Effect of a Nitrogen Impurity on the Fundamental Raman Band of Diamond Single Crystals

Abstract

The effect of nitrogen defects in natural and synthetic diamond single crystals on the position and half-width of the fundamental Raman band was investigated. Samples containing the main types of nitrogen lattice defects at impurity contents of 1-1500 ppm were studied. The parameters of the Stokes and anti-Stokes components in Raman spectra of crystals situated in a cell with distilled water to minimize the infl uence of heating by the exciting laser radiation were analyzed to determine the effect of a nitrogen impurity in the diamond crystal lattice. It was shown that an increase of impurity atoms in the crystals in the studied concentration range resulted in broadening of the Raman band from 1.61 to 2.85 cm -1 and shifting of the maximum to lower frequency from 1332.65 to 1332.3 cm -1 . The observed effect was directly proportional to the impurity concentration and depended on the form of the impurity incorporated into the diamond lattice. It was found that the changes in the position and half-width of the fundamental Raman band for diamond were consistent with the magnitude of crystal lattice distortions due to the presence of impurity defects and obeyed the Gruneisen law.

Structural, Raman and photoluminescence studies on nanocrystalline diamond films: Effects of ammonia in feedstock

“…Such a linear increase in line width with N concentration has been well documented for the N doped single crystal Table 2. UV micro-Raman fit parameters for the diamond films grown under different N/C in feedstock diamonds but a similar study on polycrystalline diamonds is scarce and also the analysis becomes complex due to other structural defects [37,38]. The present study also confirms a similar trend in broadening of Raman line width for N doped NCD films.…”

“…The present study also confirms a similar trend in broadening of Raman line width for N doped NCD films. However, Raman peak position of these diamond films exhibit a blue shift and it is in contrast to existing literature on single crystal diamonds which shows either no change in peak position for relatively low N concentration [20,37] Sampl e 1 band (cm -1 ) D* (cm -1 ) D band (cm -1 ) 3 (cm -1 ) or a red shift of ~ 0.4 cm -1 for higher N concentration [38]. The observed blue shift in Raman peak position indicates that the diamond lattice undergoes a compressive strain with N doping in diamond.…”

“…However, the analysis of peak shift and broadening of diamond Raman band in NCD films is complex. In the present study, the laser induced temperature effect can be ignored since it always redshifts the Raman peak position which is about 0.5 cm -1 for an increase in temperature upto 500 K [38]. The compressive stress can be attributed to the nature of chemical bonding in the grains and GBs that consist of highly cross-linked sp 2 phase network surrounding the nanodiamond particles [35].…”

“…K [38]. The compressive stress can be attributed to the nature of chemical bonding in the grains and GBs that consist of highly cross-linked sp 2 phase network surrounding the nanodiamond particles [35].…”

“…The Raman line broadening and position shift in NCD films can be associated with several factors such as surface and bulk structural defects, GBs, internal strain caused by impurities, growth temperature induced thermal stress that arises due to the difference in thermal expansion coefficients (TECs) of substrate and diamond and also laser induced heating on the surface [38,39].…”