Fluorescence XAFS analysis of local structures in iodine-doped Zn_1-xCr_xTe

Abstract

Abstract. Geometric structures for II-VI diluted magnetic semiconductor iodine-doped Zn 1-x Cr x Te films (x = 0.05) grown by molecular-beam epitaxy with high-temperature ferromagnetism were investigated by using fluorescence x-ray absorption fine structure (XAFS) measurement in order to elucidate the relationship between the geometric structure and the magnetic properties. The XAFS analysis has revealed that the local structures around Cr atoms are dependent on the growth temperature. For the samples grown at 360 and 390 °C, the majority of Cr atoms are tetrahedrally coordinated to Te atoms, indicating the formation of substitutional Cr on Zn-site in ZnTe lattice and/or zinc-blende (ZB) CrTe. On the contrary, for the samples grown at 300 and 330 °C the additional formation of secondary phases such as CrTe compounds was suggested. Therefore, it is deduced that the formation of secondary phase such as Cr-Te compounds are related to the increase of Curie temperature. The XAFS analysis has also revealed that the local structures do not depend on the I concentration. For the samples with different I concentrations, the Cr atoms form substitutional Cr on Zn-site in ZnTe lattice and/or ZB CrTe, corresponding to the result of TEM measurement.

Spinodal nanodecomposition in semiconductors doped with transition metals

“…On the other hand, as shown in the Cr mapping images (right column), the Cr distribution is inhomogeneous in all the films, but the degree of inhomogeneity seems to be slightly reduced with the increase of T g . The results of XAS measurements at Cr K-edge for the same series of I-doped Zn 1−x Cr x Te (x 0.05) films suggested a change in the local crystallographic structure depending on the substrate temperature (Ofuchi et al, 2009), which is correlated with the results of the TEM observation.…”