Editing Epitaxy (section)

{{Short description|Crystal growth process relative to the substrate}}
{{Redirect-distinguish|Epitaxis|Epistaxis}}
{{Use dmy dates|date=April 2024}}

{{Crystallization}}
'''Epitaxy''' (prefix ''epi-'' means "on top of”) is a type of crystal growth or material deposition in which new [[crystal]]line layers are formed with one or more well-defined orientations with respect to the crystalline seed layer. The deposited crystalline film is called an epitaxial film or epitaxial layer.  The relative orientation(s) of the epitaxial layer to the seed layer is defined in terms of the orientation of the crystal lattice of each material. For most epitaxial growths, the new layer is usually crystalline and each crystallographic domain of the overlayer must have a well-defined orientation relative to the substrate crystal structure. Epitaxy can involve single-crystal structures, although grain-to-grain epitaxy has been observed in granular films.<ref name="Prab">{{cite journal |last1=K |first1=Prabahar |title=Grain to Grain Epitaxy-Like Nano Structures of (Ba,Ca)(ZrTi)O3/ CoFe2O4 for Magneto–Electric Based Devices |journal=ACS Appl. Nano Mater. |date=26 October 2020 |volume=3 |issue=11 |pages=11098–11106 |doi=10.1021/acsanm.0c02265|s2cid=228995039 }}</ref><ref name="Hwang">{{cite journal |last1=Hwang |first1=Cherngye |title=Imaging of the grain-to-grain epitaxy in NiFe/FeMn thin-film couples |journal=Journal of Applied Physics |date=30 September 1998 |volume=64 |issue=6115 |pages=6115–6117 |doi=10.1063/1.342110}}</ref> For most technological applications, single-domain epitaxy, which is the growth of an overlayer crystal with one well-defined orientation with respect to the substrate crystal, is preferred. Epitaxy can also play an important role in the growth of superlattice structures.<ref>{{cite book |last1=Christensen |first1=Morten Jagd |title=Epitaxy, Thin films and Superlattices |date=April 1997 |publisher=Risø National Laboratory |isbn=8755022987}}</ref>

The term ''epitaxy'' comes from the [[Greek language|Greek]] roots ''epi'' (ἐπί), meaning "above", and ''taxis'' (τάξις), meaning "an ordered manner".

One of the main commercial applications of epitaxial growth is in the semiconductor industry, where semiconductor films are grown epitaxially on semiconductor substrate wafers.<ref name="Pohl2013">{{cite book|author=[[Udo W. Pohl]]|title=Epitaxy of Semiconductors: Introduction to Physical Principles|url=https://books.google.com/books?id=DShEAAAAQBAJ|date=11 January 2013|publisher=Springer Science & Business Media|isbn=978-3-642-32970-8|pages=4–6}}</ref>  For the case of epitaxial growth of a planar film atop a substrate wafer, the epitaxial film's lattice will have a specific orientation relative to the substrate wafer's crystalline lattice, such as the [001] [[Miller index]] of the film aligning with the [001] index of the substrate. In the simplest case, the epitaxial layer can be a continuation of the same semiconductor compound as the substrate; this is referred to as homoepitaxy.  Otherwise, the epitaxial layer will be composed of a different compound; this is referred to as heteroepitaxy.