The effect of thickness and loading force on wear behavior of HfO₂

The effect of annealing treatment on hafnium oxide (HfO₂) thin films with two thicknesses (20 and 50 nm) has been observed. The surface morphology and tribological properties of HfO₂ thin films were measured through atomic force microscopy (AFM). It is found that annealing treatment and increasing thickness of thin film would promote the formation and growth of island-like grains, which contributes a raise in surface roughness. During scratch test, plowing behavior dominated the deformation mechanism in the form of lumps along the edge of grooves by AFM-3D images. Besides, slower scratch speed led to larger deformation energy and caused a serious fracture. The annealing-induced crystallization resulted in reduced penetration depth and coefficient of friction (COF). The varied COF with respect to different normal forces reflected substrate effect. The thicker HfO₂ films exhibited better wear resistance regardless of annealing conditions. It is because that increase in film thickness accompanied growth of polycrystalline structure