Multilayer thin films, polyferrocenylsilanes

In addition to forming continuous organometallic multilayer thin films, we explored the LbL deposition of polyferrocenylsilane polyions onto, for instance, hydrophilically/hydrophobically modified substrates with the aim of building two-dimensionally patterned organometallic multilayers. In general, surfaces modified with microscopically patterned conducting, luminescent, or redox-active polymer films have potential use in microelectronic and optoelectronic devices and microsensor arrays. Area-selective deposition of polyferrocenylsilane polyions can be an attractive method to obtain two-dimensionally patterned redox active films, which may be used as electrochemically modulated diffraction gratings. ... 

Patterned organometallic multilayers may be of interest also as etch barriers in RIE processes. For this purpose it is essential that these films can be fabricated from etch resistant organometallic polyferrocenylsilane chains only, as organic polymers offer no resistance to reactive ion etching. This chapter deals with the formation of continuous organometallic multilayer thin films, and with the fabrication of patterned organometallic thin films, formed by area-selective deposition of organo-metaUic polyions on prepattemed substrates. 

The fitted multilayer thickness as a function of the number of deposited bUayers is shown in Figure 4, demonstrating that the thickness of the film is linearly related to the number of deposited bilayers, in accordance with the UV-Vis absorption spectroscopy results. The dashed line is a fit through the origin and indicates a thickness contribution of about 0.4 nm per bilayer. This result is influenced by the refractive index. Previously, combined ellipsometry and profilometry measurements led to a refractive index value of n=1.687 for spin-coated polyferrocenyldimethylsilane films on silicon wafers, and this value was also used for the polyferrocenylsilane multilayer thin films. However, the refractive index might be somewhat lower in this case, implying that the thickness contribution of 0.4 nm per bilayer we found could be a slight rmderestimate. 

The elemental composition of the organometallic multilayer thin film (20 bilayers of 5 and 7 on quartz) was determined using X-ray photoelectron spectroscopy (XPS). The survey scan, shown in Figure 5, indicates the presence of all expected elements in the thin film. Atomic concentrations of the polyferrocenylsilane multilayer thin film are given in Table 1. 

Figure 5 XPS survey spectrum of a multilayer thin film (20 bilayers) composed of polyferrocenylsilane polyions 5 and 7.

Table 1 XPS Atomic Percentages of the Elements of a Polyferrocenylsilane Multilayer Thin Film (5/7)2o on Quartz...

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