Evaluation of the dielectric function of colloidal Cd1−xHgxTe quantum dot films by spectroscopic ellipsometry

• Published in: Applied surface science Vol. 421; pp. 295 - 300
• Main Authors: Bejaoui, A., Alonso, M.I., Garriga, M., Campoy-Quiles, M., Goñi, A.R., Hetsch, F., Kershaw, S.V., Rogach, A.L., To, C.H., Foo, Y., Zapien, J.A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2017
• Subjects: Cd1 − xHgxTe; Colloidal quantum dots; Dielectric function; Ion exchange; Spectroscopic ellipsometry; Dielectric function; Colloidal quantum dots; Spectroscopic ellipsometry; Ion exchange; Cd1−xHgxTe
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.09.070

[Display omitted] •Structural and optical investigation of layer-by-layer films with CdHgTe quantum dots.•Determination of the dielectric function of the quantum dots from 0.7 to 6.5eV.•Taking into account surface roughness, the same dielectric function fits all films.•Quantum-confinement-related blue-shifts of interband transitions are observed. We report on the investigation by spectroscopic ellipsometry of films containing Cd1−xHgxTe alloy quantum dots (QDs). The alloy QDs were fabricated from colloidal CdTe QDs grown by an aqueous synthesis process followed by an ion-exchange step in which Hg2+ ions progressively replace Cd2+. For ellipsometric studies, several films were prepared on glass substrates using layer-by-layer (LBL) deposition. The contribution of the QDs to the measured ellipsometric spectra is extracted from a multi-sample, transmission and multi- angle-of-incidence ellipsometric data analysis fitted using standard multilayer and effective medium models that include surface roughness effects, modeled by an effective medium approximation. The relationship of the dielectric function of the QDs retrieved from these studies to that of the corresponding II–VI bulk material counterparts is presented and discussed.