The Nature of Bonding in Bulk Tellurium Composed of One-Dimensional Helical Chains

Abstract

Bulk tellurium (Te) is composed of one-dimensional (1D) helical chains which have been considered to be coupled by van der Waals (vdW) interactions. However, on the basis of first-principles density functional theory calculations, we here propose a different bonding nature between neighboring chains: i.e., helical chains made of normal covalent bonds are connected together by coordinate covalent bonds. It is revealed that the lone pairs of electrons of Te atoms participate in forming coordinate covalent bonds between neighboring chains, where each Te atom behaves as both an electron donor to neighboring chains and an electron acceptor from neighboring chains. This ligand-metal-like bonding nature in bulk Te results in the same order of bulk moduli along the directions parallel and perpendicular to the chains, contrasting with the large anisotropy of bulk moduli in vdW crystals. We further find that the electron effective masses parallel and perpendicular to the chains are almost the same as each other, consistent with the observed nearly isotropic electrical resistivity. It is thus demonstrated that the normal/coordinate covalent bonds parallel/perpendicular to the chains in bulk Te lead to a minor anisotropy in structural and transport properties.

Solution-Synthesized High-Mobility Tellurium Nanoflakes for Short-Wave Infrared Photodetectors

“…Recent theoretical works have predicated an indirect gap of 0.35 eV in bulk and a direct gap of 1.04 eV in the monolayer case. 23,24 Here, we systematically study the optical and electrical properties of solution-synthesized quasi-2D Te nanoflakes. From polarization-resolved IR transmission and reflection measurements, we experimentally extract the bandgap, absorbance, and complex refractive index of this material.…”

Evaporated SexTe1‐x Thin Films with Tunable Bandgaps for Short‐Wave Infrared Photodetectors

“…One potential material system that can meet the requirements stated above is tellurium (Te), a material with 1D crystal structure, which has an indirect bandgap around 0.31 eV. [ 16,17 ] One of the key merits is that there are no dangling bonds on the edges and surfaces of Te crystal except at termination points of molecular chains, since it is a true 1D material which forms a 3D structure through van der Waals bonding of the molecular chains. Therefore, crystalline Te does not suffer from the surface‐induced performance degradation commonly observed in conventional III–V semiconductors that requires additional surface passivation to mitigate.…”

Synthesis Techniques, Optoelectronic Properties, and Broadband Photodetection of Thin‐Film Black Phosphorus

“…[ 245–249 ] Te crystal is stacked together from individual helix molecular chains via van der Waals forces. [ 250,251 ] Therefore, the dangling‐bond‐induced recombination only occurs at the end of the chains in Te. [ 247,249 ] In addition, Te nanoflakes with high crystal quality and large lateral size can be prepared through hydrothermal method with high yield.…”