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Phosphorus a Promising Semiconductor

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Grain boundaries are rows of defects that disrupt the electronic properties of two-dimensional materials like graphene, but new theory by scientists at Rice University shows no such effects in atomically flat phosphorus. That may make the material ideal for nano-electronic applications. (Image Credit: Evgeni Penev/Rice University)

Defects damage the ideal properties of many two-dimensional materials, like carbon-based graphene. Phosphorus just shrugs. That makes it a promising candidate for nano-electronic applications that require stable properties, according to new research by Rice University theoretical physicist Boris Yakobson and his colleagues. The Rice team analyzed the properties of elemental bonds between semiconducting phosphorus atoms in 2-D sheets. Two-dimensional phosphorus is not theoretical; it was recently created through exfoliation from black phosphorus. The researchers compared their findings to 2-D metal dichalcogenides like molybdenum disulfide; these metal compounds have also been considered for electronics because of their inherent semiconducting properties. In pristine dichalcogenides, atoms of the two elements alternate in lockstep. But wherever two atoms of the same element bond, they create a point defect. Think of it as a temporary disturbance in the force that could slow electrons down, Yakobson said.

Semiconductors are the basic element of modern electronics that direct and control how electrons move through a circuit. But when a disturbance deepens a band gap, the semiconductor is less stable. When chaos reigns in the form of multiple point defects or grain boundaries — where sheets of a 2-D material merge at angles, forcing like atoms to bond – the materials become far less useful. The Yakobson lab’s calculations show phosphorus has no such problem. Even when point defects or grain boundaries exist, the material’s semiconducting properties are stable. Like perfect graphene – but unlike imperfect graphene — it performs as expected.