Confined transverse-optical phonons in ultrathin CdTe/ZnTe superlattices

In this work, the phonon spectra of atomically thin ZnSe nanoplatelets (NPLs) were studied using Raman and infrared spectroscopies. Atomically thin ZnSe NPLs were grown on the Si substrate covered with a 100 nm thick gold layer by the colloidal method in the temperature range of 100−170 °C. The triangular and rectangular NPLs with 2.5-and 4-monolayer thicknesses, respectively, were synthesized, as determined by atomic force microscopy (AFM) measurements. Longitudinal optical (LO) and transverse optical (TO) phonon modes in ZnSe NPLs were found at 198 and 252 cm −1 , respectively, and the surface optical phonon mode was observed at about 216 cm −1 . The LO and TO phonon modes revealed the opposite frequency shifts with increasing growth temperature. The effect was induced by the phonon confinement, and it confirmed the formation of NPLs of different thicknesses. Comparing the frequency positions of longitudinal and TO phonon modes confined in ZnSe NPLs with the data on the dispersion of optical phonons in bulk ZnSe, the thickness of the NPLs formed at a low temperature was derived as 0.567 nm, correlating well with the AFM results.

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“…The latter is not unique; similar positive dispersion was found, e.g. , for TO phonons for ultrathin CdTe layers …”

Section: Resultssupporting

confidence: 70%

Phonons of Atomically Thin ZnSe Nanoplatelets Grown by the Colloidal Method

et al. 2023

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“…For the case of a ZnTe/CdTe/ZnTe QW in the revised references we have not found results equivalent to those of Ref. [22] and, therefore, we think our work could serve as a motivation for making the corresponding measurements.…”

Section: Article In Presscontrasting

confidence: 47%

“…[22], where a superlattice (SL) of CdTe/ZnTe was investigated by using far-infrared reflectivity spectroscopy, and results concerning the polar optical phonons are reported. Of course, the results provided by this reference involve the SL case, and cannot be accurately compared with ours.…”

Section: Article In Pressmentioning

confidence: 99%

Polar optical phonons in a semiconductor quantum-well: The complete matching problem

Nieto

Comas

2007

Physica B: Condensed Matter

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“…As can be seen, values of ω TO are like in the strained bulk ZnTe [12,13]. Values for ω LO are even lower than in the strained bulk, where ω LO is 203-208.5 cm −1 , according to Refs.…”

Section: Resultsmentioning

confidence: 91%