Origin of the High-Frequency Shoulder in the Raman Spectra of CdSe Quantum Dots

12 August 2024, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

The origin of the high-frequency shoulder (HFS) observed above the longitudinal optical (LO) peak around 230 1/cm in the Raman spectra of CdSe quantum dots (QDs) has been a subject of intense debate. We use state-of-the-art ab initio density functional theory applied to small CdSe QDs with various realistic surface passivations and find an intense Raman signal around 230 1/cm, which corresponds to a stretching vibration of a defective twofold coordinated Se atom. We interpret this signal as being the origin of the HFS. Since the signal disappears in fully passivated and defect-free (magic size cluster) structures, it can be used as a fingerprint to distinguish defective from non-defective structures.

Keywords

Quantum Dots
Raman spectra
DFT
HFS
magic clusters
CdSe
nanoclusters
surface ligands

Supplementary materials

Title
Description
Actions
Title
Supporting Info
Description
The supporting information file contains the theoretical description of Raman intensity calculations, comparison of relaxed geometries (with Se-defect bond-lengths) of Cd$_{45}$Se$_{45}$ with MA and TOPO ligands and the Raman spectra of Cd$_{45}$Se$_{45}$\textbackslash CdS-PH core/shell showing the optical region of CdS shell which is not shown in the main text.
Actions
Title
Coordinate files for all investigated structures.
Description
coord.zip: The Cartesian coordinate (xyz) files for all structures under investigation.
Actions
Title
Vibration movies
Description
movies.zip: Movies of different vibrational modes.
Actions

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.