Dual ion plasma-beam sources used to maximise sp3 C-C bonds in carbon nitride
Por:
Rodil S.E., Milne W.I., Robertson J., Brown L.M.
Publicada:
1 ene 2001
Resumen:
Amorphous carbon nitride films grown by plasma or ion sources never achieve the limit of ?-C3N4, because the nitrogen fraction saturates below 57% and the carbon tends to become sp2-bonded at high N content. When a-CNx is grown from a single ion or plasma beam, high nitrogen pressures are needed to promote higher N contents, but this leads to a loss of ionisation. We use a dual ion beam method to grow a-CNx with a filtered cathodic arc (FCVA) to supply carbon and a low pressure, high plasma density electron cyclotron wave resonance (ECWR) source to supply atomic nitrogen ions. The film composition and fraction of unsaturated ?* bonding at C and N sites was measured by electron energy loss spectroscopy. We find that the C sp3 fraction decreases linearly with nitrogen content, rather than showing the sharp fall at N/C = 0.08-0.1 found by others. Thus, we achieve the highest C-C sp3 content for a-CNx films with N/C > 0.1. We find a rather sharp increase in the fraction of empty N ?* states, from 10 to 30% at N/C = 0.2. Whereas previous work suggests that N contents above the critical value of 0.1 induce a transition for all C sites to sp2, in our results only those C sites bonded to N revert to sp2. The film density was observed to change in a similar way to the density of ta-C films with respect to the C sp2 fraction. However, strong differences in the optical gap are observed. © 2001 Elsevier Science B.V. All rights reserved.
Filiaciones:
Rodil S.E.:
Engineering Department, Cambridge Univ., Trumpington St., C., Cambridge, United Kingdom
Milne W.I.:
Engineering Department, Cambridge Univ., Trumpington St., C., Cambridge, United Kingdom
Robertson J.:
Engineering Department, Cambridge Univ., Trumpington St., C., Cambridge, United Kingdom
Brown L.M.:
Cavendish Laboratory, Cambridge University, CB3 0HE, Cambridge, United Kingdom
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