Bridging Borophene and Metal Surfaces: Structural, Electronic, and Electron Transport Properties

Bridging Borophene and Metal Surfaces: Structural, Electronic, and Electron Transport Properties


Currently, solid interfaces composed of two-dimensional materials (2D) in contact with metal surfaces (m-surf) have been the subject of intense research, with the borophene bilayer (BBL) considered a prominent material for developing electronic devices based on 2D platforms. In this work, we present a theoretical study of the energetic, structural, and electronic properties of the BBL/m-surf interface, where m-surf = Ag, Au, and Al (111) surfaces, and investigate the electronic transport properties of BBL channels connected to the BBL/m-surf top contacts.

We find that the bottom-most BBL layer becomes metalized due to orbital hybridization with the metal surface states, resulting in ohmic contacts between BBL and m-surf, while the inner and top-most boron layers retain their semiconducting character. The net charge transfers reveal that BBL becomes n-type (p-type) doped for m-surf = Ag (Au) and Al. A thorough structural characterization of the BBL/m-surf interface, using simulations of X-ray photoelectron spectra, shows a redshift in the B-1s spectra indicative of the BBL/m-surf interface formation.

Further electronic transport results reveal the emergence of a Schottky barrier between 0.1 and 0.2 eV at the BBL/m-surf contact and the BBL channels. We believe that our findings are timely, providing important insights into the applicability of borophene bilayers for developing 2D electronic devices.

Summary for Non-Scientists

This study discusses the potential of borophene bilayers (BBL)—which consist of two layers of boron atoms—as a material for creating electronic devices that are only a few atoms thick. These 2D materials are being investigated for their interactions with metals like silver (Ag), gold (Au), and aluminum (Al) to form interfaces, which are the surfaces where two different materials meet. The study is theoretical and examines the energy, structure, and electronic properties of the BBL when it’s in contact with these metal surfaces. It also investigates the electrical conductivity across these interfaces.

One key finding is that the layer of BBL closest to the metal becomes more metallic due to electron mixing with the metal, resulting in an ohmic contact that facilitates the flow of electricity. However, the upper layers of boron remain more like semiconductors, allowing for controlled electrical conduction. The researchers also discovered that the BBL undergoes either n-type or p-type doping depending on the metal it contacts. Doping involves adding a small amount of another element to alter a material's conductivity: n-type doping adds electrons, and p-type doping removes electrons.

To analyze the structure of the BBL/metal interface, X-ray photoelectron spectroscopy was utilized—a technique using X-rays to study surface materials—revealing a redshift in the B-1s spectra, indicating a shift to lower electron energies due to the metal interaction. Additionally, the study identified a Schottky barrier ranging between 0.1 and 0.2 electron volts (eV) at the interface. This barrier is crucial for determining device performance, affecting electron mobility.

In conclusion, this research provides valuable insights into utilizing borophene bilayers to develop ultra-thin electronic devices, underscoring the significance of understanding interactions between 2D materials and metals in electronic applications.

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