Low temperature synthesis of dense MoAlB thin films
Simon Evertz, P. Pöllmann, Damian M. Holzapfel, Eva Mayer, Jochen M. Schneider
Abstract
While bulk synthesis of MoAlB requires temperatures larger than 1000 °C with up to 40 % of excess Al in the feedstock, here we report the temperature range for the formation of single phase, orthorhombic MoAlB synthesized by magnetron sputtering from a stoichiometric target is 450–650 °C. Lower synthesis temperatures yield the formation of amorphous films, while at 700 °C, impurity phases form in addition to orthorhombic MoAlB. Amorphous MoAlB films were observed by in-situ X-ray diffraction to crystallize between 545 and 575 °C. Hence, we infer that the formation of orthorhombic MoAlB thin films is surface diffusion mediated below 545 °C. As bulk diffusion is activated between 545 and 575 °C the synthesis of fully dense MoAlB films with a maximum hardness of 15 ± 2 GPa and a Young’s modulus of 379 ± 30 GPa at 600 °C is surface and bulk diffusion mediated.