Fig. 4: Domain orientation during epitaxial growth of WS2 monolayers.
a Schematic illustration of domain orientations on sapphires with or without reconstructed Al layer. The rotating angle (θ) was defined as the anticlockwise rotation required to align the zigzag edge of the WS2 triangular domain, initially parallel to the m \( < 10\bar{1}0 > \) direction of the sapphire crystal; b Calculated rotating angle-dependent adsorption energies of WS2 domain attached to the sapphire surface. The insets show representative domains with different rotating angles; c AFM images of WS2 domain orientations on sapphire substrates with atomic steps towards \( < 10\bar{1}0 > \) and \( < 11\bar{2}0 > \) directions; The inset in the top-left panel provides a higher-magnification view, clearly revealing the alignment of domains along the atomic step direction towards\(\, < 11\bar{2}0 > \). Scale bars: 4 μm (top-left, top-right, bottom-left), 1 μm (inset of top-left and bottom-right. d–f The evolution of domain orientation grown on sapphire substrate with atomic steps towards the \( < 11\bar{2}0 > \) direction; scale bars represent 20 μm; g–i The evolution of domain orientation grown on sapphire substrate with atomic steps towards the \( < 10\bar{1}0 > \) direction, with scale bars of 10 μm.
