Indentation Topometry in Glasses by Atomic Force Microscopy

Abstract

The ratio (γ) between the total penetration displacement and the contact depth is a key parameter for the determination of Young's modulus by means of indentation methods. Although γ is usually taken as constant, it was found to range between 0.8 and 1.3, depending both on the indentation load and on the glass composition. A good correlation was found between γ and Poisson's ratio. For silica-rich silicate glasses, which show a limited elastic recovery and exhibita large contact surface area with the indenter, γ is close to 0.9. On the contrary, γ approache sπ/2, the theoretical value in the case of pure elasticity, for a ZrCuAINi bulkmetallic glass and for covalent glasses from the Ge-Se system, which show a remarkable elastic recovery and a small contact area. In addition, in this latter glass forming system, the indentation size was found time-dependent.