Field emission properties and surface structure of nickel containing amorphous carbon

Nickel containing amorphous carbon (a-C:Ni) films have been deposited by filtered cathodic vacuum arc (FCVA) technique by introducing pure nickel into the graphite target. The field electron emission property of a-C:Ni was improved when compared to that of pure tetrahedral amorphous carbon (ta-C) by FCVA. The emission threshold field of a-C:Ni film is about 5 V μm−1, whilst the threshold field of the ta-C film is about 13 V μm−1. Raman spectroscopy suggests that the sp2 clusters in the carbon film increase both in size and number when Ni is introduced. However, the emission was found to degrade to threshold fields beyond 20 V μm−1 after the a-C:Ni film was left in ambient for a week. This observation is attributed to surface absorption of oxygen on the a-C:Ni film, as determined by X-ray Photoelectron Spectroscopy.