Hardness, Young’s Modulus and Elastic Recovery in Magnetron Sputtered Amorphous AlMgB₁₄ Films

• Main Author: Alexander M. Grishin
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Crystals
• Subjects: optical refractive index and extinction coefficient; Raman icosahedral boron–boron vibrations; elastic and plastic energies; hardness; Young’s modulus
• Online Access: https://www.mdpi.com/2073-4352/10/9/823

We report optical and mechanical properties of hard aluminum magnesium boride films magnetron sputtered from a stoichiometric AlMgB₁₄ ceramic target onto Corning^® 1737 Glass and Si (100) wafers. High target sputtering rf-power and sufficiently short target-to-substrate distance appeared to be critical processing conditions. Amorphous AlMgB₁₄ films demonstrate very strong indentation size effect (ISE): exceptionally high nanohardness <i>H </i>= 88 GPa and elastic Young’s modulus <em>E^∗</em>= 517 GPa at 26 nm of the diamond probe penetration depth and almost constant values, respectively, of about 35 GPa and 275 GPa starting at depths of about 2–3% of films’ thickness. For comparative analysis of elastic strain to failure index <em>H</em>³/<em>E^∗</em>, resistance to plastic deformation ratio <em>H</em>³/<em>E^∗2</em>and elastic recovery ratio <em>W_e</em>were obtained in nanoindentation tests performed in a wide range of loading forces from 0.5 to 40 mN. High authentic numerical values of <i>H = </i>50 GPa and <em>E^∗</em>= 340 GPa correlate with as low as only 10% of total energy dissipating through the plastic deformations.