Investigation On The Deposition Of Large Area Ultra-nanocrystalline Diamond Film By MPCVD

Ultrananocrystalline diamond, an extremely important branch of nanocrystalline diamond, possess more significant properties such as higher hardness and surface smoothness, lower friction coefficient, stronger fracture toughness, better electrical properties, which can play a very important role in various applications, especially in the mechanical coating, field emission and electrochemical, micro-electro-mechanical systems（MEMS）, biomedical, acoustics, optical applications. In foreign countries, the researchers have made a progress and development in the preparation of ultrananocrystalline diamond films after more than 10 years of research and hard work. In contrast, domestic related research is just started, extremely lack of systematic research on the preparation of ultrananocrystalline diamond film. In this paper, ultrananocrystalline diamond films were prepared by home-made 10 kW MPCVD device using variable H2 levels in an Ar/CH₄ resource gas mixture. And nitrogen-doped ultrananocrystalline diamond films were deposited by Woosinent-R2.0-type MPCVD device using CH₄/N₂ and CH₄/N₂/H2 as gas resources. The effect of deposition parameters on the growth of ultrananocrystalline diamond films were systematic investigated. Besides that nitrogen-doped ultrananocrystalline diamond films with large area（?=50mm） were obtained. The results show that:1. In order to improve the stability of plasma and active groups of energy and density, a small amount of hydrogen addition and the use of lower power and higher pressure（>10 kPa） conditions are necessary when using CH₄/Ar as a gas sources grow ultrananocrystalline diamond films.2. When ultrananocrystalline diamond films are grown at various H2 concentrations（from 10% to 4%） in Ar/CH₄ plasmas, with the decrease of H2 concentrations, the crystallize size and the content of diamond phase decrease, but the amorphous carbon and graphite content increase, and the films tend to（111） preferential growth.3. While ultrananocrystalline diamond films are deposited in CH₄/N₂ gas system, with the decrease of the concentration ratio of CH₄ to N₂, the shape of aggregates on the films, surface gradually transform from “needle-like” to “granular”, the grain sizes of the films increase, the densities of diamond films and the qualities improve, and the conductivities of the films decrease.4. When a small amount of hydrogen are introduced into the CH₄/N₂ system, the increasing of hydrogen concentration leads to the increasing of the grain sizes, and the declining of the defects and growth rates. The compressive stress resulted from the shift of G peak decrease. At the same time, the film qualities improve but the conductivities decrease.