The Moiré patterns created by the superposition of different crystal grains can resemble silicon hexagonal crystal phases, as shown by recent work published in the journal Nanotechnology. In the studied nanowires no hexagonal phase with long-range order was found and the "odd" images and diffraction patterns were mostly due to planar defects causing superposition of different crystal grains.

The study of a slice of a nanowire prepared by focused ion beam provides the twinning relations of the different crystal grains present in the nanowire volume. This information is then used to explain the Moiré patterns that are observed if the nanowire is studied from the side and the different crystal grains superpose.

In the report, the team describes a strategy to unambiguously distinguish a hexagonal phase from a cubic phase with defects – the nanowire should be observed from different directions and dark field images should be obtained – and points out image features that indicate the presence of hidden defects.

Full details can be found in the journal Nanotechnology.