Langmuir-Blodgett devices layers

Three-methods have been pursued to organize monolayers from different organic compounds to form molecular monolayer FETs (1) thermal evaporation of approximately monolayer thickness on the dielectric surface of FETs, (2) Langmuir-Blodgett assembly on the water surface and transfer to device surfaces, and (3) self-assembly of functionalized organic compounds on the surface of the gate, or gate dielectric layers of FETs. 

Langmuir monolayers play some part in the preparation of multi-layer systems, now mostly referred to as self-assembled monolayers or multilayers (SAM s). However, this role is modest because it is difficult to make Langmuir-Blodgett layers sufficiently perfect and stable to function in new materials, such as electronic and bio-mimetic devices. One approach of stabilizing LB films is by working with molecules having double bonds that, after deposition, are polymerized. Such layers are stable enough to serve as a substrate for protein adsorption ). 

With LED based on alkoxy-substituted PPPs, Cimrova et al. realized polarized light-emitting devices by casting the active polymer layer by a Langmuir-Blodgett technique, in order to arrange the polymer chains parallel to the plane of the substrate.63... 

An altemative means to realize well-organized thin films of small molecules is the Langmuir-Blodgett (LB) technique, which allows a fine control of both the stmcture and thickness of the film. We note, however, that this technique is in principle restricted to amphiphilic molecules, composed of a hydrophobic chain and a hydrophobic head-group, which is not the case for most molecules used in OFETs. Nevertheless, LB-grown OFETs have been reported with mixed layers of quinquethiophene (5T) and arachidic acid, which gave well-behaved devices [56]. However, the necessary mixing of the electrically active compound with an inactive compound leads to a substantial decrease in the mobility, as compared to that of a vacuum-evaporated film. 

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. 

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