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Deep‐UV exciton emission from Mg 1 − x Ca x O—A first‐principle investigation
Author(s) -
Li Qiaofen,
Tu Yan,
Yang Lanlan,
Tolner Harm
Publication year - 2014
Publication title -
journal of the society for information display
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.578
H-Index - 52
eISSN - 1938-3657
pISSN - 1071-0922
DOI - 10.1002/jsid.288
Subject(s) - exciton , binding energy , band gap , electron , atomic physics , ultraviolet , excitation , ion , physics , materials science , analytical chemistry (journal) , condensed matter physics , chemistry , optics , quantum mechanics , chromatography
In order to investigate the ultraviolet and electron emission properties of rock‐salt Mg 1 − x Ca x O, first‐principle calculations are carried out with x ranging from 0 to 0.5. The electron–hole interaction is taken into account by solving the Bethe–Salpeter equation. In pure MgO, the calculated exciton binding‐energy value of 83 ± 3 meV is quite close to the published experimental values. The electronic properties of doped MgO are investigated based on the super‐cell model. Both the optical bandgap and the exciton binding energy of the super cell of Mg 1 − x Ca x O are calculated for five discrete compositions, with an increasing amount x of CaO. The results show that there are strong excitonic effects in all of these materials. A rapid reduction in bandgap value is observed for Mg 1 − x Ca x O, when increasing the x value. The exciton binding energy of Mg 1 − x Ca x O shows a minimum value of about 40 meV around x = 0.2. In all of these cases, the exciton is stable at room temperature. The lowest excitation levels in Mg 1 − x Ca x O are determined by dark excitons. The occurrence of these dark excitons might explain why Mg 1 − x Ca x O is a strong source of delayed electron emission, after being bombarded by ions in a plasma.