ABSTRACT
It is well known that d-d* transitions of transition metals have a strong absorption coefficient and are responsible for coloration of several crystalline and non crystalline materials. Nickel is one of those and has several closely spaced excited energy levels in tetrahedral symmetry. In ZnSe crystal, the excited state Γ4 (1 G) lies very close to the bottom of the conduction band. Therefore, in Zn 1-x Ni x Se system, the transition Γ 1 (3 F) → Γ 4 (1G) combined with the band gap related transitions, absorb strongly the radiation higher than 1.98 eV. However, the region between energy state Γ 4(1G), Γ 5 (1G) is quite clean and the transmission coefficient is expected to be very high. Thus, this material could work as a window for 650 nm to 795 nm.With this view optical absorption spectra were examined for various temperatures and concentrations. As expected, the spectra show a narrow transmission range (1.6 to 1.9 eV) which is slightly shifted towards high energy side at low temperature. In short, Zn 1-x In x Se system is an adequate material for filter in the near IR region.
