Chemically specific termination control of oxide interfaces via layer-by-layer mean inner potential engineering

Abstract

Creating oxide interfaces with precise chemical specificity at the atomic layer level is desired for the engineering of quantum phases and electronic applications, but highly challenging, owing partially to the lack of in situ tools to monitor the chemical composition and completeness of the surface layer during growth. Here we report the in situ observation of atomic layer-by-layer inner potential variations by analysing the Kikuchi lines during epitaxial growth of strontium titanate, providing a powerful real-time technique to monitor and control the chemical composition during growth. A model combining the effects of mean inner potential and step edge density (roughness) reveals the underlying mechanism of the complex and previously not well-understood reflection high-energy electron diffraction oscillations observed in the shuttered growth of oxide films. General rules are proposed to guide the synthesis of atomically and chemically sharp oxide interfaces, opening up vast opportunities for the exploration of intriguing quantum phenomena at oxide interfaces.

Dichotomy of the photo-induced 2-dimensional electron gas on SrTiO 3 surface terminations

“…Recent studies of RHEED patterns during growth have shown a variation of the inner potential between the two surface terminations 22 . In addition, scanning tunneling spectroscopy studies reveal a 0.25 eV shift in the conduction band onset between the two terminations 13 .…”

“…A similar alignment methodology is described in detail by H.Y. Sun et al 22 . We were able to observe large RHEED oscillations, as seen in (Fig.…”

Impact of Cation Stoichiometry on the Crystalline Structure and Superconductivity in Nickelates

“…Effect of cation stoichiometry on NdNiO3 films Taking the advantage of MBE technique, a series of NdNiO3 films with different Nd:Ni flux ratio were grown. For many perovskite oxides ABO3, the deposition time for each source can be extracted precisely using a shuttered mode [37,38], because the alternative growth of AO and BO2 monolayers leads to RHEED intensity oscillations with intensity saturating at the end of depositing one full atomic monolayer. However, the intensity doesn't saturate at the end of growing an atomic monolayer for NdNiO3.…”

Structural properties of ultrathin SrO film deposited on SrTiO3

“…SrO deposited on the surface has a different morphology respect to the ideal chemical termination that one could expect, and this could explain why the LAO/STO interface does not develop the 2DEG when the STO is terminated by SrO. It has been reported the possibility to grow STO by depositing alternating SrO and TiO 2 planes [33][34][35][36]. In this special case, the TiO 2 deposited on top of SrO forces the entire structure to reorganize like in the STO bulk, probably due to the strong covalent bonding of the oxygen octahedron which determine the lattice size.…”

“…It has been reported the possibility to grow STO by depositing alternating SrO and TiO 2 planes [33][34][35][36]. In this special case, the TiO 2 deposited on top of SrO forces the entire structure to organize like in the STO bulk, probably due to the strong covalent bonding of the oxygen octahedron which determine the lattice size.…”