Langmuir – Blodgett film Sloviková Alexandra Zajíčková Michaela

History 17th century First discovery of optic efect 19th century The beginning of preparation of the thin layers 20th century (70th years) The expansion of plasma technologies 20th century (80th years) Development of Lamgmuir – Blodgett films

Why study molecular orientation in thin films? interfacial properties (optical, electronic and mechanical) molecular interactions organizational model for complex systems Photoresist “Chemically” cleaned silicon wafer Silicon oxide “barrier” layer

Introduction Langmuir – Blodgett films are monofilms or multifilms on solid substrate. Molecules form a monolayer at the interface air-liquid They are nanomaterials The films are layers at scale 0,1 – 0,001 nm ~ 1 nm

Monolayer Phases When 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 phase Liquid phase Solid phase

A 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.

Characteristics of substrate Hydrophilic: Glass Aluminium, chromium, Wafer Hydrophobic: trimethylchlorsilane

Film transfer Water subphase Vertical Horizontal This technique is actual for highly hydrophobic molecules. Horizontal This technique is suitable for transfer of very stif films.

Langmuir – Blodgett films Vertically prepared films 3 types: repeated submergence – type X repeated emergence – type Z switching both types – type Y X Z Y

References [1] doc.RNDr. Vladimír Čech, Ph.D. - Lectures [2] http://isi4.isiknowledge.com\portal.cgi [3] http://www.sciencedirect.com [4] http://google.com [5] http://nanotechnologweb.org