SAMs passivation

Ben-Yaakov, Sam and Gregoiy Ivensky, Passive Lossless Snubbers for High Frequency PWM Converters, Seminar 12, APEC 99. 

Recently, Melosh has obtained electrically stable LAJs as large as 9 mm2 by atomic deposition of a nanometer-thick passivating layer of aluminium oxide on top of self-assembled organic monolayers with hydrophilic terminal groups [158,159]. Obviously, interlayers based junctions limit electrical measurements only to organic SAMs less conductive than the protecting layer. 

There is not a consensus about the procedures to use to test for effects on learning and memory. The two most commonly used techniques are the water-filled maze, which is preferred for measuring learning, and passive avoidance, which is preferred for measuring memory (see Buelke-Sam et al., 1985). Retention is tested in a repeat test conducted approximately 1 week later. 

Considerable research effort was focused on systems of colloidal gold of which a broad variety of synthetic procedures were reported [140 b, fj. While native colloidal gold solutions are only stable for a restricted time, Brust et al. [141] were able to overcome this problem by developing a simple method for the in situ preparation of alkyl thiol-stabihzed gold nanoparticles. This synthetic route yields air-stable and easy to handle passivated nanoparticles of moderate polydispersity, and is now commonly employed for the preparation of inorganic-organic core-shell composites. Such composites are used as catalytic systems with principally two different functions of the protective 3D-SAM layer. Either the metal nanoparticle core can be used as the catalytically active center and the thiol layer is only used to stabihze the system [142], or the 3D-SAM is used as a Hnker system to chemically attach further catalytic functions [143]. 

The first passive remote sensing experiment to measure successfully the abundance of atmospheric aerosols from space was the Stratospheric Aerosol Measurement (SAM II) aboard Nimbus 7 (McCormick et al. 1979). This experiment was a single channel radiometer observing in solar occultation and was the forerunner of SAGE. Stratospheric aerosols have also been measured by their infrared absorptions (e.g. HALOE). 

Scanning probe lithography on metal or silicon substrates is a well known technique and can be supported by a self-assembled monolayer (SAM) [1,2], Such monolayers are of great interest e.g. for passivation of silicon surfaces [3]. Covalently bound monolayers by Si-C bonds that are formed by the reaction of 1-alkenes and a hydrogen terminated silicon surface [4,5], are known to show high thermal [6] as well as chemical stability [3,7]. 

In several cases of interest in photoconversion devices, the species D or A to be oxidised or reduced at the electrode is not in close contact with the electrode surface, but deliberately separated from it by a short distance. The separator may be, for example, a thin passivating film, a molecular spacer layer or an electron-transporting bridge B in an electrode-B-A or electrode-B-D assembly such as a self-assembled monolayer (SAM). 

Another way to avoid dewetting is to passivate the metallic surface by a self assembled monolayer (SAM), e.g. an alkane thiol monolayer (C-18). After passivation, the growth structure resembles the growth mode on inert surfaces [33], the same holds for growth of pentacene on conducting polymers such as PEDOT PSS [poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)] [39]. It is interesting to note that on bare Si, pentacene initially forms a flat lying monolayer, but on-top of this monolayer, the thin film phase readily forms [16] without need for passivation. 

By definition, mediated electron transfer of the type discussed in Section 14.4.2(c) cannot occur in blocking films. However for very thin films, e.g., self-assembled monolayers (SAM) of alkane thiols or oxide films, electrons can tunnel through the film and cause faradaic reactions. This phenomenon is important in electronic devices, in passivation of metal surfaces, and in fundamental studies of the distance dependence of the rate of electron transfer. 

On the other hand, the SAM-formation with hydroxy-terminated alkyl- thiols and -disulfides showed a complete passivation of the substrate surface for any protein adsorption. 

Fig. 6.39 Fully integrated passively mode-locked Nd-fiber laser (CFBG, chirped fiber Bragg grating for dispersion compensation SAM, saturable absorber minor) [709]...

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