  The paper reports on a theoretical description of work function of TiN, which
is one of the most used materials for the realization of electrodes and gates
in CMOS devices. Indeed, although the work function is a fundamental quantity
in quantum mechanics and also in device physics, as it allows the understanding
of band alignment at heterostructures and gap states formation at the
metal/semiconductor interface, the role of defects and contaminants is rarely
taken into account. Here, by using first principles simulations, we present an
extensive study of the work function dependence on nitrogen vacancies and
surface oxidation for different TiN surface orientations. The results
complement and explain a number of existent experimental data, and provide a
useful tool to tailoring transport properties of TiN electrodes in device
simulations.
