A DFT Study of the Components of a Hf/HfO2/TiN three-layer stack

In the present study, the unit cells of metallic Hafnium (Hf), Hafnium Oxide (HfO2), and Titanium Nitride (TiN), which are the components of a novel Hf/HfO2/TiN three-layer stack with great potential for applications in nanoelectronics, are theoretically described by employing the plane wave pseudopotential approach as implemented in the Vienna Ab Initio Simulation Package (VASP). All the calculations are performed within the Generalized Gradient Approximation (GGA) by adopting the Perdew-Burke-Ernzerhof (PBE) functional. As a result of the present study, a systematic procedure for the quantummechanical simulation of each system is proposed as follows: (i) construction of the model from experimental data, (ii) determination of the optimal value of the plane wave energy cutoff, (iii) optimization of the parameter that defines the number of k-points in the reciprocal space, and (iv) geometry optimization of the cell parameters and atomic positions. In the specific case of the HfO2 system, on-site Coulomb corrections (GGA+U method) are applied to calculate an accurate energy band gap value.