Highly twinned, oriented polycrystalline diamond film and method of manufacture thereof

A method of chemical vapor deposition (CVD) growth of a free standing polycrystalline diamond film in a CVD reactor, the free standing polycrystalline diamond film having a thickness ≥100 micron and a percentage of orientation along a [110] diamond lattice direction ≥70% of the total number of diamond crystallites forming the polycrystalline diamond film, the method comprising:

• (a) igniting and maintaining a plasma above a surface of a conductive substrate disposed in the CVD reactor in the presence of flow of a gas mixture of gaseous hydrogen (H) and a gaseous hydrocarbon (GH) into the CVD reactor, wherein the CVD reactor is maintained at a pressure (P) 100 torr<P≤350 torr during growth of the polycrystalline diamond film, whereupon the maintained plasma forms the polycrystalline diamond film on the surface of the conductive substrate;
• and
• (b) concurrent with step (a), controlling a temperature T at the center of the diamond film such that 1000° C.≤T≤1300° C.