NATURE OF THE ABSORPTION-BANDS IN ZN1-XCOXS

To study the nature of the absorption bands in Zn1-xCoxS single crystals, optical absorption measurements were made on samples with cobalt composition x = 0.03 and 0.05 as a function of temperature in the wavelength region between 400 and 3000 nm. Each spectrum showed three well-defined absorption bands below the fundamental absorption gap, corresponding to transitions from the fundamental 4A2(4F) ground state to the 4T1(4F), 4T2(4F) and 4T1(P) excited states. Besides these main bands, the infrared region has a series of small peaks. In the visible region, just below the onset of the band edge, there is a well-defined structure related to electronic transitions from the 3d shell of the cobalt ion.