Amorphous diamond films deposited by filtered cathodic vacuum arc technology as infrared protective coatings

Amorphous diamond (a-D) films deposited by filtered cathodic vacuum arc (FCVA) technology with different substrate bias were investigated. The mechanical properties were characterized with nanoindenter and the stress was calculated using Stoney equation. The optical properties were analyzed by spectroscopic ellipsometry and the microstructure was investigated by visible Raman spectroscopy and electron energy loss spectroscopy. The maximal hardness and elastic modulus consorting with the highest stress are presented as the negative substrate bias is 80V. With the bias increases or decreases, hardness, elastic modulus and stress descend gradually. However, the high impinging energy benefits the adhesion between the films and the substrate. Additionally, the optical gap and the refractive index exhibits the same changing regularities, whereas the minimal extinction coefficient is obtained at negative bias of 80 V. It is found that the negative bias of 80 V is the sp³-rich deposition condition according to the EELS measurements and the Raman slope coefficient. The changing rules of the mechanical and optical properties can be explained in light of the growth mechanism and microstructure of the films. In short, a-D films deposited by the FCVA technology are good at the infrared protective coatings because the films are transparent in the wide infrared band and the microstructure and properties can be modulated.