Abstract

The kinetics of adsorption, surface diffusion and thermal desorption of sulfur on Ni surfaces have been studied using field electron emission microscopy methods. The sticking probability for elemental sulfur sublimed onto a Ni specimen is approximately unity for Ni substrate temperatures from 77 to 530 K. The maximum average work function for ~ monolayer coverage of S ranged from 4.7 to 5.05 eV in different experiments; for fractional monolayer doses of S, surface diffusion was rapid at T 400 K, with activation energies ranging from 15 to 28 kcal mol . For multilayer adsorption of sulfur, diffusion occurs without motion of a sharp boundary, and there is evidence of extensive surface reaction between S and Ni (emission from small “crystallites” is evident in the field emission patterns). Sulfur desorbs from Ni at temperatures above 1500 K.

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