Ag:TiNx thin films for dry biopotential electrodes: the effect of composition and structural changes on the electrical and mechanical behaviour

International audience; In the present work, Agy:TiNx thin films,obtained by reactive DC magnetron sputtering, withdecreasing [N]/[Ti] atomic ratios (from 1 to 0.1) and afixed amount of Ag pellets placed in the erosion zone of apure Ti target, were studied envisaging their application asbiopotential electrodes. The strongly under-stoichiometricsamples, [N]/[Ti] = 0.1 and 10 at.% Ag; [N]/[Ti] = 0.2and 8 at.% Ag, were found to be composed of a N-dopedhcp-Ti structure, with possible formation of TiAg or Ti2Agintermetallics. These samples exhibit high electrical resistivityvalues and low hardness and reduced modulus. In theset of samples indexed to a transition zone, [N]/[Ti] = 0.3and 15 at.% Ag; [N]/[Ti] = 0.7 and 32 at.% Ag, a hcp-Tito fcc-TiN phase transformation took place, giving rise to adisaggregated N-deficient TiN matrix. It correlates with thehigh resistivity values as well as the higher hardness andreduced modulus values that were obtained. The lastidentified zone comprised the stoichiometric Ag:TiNxsample—[N]/[Ti] = 1 and 20 at.% Ag. Extensive metallicAg segregation was detected, contributing to a significantdecrease of the resistivity and hardness values.