Diamond has great potential for electronic, optical, mechanical, chemical, and nuclear applications due to its superior properties. However, natural diamond is rare and expensive, being a metastable phase at normal pressure and temperature. The diamond synthesis at high temperatures and high pressures (HTHP), where diamond is a stable phase [l], was a breakthrough for large scale industrial applications. However, synthetic diamond is used mainly in abrasive and cutting tools industries [2], the crystals obtained by the HTHP method being too small and expensive for many applications in optics, electronics, or other industries [3].Polycrystalline as well as single-crystal films of diamond on single-crystal diamond substrates were first obtained in the seventies by the Russian team of Spitsyn, Bouilov, Derjaguin, and coworkers [4 to 101 by the gas chemical transport reaction (CTR) method. Crystals of several micrometers in size and polycrystalline films, grown on various foreign substrates (Cu, Au, Si, W, Mo), were reported by the same team [8].