Synthesis, Crystal Growth, and Annealing of CdSxSe1–x and Cr:CdS0.8Se0.2 Single Crystals

Mid-infrared laser in the 2-5 μm wavelength region is in the atmospheric transmission window range, and hence, it has important application prospects in the fields of optoelectronic countermeasures, space communication, environmental remote sensing, and molecular spectroscopy. One of the most promising technological approaches to achieve mid-infrared laser output is based on direct lasing of transition-metal (TM)-doped II-VI chalcogenide crystals. In this work, CdSxSe1-x and Cr:CdS0.8Se0.2 polycrystals were synthesized by a chemical vapor synthesis method from a stoichiometric mixture of vacuum-sublimed CdS and CdSe. The structure of the synthesized products was analyzed by X-ray diffraction (XRD). Using these synthesized products, CdSxSe1-x and Cr:CdS0.8Se0.2 single crystals were grown by the physical vapor transport (PVT) method. After annealing, the band gap becomes smaller and the transmission range widens to 17 μm. The composition of the single crystals was determined by energy-dispersive spectrometry (EDS) mapping and XPS, and it was found to be uniform throughout the ingot. In addition, the absorption peak maximum for the Cr2+ ion in the Cr:CdS0.8Se0.2 crystal is at 1.84 μm.