Process characteristics and film properties upon growth of TiOx films by high power pulsed magnetron sputtering

In this work TiOx (x > 1.8) films are grown reactively from a ceramic TiO1.8 target employing high power pulsed magnetron sputtering (HPPMS) at a constant average target current. The effect of the pulse on/off time configuration on the target and the discharge characteristics as well as on the film properties is investigated. The target voltage (V-T) increases from 480 to 650V and the peak target current (I-Tp) increases from 2 to 40A when the pulse off-time is increased from 200 to 2450 mu s, while the on-time is kept constant at 50 mu s. This is accompanied by an increase in the number of Ti atoms sputtered from the target, as manifested by time-resolved optical emission spectroscopy (OES) measurements. OES also manifests an increase in the ionization of the sputtered Ti atoms with increasing I-Tp. The above changes in the target and discharge characteristics affect the deposition rate so that the latter increases with increasing I-Tp up to a value of 14 A, above which the deposition rate drops. In all the cases the deposition rates are up to similar to 40% higher compared to the rates achieved for films grown by dc magnetron sputtering (dcMS) which are also studied for reference. The increase in I-Tp from 2 to 40A also affects the films' properties. It is shown that a drop in the surface roughness from 1.1 to 0.5 nm takes place. These values are lower than the surface roughness of films grown by dcMS (1.35 nm). Moreover, films grown by HPPMS are found to have higher densities (up to 3.83 g cm(-3)) and higher refractive indices (up to 2.48) in comparison to the films grown by dcMS (3.71 g cm(-3) and 2.38, respectively).