SPEAKER: Yangang Liang
Advisor: I. Takeuchi
TITLE: W-doped VO2 thin films prepared by a combinatorial method for Li-ion battery applications
ABSTRACT: Vanadium dioxide (VO2) has been extensively studied due to its fully reversible first-order metal-insulator transition (MIT) associated with a structural phase transition at about 68 °C. For potential wider applications in rechargeable lithium batteries, we systematically studied the structural phase transition and the electronic properties of composition spread V1-xWxO2 (0 ≤ x ≤ 0.037) thin films fabricated on silicon (001) and c-cut sapphire substrates through combinatorial pulsed laser deposition of a VO2 target and a WO2 target. Electrical transport results show that both the phase transition temperature and the width of the hysteresis loop decrease with the increasing of the concentration of tungsten. Especially, epitaxial V1-xWxO2 films fabricated on c-cut sapphire substrates show narrower hysteresis loop compared to textured V1-xWxO2 films fabricated on Si (100) substrates. In addition, we also studied the effects of substrate and temperature on the crystal structures of V1-xWxO2. Moreover, their potential use as cathodes materials for rechargeable lithium batteries is investigated.
SPEAKER: Pampa Sarkar
Advisor: R. Greene
TITLE: Nernst effect in electron doped cuprate superconductor La2-xCexCuO4
ABSTRACT: For nearly three decades, high TC cuprate superconductors have gained much scientific attention to understand the pairing mechanism of superconductivity. We will discuss about the Nernst signal measurements of epitaxial thin film of La2-xCexCuO4 from underdoped (x = 0.08) to overdoped (x = 0.16) samples for a wide range of temperature above TC. These measurements will be related to our present understanding of the normal state and superconductivity in the cuprates.