Synthesis mechanism and applications of edge-controlled diamond films

Microwave plasma is an effective source for synthesizing diamond films, but the geometry of the deposition is severely affected by the plasma distribution. In this context, advanced microwave plasma jet chemical vapor deposition (MPJ-CVD) offers a more efficient, energy-saving, and uniform method for diamond deposition leading to more stable films across various substrate geometries. Previous work shows that diamonds synthesized by microwave plasma tend to have larger grain sizes and surface roughness which limit device applications. In this study, we achieve a breakthrough in diamond synthesis by adjusting the dilute methane/hydrogen ratio from 0.25 % to 4 % which can significantly reduce diamond grains, increasing edge density and enhance field emission performance. This enhancement is attributed to the primary source of electron field emission being the diamond edges allowing us to assume a mechanism called "edge related emission density (ERED)" where increasing the edge density of diamonds enhances the field emission current density. The turn-on electric field decreases from 6.56 V/mu m to 5.44 V/mu m while the current density increases from 47 to similar to 585 mu A/cm(2) (at E = 8 V/mu m). This ensures sufficient current density to drive optoelectronic devices within the range of low turn-on and control voltages, thereby improving device reliability and control precision.