Work Function for Applications -How Work Function is Determined, Modified and Applied for Band Alignment-

Abstract

From the electronic potential point of view, the origin of the work function is divided into two terms: the ‘bulk term’ and the ‘surface term’. The former is determined by the electronic states of the bulk materials, while the latter is derived from the distribution of electrons at the surface diffusing toward a vacuum. A methodology based on these two origins is provided to modify the work function. The methodology is composed of two strategies, mixing of two metals and surface modification. The first one uses their compositions to vary the work function, and can be classified according to the phase diagram of the two metals. The second one includes the variation of surface termination, and adsorption, accumulation or segregation of the second metal. Using an analogy of surface term in a solid-vacuum interface, the relationship between work function and band alignment is considered. Then, a methodology to alter the band alignment is described as an analogous way to modify the work function. In addition, examples of the Schottky barrier height modification using such methods are discussed.