Resist Langmuir-Blodgett films

Fig. 4.34. Typical response of a LuPc2 Langmuir-Blodgett film expressed as the fractional change in resistance (AR/R) x 100 towards (a) refined olive oil (b) lampante olive oil (c) extra virgin olive oil and (d) ordinary olive oil. Reproduced with permission from N. Gutierrez et al., Sensors and Actuators B 77,437, 2001.

In addition to conventional photoresist polymers, Langmuir-Blodgett (LB) films and SAMs [79-81] have been used as resists in photolithography. In such applications, photochemical oxidation, cross-linking, or generation of reactive groups are used to transfer micropatterns from the photomask into the mono-layers [82-84]. 

The organic thin films used in lithography are polymer casting films, Langmuir-Blodgett (LB) films, SAMs and plasma-polymerized films. The molecular designs and syntheses of organic monolayer materials are studied for SPNL resists [89]. 

In one example, polyanUine (PAN) films were prepared by Langmuir-Blodgett (LB) and self-assembly (SA) techniques [109]. NO2 is an oxidizing gas, which oti contact with the ji-electron network of polyaniline results in the transfer of an electron from the polymer to the gas. When this occurs, the polymer becomes positively charged. The charge carriers thus created give rise to the increased conductivity of the films, and a concomitant decrease in resistance. The response time to NO2 and the relative change of resistance of films increase with increase of the number of film layers, as show in Fig. 33. Thin films allow more contact with NO2 than thick films, which increases the response time. 

Conventional oil-based lubricants are not suitable for application in MEMS, as the viscous forces can be quite large when compared with the forces involved in operating these components because the size of the oil molecules is of the same order as those of MEMS components [5], Therefore, many researchers have proposed ultrathin organic molecular layers as the lubricants for Si-based MEMS systems [3, 5, 8]. These ultrathin molecular lubricant layers are generally formed by two methods (a) the Langmuir-Blodgett (LB) method and (b) the self-assembly method [9]. The LB monolayers have two main difficulties for their use as the lubricant layers for MEMS components (a) LB films are less wear resistant, as the interaction forces between LB films and substrate (van der Waals) are weaker [10], and (b) application of the LB method is restricted to flat surfeces only, and it is not practical to coat three-dimensional surfaces of a structure [11-14],... 

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