Energy Bands and Superlattice Formation in Titanium Diselenide

120 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.The superlattice formation in TiSe(,2) is related to a soft phonon mode near the zone boundary. This mode is supported by a coupling of the electrons at L and the holes at (GAMMA), which causes an anomalously large electronic susceptibility. When the transition occurs, a large portion of the Fermi surface gaps, new electronic states and energy-bands are formed, resulting in the lowering of the electronic energy. The 2a(,o) x 2a(,o) superlattice was directly observed by electron diffraction in dilute Zr-doped TiSe(,2) crystals. The phase transition is critically suppressed in the range 14-15% of Zr. The powerful technique of angle-resolved photoemission spectroscopy has been extended to low temperature. Changes in the energy band structure of TiSe(,2) due to superlattice formation were observed for the first time.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD