Engineering excitonic dynamics and environmental stability of post-transition metal chalcogenides by pyridine functionalization technique

Abstract

Owing to their strong photon emission, low excitonic binding energies, and nearly-ideal band offset values for water splitting reactions, direct gap quasi-2D gallium chalcogenides are potential candidates for applications in energy harvesting, optoelectronics, and photonics. Unlike other 2D materials systems, chemical functionalization of gallium chalcogenides is still at its seminal stages. Here, we propose vapor phase pyridine intercalation technique to manipulate optical properties of gallium chalcogenides. After functionalization, the excitonic dynamics of quasi-2D GaSe change significantly as evidenced by an increase in integrated PL intensity and emergence of a new emission feature that is below the band edge. Based on our DFT calculations, we attribute these to formation of bound exciton complexes at the trap sites introduced by chemical reaction between pyridine and GaSe. On the contrary, pyridine functionalization does not impact the optical properties of GaTe, instead treats GaTe surface to prevent oxidization of tellurium atoms. Overall, results suggest novel ways to control properties of gallium chalcogenides on demand and unleash their full potential for a range of applications in photonics and optoelectronics.

A first-principles Quantum Monte Carlo study of two-dimensional (2D) GaSe

“…[11][12][13][14][15][16] Due to the fact that PTMCs possess a suitable bandgap for photovoltaics and transistors, [4][5][6][7][17][18][19][20][21][22] excellent thermal transport, 21,23 inherent flexibility, [24][25][26] and smaller exciton binding energies [4][5][6] make them viable substitutes for TMDs in device applications. In addition, it has been reported that applying strain, 24,26,27 creating heterostructures, [28][29][30][31] and chemical functionalization [32][33][34] can effectively tune the electronic and optical properties of monolayer GaSe, and it has been reported that GaSe can be used as a suitable substrate for other 2D materials. 35,36 Although GaSe has been reliably synthesized and the lattice constant, quasiparticle gap, and optical gap have been experimentally characterized, 23,[37][38][39][40][41][42][43][44] results obtained...…”

A first-principles Quantum Monte Carlo study of two-dimensional (2D) GaSe

“…Due to the fact that PTMCs possess a suitable band gap for photovoltaics and transistors [4][5][6][7][17][18][19][20][21][22] , excellent thermal transport 21,23 , inherent flexibility [24][25][26] and smaller exciton binding energies [4][5][6] make them viable substitutes for TMDs in device applications. In addition, it has been reported that applying strain 24,26,27 , creating heterostructures [28][29][30][31] and chemical functionalization [32][33][34] can effectively tune the electronic and optical properties of monolayer GaSe and it has been reported that GaSe can be used as a suitable substrate for other 2D materials 35,36 .…”

Optical properties of GaS-Ca(OH)2bilayer heterostructure

“…Since then, the attention of material science and condensed matter physics has been widened towards new single layer structures such as silicene 4,5 , germanene [5][6][7] , transition-metal dichalcogenides (TMDs) [8][9][10][11] , alkaline-earth-metal hydroxide (AEMHs) 12 and post-transition metal chalcogenides (PTMCs). [13][14][15] These individual monolayers posses various significant electronic and optical properties which make them promising candidates for the next generation of nanoscale devices. [16][17][18] For instance, monolayer TMDs are direct band gap semiconductors unlike their bulk counterparts, [9][10][11] and exhibit large exciton binding energies in the order of 0.1-1.0 eV which results in exciton resonances at room temperature.…”

“…12 Similar to Ca(OH) 2 , monolayer GaS and GaSe have been synthesized recently and it has been shown that both monolayers are indirect gap semiconductors and they are suitable candidates for use in field-effect transistors and nanophotonic devices. 14,[26][27][28] Another important aspect of the mentioned layered structures is their usage as building blocks for novel multi-layer heterostructures. Recently, a new field of research in materials science has emerged that deals with the stacking of two or more different monolayers on top of each other, namely van der Waals (vdW) heterostructures.…”