Lanthanum aluminate
{{Chembox
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| IUPACName =
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|Section1={{Chembox Identifiers
| CASNo = 12003-65-5
| PubChem = 16217677
| ChemSpiderID = 17345186
| EINECS = 234-433-3
| StdInChI=1S/Al.La.3O
| StdInChIKey = KJXBRHIPHIVJCS-UHFFFAOYSA-N
| SMILES = O=[Al]O[La]=O
}}
|Section2={{Chembox Properties
| Formula = LaAlO3
| MolarMass = 213.89 g/mol
| Appearance = optically transparent, tan to brown
| Odor = odorless
| Density = 6.52 g/cm3
| MeltingPtC = 2080
| BoilingPt =
| Solubility = Insoluble in mineral acids at 25 °C. Soluble in H3PO3 > 150 °C
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Lanthanum aluminate is an inorganic compound with the formula 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 is a rhombohedral distorted perovskite with a pseudocubic lattice parameter of 3.787 angstroms at room temperature{{cite web|title=LaAlO3|url=http://www.mtixtl.com/laalo3.aspx|publisher=MTI Corp|accessdate=4 August 2015}} (although one source claims the lattice parameter is 3.82{{cite web|title=LaAlO3|url=http://www.crystec.de/laalo3-e.html|publisher=Crystec|accessdate=3 August 2015}}). 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).{{cn|date=September 2023}}
Image:LAOSTO Interface.png formed at LAO-STO interfaces]]
LAO-STO interfaces
{{main|Lanthanum aluminate-strontium titanate interface}}
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.{{cite journal |last=Ohtomo |author2=Hwang |title=A high-mobility electron gas at the LaAlO3/SrTiO3 heterointerface |journal=Nature|date=29 Jan 2004 |volume=427 |issue=6973 |pages=423–6 |doi=10.1038/nature02308 |pmid=14749825 |bibcode = 2004Natur.427..423O |s2cid=4419873 }} Individually, LaAlO3 and SrTiO3 are non-magnetic insulators, yet LaAlO3/SrTiO3 interfaces exhibit electrical conductivity, superconductivity,{{cite journal|last1=Gariglio|first1=S|last2=Reyren|first2=N|last3=Caviglia|first3=A D|last4=Triscone|first4=J-M|title=Superconductivity at the LaAlO3/SrTiO3 interface|journal=Journal of Physics: Condensed Matter|volume=21|issue=16|year=2009|pages=164213|issn=0953-8984|doi=10.1088/0953-8984/21/16/164213|pmid=21825393|bibcode=2009JPCM...21p4213G|s2cid=41420637|url=https://hal.archives-ouvertes.fr/hal-01591058/file/article.pdf}}
ferromagnetism,{{cite journal |last=Bert |author2=Kalisky, Bell |author3=Kim, Hikita |author4=Hwang, Moler |title=Direct imaging of the coexistence of ferromagnetism and superconductivity at the LaAlO3/SrTiO3 interface |journal=Nature Physics|date=4 September 2011 |volume=7 |issue=10 |pages=767 |doi=10.1038/nphys2079 |arxiv = 1108.3150 |bibcode = 2011NatPh...7..767B |s2cid=10809252 }} large negative in-plane magnetoresistance,{{cite journal |last=Ben Shalom |author2=Sachs, Rakhmilevitch |author3=Palevski, Dagan |title=Tuning Spin-Orbit Coupling and Superconductivity at the SrTiO3/LaAlO3 Interface: A Magnetotransport Study |journal=Physical Review Letters|date=26 March 2010 |volume=104 |issue=12 |pages=126802 |doi=10.1103/PhysRevLett.104.126802 |pmid=20366556 |arxiv = 1001.0781 |bibcode = 2010PhRvL.104l6802B |s2cid=43174779 }} and giant persistent photoconductivity.{{cite journal|last=Tebano|first=Antonello|author2=E Fabbri |author3=D Pergolesi |author4=G Balestrino |author5=E Traversa |title=Room-Temperature Giant Persistent Photoconductivity in SrTiO3/LaAlO3 Heterostructures|journal=ACS Nano|date=19 January 2012|volume=6|issue=2|pages=1278–1283|doi=10.1021/nn203991q|pmid=22260261}} The study of how these properties emerge at the LaAlO3/SrTiO3 interface is a growing area of research in condensed matter physics.
=Substrates=
Single crystals of lanthanum aluminate are commercially available as a substrate for the epitaxial growth of perovskites,[http://www.mtixtl.com/laalo3orn5x5x05mmsubstrate2sideepipolished-1.aspx LaAlO3 specifications from the supplier MTI Corp.] {{webarchive|url=https://web.archive.org/web/20131101133640/http://www.mtixtl.com/laalo3orn5x5x05mmsubstrate2sideepipolished-1.aspx |date=2013-11-01 }}[http://www.surfacenet.de/html/laalo3.html LaAlO3 specifications from the supplier SurfaceNet] 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 at the relevant temperatures (~1000 °C).{{cite journal|author=P. Sivasubramani|year=2005 |title=Outdiffusion of La and Al from amorphous LaAlO3 in direct contact with Si (001) |url=http://www.mse.cornell.edu/research/resgroups/schlom/pub/journal/pub196.pdf |journal=Applied Physics Letters |volume=86 |issue=20 |pages=201901 |doi=10.1063/1.1928316|display-authors=etal|bibcode=2005ApPhL..86t1901S}}
See also
References
{{reflist}}
{{Lanthanum compounds}}