Silicon motivation

The passivation of silicon, motivated by the centrality of this semiconductor to the microelectronics industry, has been well studied. In addition to excellent passivation allowed by the silicon oxide, silicon can also be passivated with silicon nitride (Si3N4), other dielectrics, metal layers, and hydrogen. Here we focus only on hydride termination, since in addition to acting as a passivating layer for the underlying silicon, the hydride groups provide a versatile starting point for subsequent attachment chemistry. 

Raman spectrometry is another variant which has become important. To quote one expert (Purcell 1993), In 1928, the Indian physicist C.V. Raman (later the first Indian Nobel prizewinner) reported the discovery of frequency-shifted lines in the scattered light of transparent substances. The shifted lines, Raman announced, were independent of the exciting radiation and characteristic of the sample itself. It appears that Raman was motivated by a passion to understand the deep blue colour of the Mediterranean. The many uses of this technique include examination of polymers and of silicon for microcircuits (using an exciting wavelength to which silicon is transparent). 

An important step toward the understanding and theoretical description of microwave conductivity was made between 1989 and 1993, during the doctoral work of G. Schlichthorl, who used silicon wafers in contact with solutions containing different concentrations of ammonium fluoride.9 The analytical formula obtained for potential-dependent, photoin-duced microwave conductivity (PMC) could explain the experimental results. The still puzzling and controversial observation of dammed-up charge carriers in semiconductor surfaces motivated the collaboration with a researcher (L. Elstner) on silicon devices. A sophisticated computation program was used to calculate microwave conductivity from basic transport equations for a Schottky barrier. The experimental curves could be matched and it was confirmed for silicon interfaces that the analytically derived formulas for potential-dependent microwave conductivity were identical with the numerically derived nonsimplified functions within 10%.10... 

So far, researchers interested in this topic have had to choose either monographs that deal with the electrochemistry of semiconductors in general or recent editions that deal with special topics such as, for example, the luminescent properties of microporous silicon. The lack of a book that specializes on silicon but which gives the whole spectrum of its electrochemical aspects was my motivation to write the Electrochemistry of Silicon. 

As stated, the capability of plasma deposits to reduce the access of water to corrosion-sensitive surfaces may be an important motivation for their application in corrosion protection. In order to study this property, Kapton polyimide film was selected as the substrate because of its high inherent permeability to water and its ability to resist elevated temperatures. The response of Kapton film overcoated by PPHMDSO to the permeation of water vapor is shown in Fig. 1. Clearly, the presence of the organo-silicone plasma film greatly reduces water permeation. The magnitude of the effect is much enhanced when plasma polymers are produced at high T and p. 

The rapid developments in the microelectronics industry over the last three decades have motivated extensive studies in thin-film semiconductor materials and their implementation in electronic and optoelectronic devices. Semiconductor devices are made by depositing thin single-crystal layers of semiconductor material on the surface of single-crystal substrates. For instance, a common method of manufacturing an MOS (metal-oxide semiconductor) transistor involves the steps of forming a silicon nitride film on a central portion of a P-type silicon substrate. When the film and substrate lattice parameters differ by more than a trivial amount (1 to 2%), the mismatch can be accommodated by elastic strain in the layer as it grows. This is the basis of strained layer heteroepitaxy. 

Thin organic films are the subject of a great deal of research, motivated by their potential application in micro-electronics. Existing applications, such as in the photo-lithographic production of silicon micro-circuits, involve relatively disordered films. However, higher degrees of order and the use of more complex molecules could lead to systems in which the organic molecules themselves become the active electronic devices. 

Zeolite modifications have been the subject of extensive studies. Some research deals with the replacement of lattice silicon or aluminum by another element (1-8). The motivation for such studies is that, even for a low substitution ratio, the modified zeolites would acquire specific catalytic properties. In fact, the location of the heteroatoms is generally uncertain, a fact bringing to question whether the heteroatoms really enter the lattice or lie in cavities or channels to generate compounds of potential interest to industries. 

PECVD of silicon nitride has been of commercial importance since 1976.1 The original motivation was to find a final passivation layer for an integrated circuit that would replace the doped silicon dioxide films then in use. The latter were not reliable enough to permit packaging of integrated circuits in plastic. Silicon nitride was recognized as a better final passivation film, but the only available technique for its deposition was the high-temperature thermal process. Since it had to cover an aluminum final metallization layer that would melt at 600°C, this clearly could not work. The solution was to use PECVD at 350° to 400°C. 

As discussed in the introduction, a major motivation for the development of methods to controllably functionalize silicon surfaces is the opportunity to create novel hybrid organic/silicon devices. By integrating organic molecules with silicon substrates it should be possible to expand the functionality of conventional microelectronic devices. Possibilities include high-density molecular memory and logic as well as chemical and biochemical sensors. Realization of these opportunities requires not only the development of the attachment chemistries, as discussed in the previous sections, but also detailed studies of the electronic properties of the resulting surfaces. 

Since the preparation of the Cp(OC)2Fe- [2], Cp(OC)3W- [3a], and Cp(OC)2(Me3P)MoAV-substituted [3b, 4] pentachlorodisilanes and their pentahydrido-derivatives, our interest is focussed on extending this series to the CsMe5(OC)2Fe- and CsR5(OC)2Ru-substituted systems (R = H, Me) These investigations are motivated by the study concerning the electronic effect of transition metal centers on the chemical properties and reactivity of the a- and p-silicon in disilanyl-complexes. 

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