Crater in a sapphire substrate hit with a femtosecond laser pulse, followed by annealing to develop the step structure. 20 µm scan. Steps on the surface are 3 Å atomic steps. A small chunk was blown out of the center of the crater. Imaged with a MFP-3D AFM.
Image courtesy of S. MacLaren (sample courtesy Fumiya Watanabe, UIUC), University of Illinois at Urbana-Champaign.