A- and B-exciton photoluminescence intensity ratio as a measure of sample quality for transition metal dichalcogenide monolayers
The photoluminescence (PL) in monolayer transition metal dichalcogenides (TMDs) is dominated by the recombination of electrons in the conduction band with holes in the spin-orbit split valence bands, and there are two distinct emission features referred to as the A-peak (ground state exciton) and B-...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
AIP Publishing LLC
2018-11-01
|
| Series: | APL Materials |
| Online Access: | http://dx.doi.org/10.1063/1.5053699 |
| _version_ | 1818388446926864384 |
|---|---|
| author | Kathleen M. McCreary Aubrey T. Hanbicki Saujan V. Sivaram Berend T. Jonker |
| author_facet | Kathleen M. McCreary Aubrey T. Hanbicki Saujan V. Sivaram Berend T. Jonker |
| author_sort | Kathleen M. McCreary |
| collection | DOAJ |
| description | The photoluminescence (PL) in monolayer transition metal dichalcogenides (TMDs) is dominated by the recombination of electrons in the conduction band with holes in the spin-orbit split valence bands, and there are two distinct emission features referred to as the A-peak (ground state exciton) and B-peak (higher spin-orbit split state). The intensity ratio of these two features varies widely, and several contradictory interpretations have been reported. In this work, we analyze the room temperature PL from MoS2, MoSe2, WS2, and WSe2 monolayers and identify the underlying cause of observed variations in emission profile. We determine that PL variations arise from differences in the non-radiative recombination associated with defect densities. Therefore, the relative intensities of the A- and B-emission features can be used to qualitatively assess the non-radiative recombination and a low B/A ratio is indicative of low defect density and high sample quality. We also performed polarization-resolved PL measurements. Emission from TMD monolayers is governed by unique optical selection rules which make them promising materials for valleytronic operations. We observe a notably higher valley polarization in the B-exciton relative to the A-exciton. The high polarization is a consequence of the shorter B-exciton lifetime resulting from rapid relaxation of excitons from the B-exciton to the A-exciton of the valence band. Our work clarifies disparities reported in the literature relating to the emission profile and provides a straightforward means to assess sample quality. |
| first_indexed | 2024-12-14T04:25:59Z |
| format | Article |
| id | doaj.art-e8acdbfd041c4e3c94dad345334253cb |
| institution | Directory Open Access Journal |
| issn | 2166-532X |
| language | English |
| last_indexed | 2024-12-14T04:25:59Z |
| publishDate | 2018-11-01 |
| publisher | AIP Publishing LLC |
| record_format | Article |
| series | APL Materials |
| spelling | doaj.art-e8acdbfd041c4e3c94dad345334253cb2022-12-21T23:17:12ZengAIP Publishing LLCAPL Materials2166-532X2018-11-01611111106111106-910.1063/1.5053699006811APMA- and B-exciton photoluminescence intensity ratio as a measure of sample quality for transition metal dichalcogenide monolayersKathleen M. McCreary0Aubrey T. Hanbicki1Saujan V. Sivaram2Berend T. Jonker3Naval Research Laboratory, Washington, District of Columbia 20375, USANaval Research Laboratory, Washington, District of Columbia 20375, USANaval Research Laboratory, Washington, District of Columbia 20375, USANaval Research Laboratory, Washington, District of Columbia 20375, USAThe photoluminescence (PL) in monolayer transition metal dichalcogenides (TMDs) is dominated by the recombination of electrons in the conduction band with holes in the spin-orbit split valence bands, and there are two distinct emission features referred to as the A-peak (ground state exciton) and B-peak (higher spin-orbit split state). The intensity ratio of these two features varies widely, and several contradictory interpretations have been reported. In this work, we analyze the room temperature PL from MoS2, MoSe2, WS2, and WSe2 monolayers and identify the underlying cause of observed variations in emission profile. We determine that PL variations arise from differences in the non-radiative recombination associated with defect densities. Therefore, the relative intensities of the A- and B-emission features can be used to qualitatively assess the non-radiative recombination and a low B/A ratio is indicative of low defect density and high sample quality. We also performed polarization-resolved PL measurements. Emission from TMD monolayers is governed by unique optical selection rules which make them promising materials for valleytronic operations. We observe a notably higher valley polarization in the B-exciton relative to the A-exciton. The high polarization is a consequence of the shorter B-exciton lifetime resulting from rapid relaxation of excitons from the B-exciton to the A-exciton of the valence band. Our work clarifies disparities reported in the literature relating to the emission profile and provides a straightforward means to assess sample quality.http://dx.doi.org/10.1063/1.5053699 |
| spellingShingle | Kathleen M. McCreary Aubrey T. Hanbicki Saujan V. Sivaram Berend T. Jonker A- and B-exciton photoluminescence intensity ratio as a measure of sample quality for transition metal dichalcogenide monolayers APL Materials |
| title | A- and B-exciton photoluminescence intensity ratio as a measure of sample quality for transition metal dichalcogenide monolayers |
| title_full | A- and B-exciton photoluminescence intensity ratio as a measure of sample quality for transition metal dichalcogenide monolayers |
| title_fullStr | A- and B-exciton photoluminescence intensity ratio as a measure of sample quality for transition metal dichalcogenide monolayers |
| title_full_unstemmed | A- and B-exciton photoluminescence intensity ratio as a measure of sample quality for transition metal dichalcogenide monolayers |
| title_short | A- and B-exciton photoluminescence intensity ratio as a measure of sample quality for transition metal dichalcogenide monolayers |
| title_sort | a and b exciton photoluminescence intensity ratio as a measure of sample quality for transition metal dichalcogenide monolayers |
| url | http://dx.doi.org/10.1063/1.5053699 |
| work_keys_str_mv | AT kathleenmmccreary aandbexcitonphotoluminescenceintensityratioasameasureofsamplequalityfortransitionmetaldichalcogenidemonolayers AT aubreythanbicki aandbexcitonphotoluminescenceintensityratioasameasureofsamplequalityfortransitionmetaldichalcogenidemonolayers AT saujanvsivaram aandbexcitonphotoluminescenceintensityratioasameasureofsamplequalityfortransitionmetaldichalcogenidemonolayers AT berendtjonker aandbexcitonphotoluminescenceintensityratioasameasureofsamplequalityfortransitionmetaldichalcogenidemonolayers |