Phonons of Atomically Thin ZnSe Nanoplatelets Grown by the Colloidal Method

• Published in: Journal of physical chemistry. C Vol. 127; no. 27; pp. 13112 - 13119
• Main Authors: Basalaeva, Lyudmila S., Grafova, Valeria P., Duda, Tatyana A., Kurus, Nina N., Vasiliev, Roman B., Milekhin, Alexander G.
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.07.2023
• Subjects: C: Spectroscopy and Dynamics of Nano, Hybrid, and Low-Dimensional Materials
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.3c02111

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.