Optical properties of amorphous diamond films evaluated by non-destructive spectroscopic ellipsometry

In order to investigate the regularities between the optical properties and the deposition conditions, the optical constants of amorphous diamond films deposited at the different substrate bias with the filtered cathodic vacuum arc technology have been measured by spectroscopic ellipsometry. It has been found that the refractive index and the optical gap of the films firstly increase and then decrease with the enhancing bias and there are respectively the maximal values when the negative bias is 80 V. However, the extinction coefficient of the films firstly minishes and then rises with the adding bias and there is the minimal value when the negative bias is also 80 V. The extinction coefficient gradually drops down with the increasing wavelength of incident light and nearly approaches to zero in the infrared band. Moreover, the adjustable scopes of refractive index and extinction coefficient changed by the substrate bias deflate little by little with the adding wavelength of incident light.