Towards imaging of defects in diamond by high‐resolution TEM

Abstract

Nitrogen‐Vacancy (NV), silicon‐vacancy (SiV), germanium‐vacancy (GeV) and other colour centres in diamond have been of rising interest in recent years due to their potential applications such as quantum information processing [1] and fluorescent labelling in biology. For such applications, it is necessary to incorporate the colour centres in diamond thin films or nanodiamond particles in a controllable way. Since the colour centres are formed by single atomic vacancy and single substitution, one fundamental step towards controlled incorporation is to characterize the structure of the colour centres with high spatial resolution. Although structural characterisation of NV‐centres has been accomplished by optical and magnetic resonance methods, atomic structures of other colour centres often remain elusive. Aberration‐corrected high‐resolution transmission electron microscopy (AC‐HRTEM) has proven to be a powerful technique for structural analysis with atomic resolution. However, the imaging conditions necessary to directly image the structure of an SiV, GeV or other colour centres remain unclear. Here we explore the optimum imaging conditions for the detection of SiV and GeV centres by using HRTEM image simulation. In order to maximize the image contrast from the SiV and GeV centres, we carried out a series of HRTEM simulations under various imaging conditions such as crystal orientation, acceleration voltage, spherical aberration coefficient (C s ) and defocus. The HRTEM image simulation was implemented using a multislice algorithm in the QSTEM software package [4]. Our results show that it should be possible to directly image both SiV and GeV centres in [120] projection at an acceleration voltage of 300 kV (see Figures 1 and 2, respectively). Under negative C s imaging conditions (C s = ‐15 µm and slight overfocus), both SiV and GeV centres can be clearly detected. Due to the higher atomic number of Germanium, GeV centres provide slightly higher contrast as compared to SiV centres.