BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//RLASKEY//CALENDEROUS//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
DTSTAMP:20261021T123200Z
LAST-MODIFIED:20140505T194045Z
DTSTART:20140519T170000Z
DTEND:20140519T180000Z
UID:event1282@bu.edu
URL:http://physics.bu.edu/internal/events/show/1282
SUMMARY:Study of the Electronic Structure of Transition-metal Oxides by Syn
	chrotron-based X-ray Spectroscopies
DESCRIPTION:Featuring Bo Chen\n\nPart of the PhD Final Oral Exams.\n\nDisse
	rtation Committee: Richard Averitt\, Kevin Smith\, Karl Ludwig\, Anders San
	dvik\, Scott Whitaker\n\nDissertation Abstract:\nTransition-metal oxides (T
	MOs) display numerous fascinating and complex properties\, such as mixed-va
	lency\, low dimensionality\, lattice distortion\, and phase transition\, et
	c. These properties arise from the partially filled d- or f-electron shells
	 of TM cations and are often accompanied by the intriguing interplay betwee
	n degrees of freedom. To understand the complexity of d-electron TMOs\, thi
	s thesis is primarily focused on studying their underlying electronic struc
	ture using x-ray absorption spectroscopy (XAS)\, x-ray emission spectroscop
	y (XES)\, x-ray photoemission spectroscopy (XPS)\, and resonant inelastic x
	-ray scattering (RIXS). The measurements at the O K- and TM L-edges are ach
	ieved by taking advantage of high-flux and high-resolution synchrotron radi
	ation light with tunable monochromatic photon energy. \nFour electronically
	 and structurally distinctive oxides are selected as representative TMOs fo
	r investigation in this thesis. To begin with\, through a comparative study
	 of WO3 and Na0.67WO3 crystals\, the narrowing of conduction band is observ
	ed with Na doping and the core-hole energy shift in the O K-edge XAS proces
	s is experimentally determined. Indirect and direct band gaps of photoanode
	 WO3 are measured from the resonant XES with polarization-dependent experim
	ental geometry. The other sodium bronze studied is quasi-one-dimensional β
	-Na0.33V2O5 polycrystalline film. The film stoichiometry\, preferential ori
	entation\, and orbital anisotropy are well characterized by a variety of ph
	oton and electron techniques and compared to density-functional theory (DFT
	) calculation. The V 3d orbital splitting of β-Na0.33V2O5 is surveyed by t
	he V L-edge RIXS and compared with isoelectronic β-Sr0.17V2O5 regarding di
	stortions to VO6 octahedra.\nFurthermore\, the complex electronic structure
	 of Mott insulators La1-xLuxVO3 is investigated to understand their spin-or
	bital phase diagram. The effects of rare-earth size on the O 2p hybridizati
	on states and the local crystal field of VO6 octahedron are found to agree 
	with the prediction of DFT calculation and the evolution of crystal structu
	re. The changes of experimental spectra with temperature are associated wit
	h Jahn-Teller distortion and orbital ordering due to structural phase trans
	ition. Lastly\, the band structure and low-energy excitations of spinel MnV
	2O4 are explored using soft x-ray spectroscopies and theoretical calculatio
	ns. The presence of Hubbard bands and the mixing between V and Mn 3d states
	 are suggested both experimentally and theoretically. \n\n\n![Bo Chen](/res
	ources/event-image/1282/78a4d5e_small)
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
END:VEVENT
END:VCALENDAR