Optimized cation exchange for mercury chalcogenides 2D nanoplatelets and its application for alloys
Résumé
II-VI 2D nanoplatelets (NPLs) are, among nanocrystals (NCs), those with the narrowest optical features. This property remains true for Hg based NPLs, despite a cation exchange procedure to obtain them from Cd based NPL which leads to structural defects (poorly defined edge and voids) inducing inhomogeneous broadening. Here, we propose an optimized procedure for which solvent, surface chemistry and reaction condition are rationally considered. The procedure is applied to the growth of alloyed HgSe1-xTex NPLs with various compositions. We report bright photoluminescence for all compositions. Because structural properties are now well defined, it is now possible to study the electronic properties of these objects. To do so, we combine k•p modeling of quantum confined structures with X-ray photoemission. In particular, we clarify the origin of the similarity of the absorption spectra of CdTe and HgTe NPLs, while bulk band structures are so different. Last, static and time resolved photoemission unveil a crossover from n-to p-type behavior in HgSe1-xTex NPLs while increasing the Te content.
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