Liquid epitaxy

R. K. Akchurin, D. V. Komarov. Formation of multilayer strained-layer heterostructures by liquid epitaxy. I. Theoretical aspects of the problem and mathematical model. Tech Phys 42 155, 1997. 

All the advantages of heterojunction II-VI sulfide-based solar cells can be utilized, with the polymer matrix preventing interdiffusion of An metal components, often the main reason for the instability observed in inorganic heterostructure II-IV solar cells produced by liquid epitaxy or thermal evaporation,... 

LPE = liquid-phase epitaxy, MOCVD = metalorganic chemical vapor deposition, VPE = vapor-phase epitaxy. 

Cathodoluminescence microscopy and spectroscopy techniques are powerful tools for analyzing the spatial uniformity of stresses in mismatched heterostructures, such as GaAs/Si and GaAs/InP. The stresses in such systems are due to the difference in thermal expansion coefficients between the epitaxial layer and the substrate. The presence of stress in the epitaxial layer leads to the modification of the band structure, and thus affects its electronic properties it also can cause the migration of dislocations, which may lead to the degradation of optoelectronic devices based on such mismatched heterostructures. This application employs low-temperature (preferably liquid-helium) CL microscopy and spectroscopy in conjunction with the known behavior of the optical transitions in the presence of stress to analyze the spatial uniformity of stress in GaAs epitaxial layers. This analysis can reveal,... 

The composition must be controlled to give the required emission wavelength. Techniques utilized include molecular-beam epitaxy (MBE) and liquid-phase epitaxy (LPE). 

Thin polymer films may also be investigated by TEM and high resolution images are obtained for e.g. thin films of liquid crystalline polymers [64]. Usually thin microtome cuts from bulk samples are investigated, but also epitaxial growth of polyoxymethylene on NaCl [152], chain folding of polyethylene crystals [153], epitaxial crystallization of polypropylene on polystyrene [154] or monomolecular polystyrene particles [155] are observed. The resolution is, however, in most cases not comparable to STM. 

Boats and crucibles for liquid phase epitaxy. Crucibles for molecular beam epitaxy. 

Most of these compounds were originally prepared by liquid-phase epitaxy. That process is now largely replaced by MOCVD, particularly in the case of gallium arsenide, gallium arsenic phosphide, and gallium aluminum phosphide. 

Other forces can arise as a result of elastic strain on the growing film, which can be due to a surface-induced ordering in the first few layers that reverts to the bulk liquid structure at larger distances. This elastic energy is stored in intermolecular distances and orientations that are stretched or compressed from the bulk values by the influence of the substrate at short distances [7]. Similar phenomena are well known to occur in the growth of epitaxial layers in metals and semiconductors. 

Lindroos S, Kanniainen T, Leskela M (1994) Growth of ZnS thin films by liquid-phase atomic layer epitaxy (LPALE). Appl Surf Sci 75 70-74... 

The primary goal of the researchers has been to produce Q-dots possessing all of the attributes of the Q-dots prepared using liquid-phase synthetic methods (that is adjustability of the nanocrystal identity and diameter and size monodispersity) and also the technological utility of Q-dots prepared by MBE (specifically, the deposition of nanocrystals with a defined orientation and an electrical output contact). It was shown that the E/C-synthesized 5-CuI and CdS Q-dots were indeed epitaxial with narrow size distribution and strong photoluminescence tunable by the particle size. Qne of the advantages of the E/C method is that it can be made size selective. The key point is that the size as well as the size dispersion of product nanoparticles are directed actually by the corresponding properties of the metal nanoparticles therefore the first deposition step assumes special importance. 

Figure 12.16b shows the a typical cross-section through a GaAsPLED fabricated from layers grown by either liquid phase epitaxy or vapor phase epitaxy. 

M. J. McCollum and G. E. Stillman, High Purity InP Grown by Hydride Vapor Phase Epitaxy T. Inada and T. Fukuda, Direct Synthesis and Growth of Indium Phosphide by the Liquid Phosphorous Encapsulated Czochralski Method O. Oda, K. Katagiri, K. Shinohara, S. Katsura, Y. Takahashi, K. Kainosho, K. Kohiro, and R. Hirano, InP Crystal Growth, Substrate Preparation and Evaluation... 

These processes can also involve reactants in the liquid phase, and we call this liquid-phase epitaxy, although the equations wiU be the same as for gases. 

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