  We present a complete characterisation at the nanoscale of the growth and
structure of single-layer tungsten disulfide (WS$_2$) epitaxially grown on
Au(111). Following the growth process in real time with fast x-ray
photoelectron spectroscopy, we obtain a singly-oriented layer by choosing the
proper W evaporation rate and substrate temperature during the growth.
Information about the morphology, size and layer stacking of the WS$_2$ layer
were achieved by employing x-ray photoelectron diffraction and low-energy
electron microscopy. The strong spin splitting in the valence band of WS$_2$
coupled with the single-orientation character of the layer make this material
the ideal candidate for the exploitation of the spin and valley degrees of
freedom.
