Alkanethiols, SAM

Why do we believe that a Cu monolayer is inserted between SAM and gold substrate The 2D-deposit grows and dissolves extremely slowly. Another indication is that the 2D deposit is very stable and shows no displacement by the scanning tip. Cu clusters on top of an alkanethiol-SAM would be only weakly bound and should be easily pushed away by the tip at higher tunnel currents, very much like metal clusters on a hydrogen-terminated Si(lll) surface, which for that very reason are difficult to image by STM (or AFM [122]). And finally, the cyclic voltammograms (Fig. 33) point to the formation of a buried monolayer . 

Figure 17. Schematic of the lithographic patterning and replacement of conjugated molecules in an alkanethiol matrix, (a) Normal STM imaging of an alkanethiolate SAM with tip bias Vb. (b) SAM removal by applying a voltage pulse Vp to the substrate, (c) Carrying out the same voltage pulse as in (b), but under a solution of molecular wires (expanded structure at bottom) causes (d) insertion of the wires into the newly vacated site.

In their study, Park et al.100 investigated the frictional properties of fluorine-terminated alkanethiol SAMs grafted to gold surfaces. The frictional properties of the system were investigated by sliding two SAMs past one another at velocities in the stick-slip regime under various external loads. The simulations yield the shear stress as and the kinetic friction coefficient pk can be estimated from the slope of a plot of as versus load, using the relationships contained in Eqs. [4] and [5]. 

While Pb is typically not a useful choice for device top contacts because of its low melting point and soft mechanical characteristics, it is of considerable interest for its superconducting characteristics. There appear to be, however, no reports on Pb deposition on SAMs. In our own preliminary experiments of Pb deposition on Cl6 alkanethiolate SAM on Au/mica from UHV AFM imaging, we observed complete penetration with no top surface cluster formation and continuing penetration into the underlying Au lattice. ... 

Lando A, Lauwaet K, Lievens P (2009) Controlled nanostructuring of a gold film covered with alkanethiol SAM by low energy cluster implantation. Phys Chem Chem Phys 11 (10) 1521-1525... 

Molecular self-assembly is a technique to form highly ordered, closely packed mono-layers on various substrates via a spontaneous chemisorption process at the interface.11,12 Earlier research done in this field includes the self-assembly of fatty acids monolayers on metal oxides,14,15 SAMs of organosilicon derivatives on metal and semiconductor oxides,16,17 and organosulfur SAMs on metal and semiconductor surfaces.18,19 Among the organosulfur SAMs, the most thoroughly investigated and characterized one is alkanethiol SAM formed on Au(l 11) surfaces.12... 

Gold is known not having a stable oxide at its surface,20 which makes it a good candidate substrate to study self-assembled monolayers. The deposition of an alkanethiol SAM on a gold surface is done by immersion of a clean gold substrate into the solution, and a spontaneous chemisorption at the interface produces gold thiolate species (See Figure 3.1) 11,12... 

The surface properties of alkanethiol SAMs have been studied thoroughly, and recently people have performed electrical characterizations and found the conduction mechanism through such self-assembled alkanethiol monolayers is tunneling due to its large HOMO-LUMO gap (HOMO highest occupied molecular orbital, LUMO lowest unoccupied molecular orbital) (>8 eV).28 Another type of molecular system is the so-called... 

In the following section we present the detailed measurement results of tunneling characteristics through alkanethiol SAMs. 

Although the HOMO-LUMO gap of alkyl chain type molecules has been reported (see Ref. 90 92), there is no experimental data on the HOMO-LUMO gap for Au/alkanethiol SAM/Au system. 8 eV is commonly used as HOMO-LUMO gap of alkanethiol. 

The conductance of SAMs produced from an alkanethiol and various aromatic and OPE thiols was measured using a tuning fork-based scanning probe microscope (SPM).45 The experimental set-up is illustrated in Figure 5.8. NDR effects were seen in some of the SAMs from the OPEs while the alkanethiolate SAM did not exhibit NDR behavior. 

The formation of an alkanethiolate SAM on Au has been used to direct subsequent metallization procedures.62 In this way, a smooth junction between adjacent Ni and Au metal layers was formed on the surface of the Si02. 

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