Xiaoxing Xi (Temple): Cracking the Nanophysics of Oxide Interface and Heterostructures with Atomic Layer-by-Layer Laser MBE
Advancements in nanoscale engineering of oxide interfaces and heterostructures have led to discoveries of emergent phenomena and new artificial materials. Combining the strengths of reactive molecular-beam epitaxy and pulsed-laser deposition, we show that atomic layer-by-layer laser molecular-beam epitaxy (ALL-Laser MBE) significantly advances the state of the art in constructing oxide materials with atomic layer precision. Using Sr1+xTi1-xO3 as example, we demonstrate the effectiveness of the technique in producing oxide films with stoichiometric and crystalline perfection. With the growth of La5Ni4O13, a Ruddlesden-Popper phase with n = 4 that has never been reported in the literature, we demonstrate that ALL-Laser MBE allows us to push the equilibrium thermodynamic boundary further. By growing LaAl1+yO3 films of different stoichiometry on TiO2-terminated SrTiO3 substrate at high oxygen pressure, we show that the behavior of the two-dimensional electron gas at the LaAlO3/SrTiO3interface can be quantitatively explained by the electronic reconstruction mechanism. In LaNiO3 films on LaAlO3 substrate with LaAlO3 buffer layer, we observed the metal insulator transition in 1.5 unit cells, which is driven by oxygen vacancies in addition to epitaxial strain and reduced dimensionality.