De-wetting of barium on W(100) and (110) surfaces observed using thermionic emission microscopy

Adsorption of barium metal on tungsten (100) and (110) surfaces at 300 K results in a condensed uniform film. Heating the barium metal layer to temperatures of 800-900 K causes the film to convert into spherical metal droplets. The droplets do not wet the W(100) or W(110) surfaces. The measured contact angle between the Ba droplets and the surface is greater than 150 degrees.