Study of Work Function Changes of La/W(110) using Electron Beam Retarding Potential Technique

摘要

The change in the work function (WFC or #DELTA##PHI#) of W(110) substrate on adsorption of La at various coverages (#theta#) has been determined using low-energy electron diffraction (LEED) optics and retarding potential technique. The data was collected using static and dynamic methods. The plot of #DELTA##PHI# versus #theta# from both the methods shows that the work function of W(110) decreases rapidly with increasing coverage of La, touches minima and then increases slightly. Thereafter further increase in coverage does not affect the work function and it remains constant. These observations are explained on the basis of difference in the electronegativity of the substrate and the adsorbate. It is found that the WFC curve of W(110) different coverages of La is quite similar to adsorption of alkali and alkaline earth metals on tungsten. The reduction in WF of W(110) on adsorption of La at a certain coverage can be used to advantage in the making of emitters.