Ultra Smooth Nanostructured Diamond Films And Methods of Production

 Inventors Valeriy V Konovalov  (Westerville, OH) , Yogesh K Vohra  (Hoover, AL)   and Shane A. Catledge  (Bessemer, AL) in U.S. Patent Application 20100209665 disclose compositions and methods for producing carbon-based films, for example, ultra smooth diamond nanostructured diamond films.

Generally, the disclosed compositions can comprise a noble gas component, hydrogen, a carbon precursor, and nitrogen. Generally, the disclosed methods comprise the steps of providing a mixture comprising a noble gas, hydrogen, a carbon precursor, and nitrogen, establishing a plasma comprising the mixture; and depositing carbon-containing species from the plasma onto the surface, thereby producing a film on the surface.

Generally, the disclosed films exhibit superior average gain size, RMS surface roughness, hardness, relative diamond crystallinity, and surface adhesion.  

Polycrystalline diamond films with a microstructure consisting generally of crystallites with sizes on the order of microns can be synthesized by a variety of chemical vapor deposition (CVD) techniques from carbon-hydrogen mixtures, typically using hydrocarbons as the carbon source. The grain size, surface morphology, and surface roughness of the polycrystalline diamond films prepared from hydrogen-rich plasmas typically depend upon the film thickness. Generally, for conventional methods of preparation, the thicker the film, the larger the grain size and the rougher the surface of the film.

Many applications of diamond films, however, demand ultra smooth surfaces, which are not prepared by conventional techniques. Consequently, such diamond films generally fail to achieve satisfactory average grain size or satisfactory surface smoothness. Additionally, the relative diamond crystallinity of such materials is generally too high, thereby resulting in brittle films that fail to achieve satisfactory surface adhesion.

Disclosed are ultra smooth diamond films having an average grain size of from about 5 nm to about 6 nm, an RMS surface roughness of from about 5 nm to about 10 nm before mechanical polishing of the film, a relative diamond crystallinity of from about 40% to about 60%, and a hardness of from about 50 GPa to about 100 GPa. Also disclosed are ultra smooth diamond films having an average grain size of from about 5 nm to about 6 nm, an RMS surface roughness of from about 5 nm to about 10 nm before mechanical polishing of the film, a relative diamond crystallinity of from about 40% to about 60%, and a hardness of from about 58 GPa to about 72 GPa. 

FIG. 1 shows 1 times 1micron AFM surface images and XRD 20-angular dependencies of two diamond films grown in He/H2/CH4/N2 plasma with (a) 0 and (b) 71 vol % He

FIG. 5 shows a schematic of Microwave Plasma Chemical Vapor Deposition (MPCVD) reactor for producing diamond films. 

FIG. 12 shows a SEM image at 300,000 times of the diamond film