Raman Analysis of Nanocrystals Based on Zinc Selenide

Abstract

This paper presents the results that were synthesized by nanocrystals based on zinc selenide by thermal synthesis and studied using micro-Raman spectroscopy before and after thermal annealing at 800 ℃ and 1000 ℃. The heat treatment of the synthesized samples was carried out in the AVERON electric vacuum furnace, lasting 60 minutes. The optical properties of the samples – photoluminescence (PL) and raman spectra – have been studied. Photoluminescence spectra were measured at room temperature using a CM2203 spectrofluorimeter. Raman spectra were measured using a Raman spectrometer (NT-MDT). The spectrometer used a solid-state laser with a wavelength of 473 nm. Raman spectra of zinc selenite (ZnSeO3) nanocrystals before annealing showed modes 665, 695, 825 and 973 cm−1. After thermal annealing, a downward shift of peaks was observed. In addition, the Raman spectra showed LO shifts with the duration of the deposition time. The Raman spectra of zinc selenide at room temperature showed the main peaks at 199, 247, 498 and 501 cm−1. During heat treatment of ZnSe at 800 °C and 1000 °C, an expansion of asymmetry was observed for horizontal optical (TO)-phonon and longitudinal optical (LO)-phonon modes with an increase in annealing temperature and redshifts in the shapes of Raman lines. The photoluminescence spectra of zinc selenide, depending on temperature, were represented by wide bands located at wavelengths of 350–650 nm. The PL spectra were recorded at room temperature from 300 to 800 nm in 5 nm increments using a xenon lamp. Zinc selenide before heat treatment showed photoluminescence bands at 1.93, 2.3, 2.56, 2.75 and 2.97 eV. The volume radiation of ZnSe at the boundary of the nearest band corresponded to the band of strong radiation at 2.84 eV. 3.2 eV is associated with the absorption of ZnO nanoparticles through the edge of the band. ZnSeO3 samples before annealing show one wide band of photoluminescence in the blue region of the electromagnetic spectrum about 2.82 eV. After thermal annealing at 1000 °C, a transition to a longer wave region with a wavelength of 2.86 eV is observed. Since thermal annealing is suitable for crystallization, it has led to an increase in luminescent efficiency. 60 minutes of high-temperature firing of the samples resulted in a loss of Se due to the effect of temperature on the zinc selenide content. Thermal combustion of zinc selenide-based nanocrystals was characterized by an increase in FWHM and a decrease in intensity in the photoluminescence spectra with increasing temperature.