Layer by layer
Encyclopedia
Layer-by-Layer deposition is a thin film
fabrication technique. The films are formed by depositing alternating layers of oppositely charged materials with wash steps in between. A simple representation can be made by defining two oppositely charged polyions as + and -, and defining the wash step as W. To make an LbL film with 5 bilayers one would deposit W+W-W+W-W+W-W+W-W+W-W, which would lead to a film with 5 bilayers, specifically +-+-+-+-+-. The bilayers and wash steps can be performed in many different ways including dip coating, spin-coating, spray-coating and flow based techniques. Characterisation of LbL film deposition is typically done by optical techniques such as dual polarisation interferometry
or ellipsometry
or mechanical techniques such as QCM or QCMD.
LbL offers several advantages over other thin film deposition methods. LbL is extremely simple and cheap. There are a wide variety of materials that can be deposited by LbL including polyions, metals, ceramics, nanoparticles, and biological molecules. Another important quality of LbL is the high degree of control over thickness, which arises due to the linear growth of the films with the number of bilayers. By the fact that each bilayer can be as thin as 1 nm, this method offers easy control over the thickness with 1 nm resolution.
LbL has found applications in corrosion control, biomedical applications, and many more.
Thin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
fabrication technique. The films are formed by depositing alternating layers of oppositely charged materials with wash steps in between. A simple representation can be made by defining two oppositely charged polyions as + and -, and defining the wash step as W. To make an LbL film with 5 bilayers one would deposit W+W-W+W-W+W-W+W-W+W-W, which would lead to a film with 5 bilayers, specifically +-+-+-+-+-. The bilayers and wash steps can be performed in many different ways including dip coating, spin-coating, spray-coating and flow based techniques. Characterisation of LbL film deposition is typically done by optical techniques such as dual polarisation interferometry
Dual Polarisation Interferometry
Dual polarization interferometry is an analytical technique that can probe molecular scale layers adsorbed to the surface of a waveguide by using the evanescent wave of a laser beam confined to the waveguide...
or ellipsometry
Ellipsometry
Ellipsometry is an optical technique for the investigation of the dielectric properties of thin films....
or mechanical techniques such as QCM or QCMD.
LbL offers several advantages over other thin film deposition methods. LbL is extremely simple and cheap. There are a wide variety of materials that can be deposited by LbL including polyions, metals, ceramics, nanoparticles, and biological molecules. Another important quality of LbL is the high degree of control over thickness, which arises due to the linear growth of the films with the number of bilayers. By the fact that each bilayer can be as thin as 1 nm, this method offers easy control over the thickness with 1 nm resolution.
LbL has found applications in corrosion control, biomedical applications, and many more.
External links
- http://www.azonano.com/news.asp?newsID=2524