Effect of rearranging sp2/sp3 hybridized-bonding on the field emission characteristics of nano-crystalline diamond films

The electron field emission properties of nano-crystalline diamond (ND) thin-film can be enhanced through nitrogen incorporation, resulting in increased sp2 carbon concentration leading to low binding energy beneficial for electron field emission. Three distinct ND films exhibiting differentiable grain structures and carbon chemical bonding were grown by microwave plasma chemical vapor deposition (MPCVD) using different growth conditions. The ND films were grown on highly conductive silicon substrates using MPCVD-facilitated reaction of CH4/H2/N2 precursor gases. The nitrogenated ND film deposited under relatively low-pressure low-power growth condition yielded a turn-on field of 3.5 V/µm, which is the lowest value of the three films. XPS results reveal that the lowest turn-on field corresponded with the highest sp2 intensity. The same film also exhibited the shallowest Fowler–Nordheim slope, indicating a stronger field enhancement factor and lower effective work function.