Adsorption SILAR

Successive Ionic Layer Adsorption and Reaction (SILAR) and Related Sequential Solution-Phase Deposition Techniques... 

Figure 8.1. Schematic view of thin-film growth during one SILAR cycle, (a) cation adsorption cation O anion (b) rinsing (c) anion reaction anion o cation and (d) rinsing. Reprinted with permission from Lindroos 1997.

Two basic methods have been used to grow metal oxide thin films by the SILAR technique (see Table 8.1). The more common of these methods consists of the adsorption of metal hydroxide ions on the substrate surface followed by thermal treatment to convert hydroxide to an oxide. Another way to produce metal oxide films is to use hydrogen peroxide as the anion precursor and then to convert the formed metal peroxide film to an oxide film. Several examples of each approach are discussed in more detail below. 

Pathan, H. M. Lockhande, C. D. 2004. Deposition of metal chalcogenide thin films by successive ionic layer adsorption and reaction (SILAR) method. Bull. Mater. Sci. 27 85-111. 

Lindroos, S. 1997. The successive ionic layer adsorption and reaction (SILAR) growth and characterization of ZnS and ZnS Mn thin films. Ph.D. thesis. University of Helsinki, Helsinki, Finland. 

Jimenez-Gonzalez, A. Suarez-Parra, R. 1996. Effect of heat treatment on the properties of ZnO thin films prepared by successive ion layer adsorption and reaction (SILAR)./. Cryst. Growth 167 649-655. 

Lindroos, S. Valkonen, M. Leskela, M. 1999. Growth of Zn02/Zn0 thin films by successive ionic layer adsorption and reaction—SILAR—technique. Adv. Sci. Technol. 20 43-50. 

Lindroos, S. Leskela, M. 2000. Growth of zinc peroxide (Zn02) and zinc oxide (ZnO) thin films by the successive ionic layer adsorption and reaction—SILAR— technique. Inter. J. Inorg. Mater. 2 197-201. 

Lindroos, S. Charreire, Y. Bonnin, D. Leskela, M. 1998. Growth and characterization of zinc sulfide thin films deposited by the successive ionic layer adsorption and reaction (SILAR) method using complexed zinc ions as the cation precursor. Mater. Res. Bull. 33 453—459. 

Sasagawa, M. Nosaka, Y. 2002. Electrochemical evaluation of the roles of chelating reagents in Cd ion adsorption on CdS surface for the successive ionic layer adsorption and reaction (SILAR) deposition. J. Electroanal. Chem. 536 141-144. 

Electrodeposition is by its nature a condensed phase process, whereas most studies of ALE have been performed using gas phase or vacuum methodologies, CVD or MBE. A solution phase deposition methodology related to ALE has been developed in France by Nicolau et al. [27-32] (Fig. 2), in which adsorbed layers of elements are formed by rinsing a substrate in aqueous solutions containing ionic precursor for the desired elements, sequentially, in a cycle. After exposure to each precursor, the substrate is copiously rinsed and then transferred to a solution containing the precursor for the next element. The method is referred to as successive ionic layer adsorption and reaction (SILAR). Reactivity in SILAR appears to be controlled by the rinsing procedure, solution composition, pH, and specifically... 

To allow the growth of another semiconducting material having the sulfide ion as the anion component, for example, CdS. The SILAR process has been proposed. For InP (n), the mechanism of sulfurization (the first step of CdS deposition) has been described [104] reversible adsorption of HS ions, followed by the irreversible expulsion of... 

NCs is indispensable. In the case of cadmium chalcogenide NCs, the concentration of a colloidal solution can be determined in good approximation by means of UV-vis absorption spectroscopy thanks to tabulated relationships between the excitonic peak, the NC size, and the molar absorption coefficient.96 An advanced approach for shell growth derived from chemical bath deposition techniques and aiming at the precise control of the shell thickness is the so-called SILAR (successive ion layer adsorption and reaction) method.97 It is based on the formation of one monolayer at a time by alternating the injections of cationic and anionic precursors and has been applied first for the synthesis of CdSe/CdS CS NCs. Monodispersity of the samples was maintained for CdS shell thicknesses of up to five monolayers on 3.5 nm core CdSe NCs, as reflected by the narrow PL linewidths obtained in the range of 23 to 26 nm FWHM. 

The two processes are known as SILAR (successive ion layer adsorption and reaction) and ILGAR (ion layer gas reaction). Both methods work best when a metal salt is chosen in which the metal ion has the same valence state as in the desired final compound. Depending on concentration, temperature and duration, the thickness of the deposited metal can be varied from approximately monolayer thickness to more continuous single- or multi-layer coverage. 

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