Defects density and carrier lifetime in nitrogen-doped ultrananocrystalline and polycrystalline diamond films

M. C. Rossi; S. Salvatori; A. Minutello; G. Conte; V. Ralchenko

doi:10.1117/12.722083

22 May 2007 Defects density and carrier lifetime in nitrogen-doped ultrananocrystalline and polycrystalline diamond films

M. C. Rossi, S. Salvatori, A. Minutello, G. Conte, V. Ralchenko

Author Affiliations +

Proceedings Volume 6591, Nanotechnology III; 65910B (2007) https://doi.org/10.1117/12.722083
Event: Microtechnologies for the New Millennium, 2007, Maspalomas, Gran Canaria, Spain

Abstract

The electrical activity of nitrogen related defects are investigated in ultra-nanocrystalline diamond (UNCD) films achieved using different N₂% in the gas phase by transient photocurrent technique at λ = 193 nm, and by steady state photocurrent measurements in the photon energy range 1-6 eV. In undoped UNCD films, spectrally resolved photocurrent measurements reveal a threshold at about 1 eV, related to the absorption of non diamond carbon phases, followed by a monotonic increase by more than one order of magnitude up to about the diamond energy gap, where a steep rise occurs due to band to band transitions. In nitrogen doped UNCD films a clear onset of the spectral photocurrent signal is hardly detectable, although an apparent shift towards higher energies is evidenced, in agreement with a possible nitrogen induced Fermi level shift upward in the band gap. The main N-related feature of the spectra is however a sharp peak at about 4 eV, which is also observed in polycrystalline diamond films grown in a nitrogen rich gas mixture, particularly close to the boundary of the deposition area. On the other hand, photocurrent pulse shape analysis gives carrier lifetime values in the 6-10 ns range, almost independent of nitrogen content. Instead, N-related defects appear mainly responsible for trapping processes, which slow down carrier transport and give rise to long transit times. Such results are discussed in terms of photoionization of N-related defects formed in the non diamond carbon phase.

Citation Download Citation

M. C. Rossi, S. Salvatori, A. Minutello, G. Conte, and V. Ralchenko "Defects density and carrier lifetime in nitrogen-doped ultrananocrystalline and polycrystalline diamond films", Proc. SPIE 6591, Nanotechnology III, 65910B (22 May 2007); https://doi.org/10.1117/12.722083

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