The diffusion behavior of carbon in sputtered tungsten film and sintered tungsten block and its effect on diamond nucleation and growth

• Diamond films are deposited on tungsten substrates with different surface reactivity.
• The influences of six parameters on diamond growth and phase transition are studied.
• The diffusion behavior of carbon in PVD tungsten film is investigated.
• Diamond nucleation surface and its potential applications are discussed.

Diamond was done on sintered tungsten block with or without sputtered tungsten films. The effects of various depositing conditions, including methane concentration, temperature, pressure, the diamond seeding step and reaction time, on diamond growth were investigated in detail. The results show that the sputtered tungsten film has a dual effect on diamond growth. Firstly, after ultrasonication with diamond slurry, the tungsten film will adsorb a large number of diamond nanoparticles. Therefore, the nucleation density of diamond will be substantially improved. Secondly, the film will be carbonized during the deposition process and the carbon on the surface of the film will decrease. Methane concentration generally does not affect the carbonization level of the tungsten film but higher temperature will lead to a higher level of carbonization. The carbonization process of sputtered tungsten films during deposition is made up of two steps. Also, the nucleation surface of diamond was revealed. The nucleation surface was a layer of ultrasmooth and seamless nanocrystalline diamond film with high-quality and special surface architecture (tiny peaks arrays), which is potential to be applied in MEMS and field-emission devices. A potential method to prepare ultrasmooth nanocrystalline diamond films is proposed.