title: Nanotwinning and structural phase transition in CdS quantum dots.
abstract: 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 I2LO/I1LO 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.
authors.affiliation: Department of Physics, Bareilly College, Bareilly, Uttar Pradesh, 243005, India. pkumar.phy@gmail.com.
authors.forename: Pragati
authors.initials: P
authors.lastname: Kumar
authors.forename: Nupur
authors.initials: N
authors.lastname: Saxena
authors.forename: Ramesh
authors.initials: R
authors.lastname: Chandra
authors.forename: Vinay
authors.initials: V
authors.lastname: Gupta
authors.forename: Avinash
authors.initials: A
authors.lastname: Agarwal
authors.forename: Dinakar
authors.initials: D
authors.lastname: Kanjilal