Surface patterning by means of soft lithography for molecular and bio-electronics [Elektronische Ressource] / vorgelegt von Daniel Christian Johannes Wendelin Schwaab

Witkowski

Sujets

• Physik

Informations

• Publié par: rheinisch-westfalischen_technischen_hochschule_-rwth-_aachen
• Publié le: 01 janvier 2007
• Nombre de lectures: 12
• Langue: English
• Poids de l'ouvrage: 11 Mo

Extrait

Surface patterning
by means of Soft Lithography
for Molecular and Bio-Electronics
Von der Fakultät für Mathematik, Informatik und Naturwissenschaften der
Rheinisch-Westfälischen Technischen Hochschule Aachen
zur Erlangung des akademischen Grades eines Doktors
der Naturwissenschaften genehmigte Dissertation
vorgelegt von
Diplom-Physiker
Daniel Christian Johannes Wendelin Schwaab
aus Landau in der Pfalz
Berichter: Universitätsprofessor Dr. rer. nat. Andreas Offenhäusser
Univ Dr. rer. nat. Markus Morgenstern
Tag der mündlichen Prüfung : 12.01.2007
Diese Dissertation ist auf den Internetseiten der Hochschulbibliothek online verfügbar.

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The aim of this thesis was establishing Soft Lithography, mainly Microcontact
Printing, as a powerful patterning technique for Molecular and Bio-Electronics. Es-
pecially patterns having sub 100nm dimensions were subject of this thesis. Therefore
a main issue addressed was the adoption of stamp materials with a Young´s modulus
larger than 100MPa that allowed the transfer of patterns with low critical dimensions.
The Young´s modulus of these materials was more than an order of magnitude larger
than that of materials commonly used. From a functional point of view emphasis was
laid on the transfer of proteins. A process was to be developed that allowed the trans-
fer of fully functional protein patterns. In addition the influence of Contact Inking
on the functionality of transferred proteins was investigated. Beside that, protein pat-
terns were used to demonstrate the influence of sub 1µm patterns on the cell culture of
neurons. Another major object of this thesis was the establishment of a technique to
transfer metal patterns to arbitrary surfaces. Commonly used methods only work with
a specific choice of stamp material, metal and target surface. The concept proposed
and demonstrated in this thesis was more universal. Crossbar junctions having molec-
ular interlayers were demonstrated as one application for this process.
A special design was developed based on lines and spaces with variable widths and
gaps, which allowed the detailed investigation of various scaling issues. This pattern
was used as template for the fabrication of masters. A process compromising Electron-
Beam Lithography of PMMA resist and megasonic development followed by a Reac-
tive Ion Etching process using a hydrogen-bromide plasma to etch into polysilicon
provided best results. Ideal passivation of masters was obtained by vapor deposition
of a perfluoro-octyl-trichlorosilane. It formed a smooth monolayer on the master´s
surface prohibiting sticking of the stamp. PDMS stamps were fabricated by casting
the liquid pre-polymer against the master. Since PDMS has got a rather low Young´s
modulus defects such as Pairing were observed for the pattern design used. Thermo-
plastic material Affinity VP polyolefin was used as stamp material patterned by Hot
Embossing. Although its Young´s modulus is fifty times higher than that of PDMS
Pairing was observed. Therefore thermoplastic materials with an even higher Young´s
modulus were used, namely polyolefins Zeonor, Zeonex, Topas, ionomere Surlyn and
methacrylate Plexiglas. All these materials could be used to obtain defect free repli-
cations of the master. For Surlyn the edges were slightly rounded, while for the other
materials the shape of the stamp pattern were rectangular.
Alkanethiols served as model molecules to investigate the printing process since
they are commonly used in various applications and widely studied. For printing oc-
tadecanethiol Contact Inking was performed. Diffusion of the molecules for printing
with PDMS stamps was found in agreement with previous publications. For Affinity
VP stamps however, the diffusion was found to be less pronounced due to the dif-
ferent composition of the stamp material. For printing with Surlyn, which is rather