On the possibility of synthesizing multilayered coatings in the (Ti,Al)N system by RGPP: A microstructural study

Radiofrequency magnetron sputtering combined with reactive gas pulsing process was used to synthesize two titanium aluminum nitride multilayer films using a periodically controlled nitrogen flow rate changing from 0.4 to 1 sccm (sample SO4-1) and from 0 to 1 sccm (sample SO-1). A metallic TiAl buffer layer was deposited on the etched substrates before the deposition to enhance their adhesion. The films were characterized using mainly transmission electron microscopy and electron diffraction. The role of the crystallinity of the buffer TiAl metallic layer deposited before gas introduction on the growth orientations is emphasized. It is shown that the formation of a multilayer structure is conditioned by stopping periodically and completely the nitrogen flow rate. Particular attention is paid to the role that residual oxygen can play on the microstructure and to transient regime that occurs when the flow rate drops from 1 sccm to 0 sccm.