University of Oulu

Chem. Mater. 2023, 35, 16, 6374–6381

Composition dependence of the band gaps of semiconducting GeSₓSe1–x van der Waals alloys

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Author: Sutter, Eli1,2; Komsa, Hannu-Pekka3; French, Jacob S.4;
Organizations: 1Department of Mechanical and Materials Engineering, University of Nebraska─Lincoln, Lincoln, Nebraska 68588, United States
2Nebraska Center for Materials and Nanoscience, University of Nebraska─Lincoln, Lincoln, Nebraska 68588, United States
3Microelectronics Research Unit, University of Oulu, FI-90014 Oulu, Finland
4Department of Electrical and Computer Engineering, University of Nebraska─Lincoln, Lincoln, Nebraska 68588, United States
Format: article
Version: accepted version
Access: embargoed
Persistent link:
Language: English
Published: American Chemical Society, 2023
Publish Date: 2024-07-31


Alloying of two-dimensional (2D)/layered chalcogenide semiconductors by forming ternaries with properties that span the range between the binary constituents allows tuning of the electronic and optical properties and achieving the full potential of these materials. While the focus so far has been on transition-metal dichalcogenides, alloying in layered group IV chalcogenides─promising for optoelectronics, photovoltaics, ferroelectrics, etc.─remains less understood. Here, we investigate alloying in the GeSe–GeS system and its effect on the fundamental band gap. We synthesize single-crystalline layered GeSₓSe1–x alloy micro- and nanowires whose compositions are tunable over the entire range of S content, x, via the GeS and GeSe precursor temperatures. Cathodoluminescence in scanning transmission electron microscopy is used to investigate the composition dependence of the band gaps of GeSₓSe1–x alloy micro- and nanowires. The band gaps of bulk-like microwires increase systematically with the sulfur content of the alloys, thereby covering the entire range between GeSe (1.27 eV) and GeS (1.6 eV). The composition dependence of the fundamental band gap is close to linear with a bowing coefficient b = 0.173 eV. Density functional theory calculations support the isomorphous behavior of GeSe–GeS solid solutions and demonstrate that the band gaps are indirect and have similar small bowing as determined experimentally. Finally, we establish pronounced size effects in GeSₓSe1–x alloy nanowires that provide access to higher-energy optoelectronic transitions than can be realized in bulk alloys of the same composition. Our results support applications of germanium monochalcogenide alloys in areas such as optoelectronics and photovoltaics.

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Series: Chemistry of materials
ISSN: 0897-4756
ISSN-E: 1520-5002
ISSN-L: 0897-4756
Volume: 35
Issue: 16
Pages: 6374 - 6381
DOI: 10.1021/acs.chemmater.3c01069
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: The research was sponsored by the Army Research Office and was accomplished under Award Number: W911NF-23-1-0060. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Office or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein. EDS measurements were performed in the Nebraska Nanoscale Facility: National Nanotechnology Coordinated Infrastructure and the Nebraska Center for Materials and Nanoscience, which are supported by the National Science Foundation under Award ECCS: 2025298, and the Nebraska Research Initiative. The authors acknowledge CSC-IT Center for Science, Finland, for computational resources.
Copyright information: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Chemistry of materials, copyright © 2023 American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see