X-ray spectroscopic study of some chalcopyrites

The position, shape and extended fine structure of the copper K discontinuity in the chalcopyrites CuMS 2 (M=Al, Fe, Ga, In) and CuGaSe 2 have been studied, using a Cauchois type bent crystal X-ray spectrograph. From the chemical shifts of the X-ray absorption discontinuity it has been shown that the copper ion is monovalent in all these compounds. Levine's theory of ionicity has been used to calculate the various bond parameters for the chalcopyrites. It is found that there exists a linear relationship between the chemical shift Delta E and the ionic energy parameter C; so is the case between Delta E and the total energy parameter E g . From these two relations an empirical expression has been obtained between the chemical shift Delta E and the bond ionicity f i . The shapes of the copper absorption edge in these compounds have been explained on the basis of their band structure. The extended fine structure (EFS) has been interpreted on the model given by Chivate et al., whereby it has been shown that the covalencies of these systems are in the sequence CuGaSe 2 >CuInS 2 >CuGaS 2 >CuAlS 2 >CuFeS 2 . The EFS has also been discussed in the light of a recent theory given by Lytle, Sayers and Stern.