SAM

Due to the unique sensitivity to layer thickness-, refractive index or density changes, ellipsometry is state of the art in SAM characterization and methrology. The benefit of imaging ellipsometry is the ellipsometric enhanced contrast of very thin films and the microscopic lateral resolution. Additional, Imaging ellipsometry is a cheap, fast, and marker-free detection method on Microarrays. Special features of nanofilm_ep4 are ellipsometric contrast mircrographs and microscopic Delta, Psi or thickness maps with a lateral resolution down to 1 µm. For thin layers it is also important to have the option of four zone nulling for highest accuracy.

Typical applications are patterned thiol films with areas of different packing density, C-terminated head groups or chain length, but even in an expected homogenous area, variations in the optical thickness of the film can be detected.

• Loosely-packed structure of low-density self-assembled monolayers (SAMs) enables the constituent molecules of these surfaces to undergo reversible conformational transitions.

References:

Peng D.(2010) Structure and function of switchable surfaces. Diss., Univ. Michigan, Ann Arbor, US

• Bhat et al. (2008) prepared Self-assembled monolayers (SAMs) of N-(3-diethylphosphatoxy)propyl-11-mercaptoundecanamide (PPMA) on gold surfaces. The SAMs, consisting originally of a phosphonate surface functionality, were subjected to step-by-step acidic hydrolysis to reveal two different functional groups: (a) a hydroxyl and (b) a carboxylic group.

Reference:

Bhat R, Sell S, Trimbach DC, Zankovych S, Zhang J, Bossert J, Klemm E, Jandt KD (2008) Multiple Surface Functionalities through Step-by-Step Hydrolysis of Self-Assembled Monolayers. Chem. Mater. 20, 5197–5202.

• The article shows a pathway to generate spatially tailored chemical patterns on planar surfaces. Bergkvist et al. use substrate specific patterning (SSP) based on the specific interaction of organic molecules to a particular substrate material – in this case gold and silica. By combining two types of SSP molecules it is possible to chemically pattern a device based on areas of different substrate.

Reference

Bergkvist M, Niamsiri N, Strickland AD, Batt CA (2008) Substrate selective patterning on lithography defined gold on silica: Effect of end-group functionality on intermolecular layer formation. Surface Science 602, 2121-2127.

Microcontact Printing is a simple and cheap alternative to the rather complicated and expensive Photolithography for the production of microstructures. Microcontact Printing of SAMs can produce Microarrays carrying thousands of different sensor properties within one cm². Microarrays are applicable in Genomics and Proteomics in biotechnology

• Microcontact printed oligo(ethylene glycol)-terminated alkanethiol layers

Zhou et al (2004) reports on the structural characteristics of microcontact printed oligo(ethylene glycol)-terminated alkanethiol layers, HS(CH2)15CONH −(CH2CH2O)6−H (hereafter EG6), on gold.

References:

Zhou Y., Valiokas R., Liedberg B. (2004) Structural Characterization of Microcontact Printed Arrays of Hexa (ethylene glycol)-Terminated Alkanethiols on Gold. Langmuir 20, 6206-6215.