The effect of the interaction of barium atoms on the surface of the rhenium field emitter on the work function

Modification of the emission surface on a nanometer scale during adsorption of barium atoms on the surface of a rhenium field emitter was investigated using field electron and desorption microscopy. Field electronic images of the emitter surface reflecting the localization of barium atoms on the emitter surface, representing the quasi-spherical surface of a rhenium single crystal, were obtained. The influence of the temperature of the emitter with adsorbed barium on the change in the emitter work function is shown. Deposition at room temperature leads to the appearance of a dependence of the work function on the concentration of adsorbate with a minimum in the area of optimal coating. Annealing of the emitter at T = 600 K after deposition of each portion of barium causes the minimum to disappear. After reaching the minimum value (optimal coverage with adsorbed atoms), the work function remains constant with an increase in the number of adsorbed barium atoms on the surface of the emitter. A sharp change in the localization of barium atoms due to a phase transition with the formation of islands in the region of the rhenium face was detected on the field electronic image. The change in the nature of the dependence of the work function is associated with a phase transition in the barium film with the formation of barium islands. The concentration of barium in the islet is constant and corresponds to the optimal coating