Interaction of Hydrogen with Vanadium Layers Preadsorbed on Tungsten Field Emitter Tip

Interaction of hydrogen with vanadium layers preadsorbed on a thermally cleaned tungsten field emitter was studied at room temperature and 78 K through measurements of the total work function changes. An increase in the work function followed by its slight decrease at higher exposure can be understood taking into account the possibility of negatively (β$\text{}^{-}$) and positively (β$\text{}^{+}$) polarized adspecies formation on thin vanadium layer. This process leads to vanadium hydride formation. The work function results suggest that hydrogen diffusion into the vanadium layer is meaningful at room temperature. Thermal desorption of hydrogen adsorbate carried out within the temperature range 409-461 K from thin vanadium layer (Θ$\text{}_{V}$ = 40) provided a value of 127 ± 6 kJ/mol for the activation energy for desorption.