A new quasi-one-dimensional transition metal chalcogenide semiconductor (Nb$_4$Se$_{15}$I$_2$)I$_2$

Kejian Qu; Zachary W. Riedel; Irián Sánchez-Ramírez; Simon Bettler; Junseok Oh; Emily N. Waite; Nadya Mason; Peter Abbamonte; Fernando de Juan Sanz; Maia G. Vergniory; Daniel P. Shoemaker

arXiv · 2210.11615

A new quasi-one-dimensional transition metal chalcogenide semiconductor (Nb$_4$Se$_{15}$I$_2$)I$_2$

Kejian Qu·Zachary W. Riedel·Irián Sánchez-Ramírez·Simon Bettler·Junseok Oh·Emily N. Waite·Nadya Mason·Peter Abbamonte·Fernando de Juan Sanz·Maia G. Vergniory·Daniel P. Shoemaker

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Abstract

The discovery of new low-dimensional transition metal chalcogenides is contributing to the already prosperous family of these materials. In this study, needle-shaped single crystals of a new quasi-one-dimensional material (Nb$_4$Se$_{15}$I$_2$)I$_2$ were grown by chemical vapor transport, and the structure was solved by single crystal X-ray diffraction (XRD). The new structure has one-dimensional (Nb$_4$Se$_{15}$I$_2$)$_n$ chains along the [101] direction, with two I$^-$ ions per formula unit directly bonded to Nb$^{5+}$. The other two I$^-$ ions are loosely coordinated and intercalate between the chains. Individual chains are chiral, and stack along the $b$ axis in opposing directions, giving space group $P2_1/c$. The phase purity and crystal structure was verified by powder XRD. Density functional theory calculations show (Nb$_4$Se$_{15}$I$_2$)I$_2$ to be a semiconductor with a direct band gap of around 0.6 eV. Resistivity measurements of bulk crystals and micro-patterned devices demonstrate that (Nb$_4$Se$_{15}$I$_2$)I$_2$ has an activation energy of around 0.1 eV, and no anomaly or transition was seen upon cooling. (Nb$_4$Se$_{15}$I$_2$)I$_2$ does not undergo structural phase transformation from room temperature down to 8.2 K, based on cryogenic temperature single crystal XRD. This compound represents a well-characterized and valence-precise member of a diverse family of anisotropic transition metal chalcogenides.

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Kejian Qu, Zachary W. Riedel, Irián Sánchez-Ramírez, Simon Bettler, Junseok Oh, Emily N. Waite, Nadya Mason, Peter Abbamonte, Fernando de Juan Sanz, Maia G. Vergniory, Daniel P. Shoemaker. 2022-10-20. A new quasi-one-dimensional transition metal chalcogenide semiconductor (Nb$_4$Se$_{15}$I$_2$)I$_2$. https://arxiv.org/abs/2210.11615

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