To avoid unwanted precursor condensation on the QCM, 50 °C water was circulated in the cooling water system of the sensor, to heat the QCM. To maintain consistent surface conditions, the QCM crystals were replaced after each deposition experiment. A DC bias voltage ranging from -60 to +80 V was applied to the substrate holder or to the QCM sensor via an additional DC voltage supply. Two methods were employed for thin film deposition, a continuous process, where the precursor was continuously fed to the substrate while maintaining a plasma discharge, and a pulsed process, where the precursor and plasma were introduced in sequential pulses separated by argon purges. The durations of the precursor pulse, argon purge, and plasma pulse were varied to determine suitable conditions for saturation growth. It was found (as discussed in section III) that a cyclic deposition schedule of 5 s for the Cu(hfac)2 pulse, followed by 20 s for argon purge, 5 s of plasma pulse, and another 20 s of argon purge, achieved a self-limiting growth behaviour. Consequently, this set of parameters was used for subsequent depositions unless stated otherwise.