Spatial variation of the work function in nano-crystalline TiN films measured by dual-mode scanning tunneling microscopy

We explored novel approach to measure spatial variation of work function (WF) on polycrystalline 20-nm-thick TiN films by using simultaneous measurements of tunneling current and interaction force in scanning tunneling microscopy. Upon processing at 860 °C in N2 atmosphere, the mean grain size increased from 3–5 to 20–30 nm. For multi-facet grains, facet-dependent variation of the WF was observed in the maps. Three WF values were ascribed to (001) and (111) crystal planes of cubic TiN. The area fraction of high-WF facets increased from ∼55% for as-grown to 70% for processed films.