Fabrication and Characterization of LaOBr:Eu3+ Luminescent Nanofibers

LaOBr:Eu3+ nanofibers have been successfully fabricated by electrospinning combined with a double-crucible bromination technique using cetyltrimethylammonium bromide (CTAB) powers as bromine source. The products were characterized in detail by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and fluorescence spectroscopy. The results indicate that LaOBr:Eu3+ luminescent nanofibers are tetragonal in structure with space group P4/nmm. The diameter of LaOBr:Eu3+ luminescent nanofibers is ca. 150 nm. Fluorescence spectra analysis shows that under the excitation of 302-nm ultraviolet light, the LaOBr:Eu3+ nanofibers exhibit red emission centering at 620 nm, which is attributed to the 5D0→7F2 energy levels transitions of Eu3+ ions.

Growth of Semi-Insulating GaAs Crystal with Uniform Si Doping

An improved double crucible method of melt replenishing to counteract the dopant segregation effect in order to grow homogeneous doped GaAs crystals is brought forward, and its validity and feasibility are demonstrated by analytical and numerical study. The numerical results show that the new method can suppress the increase of dopant concentration near the growth interface and can maintain the homogeneity of dopant distribution along the radial direction. The positions of replenishing melt exit almost have no effects on the axial and radial distribution homogeneity of dopant Si in the crystal. So the new method has many distinct advantages: it can improve the crystallization rate and size, the operation is flexible, etc.