Measurement of work function change with surface segregation of substrate element on a deposited film

Surface composition saturates when metal atoms of substrate diffuse through the deposited film on the substrate and segregate on the surface of the film. The properties of surfaces with segregation are expected to be similar to that with adsorption. Therefore, it seems possible to modify work function by segregation phenomena as well as adsorption. Saturation behavior of surface composition in segregation phenomena is useful for easy fabrication of surfaces with stable work function. Work function change by the surface segregation of Cu on Ti film and of Ti on Cu film has been measured. Work function was decreased approximately 0.3 eV by surface segregation of Cu on Ti film and slightly increased by surface segregation of Ti on Cu. The work function decrease caused by Cu segregation is reproducible when the surface is removed and Cu segregates again by heating. Therefore, the original idea of getting stable work function by using features of segregation phenomenon is verified. q1999 Elsevier Science B.V. All rights reserved