EPR study of the peculiarities of incorporating transition metal ions into the diamond structure

Abstract

Abstraet.In this paper previously obtained data is reviewed and new data is discussed about nickelcontaining centers in diamonds. These data ate used to suggest interpretation of new data about cobalt-containing centers and to understand the influence of iron on the defects in diamonds grown in the iron system. A newly discovered nickel-nitrogen center has three nitrogen atoms in the first neighbor sphere around the double semi-vacancy and looks like the N3 (P2) center. In diamonds grown in the cobalt system two new types of cobalt-containing centers were found (NLO2 and NWO1). Both centers have electron spin S = 1/2 and hyperfine structure from one cobalt ion (I = 7/2 with natural abun:ldnce 100%). A case can be made fora double semi-vacancy structure for these defects. Special"~i-owth of diamond in the system enriched in tSN decreased the line width down to 0.6 G, but gave no direct evidence of the existence of nitrogen in the defeet structure. Asymmetrical shapes of the hnes in the electron paramagnetic resonance (EPR) spectra of cobalt-containing centers with opposite signs in low and high magnetic field parts of spectra are due to very sensitive spin-Hamiltonian parameters of these defects to the lattice distortions. Annealing of cobalt-containing crystals at 2600 K produces the disappearance of all cobalt-containing EPR spectra, probably due to the capture of an additional nitrogen atom and the creation of a 3d 6 diamagnetic state. In diamonds grown in the iron system with a high content of nitrogen there is evidence of an influence of ferromagnetic inclusion on the exchange interaction between substitutional nitrogen as an additional channel of indirect exchange interaction. lntroductionThe development of the technology of both synthesis and annealing of diamond crystals allows the study of a means of successively incorporating impurity ions into the diamond structure. Progress in understanding the formation of nitrogen defects created in diamonds began with the seminal papers of Chrenko et al. [1]

Incorporation of Large Impurity Atoms into the Diamond Crystal Lattice: EPR of Split-Vacancy Defects in Diamond

“…At the same time, the HPHT annealing procedure of diamonds was elaborated in detail. Using these new techniques, diamond crystals were synthesized in the Fe-Ni-C and Ni-C systems in Novosibirsk, Russia [19][20][21][22]. The P1 and W8 centers were observed in the EPR spectra of diamond crystals synthesized at a temperature of 1700 K and a pressure of 5.5 GPa.…”

“…Table 1. Parameters of the spin Hamiltonian for different nickel-containing centers with S = 1/2 in diamond [19][20][21][22]. The directions are for a C 2h symmetry site with (1-10) as its plane of reflection symmetry.…”

“…These centers have spin S = 1/2 and the HFS characteristic of one 59 Co atom (cobalt has only one stable isotope). The spin-Hamiltonian parameters of the cobalt-containing spectra were determined (Table 4) [22].…”

“…Table 4. EPR parameters for the cobalt-containing centers with S = 1/2 in diamond [22]. g2, A2 corresponds to (011), and α is the angle between g1, A1 and (100).…”

Controlled incorporation of mid-to-high Z transition metals in CVD diamond

“…Unfortunately, diamond's high atomic density makes the incorporation of these larger atoms difficult. On the other hand, the principal possibility to incorporate larger metal atoms is demonstrated by the observation that diamond grown by high pressure-high temperature (HPHT) [9][10][11][12] or hot filament CVD (HFCVD) [13][14][15][16][17][18] methods commonly contains metal impurities from the catalyst (Ni, Co, Fe) or the filament material (W, Re, Ta). For the microwave plasma (MP) CVD technique, the incorporation of Mo impurities from the substrate holder has been reported [19].…”