Langmuir-Blodgett technology enables the deposition of single- or multimolecular layers from a liquid surface onto a solid substrate with excellent film structure control. LB is suited especially well for example for creating highly organized nanoparticle coatings.
A Langmuir-Blodgett film (or LB film) can be defined as one or more monolayers of material deposited from a liquid surface onto a solid substrate by dipping the substrate through a floating monolayer at a constant molecular density. LB films are formed by one or several Langmuir films deposited onto a solid surface by vertical dipping of the solid substrate from the gas phase into the liquid phase (or vice versa).
The films obtained by this process can be highly organized, ranging from ultrathin monolayer to multilayer structures built up of hundreds of monolayers.
Most typical applications of LB include creating highly organized and controlled nanoparticle coatings on solid substrates. These coatings can be used as an end product for instance in electronics, biomaterials, sensors or functional surfaces.
Repeated deposition can be used to create well-organized multilayers on solid substrates. There are several parameters that affect the type of LB film produced. These include, the nature of the spread film, the sub-phase composition and temperature, the surface pressure during the deposition and the deposition speed, the type and nature of the solid substrate, and the time the solid substrate is stored in air or in the sub-phase between the deposition cycles.
Density, thickness and homogeneity properties are preserved when transferring the Langmuir film onto the substrate, allowing the construction of organized multilayer structures with varying layer composition.
Different kind of LB multilayers can be produced and/or obtained by successive deposition of monolayers on the same substrate. The most common type is the Y-type multilayer, which is produced when the monolayer deposits onto the solid substrate in both up and down directions. When the monolayer deposits only in the up or down direction the multilayer structure is called either Z-type or X-type. Intermediate structures are sometimes observed for some LB multilayers and they are often referred to as XY-type multilayers.
Langmuir-Schaefer films are very similar to Langmuir-Blodgett films except that deposition is made horizontally rather than vertically.