The study of textured diamond films and improved adhesion via microwave plasma chemical vapor deposition

The textured orientation of diamond films is elaborated by microwave plasma chemical vapor deposition (MPCVD) in 1200 W, 110 torr, CH4/H2=1/20, and 0.5-4.0 h deposition time. The special morphology revealed the rectangular structure stacked regularly on diamond films after growing 2.0-4.0 h. The {111} textured orientation of diamond films grew {110} preferred orientation on the surface that measured by XRD results. The formation of the diamond film epitaxial formed the textured octahedron on the ball-shape (or cauliflower-like) diamonds in an early duration 0.5 h, then the surface of diamond films extended to pile the rectangular structure at 4.0 h. And the width of the tier was about 200 nm in the 3.0 h deposition time by TEM images. The result revealed that textured diamond films in different deposition time had two morphology properties of typical ball-shape and rectangular diamonds in the growth period. The I-V characteristics of the oriented diamond films in 4.0 h deposition time was more conform to the ohmic contact.
To increase the adhesion of diamond films and avoid the negative effects of using cobalt, previous treatments have employed tungsten particles to cover the surface of the 6 wt.% cobalt-cemented tungsten carbide (WC-Co) substrate. The surface of the tungsten particles is transformed into W2C and WC, which attracts and traps carbon. Through the process of nucleation, the carbon forms around the tungsten particles, thereby satisfying the conditions necessary for the formation of diamond film. Rockwell indentation tests indicate that addition of tungsten particles promotes the interfacial adhesion of diamond films with WC-Co substrates. We determined that using smaller tungsten particles decreased the number of gaps and cavities on the surface of the substrate, thereby enhancing the adhesion of the diamond film. Using Raman spectroscopy, we determined that diamond films of excellent quality with good adhesive properties and a hardness level as high as 27.78 GPa could be produced following pretreatment with 2.0 μm tungsten particles.