Epitaxy definition

Fundamental to forming high quality structures and devices with thin-films of compound semiconductors is the concept of epitaxy. The definition of epitaxy is variable, but focuses on the formation of single crystal films on single crystal substrates. Homoepitaxy is the formation of a compound on itself. Heteroepitaxy is the formation of a compound on a different compound or element, and is much more prevalent. 

There are many deposit-substrate combinations where the basic lattice mismatch is very large, such as when a compound is formed on an elemental substrate, but where excessive strain does not necessarily result. Frequently a non one-to-one lattice match can be formed. If a material can match up every two or three substrate surface unit cells, it may still form a reasonable film [16]. In many cases the depositing lattices are rotated from the substrate unit cells, as well. In a strict definition of epitaxy, these may not be considered, however, it is not clear why high quality devices and materials could not be formed. 

Air at 750°C A fine grained oxide forms pre- (68) ferentially on 100 planes of Ta and in <100> directions with both surface and internal oxidation occurring. There is no definite indication of an epitaxial relationship. 

At low coverages, most metallic adsorbates form ordered overlayers with a (1 x 1) surface structure on metal substrates. This implies that the substrate acts as a template and has a significant influence on the growth mode of the deposited material. This effect is usually called epitaxial growth. A more restricted definition of epitaxial growth would include only those examples where the substrate imposes its own crystal structure, orientation, and lattice parameter on the adsorbed overlayer. (This restricted definition is also called pseudomorphic growth.)... 

The structure of such precipitates can be influenced by the carrier. Thus, oriented deposits are known in which the crystallites of the deposit are preferentially attached to a specific crystal plane of the carrier. Further, there exists the phenomenon of epitaxy, in which the crystal axes of the individual deposit particles have a definite spatial and geometric relationship to each other and to the crystal axes of the carrier. Under such conditions, there may occur significant changes in the relative proportions of some crystal surfaces to the total surface area. Precipitation on a surface is not necessarily preceded by a chemical reaction. 

Avoidance of Lateral Epitaxial Autodoping Elimination of Sub-isolation Diffusion Single Mask Isolation and Subcollector Definition Absence of Bird s Beak... 

The term epitaxy is used to describe the growth of a monocrystalline film of one material in a definite crystallographic orientation on a crystal face of another material, the substrate. To promote growth, there must be a correspondence of both lattices at the interface. A misfit between film and substrate results in stresses as the film grows laterally, which may affect the stability of the deposited crystal. The magnetic properties of LPE garnet films can be optimised by varying this misfit. 

On the other hand. X-ray diffraction (XRD) measurements of the deposited platinum films (ca. 250 ML) on the Au(lll) substrate demonstrated that a (lll)-orientated platinum-bulk phase was definitely formed on the Au(lll) electrode surface by electrochemical epitaxial growth [32]. 

Electrochemical atomic layer epitaxy (EC-ALE) is the combination of underpotential deposition (UPD) and ALE. UPD is the formation of an atomic layer of one element on a second element at a potential under, or prior to, that needed to deposit the element on itself [5, 6]. The shift in potential results from the free energy of the surface compound formation. Early UPD studies were carried out mostly on polycrystalline electrode surfaces [7], This was due, at least in part, to the difficulty of preparing and maintaining single-crystal electrodes under well-defined conditions of surface structure and cleanliness [8]. The definition of epitaxy is variable but focuses on the formation of single crystal films on single crystal substrates. This is different from other thin film deposition methods where polyciystalline or amorphous film deposits are formed even on single crystal substrates. Homoepitaxy is the formation of a compound on itself. Heteroepitaxy is the formation of a compound on a different compound or element and is much... 

In this regime, the epitaxial film behaves as a perfect crystal that is elastically strained. Properties in this regime should thus, by definition, be predictable from the properties of bulk single crystals in the presence of uniform elastic strains. Unfortunately, data on the common thermal and mechanical properties of thin films are lacking for fliis range of thickness, owing mainly to the difficulty of such measurements. Transport properties are easier to measure but may be dominated by geometrical and interfacial effects. 

---