Optical properties of CdS nanoparticles upon annealing

• Published in: Physica. E, Low-dimensional systems & nanostructures Vol. 31; no. 1; pp. 93 - 98
• Main Authors: Sivasubramanian, V., Arora, A.K., Premila, M., Sundar, C.S., Sastry, V.S.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 2006; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electron–phonon interaction; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Frohlich mode and photoluminescence; Nanocrystals and nanoparticles; Nanoparticles; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures; Physics; Specific phase transitions; Structural transitions in nanoscale materials; 61.46.+w; Nanoparticles; 78.55.−m; 78.30.−j; Frohlich mode and photoluminescence; Electron–phonon interaction; 61.46.+W; 78.30.-j; Cubic lattices; Raman spectra; Annealing; 78.55.-m Nanoparticles; Semiconductor materials; Metastable phases; Chemical precipitation; Blende structure; Phase transformations; Cadmium sulfides; Photoluminescence; Electron-phonon interaction; XRD; Electron-phonon interactions; Infrared spectra; Optical properties; Wurtzite structure; Absorption spectra; Surface phonons; Nanocrystal
• ISSN: 1386-9477; 1873-1759
• DOI: 10.1016/j.physe.2005.10.001

The metastable cubic phase of CdS has been found to be stabilized in the form of nanoparticles. Zinc-blende to Wurtzite structural transformation of CdS nanoparticles, synthesized using chemical precipitation, was investigated using X-ray diffraction (XRD), Raman, photoluminescence (PL) and infrared (IR) absorption spectroscopy. The nanocrystalline powder was annealed in argon atmosphere in the temperature range 473–773 K for 2 h at each temperature. The hexagonal fraction increased monotonically during annealing and the shape of the particle becomes anisotropic. PL spectra exhibited a marginal decrease in peak position for annealing up to 573 K and then an increase. In Raman spectra, the intensity of 1-LO phonon decreases while that of 2-LO phonon increases indicating an increase in electron–phonon interaction with increase in particle size. In addition to the Frohlich surface optical phonon mode and TO phonon mode, a new mode at 195 cm −1 is found in IR spectra, which is attributed to a defect-activated zone-boundary phonon. The changes in the optical properties are attributed to those arising from particle growth and structural transformation.