Stoichiometry control of the electronic properties of the LaAlO_3/SrTiO_3 heterointerface

TL;DR

This study demonstrates that precise control of stoichiometry in LaAlO_3 films significantly influences the electronic properties of LaAlO_3/SrTiO_3 heterointerfaces, especially carrier density, through modifications in lattice expansion and electrostatic boundary conditions.

Contribution

It reveals how laser deposition parameters affect film stoichiometry and interface conductivity, highlighting the importance of cation vacancies and lattice expansion in electronic behavior.

Findings

Carrier density varies over two orders of magnitude with stoichiometry.

Lattice expansion correlates with cation vacancies and interface conductivity.

Stoichiometry influences electrostatic boundary conditions at the interface.

Abstract

We investigate the effect of the laser parameters of pulsed laser deposition on the film stoichiometry and electronic properties of LaAlO_3/SrTiO_3 (001) heterostructures. The La/Al ratio in the LaAlO_3 films was varied over a wide range from 0.88 to 1.15, and was found to have a strong effect on the interface conductivity. In particular, the carrier density is modulated over more than two orders of magnitude. The film lattice expansion, caused by cation vacancies, is found to be the important functional parameter. These results can be understood to arise from the variations in the electrostatic boundary conditions, and their resolution, with stoichiometry.