SAMs thickness

TABLE 5.1. The ellipsometry SAM thickness data for the SAMs formed from 2 and 3. 

Figure 4. SAM thickness versus number of carbon atoms measured for the alkyl phosphate monolayers. The data are compared with a theoretical thickness calculated for 30° and 45° tilt angles of the alkyl chains. The data are obtained by XPS (filled symbols) (using a three-layer model) and VASE (open symbols) measurements.

Figure 4. (a) Inker pad experiment on a 4 in. wafer coated with 30 nm An and marked with a grid for consecutive printing, (b) Gradient of printed gold spots after selective etching, (c) Ellipsometry measurement to determine the diffusion time (fd). The SAM thickness is measured for each printed spot, and a linear estimation is applied to the slope of the increasing monolayer to find the... 

A second class of monolayers based on van der Waal s interactions within the monolayer and chemisorption (in contrast with physisorption in the case of LB films) on a soHd substrate are self-assembled monolayers (SAMs). SAMs are well-ordered layers, one molecule thick, that form spontaneously by the reaction of molecules, typically substituted-alkyl chains, with the surface of soHd materials (193—195). A wide variety of SAM-based supramolecular stmctures have been generated and used as functional components of materials systems in a wide range of technological appHcations ranging from nanoHthography (196,197) to chemical sensing (198—201). 

By examining the dispersion properties of surface acoustic waves, the layer thickness and mechanical properties of layered solids can be obtained using the SAM. It can be used to analyze the wear damage progress [104], and detect the defects of thermally sprayed coatings [105]. 

By examining the dispersion properties of surface acoustic waves, the layer thickness and mechanical properties of layered solids can be obtained using the SAM. 

Unlike traditional textbooks of tribology, in this book we regard boundary lubrication as a limit state of hydrodynamic lubrication when film thickness is down to molecular dimension and independent of the velocity of relative motion. The discussions are based on the existing results, some from literatures but mostly from the authors own work. The topics are mainly focused on the mechanical properties of boundary films, including rheology transitions, molecular ordering, and shear responses. Ordered molecule films, such as L-B films and SAM, are discussed, with emphasis on the frictional performance, energy dissipation and the effects from structural features. Boundary films can be modeled either as a confined substance, or an adsorbed/reacted layer on the... 

The X-ray photoelectron spectra were obtained to examine Cj s peaks of the SAMs by using PHI Quantum 2000 X-ray photoelectron spectroscopy (XPS) with a Al X-ray (1,468.6 eV) anode source operated at 15 kV. The diameter of the X-ray beam was 100 yam. A 1.5 nm thick DLC film was coated on a 1.5 nm thick intermediate Si layer which was... 

Fig. 21—The thickness and water contact angle of FTE SAMs on the DLC surfaces as a function of the immersing time in a 10 mM FTE solution at temperature of 20°C (a) film thickness of FTE SAM, and (b) water contact angle.

The solution concentration also has an influence on the formation of the SAMs. The maps of X-ray photoelectron spectra show that the C(ls) peaks for the samples in 1 mM and 5 mM FTE solutions with 24 h immersing are similar to those in Fig. 20(a), which indicates that there was hardly any SAMs on the DLC surface. The thickness of FTE SAMs and the water contact angle value increased with the immersing time. Hu et al. [26,34] obtained FTE SAMs with a thickness of 1.2 nm and a water contact angle value of about 110° by immersing a sample in a 10 mM FTE solution for 35 hours as shown in Figs. 21 (a) and 21(b). 

No. Reagent Chain Length Immersing Time Thickness (nm) Contact Angle (°) Roughness (nm) Description of SAMs... 

For the three sorts of molecules, the film thickness and the water contact angle value of the SAMs grow with increasing chain length. In the immersing time of 1 h, the film thickness obtained is 0.48 nm, 0.8 nm, 1.2 nm, corresponding to the molecules with the number of carbon of 3, 8, and 10, respectively, and the contact angle value is 94°, 107.6°, 110.4°. 

The variations of film thickness and the contact angle value of FDTS SAM are also closely related to the immersing time as shown in Fig. 22. The film thickness of FDTS SAM increases to about 20 A within 2 h, which is close to the molecular chain length of FDTS, and then the thickness in-... 

The FAS SAMs have been grafted on magnetic heads by a robust covalent bond. The thickness, morphology, and the tri-... 

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. 

Fig. 7 Schematics of a nanometer scale M-A-M diode (not drawn to scale in relative thickness). Top schematic is the cross section of a silicon wafer with a nanometer scale pore etched through a suspended silicon nitride membrane. Middle and bottom schematics show a Au/SAM/Au junction formed in the pore area. (Reprinted with permission from [30])...

Wasserman [186] has described the use of both low-angle X-ray reflectivity and ellipsometry for the determination of thickness of Cio-Cig SAMs prepared on surface silanol groups of silicon plates. Ellipsometry is based on the reflection of polarized light from a sample and depends on the sample s thickness and refractive index. X-ray reflectivity measures the intensity of X-rays reflected from a surface (or interference pattern) that is characteristic of the distance between interfaces. The thickness of the SAMs was consistent with fully extended alkyl chains with all-trans conformations and excellent agreement was observed between the two methods. 

Fig. 9.1 A schematic illustration of surface coatings with their typical thickness ranging from angstroms to micrometers. Selected are monomolecular layers fabricated by the transfer of Langmuir-Blodgett (LB) films onto solid substrates (1) self-assembled monolayers (SAMs) (2) multilayers thereof (3) polymer-...

The dotted line on the left is a bond in a possible precursor trimer. X-ray data suggest an area of 21 3 per alkyl chain, with a thickness of 25 2 A. FTIR spectroscopy suggest that the alkyl chains in -octadecyltrichlorosi-lane SAMs are perpendicular to the surface (Reprinted with permission from [5] A. Ul-man, Introduction to Thin Organic Films From Langmuir-Blodgett to Self Assembly, Academic Press, Boston, 1991. p. 257 and 258. Copyright 1991 Academic Press/Elsevier Science)... 

Auer et al. [134] presented an example for multilayer formation and controlled deposition of functionalized nanoparticles on SAM of mercaptohexadecanoic acid (MHA) using electrostatic interactions. As a pH-sensitive switchable linker between the SAM of MHA and negatively charged gold nanoparticles, bis-benzami-dine bolaamphiphiles having different alkyl spacers were used [135]. This strategy resulted in a potentially tunable and switchable property of the entire assembly. For example, the kinetics of adsorption as well as the final particle layer thickness can be controlled by the kind of bis-benzamidine used as the linker (Fig. 9.16). 

The main difference between a 2D-SAM on a flat surface and a 3D-SAM on a nanoparticle is their high surface curvature . The entire size of the substrate is within the similar dimension as the thickness of the SAM. This does not allow the formation of a uniform crystalline SAM but can rather be pictured as a SAM... 

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