was measured as a
function of temperature using Raman scattering spectroscopy on clean samples
prepared directly on a prepatterned substrate by mechanical exfoliation without
chemical treatments. The temperature at the laser spot was monitored by the
frequency of the Raman 2$D$ band of the Raman scattering spectrum, and the
thermal conductivity was deduced by analyzing heat diffusion equations assuming
that the substrate is a heat sink at ambient temperature. The obtained thermal
conductivity values range from $\sim$1800 Wm$^{-1}$K$^{-1}$ near 325 K to
$\sim$710 Wm$^{-1}$K$^{-1}$ at 500 K.
