A fundamental understanding of the atomic and electronic structures of metallic nanowires (NWs) on semiconductors is critical for micro- or molecular electronics. The deposition of Au atoms on Ge(001) surfaces can trigger the self-assembly of atomic NWs extending for hundreds of nanometers, and these NWs raised much controversy on their atomic/electronic configurations. In this work, different types of NWs were characterized on Au/Ge(001) surfaces via scanning tunneling microscopy (STM). Combined with density functional theory (DFT) calculations, the atomic structures of Au-induced NWs on Ge(001) surfaces were decoded, including the NWs-H/L and complex chevron and zigzag (V–W) reconstructions, where simulated V–W patterns at filled states transform to triplets at empty states. Moreover, a quasi-one-dimensional (1D) electronic behavior and anisotropic two-dimensional (2D) electronic states are uncovered in the Au–Ge-modified-dimer-row (AGMDR) and Au-NWs-in-trench (ANT) models, respectively, reconciling the previous controversy about electronic behaviors of NWs on Au/Ge(001) surfaces. Because of the quantum instability, 1D electron systems undergo a transition from metallic to nonconducting, while the atomic NWs (i.e., NWs-H and NWs-L) in the ANT model are metallic, rendering them good conductive channels for micro- or molecular electronics. Our findings provide insights into ascertaining the atomic structures of self-assembled NWs and understanding the discrepancies of the Au/Ge(001) material system.

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Double perovskites with bright emission, low toxicity, and excellent stability have drawn considerable attention. Herein, we report the hydrothermal synthesis of Mn2+-doped Cs2Na1–x Ag x BiCl6 double perovskites that exhibit dual emission modes. Introducing Ag+ ions to Cs2NaBiCl6 samples enables a bright self-trapped exciton (STE) emission in orange-red color, whereas Mn2+ dopants induce a yellow-orange emission. Importantly, Mn2+ doping into Cs2Na1–x Ag x BiCl6 double perovskites with an indirect bandgap enables a high photoluminescence quantum yield of 49.52 ± 2%. Density functional theory calculations reveal that bringing Ag+ ions into Cs2NaBiCl6 can localize wave function to the [AgCl6]5– octahedron and convert dark transitions to bright STE transitions. Moreover, the 3d orbitals of Mn2+ dopants hybridize with Bi-6p and Cl-3p orbitals at the conduction band minimum, resulting in direct electron transfer from the host to Mn2+ and a significant increase in photoluminescence efficiency. These results shed light on the optical physical process of Mn2+-doped systems, providing useful information for further improvement of the photoluminescence efficiency of double perovskites.