Modification of the Work Function

Abstract

This chapter explains how to modify the work function based on the discussion in Sect. 2.3. Because the work function is primarily an atomic quantity, the first strategy is to mix an element with the mother element, which is $\mathrm{often}$ carried out by material scientists. The aim of mixing elements is to modify the bulk term of the work function, but the surface term is inevitably modified at the same time. Upon mixing elements, the relationship between the composition and the work function is categorized based on phase diagram; substitutional alloy, interstitial alloy, intermetallic compound (ordered alloy) and two elements with miscibility gap. For each category, the relationship is discussed from scientific principles and some examples are demonstrated. When the work function should be modified without changing bulk composition, methods to modify only surface term of the work function are required. Modifying surface termination is one of methods to modify only surface term in multi-component materials such as intermetallic compounds and compound semiconductors and insulators. Other methods are adsorbing the second element or utilizing surface segregation phenomenon in dilute alloys or layered films. Experimental examples of surface term modification are demonstrated.