Diamond luminescence spectra

Fig. 2. Temperature dependence of the homogeneous width (a) and the peak shift (b) of the 637 nm zero-phonon line in luminescence spectrum of N-V centers in diamond films points experiment the line theoretical approximations according to the laws y — y0 + aT3 + bT1 and 8 = fiT2 - vT4.

Figure 5.23 Luminescence spectrum of an N-V-defect in the diamond iattice at room temperature ( F. Jeiezko).

I440/I415 is substantially different. Another parameter is decay time of diamonds fast blue luminescence, which is different in different samples and may be used for identification purpose. The main reason is that several luminescence centers exist with emission spectrum very similar to those of N3, but with longer decay time of 500-700 ns. Under steady-state conditions there is some superposition of luminescence and excitation spectra of N3 and this center and they cannot be spectroscopically separated. By time-resolved spectroscopy the centers were separated and the second one, named 2.96 eV was connected with A1 impurity. Figure 6.34b, c demonstrate that the ratio between the second and the third components in kinetic series with delay difference between them of 10 ns is different, which evidently connected with the presence of N3 and 2.96 eV centers together, but in different ratios. 

Here, UV Raman spectroscopy is chosen in order to give a better Raman signal of diamond and to confirm its presence in the centre of the nanoparticles. As first shown by Sun et ai, the spectrum of nanodiamond excited by a visible radiation contains a luminescent background which should be removed [53]. Mykhaylyk et al. recently compared spectra obtained at 633, 488 and 244 nm (Figure 3.14) [16]. This comparison clearly demonstrated the advantage of using UV excitation, which also allows the intense diamond optic mode to generate in the spectrum. 

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