Presentation on theme: "Langmuir – Blodgett film"— Presentation transcript:
1Langmuir – Blodgett film Sloviková AlexandraZajíčková Michaela
2History 17th century First discovery of optic efect 19th century The beginning of preparation of the thin layers20th century (70th years)The expansion of plasma technologies20th century (80th years)Development of Lamgmuir – Blodgett films
3Why study molecular orientation in thin films? interfacial properties(optical, electronic and mechanical)molecular interactionsorganizational model for complex systemsPhotoresist“Chemically” cleanedsilicon waferSilicon oxide “barrier”layer
4IntroductionLangmuir – Blodgett films are monofilms or multifilms on solid substrate.Molecules form a monolayer at the interface air-liquidThey are nanomaterialsThe films are layers at scale 0,1 – 0,001 nm~ 1 nm
5Monolayer PhasesWhen the molecules are first spread on the water surface, they are loosely packed and form a so-called gas phase.Increasing the surface pressure translates as a transition to a liquid phase.Further increases in pressure bring about a last compressibility change that is associated to a liquid-solid phase transition.Molecular area (nm2/molecule)Surface pressure (mN/m)Gas phaseLiquid phaseSolid phase
6A barrier on the water surface pushes and compacts the molecules. Spreading amphiphile molecules on a water surface yields monolayers or films where the hydrophobic segments stem at the water/air interface.Films with tailored stability, orientation of molecules or phase transition can thereby be transferred to the substrate.
7Characteristics of substrate Hydrophilic:GlassAluminium, chromium,WaferHydrophobic:trimethylchlorsilane
8Film transfer Water subphase Vertical Horizontal This technique is actual for highly hydrophobic molecules.HorizontalThis technique is suitable for transfer of very stif films.
9Langmuir – Blodgett films Vertically prepared films3 types:repeated submergence – type Xrepeated emergence – type Zswitching both types – type YXZY