Jan 31, 2007
Mapping the location and configuration of nitrogen in diamond nanoparticles
Although experimentalists routinely focus on defects and impurities in nanoparticles they are often omitted from many theoretical and computational studies. This is unfortunate, since new sophisticated computational techniques are ideal for investigating the structure, stability and electronic properties of defects, both locally and by treating nanostructures as a whole.
For example, we can now probe the stability and properties of intentional dopants and unintentional impurities in nanoparticles, both of which will be important for ensuring reliability and reproducibility of nanodevices in the future. The aim of our research program is to develop a general algorithm for mapping the potential energy surface (PES) of point defects in faceted nanocrystals, for identifying whether impurities will be stable within the core or at the surfaces, edges or corners. In this respect, nitrogen in nanodiamond is an ideal model system, since commercial nanodiamond contains approximately 2–3% nitrogen with an unknown distribution.
Density functional tight-binding simulations of local configuration and PES of substitutional nitrogen in a collection of nanodiamond structures revealed that N is metastable within the core of nanodiamond, irrespective of the shape or degree of surface passivation. However, the precise binding energy, coordination and preferred (geometric) location is dependent upon the structure of the nanoparticle as a whole.
Combined with knowledge of diffusion barriers this work will be instrumental in developing operating frameworks for nanodevices containing nanodiamond. Our future plans include the investigation of more complicated point defects, as well as other impurities in a variety of nanomaterials.
About the author
Amanda Barnard is the Violette & Samuel Glasstone Fellow in the Department of Materials at the University of Oxford, UK, where her research focuses on the relationship between shape, phase and stability of materials at the nanoscale.