Influence of Surface Roughness on Surface Energy and Work Function of Tungsten Based on First-Principles Study

The formation of surface morphology under ion irradiation has been widely studied in various metals and metal surfaces. Nanoscale roughening or smoothing of the surface leads to changes in the thermal, electronic, and even antibacterial properties of metallic materials. In this study, first-principles calculations were used to gain insight into the modification of surface dipole moment due to changes in surface roughness for the case of tungsten (W). The physical nature of the change in work function (WF) due to surface roughness was found. For the W(100) surface, it was shown that the negative dipole layer formed on the surface prevents the outflow of electrons from the base metal, which leads to an increase in the WF from 3.92 eV to 4.17 eV with increasing surface roughness. The opposite was observed on the W(110) surface, where the decrease in the WF from 4.76 eV to 4.58 eV is due to a small dipole layer blocking electrons on the surface due to charge redistribution within the base metal. This study evaluates the changes in the electronic properties of W due to its surface modification under the ion beam irradiation, which can be applied in future experiments.