Analysis of small particles via HRTEM lattice images: Contrast mechanisms and effects of particle shape

Abstract

It is well known that because of their large surface area, small particles possess unusual physical properties. What is not so well known is that small particles often exhibit unusual diffraction behaviour. The diffraction behaviour of small particles is a function of their size, shape and chemical composition. This diffraction behaviour is essentially the same for small precipitates within a parent matrix as it is for small particles dispersed on the surface of a thin film. The unusual diffraction behaviour of small particles falls into two categories.1)The apparent lattice fringe spacing may differ significantly from the actual lattice parameter for particles of irregular shape.2)One of the surprises of dynamical diffraction is that structures with heavy atoms do not necessarily give strong scattering into Bragg beams. For small particles this means that light elements are often visible on the surfaces of heavy-atom particles.In this paper an analysis of small particles is made with reference to the microscopic diamonds found in oxidized acid residues from carbonaceous chondrite meteorites.