Film, epitaxial

In heteroepitaxial film growth, the substrate crystal structure provides a template for positioning the first arriving atoms of film material, and each 

Consider an elementary cubic lattice with elastic modulus E and free surface energy 7. The elastic strain energy per atom due to biaxial strain of magnitude em is on the order of Ee o. On the other hand, the in-plane chemical bonding energy per atom is on the order of 2 af. For a choice of parameters oi E = 10 N/m, 7=1 J/m, Cm = 0.02, and af = 0.3nm, the 

the elastic effect is very small compared to the chemical effect on an atom-by-atom basis. The elastic effect can come into play only when the chemical effect is sufficiently diluted by symmetry or scale so that it is no longer the dominant effect. 

Carrying this simple comparison one step further, both elastic energy and bonding energy might be compared to kTs, the Boltzmann constant times the absolute temperature of the substrate. This quantity is an indicator of the mean energy per adatom in the substrate. At the temperature of 800 K, a typical deposition temperature, the value of kTg is on the order of 

As the coherent film becomes thicker, it grows with essentially uniform elastic strain over most of the growth area. The strain energy per unit volume is constant consequently, over most of the growth area, the stored strain energy per unit area of interface increases linearly with film thickness beyond thicknesses of a few atomic dimensions. This increasing energy reservoir is available to drive various physical mechanisms for relaxation of elastic strain. 

In general, it is assumed that the growth of epitaxial thin films from solution deposition methods is very difficult. However, a number of different phenomena can convert the polycrystalline layer formed during drying and pyrolysis into an epitaxial layer [64]. This can be relatively easy when the deposited layer and the substrate have identical crystal structures with close lattice parameters. The lattice mismatch between the film and the substrate is therefore very small. For dissimilar substrates, template layers on the substrate surfece, with crystal structure and lattice parameters close to those of the deposited film, can be used. In 

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Film Contamination from Bulk Phase. The contamination of an epitaxial film of GaAs from an oven charge can be corrected by doping... 

Figure 5 Images of a thin region of an epitaxial film of Ge on Si grown by oxidation of Ge-implanted Si (a) conventional TEM phase contrast image with no compositional information and b) high-angle dark-field STEM image showing atomically sharp interface between Si and Ge. (Courtesy of S.J. Pennycook)...

Besides phase identification XRD is also widely used for strain and particle size determination in thin films. Both produce peak broadenings, but they are distinguishable. Compared to TEM, XRD has poor area resolution capability, although by using synchrotron radiation beam diameters of a few pm can be obtained. Defect topography in epitaxial films can be determined at this resolution. 

For ultrathin epitaxial films (less than "100 A), Grazingincidence X-ray Diffraction (GrXD) is the preferred method and has been used to characterize monolayer films. Here the incidence angle is small ("0.5°) and the X rays penetrate only "100-200 A into the specimen (see below). The exit angle of the diffracted X rays is also small and structural information is obtained about (hkl) planes perpendicular to the specimen sur e. Thus, GIXD complements those methods where structural information is obtained about planes parallel to the surface (e.g., Bra -Brentano and DCD). 

The SSMS point-to-plane surface technique has been shown to be particularly useful in the survey analysis of epitaxial films, heavy metal implant contamination, diflRision furnace contamination, and deposited metal layers. 

Impurity suffice (4 p) Concentrarion (atoms/x) Epitaxial film (> 4 p)... 

K. Kaigawa, T. Kawaguchi, M. Imaeda, H. Sakai, T. Fukuda. Crystal structure of LPE-grown LiNb03 epitaxial films. J Cryst Growth 777 217, 1997. 

Generally, epitaxial films have superior properties and, whenever possible, epitaxial growth should be promoted. The epitaxial CVD of silicon and III-V and E-VI compounds is now a major process in the semiconductor industry and is expected to play an increasingly important part in improving the performance of semiconductor and optoelectronic designs (see Chs. 13-15). 

Iron has been deposited by the hydrogen reduction of its chloride at 650°C or the pyrolysis of its iodide at 1100°C, as well as the decomposition of its carbonyl at 370-450°C with CO as carrier gas. Carbon tends to be incorporated in the deposit requiring a 900°C annealing in H2 to remove it.PH l A potential application is epitaxial films on GaAs. 

Silicon Epitaxy. Silicon epitaxial films have superior properties. The applications are, however, limited by the high temperature of deposition, which is generally above 1000°C. These reactions use chlorinated compounds of silicon (tetrachloride, trichlorosilane, or dichlorosilane) as precursors as follows ... 

Huelsman, A. D., and Reif, R., Plasma Deposition of GaAs Epitaxial Films from Metal-Organic Sources, Proc. 10th Int. Conf. on CVD, (G. Cullen, ed.), pp. 792-802, Electrochem. Soc., Pennington, NJ 08534 (1987)... 

Epitaxy is a term that denotes the growth of a thin crystalline film on a crystalline substrate. When the epitaxial film is of the same material as the substrate (for instance silicon on silicon), the process is known as homoepitaxy. When film and substrate are of different... 

Froment M, Bernard MC, Cortes R, Makili B, Lincot D (1995) Study of CdS epitaxial films chemically deposited from aqueous solutions on InP single crystals. J Electrochem Soc 142 2642-2649... 

Significant improvements in ECALE deposit morphology and quality were reported as achieved by switching from a thin layer cell to a thick layer H-form cell, integrated in an automated deposition system [46]. Thin epitaxial films of zinc blende CdTe, CdSe, and CdS with predominate (111) orientations were grown. 

Cachet H, Cortes R, Froment M, Mamin G (1999) Epitaxial growth of electrodeposited cadmium selenide on (111) gallium arsenide. Philos Mag Lett 79/10 837-840 Muthuvel M, Stickney JL (2006) CdTe Electrodeposition on InP(lOO) via Electrochemical Atomic Layer Epitaxy (EC-ALE) Studies Using UHV-EC. Langmuir 22 5504-5508 Streltsov EA, Osipovich NP, Ivashkevich LS, Lyakhov AS (1999) Effect of Cd(ll) on electrodeposition of textured PbSe. Electrochim Acta 44 2645-2652 Beaunier L, Cachet H, Cortes R, Froment M (2000) Electrodeposition of PbSe epitaxial films on (111) InP. Electrochem Commun 2 508-510... 

Several routes have been used to produce defect sites on MgCl2 surfaces One way is to grow the MgCl2 film at low temperatures so that the mobility of the MgCl2 is too low to allow for the formation of a fully epitaxial film. However, a major problem of this procedure is the tendency to produce films containing pinholes, which change the reactivity of the system [21]. Another option is to bombard the surface either with electrons or ions [22,87-90,106,107]. 

Many of the various techniques associated with metal film preparation have recently been reviewed by Klemperer (76). Much of the catalytic work with thick continuous films has used a cylindrical reaction vessel (Fig. 7a). This cylindrical geometry permits a cylindrical sleeve of mica sheet to be inserved and used as the film substrate for epitaxial film growth... 

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