Features of the 1640 cm⁻¹ band in the Raman spectra of radiation-damaged and nano-sized diamonds

Abstract

Raman spectra of irradiated with fast neutrons or MeV ion-implanted radiation-damaged natural and CVD diamonds and chemically purified detonation nanodiamonds are investigated. The influence of radiation damage level and effects of high-temperature annealing on the intensity and spectral shape of the 1640 cm−1 band is studied. It is shown that in radiation-damaged diamonds this band consists of at least six Gaussian peaks, the intensity of which varies one to one both with the level of radiation disordering and the temperature of the subsequent annealing. The “1640” band in radiation-damaged diamonds is completely annealed at temperatures above 1000 °C, while in detonation nanodiamonds annealing up to 1200 °C does not significantly affect its shape and intensity.

Probing the Nanostructure of Neutron-Irradiated Diamond Using Raman Spectroscopy

“…The irradiation of two plates, cut out of the same CVD wafer, by fast neutrons with F = 1 × 10 18 and 3 × 10 18 cm −2 leads to a decrease in the intensity, an increase in FWHM by 4.6 and 6.3 cm −1 , and a shift in the diamond line by 1331.2 and 1328.8 cm −1 , respectively. In these two samples, the maximum of the band near 1630 cm −1 , which is characteristic of the Raman spectra of radiation damaged diamonds [ 21 , 22 ], was at 1637 and 1634 cm −1 , respectively. The spectra also contain a band at 1420 cm –1 , which is attributed to intrinsic defect containing interstitial atoms [ 23 ].…”

Magnetic and Optical Properties of Natural Diamonds with Subcritical Radiation Damage Induced by Fast Neutrons

“…The transformations of the "1640" band are of particular interest. This band has an asymmetric shape; after annealing at temperatures above 800 • C, several separate bands are spectrally resolved in it (as was observed in [55] in the Raman spectra of diamonds with a lower level of radiation damage), decreasing to the background level after annealing at temperatures above 1000 • C (Figure 3).…”

“…The irradiation with fast neutrons with fluence F = 3 × 10 18 cm −2 leads to a decrease in the intensity of diamond Raman peak, an increase in FWHM up to ≈ 6 cm −1 , and a shift of the diamond line to 1328.8 cm −1 . The maximum of the band near 1630 cm −1 , which is characteristic of the Raman spectra of radiation damaged diamonds [54,55], was at 1634 cm −1 . The spectra also contain a rather sharp defect-induced band at 1420 cm −1 , which is attributed to intrinsic defect containing interstitial atoms [56].…”

“…The nature of the "1640" band in diamonds with a damage level below the critical level is complex. The measurements were performed on ion-implanted and fast neutron-irradiated diamonds [55], and the "1640" band consists of several peaks, which shift to higher frequencies and become narrower with decreasing in the radiation damage level. The decomposition of the "1640" band showed that it consists of at least six Gaussian peaks (FWHM of 6-10 cm −1 ), which shift to lower fre- The position of the "1640" band is higher than the graphitic mode at 1580 cm −1 (G peak) [70], which is doubly degenerate (TO and LO) phonon mode (E 2g symmetry) at the center of the Brillouin zone.…”

“…Decomposition of the "1640" band into Lorentz contours (Figure 4) showed that it consists of at least three components with maxima near 1465, 1530, and 1620 cm −1 , and the four main components of the second-order band are presumably overtones of the "1640" band components with frequencies approximately equal to twice the firstorder frequencies (2925, 3050 and 3230 cm −1 , respectively) and a combination of the 1530 + 1620 cm −1 (≈ 3135 cm −1 ) components. In this case, it should be kept in mind that the lattice parameter of neutron-irradiated crystals is increased compared to unirradiated diamond [48,74], which causes a shift of the bands in the Raman spectra to the low-frequency region [49,54,55,67].…”