Lanthanum aluminate is an

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...

LaAlO₃, often abbreviated as LAO. It is an optically transparent ceramic oxide with a distorted perovskite structure.

Properties

Crystalline LaAlO₃ has a relatively high relative dielectric constant of ~25. LAO's

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

is a rhombohedral distorted perovskite with a pseudocubic lattice parameter of 3.787 angstroms at room temperature (although one source claims the lattice parameter is 3.82). Polished single crystal LAO surfaces show twin defects visible to the naked eye.

Uses

Epitaxial thin films

Epitaxially grown thin films of LAO can serve various purposes for correlated electrons heterostructures and devices. LAO is sometimes used as an epitaxial insulator between two conductive layers. Epitaxial LAO films can be grown by several methods, most commonly by pulsed laser deposition (PLD) and molecular beam epitaxy (MBE). LAO-STO interfaces The most important and common use for epitaxial LAO is at the lanthanum aluminate-strontium titanate interface. In 2004, it was discovered that when 4 or more unit cells of LAO are epitaxially grown on strontium titanate (SrTiO₃, STO), a conductive 2-dimensional layer is formed at their interface. Individually, LaAlO₃ and SrTiO₃ are non-magnetic insulators, yet LaAlO₃/SrTiO₃ interfaces exhibit

electrical conductivity Electrical resistivity (also called volume resistivity or specific electrical resistance) is a fundamental specific property of a material that measures its electrical resistance or how strongly it resists electric current. A low resistivity in ...

superconductivity Superconductivity is a set of physical properties observed in superconductors: materials where Electrical resistance and conductance, electrical resistance vanishes and Magnetic field, magnetic fields are expelled from the material. Unlike an ord ...

ferromagnetism Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagne ...

, large negative in-plane magnetoresistance, and giant persistent

photoconductivity Photoconductivity is an optical and electrical phenomenon in which a material becomes more electrically conductive due to the absorption of electromagnetic radiation such as visible light, ultraviolet light, infrared light, or gamma radiation. ...

. The study of how these properties emerge at the LaAlO₃/SrTiO₃ interface is a growing area of research in

condensed matter physics Condensed matter physics is the field of physics that deals with the macroscopic and microscopic physical properties of matter, especially the solid and liquid State of matter, phases, that arise from electromagnetic forces between atoms and elec ...

Substrates

Single crystal In materials science, a single crystal (or single-crystal solid or monocrystalline solid) is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no Grain boundary, grain bound ...

s of lanthanum aluminate are commercially available as a substrate for the epitaxial growth of perovskites,LaAlO₃ specifications from the supplier MTI Corp.
and particularly for cuprate superconductors.

Non-epitaxial thin films

Thin films of lanthanum aluminate were considered as candidate materials for high-k dielectrics in the early-mid 2000s. Despite their attractive relative dielectric constant of ~25, they were not stable enough in contact with

silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...

at the relevant temperatures (~1000 °C).

References