3.3 Results

The most important process parameters of the nine coating experiments are summarized in Table 3, whereby the oxygen control range presents the limits of regulation to maintain the specified magnetron voltage. During the coating process, over the duration of five hours, the real magnetron voltage was controlled to the specified magnetron voltage with the oxygen control loop, which was able to maintain the operating points very closely, and thus the absolute process pressure remained constant over the entire coating period. The maximum substrate temperature was measured with a drag indicator thermometer, whereby the lowest substrate temperature measured is 110 °C and the highest substrate temperature is 220 °C. Furthermore, the lowest settled oxygen ratio is 13 % and the highest is 33 %. The scanning electron microscopy images of the fracture surfaces of coating experiments No. 1 to No. 9 were captured using a Zeiss DSM 982 scanning electron microscope. The coated slides were broken in such a way as to crack the coating under tensile load so that the layer structure of the coating thus becomes visible.