Low temperature growth of ultrananocrystalline diamond film and its field emission properties

Ultrananocrystalline diamond (UNCD) film is deposited at a substrate temperature lower than 500 °C. This film possesses diamond crystal of nanometer size embedded in a graphitic (or non-diamond carbon) phase. The presence of non-diamond carbon in the grain boundaries of diamond crystal plays a crucial role to the film properties and its corresponding application such as electron field emission. The present work reports the growth of UNCD films at different methane concentrations to alter the film properties that could make it suitable for higher electron field emission. The surface morphology of an as-grown film was examined with a field emission scanning electron microscope. Nucleation density in the range of 10 11–10 12/cm 2 is obtained in the as-grown films. The grain size of diamond increases from 5 nm to 25 nm with an increase in CH 4 concentration from 1% to 7.5% in the argon plasma. The presence of different carbon phases in the diamond films was investigated qualitatively by Raman studies. Near edge X-ray fine structure study ascertains that the as-grown films mainly possess diamond phase. A direct correlation of field emission properties with the CH 4 concentration during UNCD growth is obtained.