Langmuir-Blodgett devices metal

The focus in this chapter is on the scientific issues and challenges in the application of vapor deposited top metal contacts to devices fabricated from self-assembled monolayers (SAMs) and related films such as Langmuir Blodgett (LB) monolayers. Specifically the chapter will review the types of possible interactions... 

Besides self-assembly on the surface of metals, another example of self-assembly is the formation of Langmuir-Blodgett monolayers on the surface or at the interface of liquids.47,48 One approach to molecular-based electronic devices that has made use of self-assembled Langmuir-Blodgett films is the crossbar-based defect-tolerant approach to molecular computing 49 Rotaxane molecules that depend on physical dislocations within the molecule to produce switching functionality have been designed such that they will... 

The careful design and delicate synthesis of a number of catenanes and rotaxanes have led to their incorporation into monolayers, and then from these monolayers in the form of Langmuir-Blodgett films onto patterned silicon substrates. This step, followed by the deposition of a second metal layer in the perpendicular direction to form a crossbar, has resulted in the production of an ever-growing number of electrical devices in which the switching is carried out at junctions one molecule thick. 

For the proposed unimolecular devices, the problem of assembly and device interrogation or control is a very serious one. If one cannot talk to a single molecule, one can perhaps talk to a monolayer of identical molecules transferred to a suitable (metal) substrate by the Langmuir-Blodgett film method [70] then, many identical molecules can be addressed electrically, provided that electrical short circuits through defects do not occur. However, LB... 

Atto-engineering for more than a whole century is in permanent and almost infinite development. Theoretical background is related to the surface physics and chemistry, quantum and wave mechanics, and quantum electrodynamics. Discrete and constrained discrete models are convenient for describing related events. Tools and equipment are nano- and atto-dispersions and beams (demons, ions, phonons, infons, photons, electrons), ultra-thin films and membranes, fullerenes and bucky tubules, Langmuir-Blodgett systems, molecular machines, nano-electronic devices, and various beam generators. Output is, generally, demonstrated as finely dispersed particles (plasma, fluosol-fog, fluosol-smoke, foam, emulsion, suspension, metal, vesicle, dispersoid). 

Hybrid phospholipid bilayers consisting of an outer phospholipid monolayer on a thiol SAMs (formed by liposome or vesicle fusion or by the Langmuir-Blodgett technique) have been prepared by this approach. These bilayers exhibit extremely low capacitance values, so that they can be used in sensor devices to test ions and lipophilic molecules. Thiolipids can also be used as an alternative to directly form the hybrid bilayer on the metal surface (Figure 3). ... 

While silica is probably the most frequently encountered oxide surface, other materials particularly alumina, titania and zirconia also have considerable use and spectroscopic characterization is beneficial. One study mentioned above explored the potential for modifying alumina, zirconia, titania and thoria surfaces in a marmer similar to silica [6]. While bonding of the moiety is usually the method of choice, in some cases adsorption is sufficient. For example, polyacrylates adsorbed on alumina are a useful dispersent in the production of certain ceramic products. The successful adsorption of these compounds on aluminia has been monitored by FTIR using the carbonyl stretching frequency for the acrylate species which appears between 1602-1606 cm [15]. Polybutadiene which has been adsorbed on alumina for use as a chromatographic phase can be detected by FTIR [16]. A similar adsorption process has also been tested on zirconia [17,18]. It has also been shown that FTIR can be used to detect Langmuir-Blodgett layers on the metal surfaces of thin-film devices [19]. 

Currently, these molecular systems are studies as SAMs on a metal surface. An additional method of preparing ordered monolayers of molecular devices is the use of Langmuir-Blodgett (LB) films. Therefore, a compound with hydrophilic and hydrophobic subunits with the central nitroaniline core similar to 70 was synthesized as in Scheme 3.40. n-Hexylbenzene was easily brominated on neutral alumina and coupled to TMSA followed by silyl removal and coupling to the nitroacetanilide core intermediate, 68, to afford 88. The methyl ester, intermediate 90, was synthesized by the coupling of methyl 4-ethynylbenzoate (89) to 88. The amine was unmasked and the methyl ester was saponified with lithium hydroxide to afford molecular scale device 91. Compound 91 is suitable for the formation of a LB film due to its hydrophilic carboxylic acid end-group and the hydrophobic n-hexyl end-group. 

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