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.

Influence of Ag doping concentration on structural and optical properties of CdS thin film

“…It reveals that CdS film shows broad green emission (GE) centered at 2.35 eV. The origin of GE at this position is attributed to the transition of S-vacancy (V S ) donors to the valence band and conduction band to S-interstitial (I S ) 9,12,13 . It is expected that some sulfur vacancies may be created during deposition at substrate temperature 200 °C as XPS study reveals that film is sulfur deficient.…”

“…The origin of YE is ascribed to the recombination via surface localized states, radiative transition from donor levels i.e. Cd atoms located in interstitial sites (I Cd ) to the valence band 9,12-14 , or the transition from interstitial cadmium-cadmium vacancy complexes which is a donor to acceptor level transition 9,12,13 . The cause of YE in doped films may be either due to I Cd , ( ) or due to the trap level created by dopant ions near the bottom of conduction band and top of valance band.…”

Effect of electrolytes on photoelectrochemical performance of a CuS–CdS heterojunction

“…The photoluminescence (PL) study is focussed on different energy states available between the valence and conduction bands, which are responsible for radiative recombination [17]. Figure 6 shows the room-temperature PL spectra of CuS, CdS and CuS-CdS heterojunctions.…”

Structural tuning of CdS nanoparticles with nucleation temperature and its reflection on the optical properties

“…Cd/Zn chalcogenides crystalize either in hexagonal wurtzite or cubic zinc blend structure. Biphasic CdS was reported with different synthesis methods [7][8][9]. When dealing with nano or quantum dots chalcogenides, the diffraction peaks are broad and heavy overlapping of peaks may occur.…”