EPR studies of interstitial Ni centers in synthetic diamond crystals

Abstract

Two new electron-paramagnetic-resonance (EPR) spectra, tentatively labeled NIRIM-1 and NIRIM-2, have been studied using synthetic diamond crystals grown from the Ni solvent to which various amounts of nitrogen getters (Ti, Zr) and/or boron were added. The NIRIM-1 spectrum (g =2.0112) having the effective spin S =~, which has been determined from the microwave pulsewidth dependence of the two-pulse echo intensity, is assigned to be isolated interstitial Ni+ with electronic configuration 3d'. The anisotropic spectra of powderlike line shape at 4 K might be ascribed to an intermediate Jahn-Teller effect coupled predominantly with trigonal distortions. The NIRIM-2 spectrum having an axially symmetric g tensor (S= -, ', g~~= 2.3285, g, =0) arises from a 3d' ion in a crystal field of trigonally distorted octahedron. It is proposed that the center is interstitial Ni+ associated with a vacancy or with local charge compensation.

Investigation of nickel lattice sites in diamond: Density functional theory and x-ray absorption near-edge structure experiments

“…From an experimental point of view, the various lines detected by electronic paramagnetic resonance (EPR) [31][32][33][34][35][36] or by magneto-optical (including magnetic circular dichroism) or piezo-optical spectroscopy 21,[37][38][39] have been attributed to specific incorporation sites of Ni in diamond. This has been a challenge since the early days when it was recognized that an isolated Ni atom was incorporated in a site of trigonal symmetry at low temperatures (below 25 K) changing over to a tetrahedral symmetry at higher temperatures.…”

Lattice sites of ion-implanted Cu atoms in diamond

“…Radioactive TM nuclides, such as 59 Fe, 57 Fe and 67 Cu, are ideal probes for investigations on implantation parameters and the annealing of radiation-induced lattice damage, as well as on the location of implanted atoms and the defect complexes that they form. Electron paramagnetic resonance (epr) studies on Ni and Co in HTHP-synthesized diamonds [4][5][6][7][8] have identified three main lattice sites for these impurity atoms: substitutional, tetrahedral (T d ) interstitial, and the 'divacancy' site in which the impurity atom is located at the bond center between two neighbouring vacancies. Little direct information exists on other TM atoms such as Fe, Cu and Ti, and the defects they form in diamond, although Baker [9] has argued that the W36 centre observed in epr measurements on a type IIb diamond may be related to Cu in the divacancy.…”

Estrutura eletrônica e campo hiperfino de impurezas complexas de cobalto e de níquel em diamante

“…Outros dois importantes centros encontrados em diamante sintético, os centros NIRIM-1 e NIRIM-2 [11], foram associados aó atomo de níquel intersticial. O centro NIRIM-1 foi identificado com spin 1/2 e apresentando, a baixas temperaturas (T< 25 K) uma simetria trigonal, passando a apresentar uma simetria tetraédrica a temperaturas mais altas.…”

“…O modelo micróscopico proposto para este centroé o de umátomo de níquel intersticial isolado, em estado de carga positivo (Ni + i ) [11]. O centro NIRIM-2 foi identificado com spin 1/2 e com uma grande distorção trigonal [11].…”

“…Inicialmente este centro foi associado a um complexo envolvendo uma impureza de níquel intersticial com um impureza desconhecida ou uma vacância em um sítio próximo [11]. Mais recentemente, a proposta microscópica para este centroé que ele seria formado por um par de impurezas níquel-boro [12] ou, ainda por um níquel isolado intersticial [10].…”