From hill-and-valley faceting to global faceting of a crystal: oxygen-covered tungsten, A. Szczepkowicz, R. Bryl, Surf. Sci. Lett. 559 (2004) L169.

A tungsten crystal with a curved surface (radius of curvature = 0.2 micrometers),
exposed to 1.3+-0.2 Langmuir of oxygen, undergoes massive atomic rearrangement upon
annealing. Hill-and-valley faceting in the form of  {211} steps is observed
between (211)-(121), (121)-(112), (112)-(211) crystal facets.
As the annealing temperature is increased, the number of steps decreases.
Finally only one step remains and the crystal assumes a globally faceted shape
for temperatures between 1400 K and 1600 K. For higher temperatures
the number of steps increases with temperature.

68.35.Bs (Surface structure and topography)
68.60.Dv (Thermal stability; thermal effects)
61.16.Fk (Field emission and field-ion microscopy)

Faceting, Surface topography, Tungsten, Oxygen, Chemisorption, Single crystal surfaces, Curved surfaces, Field ion microscopy.