Chemical and Electronic Structure of Buried W/Cu, W/Cr, and W/Mo Interfaces by In Situ XPS/HAXPES Auger Parameter Analysis

ABSTRACT The changes in the local chemical state of W interfacial atoms at buried W/Cu, W/Cr, and W/Mo interfaces in multilayers and cosputtered alloys have been investigated by chemical state analysis using in situ XPS/HAXPES. An Auger parameter shift of W interfacial atoms is found to depend on the degree of chemical miscibility of the atoms at the interface being maximum for the Mo/W system. This experimental trend cannot be rationalized by the electronegativity differences between W, Cu, Cr, and Mo. The nonuniformity of the electron density at the studied interfaces with W (and possible also the structural mismatch and intermixing) should be accounted for to accurately predict the measured trend of the Auger parameter for the different interfaces with W. The experimental data are supported by ab initio calculations of the charge transfer at the metal interfaces. This work demonstrates that the Auger parameter shift provides a very sensitive probe for studying the chemical and electronic structure of buried interfaces at an atomic scale.