Zinc selenide (ZnSe) having  direct and wide band gap  belonging to II–VI compound semiconductor [] and keeps optical band gap (E_g) of 2.6 eV at 〖20〗^o C (room temperature) []. ZnSe linked with class of chalcogenides, which is a favorable material for the fabrication of blue and green Light Emitting Diode (LED) []. ZnSe based laser diodes have been successfully verified by Harris Liao et al. [] as it can be operated in a continuous wave mode at 〖20〗^o C (room temperature). ZnSe with very low absorption for wavelengths between 0.63 μm to 18 μm and used for infrared windows, lenses and prisms.
Synthesis of ZnSe:
ZnSe Synthesis was described by many researchers []. The simple chemical reaction method proposed by Junli Wang and Qing Yang [] was followed in this work to synthesis ZnSe at 〖205〗^0C. 1.1 mmol of ZnCl2 (0.765 g) and 1 mmol of selenium metal powder (0.395 g) were taken in a Teflon lined stainless steel autoclave (250 ml capacity). 100 ml of absolute ethanol and 100 ml of olic acid were added to the autoclave. Then the autoclave was closed tightly and placed in the hot furnace maintained at 〖205〗^0C for 24 hours. After 24 hours the autoclave was cooled to room temperature and the precipitated product was separated from the solution by filtering. The product material was washed in distilled water and in absolute ethanol (5 times) subsequently. Finally the product was dried in oven at 〖60〗^0C for 1 hour ZnSe powder was subjected to the powder X-ray diffraction (XRD) studies and the XRD peaks are shown in Fig. 1. The peaks were indexed with PowderX software and compared with the standard JCPDS card file No. 37-1463 (space group F43m) which confirmed the formation of ZnSe in cubic crystal system (a = b = c = 5.668 Å). X-ray diffraction pattern showed that the synthesized material has relatively strong orientation along (111) direction. In addition to ZnSe peaks there are some additional peaks due to the formation of ZnO phase (JCPDS card file No. 89-1397) marked with asterisks symbol. Thus the prepared compound has mixed phases of ZnSe and ZnO. The crystallite size (G) of the synthesized powder was expected using the Scherrer’s formula
G=0.9λ/βcosθ                      (1)
where, λ is the wavelength of CuKα1 radiation (λ = 1.5405 Å), β is the full-width at half maximum (FWHW) of the intensity of the corresponding peak and θ is half the angle between the incident and the scattered X-ray beams. From the calculated crystalline size, presented in Table 1, it is clear that the crystallite size of the synthesised ZnSe is in the order of a 10-31nm.