Twisting 2D diamond layers creates ultra-wide bandgap

2D materials can exhibit drastically different physical properties depending on their structure. Diamond films, known as diamanes, have been considered to be used as semi-conductors in nanodevices. To further realize this goal, Chernozatonskii et. al identified a method that can significantly widen the bandgap in diamanes.

Using an ab initio approach, the researchers considered Moiré-patterned diamanes where the layers were rotationally offset to each other at specific angles. When the layers are twisted by 29.4 and 27.8 degrees, the electronic spectrum in the valence and conduction bands becomes sharply resonant, making the bandgap of these diamanes larger than that of any other known diamane.

The key to this wide bandgap, according to author Leonid Chernozatonskii, was the formation of interlayer covalent bonds, which results in a structure with only sp3-hybridized atoms, leading to the wide gap. Their simulations showed a fluorinated diamane with a twisting angle of 27.8 degrees to have a bandgap of 4.5 eV, significantly larger than the dielectric gaps of about 3eV in ordinary diamanes with non-twisted AA- or AB- bigraphenes.

“It is very important and very impressive when your thoughts and predictions correlate with experimental observations and computational results,” Chernozatonskii said.

The robust mechanical properties of these proposed diamanes make them good candidates for protective layers around electronic devices, and the resonance of their electronic spectrum in the UV range holds promise for solar radiation absorption and opto-electronic devices.

Source: “Ultrawide-bandgap Moiré diamanes based on bigraphenes with the twist angles Ɵ∼30°,” by Leonid A. Chernozatonskii, Victor A. Demin, and Dmitry G. Kvashnin, Applied Physics Letters (2020). The article can be accessed at https://doi.org/10.1063/5.0027839 .

This paper is part of the Ultrawide Bandgap Semiconductors collection, learn more here .