‘Natural’ and ‘man-made’ platelets in type-Ia diamonds

Ferromagnetic Properties of Hybrid Cementite and Diamond Nanocomposite

“…These results were expected because most natural or synthetic diamonds have defects in the <100> lattice plane. These results are consistent with those reported by Kiflawi et al, who also found that defects in diamond occurred along the <100> lattice plane [22]. Fig.…”

HPHT-Treated Diamonds

“…It is a very rare event that the presence of C defects in a natural diamond could not be detected (Sobolev et al 1986;Fisher 2012). However, Platelets can be as large as tens of micrometers and then they can be observed in cathodoluminesence (Collins and Woods 1982) and electron microscope (Kiflawi et al 1998). Atomic models of C-, A-, and B defects are shown in Fig.…”

“…For instance, it is produced by HPHT treatment in cape yellow diamonds (Collins 2001). It is a very temperature stable center and it is not destroyed by annealing at a temperature as high as 2,750°C (Kiflawi et al 1998). It is a very temperature stable center and it is not destroyed by annealing at a temperature as high as 2,750°C (Kiflawi et al 1998).…”

Stacking-Fault Based Microscopic Model for Platelets in Diamond

“…Following that, Lang [14] proposed that the defect would be constituted by a double layer of N atoms (one layer of substitutional N atoms and one layer of interstitial N atoms). However, as mentioned above, the N content in the platelets can vary substantially [5,6,7], ruling out N impurities as the main constituent of the defect. Since foreign impurities could not account for the existence of platelets, Evans [15] proposed that platelets could be formed by interstitial carbon atoms.…”

“…From then on, a plethora of experimental data on this planar defect has been gathered, but a complete understanding of its origin and microscopic structure is still lacking. The current knowledge on this defect can be summarized as follows: i) platelets have been detected only in type Ia diamonds [2]; ii) transmission electron microscopy (TEM) experiments have shown that there is an asymmetry between the [110] and [110] directions [3]; iii) TEM experiments have also determined that platelets displace the crystalline lattice by approximately 0.4a 0 [4], along the [001] direction, where a 0 is the lattice parameter of diamond; iv) electron energy loss spectroscopy (EELS) experiments indicate that the nitrogen content in platelets can vary from 6% to 61% of a monolayer [5,6,7]; v) an infrared absorption line around 1370 cm −1 is always present in samples containing platelets [8]; vi) platelets have been associated with broad luminescence bands, one centered at 1.25 eV [9], which reduces the efficiency of optical windows made of natural diamond, and another at 2.14 eV [10], and possibly with high energy absorption and luminescence bands around 4.6 and 4.4 eV, respectively [11].In the microscopic model first proposed for platelets in diamond, Frank [12] considered that the defect should be formed by Si impurities replacing part of the carbon atoms in a (001) plane. However, it was later shown that Si is an uncommon impurity in diamond.…”