Red-to-Ultraviolet Emission Tuning of Two-Dimensional Gallium Sulfide/Selenide.
Graphene-like two-dimensional (2D) nanostructures have attracted significant attention because of their unique quantum confinement effect at the 2D limit. Multilayer nanosheets of GaS-GaSe alloy are found to have a band gap (Eg) of 2.0-2.5 eV that linearly tunes the emission in red-to-green. However, the epitaxial growth of monolayers produces a drastic increase in this Eg to 3.3-3.4 eV, which blue-shifts the emission to the UV region. First-principles calculations predict that the Eg of these GaS and GaSe monolayers should be 3.325 and 3.001 eV, respectively. As the number of layers is increased to three, both the direct/indirect Eg decrease significantly; the indirect Eg approaches that of the multilayers. Oxygen adsorption can cause the direct/indirect Eg of GaS to converge, resulting in monolayers with a strong emission. This wide Eg tuning over the visible-to-UV range could provide an insight for the realization of full-colored flexible and transparent light emitters and displays.
Department of Chemistry, Korea University , Jochiwon 339-700, Korea.
Chan Su
CS
Jung
Department of Chemistry and Bioactive Material Sciences and Research Institute of Physics and Chemistry, Jeonbuk National University , Jeonju 560-756, Korea.
Fazel
F
Shojaei
Department of Chemistry, Korea University , Jochiwon 339-700, Korea.
Kidong
K
Park
Department of Chemistry, Korea University , Jochiwon 339-700, Korea.
Jin Young
JY
Oh
Department of Chemistry, Korea University , Jochiwon 339-700, Korea.
Hyung Soon
HS
Im
Department of Chemistry, Korea University , Jochiwon 339-700, Korea.
Dong Myung
DM
Jang
Department of Chemistry, Korea University , Jochiwon 339-700, Korea.
Jeunghee
J
Park
Department of Nano and Advanced Materials, College of Engineering, Jeonju University , Jeonju 560-759, Korea.
Hong Seok
HS
Kang
GaS; GaSe; chemical vapor transport; first-principles calculation; monolayers; nanosheets