Adhesion of two-dimensional titanium carbides (MXenes) and graphene to silicon

Two-dimensional transition metal carbides (MXenes) have attracted a great interest of the research community as a relatively recently discovered large class of materials with unique electronic and optical properties. Understanding of adhesion between MXenes and various substrates is critically important for MXene device fabrication and performance. We report results of direct atomic force microscopy (AFM) measurements of adhesion of two MXenes (Ti₃C₂T_x and Ti₂CT_x) with a SiO₂ coated Si spherical tip. The Maugis-Dugdale theory was applied to convert the AFM measured adhesion force to adhesion energy, while taking into account surface roughness. The obtained adhesion energies were compared with those for mono-, bi-, and tri-layer graphene, as well as SiO₂ substrates. The average adhesion energies for the MXenes are 0.90 ± 0.03 J m^-2 and 0.40 ± 0.02 J m^-2 for thicker Ti₃C₂T_x and thinner Ti₂CT_x, respectively, which is of the same order of magnitude as that between graphene and silica tip.