Lauren Miller

University: Clemson University
Major: Bioengineering
Gradation Date: May 2011
Hometown: Derwood , Maryland

My Project:

The use of organic molecules in replacing existing electrical functionality, such as switching or wires is an emerging technology which holds great potential to meet the demands of the electronics world for “More than Moore ” devices. One of the main challenges to this technology is the application of the top metal electrode on molecule-semiconductor hybrid devices because metal filaments diffuse through the organic monolayer and alter the electrical response instead of forming the idealized metal-molecule-substrate sandwich structure. To approach this issue, it is necessary to consider metallization methods beyond traditional evaporation such as Nanotransfer printing (nTP). The principle of this method consists in transferring material from one substrate to another by mechanical contact and sometimes it requires applying temperature and pressure. Since the molecular conformation is an integral aspect of the functionality of the components, understanding the influence of temperature on monolayers, in conjunction with related studies in the influence of pressure, is a needed step toward their future application that will help explain changes in molecular conformation during the placement of the electrode on the monolayer. Then, this structural knowledge will be correlated with electrical properties to begin to engineer devices with desired properties.

We have investigated molecules of varying hydrocarbon length and terminal functional groups to ensure chemical bonds between the molecules and the substrate. In addition, the effect of UV-Ozone treatments on monofunctional monolayers was studied in hopes of converting the methyl-terminated molecules to bifunctional molecules. Then, we have utilized these molecules to explore the influence of temperature (70-120ºC) on self assembled monolayers on three different substrates: evaporated gold on Silicon, nanolaminated gold on plastic substrate (PET), which presents an atomically flat surface and enhances the conformal contact with the molecules, and Silicon substrate. The monolayers are characterized by means of FT-Infrared spectroscopy and contact angle measurements. In general, the monolayers became more disordered and trends based on molecule and substrate were observed. Long chain molecules exhibited different behavior depending on the substrate: molecules on Au/PET are more ordered than Au/Si and desorb at a higher temperature. Short chain molecules lead to less well packed chains and show no dependence on the substrate. The temperature tests were performed on a silicon substrate with similarly structured molecules to draw comparisons.

As seen on the left, monolayers were also assembled on the evaporated gold on silicon substrate that has much larger grains creating a rougher surface for the molecules to attach to.

Monolayers formed on nanolaminated gold on plastic substrate (PET) seen on the left promote conformal contact with the molecules because the gold surface is very smooth. The picture on the right shows there is a dramatic decrease in roughness using the Nanotransfer printing method.

The above results of temperature tests on AuPET and AuSi with ODT, MHDA and MUA molecules demonstrate the trends found in the FT-IR reading of the methylene peak absorbance and frequency and the contact angle measurements of the surface (left-right).

100 Bureau Drive, M/S 8100
Gaithersburg, MD 20899-8110
301-975-2220 Telephone
301-975-4091 Facsimile

NIST is an agency of the U.S. Commerce Department

|Privacy Policy|

Date created: 8/4/2008
Last updated: 11/3/2008