Borophene nanoribbons (BNRs) are one-dimensional strips of atomically thin boron expected to exhibit quantum-confined electronic properties that are not present in extended two-dimensional borophene. While the parent material borophene has been experimentally shown to possess anisotropic metallicity and diverse polymorphic structures, the atomically precise synthesis of nanometer-wide BNRs has not yet been achieved. Here, we demonstrate the synthesis of multiple BNR polymorphs with well-defined edge configurations within the nanometer-scale terraces of vicinal Ag(977). Through atomic-scale imaging, spectroscopy, and first-principles calculations, the synthesized BNR polymorphs are characterized and found to possess distinct edge structures and electronic properties. For single-phase BNRs, v1/6-BNRs and v1/5-BNRs adopt reconstructed armchair edges and sawtooth edges, respectively. In addition, the electronic properties of single-phase v1/6-BNRs and v1/5-BNRs are dominated by Friedel oscillations and striped moiré patterns, respectively. On the other hand, mixed-phase BNRs possess quantum-confined states with increasing nodes in the electronic density of states at elevated biases. Overall, the high degree of polymorphism and diverse edge topologies in borophene nanoribbons provide a rich quantum platform for studying one-dimensional electronic states.
Borophene nanoribbons (BNRs) are incredibly thin strips of boron atoms arranged in a line. They're expected to exhibit unique electronic properties that manifest only at such a small scale, unlike their larger, flat borophene counterparts. Borophene itself is known for its directional conductivity and structural variability. Until now, creating these tiny BNRs with precise control over their width and atomic structure has been challenging. However, researchers have achieved a breakthrough by synthesizing several types of BNRs with specific edge shapes on a silver surface. Using advanced imaging and analytical techniques, they studied these BNRs and discovered unique edge structures and electronic behaviors. Specifically, they identified two types of BNRs: one with edges resembling the steps of a staircase and another with edges resembling saw teeth. These distinct shapes influence electron behavior within the BNRs, resulting in unique patterns of electron distribution. Furthermore, when different types of BNRs were mixed, researchers observed even more complex electron behaviors, particularly with changes in energy levels. Overall, the diverse shapes and structures of these borophene nanoribbons make them an exciting area of study for understanding electron behavior in one-dimensional systems, with potential implications for future electronic devices.
