Direct atomic imaging of Mn in the GaN growth surface: High-density, Two-dimensional, Striped Superstructures

A class of novel well-ordered striped superstructures have been observed by depositing submonolayer Mn onto GaN(0001)-``1$\times$1'' surface. These superstructures consist of stripe domains along [1$\bar{1}$00]$_{GaN}$ with various widths, while scanning tunneling microcopy images resolved a common local $\sqrt{3}$$\times$$\sqrt{3}$-R30$^{\circ}$ structure for the stripes. Combined with first-principles calculations, a new two-dimensional structural model is proposed having a dense Mn$_{x}$Ga$_{1-x}$ surface layer. Mn atomic sites within the GaN surface are directly identified. A spin-induced asymmetry in the Mn electronic structure is revealed in real-space for the narrow stripes. These findings explain the behavior of Mn atoms in the GaN growth surface and herald the development of magnetic nanostructures on GaN surfaces.