Electrochemical atomic layer epitaxy ECALE

Goodman CHL, Pessa MV (1986) Atomic layer epitaxy. J Appl Phys 60 R65-R81 Gregory BW, Stickney JL (1991) Electrochemical atomic layer epitaxy (ECALE). J Electroanal Chem 300 543-561... 

Colleti LP, Thomas S, WUmer EM, Stickney JL (1997) Thin layer electrochemical studies of ZnS, ZnSe, and ZnTe formation by Electrochemical Atomic Layer Epitaxy (ECALE). Mater Res Soc Symp Proc 451 235. 

The electrochemical atomic layer epitaxy (ECALE) technique, also known as electrochemical atomic layer deposition (EC-ALD), is based on layer-by-layer electrodeposition. Each constituent of the thin him are deposited separately using underpotential deposition (UPD) of that element. UPD is a process wherein an atomic layer of one element is deposited on the surface of a different element at a potential under that needed to deposit the element on itself. ECALE has been used to grow mainly II-VI and III-V compounds. A thorough review of ECALE research has been published by Stickney.144 A summary of the materials deposited using ECALE are given in Table 8.4, with a more detailed discussion for a few select examples given below. 

Cecconi, T. Atrei, A. Bardi, U. Forni, F. Innocenti, M. Loglio F. Foresti M. Rovida G. 2001. X-ray photoelectron diffraction (XPD) study of the atomic structure of the ultrathin CdS phase deposited on Ag(lll) by electrochemical atomic layer epitaxy (ECALE). J. Electron Spectrosc. Relat. Phenom. 114-116 563-568. 

Vaidyanathan, R. Stickney, J. L. Happek, U. 2004. Quantum confinement in PbSe thin films electrodeposited by electrochemical atomic layer epitaxy (ECALE). Electrochim. Acta 49 1321-1326. 

An electrochemical scarming probe microscopy and Raman spectroscopy investigation of thin CdS films grown by electrochemical atomic layer epitaxy (ECALE) aimed at understanding the role played by the order of deposition on film quality were reported [161]. 

Atomic layer epitaxy (electrochemical) — Electrochemical atomic layer epitaxy (ECALE) is a self-limiting process for the formation of structurally well-ordered thin film materials. It was introduced by Stickney and coworkers [i] for the layer by layer growth of compound semiconductors (CdTe, etc.). Thin layers of compound semiconductors can be formed by alternating - underpotential deposition steps of the individual elements. The total number of steps determines the final thickness of the layer. Compared to flux-limited techniques... 

A similar UPD technique called electrochemical atomic layer epitaxy" (ECALE) was introduced by Stickney et al. [6.170-6.172] to form mbced 2D MexMey UPD overlayers using simultaneously electrochemical reduction and oxidation of different electrolyte components. 

We applied the Electrochemical Atomic Layer Epitaxy (ECALE) methodology to obtain deposits of CdS and ZnS on Ag( III), by alternate underpotenlial deposition of the elements forming the compound. The amount of the elements deposited, determined by their stripping, always yielded the stoichiometric I I ratio. 

The second example involves the surface chemistry of the compound semiconductor CdSe synthesized epitaxially on Au(100) by underpotential deposition (UPD). By analogy with the gas-phase epitaxial deposition procedure, this UPD-based method has been dubbed electrochemical atomic layer epitaxy (ECALE) [6]. Unique information on the interfacial structure of the first adlayer of Se electrodeposited was revealed by STM experiments. 

Metal compound semiconductors such as CdS, CdSe, Hg(i CdjTe, BijScj, and InAs can also be produced by electrodeposition. Films of these materials have been produced by codeposition of the elements,or by a technique known as electrochemical atomic layer epitaxy (ECALE). 2-5s In codeposition, the films or nanostructures are produced from solution precursors by EC reactions, such as those shown in Equations 17.3 through 17.5. ECALE is the electrochemical equivalent of atomic layer epitaxy (ALE), because the material is assembled monolayer-by-monolayer using surface-limited reactions. The alternating layers in ECALE are deposited by UPD. 

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