Dangling bond modulating the electronic and magnetic properties of zigzag SiGe nanoribbon

• Si–Ge bond is a covalent bond, while the Si–H and Ge–H bonds are the ionic bonds.
• Perfect ZSiGeNR is a weak magnetic semiconducting.
• ZSiGeNR with bare Si or Ge edge is a weak magnetic metal.
• ZSiGeNR with bare Si and Ge edges is a nonmagnetic metal.

First-principles nonmagnetic calculations reveal a metallic character in zigzag SiGe nanoribbons (ZSiGeNRs) regardless of their width. The partial DOS projected onto the Si and Ge atoms of ZSiGeNR shows that a sharp peak at the Fermi level is derived from the edge Si and Ge atoms. The charge density contours show the Si–Ge bond is covalent bond, while for the Si–H bond and Ge–H bond, the valence charges are strongly accumulated around H atoms due to their stronger 1 s potential and the higher electronegativity of 2.20 than that of 1.90 for Si atom and 2.01 for Ge atom, so that a significant charge transformation from Si or Ge atoms to H atoms and thus an ionic binding feature. Spin–polarization calculations show that the band structures of ZSiGeNR are modified by the dangling bonds. Compared with perfect ZSiGeNR which is a ferrimagnetic semiconductor, the bands of the ZSiGeNRs with bare Si edge, bare Ge edge, and bare Si and Ge edges shift up and nearly flat extra bands appear at the Fermi level. The ZSiGeNR with bare Si edge or bare Ge edge is a ferrimagnetic metal, while ZSiGeNR with bare Si and Ge edges is a nonmagnetic metal.

Difference charge densities on ribbon plane of the 6-ZSiGeNR with (a) H atoms terminated at both edges (perfect), (b) bare Si edge, (c) bare Ge edge, (d) bare Si and Ge edges.Figure optionsDownload as PowerPoint slide