@article{a47878cde53543858e85b3c7ba27081a,
title = "Tunable electronic structure in gallium chalcogenide van der Waals compounds",
abstract = "Transition-metal monochalcogenides comprise a class of two-dimensional materials with electronic band gaps that are highly sensitive to material thickness and chemical composition. Here, we explore the tunability of the electronic excitation spectrum in GaSe by using angle-resolved photoemission spectroscopy. The electronic structure of the material is modified by in situ potassium deposition as well as by forming GaSxSe1-x alloy compounds. We find that potassium-dosed samples exhibit a substantial change of the dispersion around the valence-band maximum (VBM). The observed band dispersion resembles that of a single tetralayer and is consistent with a transition from the direct-gap character of the bulk to the indirect-gap character expected for monolayer GaSe. Upon alloying with sulfur, we observe a phase transition from AB to AA′ stacking. Alloying also results in a rigid energy shift of the VBM towards higher binding energies, which correlates with a blueshift in the luminescence. The increase of the band gap upon sulfur alloying does not appear to change the dispersion or character of the VBM appreciably, implying that it is possible to engineer the gap of these materials while maintaining their salient electronic properties.",
author = "Brian Shevitski and S{\o}ren Ulstrup and Koch, {Roland J.} and Hui Cai and Sefaattin Tongay and Luca Moreschini and Chris Jozwiak and Aaron Bostwick and Alex Zettl and Eli Rotenberg and Shaul Aloni",
note = "Funding Information: This work was supported primarily by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under Contract No. DE-AC02-05CH11231, within the van der Waals Heterostructures Program (KCWF16), which provided for HRSTEM and ARPES support. This work was also supported in part by the National Science Foundation under Grant No. DMR-1807233, which provided for PL measurements and preliminary exploration of sample growth parameters. S.U. acknowledges financial support from VILLUM FONDEN under the Young Investigator Program (Grant No. 15375). R.J.K. was supported by a fellowship within the Postdoc-Program of the German Academic Exchange Service (DAAD). The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No. DE-AC02-05CH11231. B.S. acknowledges support from the NSF LSAMP BD fellowship (Award No. 1249249).",
year = "2019",
month = oct,
day = "9",
doi = "10.1103/PhysRevB.100.165112",
language = "English (US)",
volume = "100",
journal = "Physical Review B",
issn = "2469-9950",
publisher = "American Physical Society",
number = "16",
}