“…[118] Currently, the most utilised method for nitrogen doping of anodic oxides is annealing in a suitable atmosphere (nitrogen, urea or ammonia). [44,118,119] 3.3.4. Memristive behaviour of non-stoichiometric oxides TiO 2 films generally present an insulating behaviour, but the presence of oxygen vacancies at the metalÀoxide interface introduces a peculiar electrical response as circuital elements known as memristance [120]: in some anodic oxides with nanoscale thickness resistivity is a function of current previously travelled through the oxide in the past (from where the memristor term arises), thus showing a bias-dependent bipolar switching response to current.…”