Skip to Main content Skip to Navigation
Theses

Synthèse de nanoplaquettes épaisses de chalcogénures de cadmiumet étude des propriétés électroniques de nanoplaquettes de tellure de mercure

Abstract : Cadmium chalcogenide nanoplatelets II-VI semiconductors. Their thickness is controlled at the atomic scale with extreme narrow optical features. These materials are few hundreds of nanometers in length and wide with a few nanometers thickness.When passivated by halides, using a CdX2 (X = Cl, Br, I) precursor at room temperature, the CdSe 3 monolayers nanoplatelets surface energy decreases. On heating at mild temperature (160 °C), CdSe monomers dissolve from the edges and recrystallize on the wide facets. Here, nanoplatelets become a chalcogenide reservoir. The modification of the surface chemistry allows then to obtain thickernanoplatelets up to 9 monolayers and monodisperse. The versatility of the method has been proven on other cadmium chalcogenides. Thanks to the comprehension of the dissolution/recrystallization process we developed a new tool to grow shells with controlled thickness. Homo- and heterostructures have been grown by this method. For the very first time, a CdTe layer has been grown on CdSe andCdTe core NPLs. Unique stepped nanoplatelets have also been synthesized. These amazing materials are the first exemple of stress free semiconductors homostructures with confinement-induced intraparticle type I energy level alignment.The comprehension of the electronic structure of HgTe nanoplatelets was also addressed. We systematically studied the phase diagram in function of the confinement, pressure and temperature. Our results show that with pressure, nanoplatelets (strong confinement) and nanocrystals (weaker confinement) of HgTe have a similar behavior than the bulk : the gap increases with the pressure.However, the confinement regime becomes a key factor in function of temperature. When it is decreased from 300 K to 10 K, the gap decreases for large nanocrystals. This trend is less important when nanocrystals are smaller. The gap even decreases for the most confined materials which are the nanoplatelets. The modelisation of this effect showed that the second conduction band bends the firstone when the temperature is decreased.
Document type :
Theses
Complete list of metadata

https://pastel.archives-ouvertes.fr/tel-03609431
Contributor : ABES STAR :  Contact
Submitted on : Tuesday, March 15, 2022 - 3:26:08 PM
Last modification on : Friday, June 24, 2022 - 3:09:05 AM
Long-term archiving on: : Thursday, June 16, 2022 - 6:41:49 PM

File

ESPCI_NicolasMOGHADDAM_2021.pd...
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-03609431, version 1

Citation

Nicolas Moghaddam. Synthèse de nanoplaquettes épaisses de chalcogénures de cadmiumet étude des propriétés électroniques de nanoplaquettes de tellure de mercure. Matériaux. Université Paris sciences et lettres, 2021. Français. ⟨NNT : 2021UPSLS090⟩. ⟨tel-03609431⟩

Share

Metrics

Record views

90

Files downloads

33