Red Photoluminescence of α‐HgS Single Crystals

Abstract

Cathodoluminescence measurements on cinnabar (a-HgS) published in a previous paper show that the emission peaked a t 1.9 eV obeys a vibronic mechanism. The purpose of the present paper is to complete this characterisation by photoluminescence and excitation measurements (shape of spectrum, kinetics, thermal quenching). These different results allow to calculate the configurational coordinate diagram and to determine its location in the gap. It is also pointed out the influence of the traps and the non-radiative centres revealed by measurements of photoconduction and thermal-stimulated current.Des mesures de cathodoluminescence sur le cinabre (cc-HgS) publi6es dans un article pr6cBdent nous ont montrc5 que 1'Bmission centr6e & 1,9 eV obBissait B un mecanisme vibronique. L'objet du prBsent article est de complBter cette caractBrisation par des expbriences de photoluminescence et d'excitation (forme des spectres, cinbtique, extinction thermique). Ces diffbrents rbsultats nous ont permis de calculer le diagramme de configuration et de le localiser dans la bande interdite. Nous signalons Bgalement l'influence des pibges et des centres non radiatifs mis en dvidence par photoconduction et courant thermostimul6.

Colour degradation of artworks: an ab initio approach to X-ray, electronic and optical spectroscopy analyses of vermilion photodarkening

“…41 We thus provide rmer proof that the band edges of a-HgS used in that discussion were correctly estimated. Table 1 also demonstrates that our results for a-HgS (2.24 eV for the indirect gap) are in excellent agreement with the experimental values from photoemission experiments at 300 K as well as with those from optical measurements (reporting an indirect band gap of 2.28 eV at liquid helium temperatures, 2.225 eV at liquid nitrogen temperatures, and 2.1 eV at room temperature [42][43][44] ). Although in principle our G 0 W 0 results do not give access to optical properties (due to the neglect of particlehole excitations), such favorable comparison suggests that excitonic coupling does not lead to a large difference between the electronic and optical gaps, and thus that excitonic effects in this compound are relatively small, conrming previous experimental ndings.…”