  Individual highly pure single crystalline silver nanowires (Ag NWs) were
investigated with regard to the electrical conductivity $\sigma$, the thermal
conductivity $\lambda$ and the Seebeck coefficient $S$ as function of the
temperature $T$ between $1.4\,\mathrm{K}$ and room temperature (RT).
Transmission electron microscopy was performed subsequently to the
thermoelectric characterization of the Ag NWs, so that their transport
properties can be correlated with the structural data. The crystal structure,
surface morphology and the rare occurrence of kinks and twinning were
identified. The thermoelectric properties of the Ag NWs are discussed in
comparison to the bulk: $S_{\mathrm{Ag,Pt}}(T)$ was measured with respect to
platinum and is in agreement with the bulk, $\sigma(T)$ and $\lambda(T)$ showed
reduced values with respect to the bulk. The latter are both notably dominated
by surface scattering caused by an increased surface-to-volume ratio. By
lowering $T$ the electron mean free path strongly exceeds the NW's diameter of
$150\,\mathrm{nm}$ so that the transition from diffusive transport to quasi
ballistic one dimensional transport is observed. An important result of this
work is that the Lorenz number $L(T)$ turns out to be independent of surface
scattering. Instead the characteristic of $L(T)$ is determined by the
material's purity. Moreover, $\sigma(T)$ and $L(T)$ can be described by the
bulk Debye temperature of silver.
