ABSTRACT
CdS nanoribbons with various cross sections offer the opportunity to deeply understand the interaction between optical cavity and spontaneous emission. Herein, long tapered nanoribbons with the cross sections gradually changing were synthesized by a simple physical vapour deposition method. Morphology dependent micro-region photoluminescence (PL) spectroscopy is employed to show Purcell effect along different low symmetry cross sections. Spikes on the PL spectra reveal that local density of optical modes increases when the mode match happens between optical cavity and spontaneous emission. Bound exciton complex related amplified spontaneous emission is observed in a single CdS nanoribbon with well-defined elliptical cross sections and optimized width/thickness ratio â¼1.45. Polarized Raman and TEM confirmed that the nanoribbon with the elliptical cross section adopts the [0002] growth direction with good quality. The results suggest that the cross section resonant cavity would be of importance for both fundamental and practical application of cavity quantum electrodynamics in CdS nanoribbon.
ABSTRACT
Nanocrystalline Gd2O3 doped with europium was synthesized by the low-temperature combustion method. By using the X-ray diffraction (XRD), high resolution transmission electron microscopy( HRTEM), and fluorescence spectrophotometer, the structural, morphological and luminescence properties of the nanocrystal were investigated. The results show that by varying the glycine-to-metal nitrate (G/M) molar ratio and the annealing temperature, nanocrystalline Gd2O3: Eu3+ with different structure and grain size could be achieved. The structure changed from cubic to monoclinic with the increment of G/M ratio after the samples had been calcined at 800 degrees C for 0.5 hour. When the G/M ratio was 0.83 and 1.0, the nanosized and pure cubic phase Gd2O3: Eu3+ was produced. The crystalline size became bigger with increasing the annealing temperature. The grain size was about 10-30 nm. The main emission peak in cubic Gd2O3: Eu3+ nanocrystal was at 612 nm(the (5)D0-->F2 transition). In addition, a red shift for charge transfer state occurred in the excitation spectrum.
