TY - JOUR
KW - Titanium dioxide
KW - Lanthanum compounds
KW - Domain walls
KW - Ferroelectric materials
KW - Calculations
KW - First-principles calculation
KW - Strontium titanates
KW - Electronic properties
KW - Heterojunctions
KW - Atomic level control
KW - Domain wall formation
KW - Electron accumulation
KW - Oxide heterostructures
KW - Surface chemicals
KW - Surface termination
KW - Tunneling measurement
KW - Aluminum compounds
AU - G Singh-Bhalla
AU - P.B Rossen
AU - G.K Pálsson
AU - M Mecklenburg
AU - T Orvis
AU - S Das
AU - Y.-L Tang
AU - J.S Suresha
AU - D Yi
AU - A Dasgupta
AU - D Doenning
AU - V.G Ruiz
AU - A.K Yadav
AU - M Trassin
AU - J.T Heron
AU - C.S Fadley
AU - R Pentcheva
AU - J Ravichandran
AU - Ramamoorthy Ramesh
AB - Polar crystals composed of charged ionic planes cannot exist in nature without acquiring surface changes to balance an ever-growing dipole. The necessary changes can manifest structurally or electronically as observed in semiconductors and ferroelectric materials through screening charges and/or domain wall formation. In the case of prototypical polar complex oxides such as the LaAlO3/SrTiO3 system the nature of screening charges for different interface terminations is not symmetric. Electron accumulation is observed near the LaAlO3/TiO2-SrTiO3 interface, while the LaAlO3/SrO-SrTiO3 stack is insulating. Here, we observe evidence for an asymmetry in the surface chemical termination for nominally stoichiometric LaAlO3 films in contact with the two different surface layers of SrTiO3 crystals, TiO2 and SrO. Using several element-specific probes, we find that the surface termination of LaAlO3 remains AlO2 irrespective of the starting termination of SrTiO3 substrate surface. We use a combination of cross-plane tunneling measurements and first-principles calculations to understand the effects of this unexpected termination on band alignments and polarity compensation of LaAlO3/SrTiO3 heterostructures. An asymmetry in LaAlO3 polarity compensation and resulting electronic properties will fundamentally limit atomic level control of oxide heterostructures. © 2018 American Physical Society.
BT - Physical Review Materials
DO - 10.1103/PhysRevMaterials.2.112001
LA - eng
M1 - 11
N1 - cited By 3
N2 - Polar crystals composed of charged ionic planes cannot exist in nature without acquiring surface changes to balance an ever-growing dipole. The necessary changes can manifest structurally or electronically as observed in semiconductors and ferroelectric materials through screening charges and/or domain wall formation. In the case of prototypical polar complex oxides such as the LaAlO3/SrTiO3 system the nature of screening charges for different interface terminations is not symmetric. Electron accumulation is observed near the LaAlO3/TiO2-SrTiO3 interface, while the LaAlO3/SrO-SrTiO3 stack is insulating. Here, we observe evidence for an asymmetry in the surface chemical termination for nominally stoichiometric LaAlO3 films in contact with the two different surface layers of SrTiO3 crystals, TiO2 and SrO. Using several element-specific probes, we find that the surface termination of LaAlO3 remains AlO2 irrespective of the starting termination of SrTiO3 substrate surface. We use a combination of cross-plane tunneling measurements and first-principles calculations to understand the effects of this unexpected termination on band alignments and polarity compensation of LaAlO3/SrTiO3 heterostructures. An asymmetry in LaAlO3 polarity compensation and resulting electronic properties will fundamentally limit atomic level control of oxide heterostructures. © 2018 American Physical Society.
PB - American Physical Society
PY - 2018
T2 - Physical Review Materials
TI - Unexpected termination switching and polarity compensation in LaAlO 3 /SrTiO 3 heterostructures
VL - 2
SN - 24759953
ER -