TiB1.8 single layers and epitaxial TiB2-based superlattices by magnetron sputtering using a TiB (Ti:B = 1:1) target

Sputter-deposited titanium diborides are promising candidates for protective coatings in harsh and extreme conditions. However, growing these layers from TiB 2 diboride targets by DC magnetron sputtering usually leads to over-stoichiometric layers with low crystal qualities. Moreover, superlattices with TiB 2 as one of the constituents have been becoming popular, owing to their superior mechanical properties compared to single layer constituents in addition to their use in other applications such as neutron optics. Here, we propose the use of a TiB (Ti:B = 1:1) sputtering target in an on-axis deposition geometry and demonstrate the growth of epitaxial sub-stoichiometric TiB 1.8 thin films. Furthermore, we present the growth of CrB 1.7 /TiB 1.8 superlattices, from TiB (Ti:B = 1:1) and stoichiometric CrB 2 targets, with abrupt interfaces as promising materials system for neutron interference mirrors. The high crystal quality structure with well-defined interfaces is the common feature of superlattices which, regardless of application, should be addressed during the growth process. Utilizing TiB target, all films crystallize in the hexagonal AlB 2 structure. The sub-stoichiometry of the TiB 1.8 films was accompanied by the presence of planar defects embedded in the films. CrB 1.7 /TiB 1.8 superlattices exhibited a homogeneous boron distribution within the layers with no sign of B-rich tissue phases through the layers. This study demonstrates the feasibility for TiB as sputter target material, that offers a solution for deposition of TiB 2 -based superlattices without the need to adjust the deposition parameters. Such adjustments would otherwise be unavoidable for tuning the TiB 2 composition and could affect the growth of the other constituent materials. • Magnetron sputter epitaxy of TiB 2 single layers from TiB (Ti:B = 1:1) target • Epitaxial TiB 2 -based superlattices with homogenous distribution of boron • Elimination of boron-rich tissue phases in the structure