Include Product Page LAO_Material information

LaAlO3 (LAO)
  • Name: LAO (LaAlO3), Lanthanum Aluminate Single Crystal Substrates
  • Lattice parameter: a = 3.787 Å
  • Crystal Structure:  Rhombohedral distorted perovskite
  • Commonly used as substrate for: High temperature super conductors e.g. YBCO, many perovskites including titanates, aluminates, ferrites, zirconates and stannates.
  • Orientation of LaAlO3 substrates: (100), (110), (111)
  • Surface Roughness: Ra < 0.2nm (measured 5x5 µm AFM scan)
  • Crystal has a relatively high dielectric constant (25)
  • Wide energy gap
  • Good lattice matching; A substrate for high-temperature superconducting films
  • Good chemical stability
  • High Transparent

LaAlO3 (LAO) single crystal substrates are optically transparent with a pseudo-perovskite structure provides a good lattice match to many other materials with perovskite structure making them well suited to support complex oxides thin films. LAO is a favoured crystal for growing BiFeO3 films which when grown on LAO exhibit exotic multifunctional properties. LAO is an excellent substrate for epitaxial growth of high Tc superconductors, particularly for cuprate superconductors such as YBCO and GdBCO as well as magnetic and ferro-electric thin films. The dielectric properties of LaAlO3 crystal are well suitable for low loss microwave and dielectric resonance applications. 

Crystalline LaAlO3 has a relatively high relative dielectric constant of ~25. As a high-k material, LAO is a promising replacement for SiO2 as a gate dielectric materials in MOSFET transistors (LaAlO3 is insoluble in mineral acids at 25 °C but soluble in H3PO3 > 150 °C). 

LAO's crystal structure is a rhombohedral distorted perovskite with a pseudocubic lattice parameter of 3.787 Å. A crystal twin is formed due to the phase transition  from cubic to rhombohedral (Tc = 813 K) on cooling the single crystal therefore LAO surfaces can show twin defects visible to the naked eye as a straight line through the crystal.

Hayward et al. 2005 - Schematic representation of the AlO6 polyhedral network in a) cubic and b) rhombohedral LaAlO3, viewed down the (001) trigonal, equivalent to (111) cubic. 

One of the most important and common uses for epitaxial LAO grown on STO substrates is at the lanthanum aluminate-strontium titanate interface. Whist this does not involve the use of LAO substrates, as typically LAO layer grown on STO it is still noteworthy here: 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, superconductivity, ferromagnetism, large negative in-plane magnetoresistance, and giant persistent photoconductivity. The study of how these properties emerge at the LaAlO3/SrTiO3 interface is a growing area of research in condensed matter physics.

In short if you are growing perovskites then you might be looking at using SrTiO3 and LaAlO3 among other substrates. LAO offers a lower lattice parameter which may be important to get good epitaxy or to add strain into your system after growth.