TRIGONAL MANGANESE CLUSTER IN SILICON - AN ELECTRON-PARAMAGNETIC-RESONANCE STUDY

Besides the known tetrahedral Mn4(0) cluster, a second Mn cluster is o bserved by electron paramagnetic resonance in high-resistivity silicon doped with manganese. The spectrum shows trigonal symmetry. The analy sis of the fine structure and the hyperfine structure suggests that th e spectrum is due to a cluster consisting of four Mn ions forming a te trahedron, [Mn3i0-Mn(i)x], where the fourth Mn(x) ion gives rise to th e trigonal symmetry. Most likely it is either a Mn- ion at an intersti tial site or a Mn+ ion at a substitutional site. The [Mn3i0-Mn(i)-] cl uster model is favored. The observed S = 11/2 ground-state manifold is the result of the dominant exchange coupling between the electronic s pins of the four Mn constituents. The coordination of four ions in a t etrahedron seems to be an energetically preferred state during the for mation of bigger clusters in the silicon lattice.