Behaviour of Litihium Atoms InIII in Doped Znse

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Addis Ababa University


This thesis work focuses at investigating the behaviour of diffused Lithium atoms into the II-VI semiconductor ZnSe doped with the radioact ive dopant 111 In using the PAC (perturbed <r<r angular correlation) technique. The atomistic information about defects surrounding the probe atom can be obtained using this technique. Inorder to investigate the p-doping problems in ZnSe, PAC experiments were conducted on ZnSe after diffusion with the potential p-type dopant Li thium using the PAC spectroscopy. Obviously, it was found much more difficult to prepare a p-type sample by doping ZnSe with Lithium atoms. The failure of p-doping after doping with Lithium may be associated with the diffusion mechanism which prevents the Lithium atoms from occupying lattice sites in the metal sublattice, a necessary condition for Lithium to act as an acceptor. However, Lithium induced effects were properly investigated through special experimental treatments and the various dependence of the diffusion of Lithium on the matrix temperature and the vapour pressure of Li thium were noted. From the PAC experiments, it was observed that Li thium diffusion introduces vacancies in the metal sublattice which are observed by their pairing with the In probe atom. The generation of In Zn- VZn pairs is known to occur if both the sample and the Lithium source are held at temperatures exceeding a characteristic value. A better understanding of the mechanism of vacancy creation during LI incorporation might also shed new light on the problem of the missing p-type conductivity after LI-diffusion



Atoms in 111in Doped Znse