Diamond attracts the interest of researchers from different fields due to its extraordinary properties. However, many applications demand diamond films over large areas hence limiting usage of natural diamonds. Here we compare two microwave (2.45 GHz) plasma systems with ellipsoidal and multimode clamshell cavity for diamond synthesis by chemical vapor deposition. We use H2/CH4/CO2 gas mixture for diamond film deposition on Si <100> wafers. Both systems are capable of high pressure (up to 20 kPa) operation and high growth rates (several µm/h). We compare the cavity systems from the point of diamond quality (Raman shift measurement), substrate size (2” versus 4”) and grown film homogeneity together with surface morphology (SEM), deposition rate and parasitic doping levels (photoluminescence). For instance, we show that by using the multimode operation of the clamshell cavity system and specially design sample holder, it is possible to sustain a plasma in a cavity and reach good enough process reproducibility and diamond film quality over 4-inch substrates. We discuss effects of the cavity design on deposited layers for large area applications of diamond such as thermal management, electrodes and sensor arrays fabrication, photoluminescence, photonics and light sources.Keywords: Large area diamond, microwave cavity plasma, high-power density plasma
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