Film coating equipment concepts

The drawback of this concept is the severe contamination of the coating equipment because of desorption of surplus Zn that condenses on all low-temperature interior surfaces of the coater. Furthermore, the Al doping level increases when the substrate temperature is raised since the highly reactive Al does not desorb. This is shown in Fig. 5.11 where the dependence of the elemental composition on substrate temperature is shown. The Al doping level corresponding to the Al alloy of the targets is 2.1 at.%. However, the observed Al concentration is more than 5 at.% for films deposited at Ts = 300°C. Even at 100°C, the Al concentration is 3.5 at.%. This effect allows transparent ZnO Al films to be deposited at a low substrate temperature. A resistivity of 480 pQ cm has been achieved at Ts = 100° C. 

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