Properties of TiO2 thin films deposited by rf reactive magnetron sputtering on biased substrates

•TiO2 thin films were deposited on negatively biased substrates by rf magnetron sputtering technique.•The bias favors the formation of TiO2 crystalline phase.•The roughness of the films increases and the grain size decreases as the bias voltage is varied between (0 and −100V).•XPS reveals the presence of adsorbed humidity of the surface and Ti4+ oxidation state in the as prepared samples.