Calculation of lattice vibrational and thermal properties of cadmium sulfide nanocrystal and growth preference of cadmium sulfide powder during microwave‐hydrothermal process

Abstract

CdS nanocrystal is investigated by first-principles calculations and experiments. Based on phonon spectra, the wurtzite CdS structure is thermodynamically stable. Debye temperature, specific heat capacity and thermal expansion coefficient are calculated to be 221.51 K, 47.68 JÁmol À1 ÁK À1 and 1.95Â10 À4 K À1 , respectively. Band gaps of CdS single crystal and monolayer CdS supercell calculated by GGA-mBJ function are 2.74 eV and 2.38 eV. CdS powder is synthesized by microwave-hydrothermal process (140 C + 15 min), with particle size ranging from 50 to 1000 nm. HRTEM shows the nanocrystal distance of 6.676 Å between the (0001) crystal faces and growth preference along the [002] direction. The band gap of CdS thin film evaluated by UV-Vis absorption spectra is 2.41 eV, close to 2.38 eV of monolayer supercell, which provides theoretical basis for CdS doping to improve photoanode performance of piezoelectric semiconductors.

Temperature-Dependent Photoluminescence of CdS/ZnS Core/Shell Quantum Dots for Temperature Sensors

“…Equation ( 1) is first proposed for infinite crystals; it can still be used to analyze bulk semiconductors and QDs. The α and β values of CdS/ZnS core/shell QDs are obtained to be 1.84 × 10 −4 eV/K and 230 K, which are analogue to those for bulk CdS materials (α = 3.3 × 10 −4 eV/K, β = 221 K) [31,32]. This shows that the main emission in CdS/ZnS core/shell QDs comes from the recombination of holes and electrons near the band edge of CdS core.…”