Light scattering study of the diluted magnetic semiconductors zinc(1-x) cobalt(x) selenide and zinc(1-x) iron(x) selenide.

摘要

Crystal field and Band theories provide good descriptions of electrons in the localized and itinerent limits. The 4f and outer s,p electrons are examples of carriers in a solid classified under these respective schemes. In doped semiconductors such as Si:P, the excess electrons approximate as s-like discrete hydrogenic levels that broaden into a band beyond a critical concentration leading to insulator-metal transitions. On the other hand, d-electrons, as realized in diluted magnetic semiconductors (DMS) have intraatomic interactions of intermediate strength and generally fall between these oppositing limits. The interactions between 3d levels can be varied through choice of magnetic dopants as Mn, Fe and Co that are characterized by very different s,p-d and d-d interactions. Further, since the d-level impurity does not provide an excess carrier to the II-VI host lattice, these DMS compounds generally remain insulating. In this thesis, I will discuss the effects of the enhanced exchange interactions, the disorder and the influence of external pressure on the emission spectra and lattice vibrations in both {dollar}rm Znsb{lcub}1-x{rcub}Cosb{lcub}x{rcub}Se{dollar} and {dollar}rm Znsb{lcub}1-x{rcub}Fesb{lcub}x{rcub}Se.{dollar}