Nanotwinning and structural phase transition in CdS quantum dots

• Published in: Nanoscale research letters 2012-10, Vol.7 (1), p.584-584, Article 584
• Main Authors: Kumar, Pragati, Saxena, Nupur, Chandra, Ramesh, Gupta, Vinay, Agarwal, Avinash, Kanjilal, Dinakar
• Format: Article
• Language: English
• Subjects: Chemistry and Materials Science; International Conference on Superlattices; Materials Science; Molecular Medicine; Nano Express; Nanochemistry; Nanodevices (ICSNN 2012); Nanoscale Science and Technology; Nanostructures; Nanotechnology; Nanotechnology and Microengineering
• ISSN: 1556-276X; 1931-7573; 1556-276X
• DOI: 10.1186/1556-276X-7-584

Nanotwin structures are observed in high-resolution transmission electron microscopy studies of cubic phase CdS quantum dots in powder form by chemical co-precipitation method. The deposition of thin films of nanocrystalline CdS is carried out on silicon, glass, and TEM grids keeping the substrates at room temperature (RT) and 200°C by pulsed laser ablation. These films are then subjected to thermal annealing at different temperatures. Glancing angle X-ray diffraction results confirm structural phase transitions after thermal annealing of films deposited at RT and 200°C. The variation of average particle size and ratio of intensities in Raman peaks I 2LO / I 1LO with annealing temperature are studied. It is found that electron-phonon interaction is a function of temperature and particle size and is independent of the structure. Besides Raman modes LO, 2LO and 3LO of CdS at approximately 302, 603, and 903 cm −1 respectively, two extra Raman modes at approximately 390 and 690 cm −1 are studied for the first time. The green and orange emissions observed in photoluminescence are correlated with phase transition.