Two-phase single layer Al-O-N nanocomposite films with enhanced resistance to cracking

The article reports on dc pulsed reactive sputtering of two-phase single layer Al-O-N nanocomposite films using dual magnetron in a mixture of N2 + O2 with pulsed inlet of oxygen. Two kinds of nanocomposite films were sputtered: (1) nc-AlN/a-(Al-O-N) film and (2) nc-(γ-Al2O3)/a-(Al-O-N) nanocomposite film; here nc- and a- denotes the nanocrystalline and amorphous phase, respectively. The transition from the nc-AlN/a-(Al-O-N) nanocomposite to the nc-(γ-Al2O3)/a-(Al-O-N) nanocomposite was controlled by the length of the period of oxygen pulses TO2. It was found that both nanocomposites are highly elastic films with relatively high hardness H = 15 to 20 GPa, low effective Young's modulus E⁎ satisfying the condition that the ratio H/E⁎ > 0.1, high elastic recovery We > 60% and high resistance to cracking in bending. Correlations between the film structure and its mechanical properties are discussed in detail.

► Nanocomposite films composed of nitride and oxide phase. ► Formation of nanocomposite films by reactive sputtering with pulse injection of oxygen. ► Hard films composed of nanograins embedded in amorphous matrix. ► Hard films with enhanced toughness and enhanced resistance to cracking.