Zintl layer formation during perovskite atomic layer deposition on Ge (001).
Using in situ X-ray photoelectron spectroscopy, reflection high-energy electron diffraction, and density functional theory, we analyzed the surface core level shifts and surface structure during the initial growth of ABO3perovskites on Ge (001) by atomic layer deposition, where A = Ba, Sr and B = Ti, Hf, Zr. We find that the initial dosing of the barium- or strontium-bis(triisopropylcyclopentadienyl) precursors on a clean Ge surface produces a surface phase that has the same chemical and structural properties as the 0.5-monolayer Ba Zintl layer formed when depositing Ba by molecular beam epitaxy. Similar binding energy shifts are found for Ba, Sr, and Ge when using either chemical or elemental metal sources. The observed germanium surface core level shifts are consistent with the flattening of the initially tilted Ge surface dimers using both molecular and atomic metal sources. Similar binding energy shifts and changes in dimer tilting with alkaline earth metal adsorption are found with density functional theory calculations. High angle angular dark field scanning transmission microscopy images of BaTiO3, SrZrO3, SrHfO3, and SrHf0.55Ti0.45O3reveal the location of the Ba (or Sr) atomic columns between the Ge dimers. The results imply that the organic ligands dissociate from the precursor after precursor adsorption on the Ge surface, producing the same Zintl template critical for perovskite growth on Group IV semiconductors during molecular beam epitaxy.
Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
Shen
S
Hu
Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
Edward L
EL
Lin
Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
Ali K
AK
Hamze
Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
Agham
A
Posadas
School of Engineering for Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, USA.
HsinWei
H
Wu
Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.
David J
DJ
Smith
Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
Alexander A
AA
Demkov
Department of Chemical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
John G
JG
Ekerdt