Metal Atom-Molecule Interactions in Self-Assembled Monolayers

Open Access
- Author:
- Tighe, Timothy Bernard
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 13, 2003
- Committee Members:
- David Lawrence Allara, Committee Chair/Co-Chair
Nicholas Winograd, Committee Member
Thomas E Mallouk, Committee Member
Carlo G Pantano, Committee Member - Keywords:
- metal organic interface
alkane thiol
self-assembled monolayers
metallization - Abstract:
- ABSTRACT Determining the underlying chemistry of the interaction of deposited metal/inorganic oxide molecules with organic thin films and polymer surfaces is becoming increasingly important for a wide variety of research areas. Determination of reaction pathways between organic surfaces and deposited metal/inorganic oxides has proven to be very difficult in past years due to the inexact knowledge of the structure and nature of the organic surfaces. For this reason, self assembled monolayers (SAMs), which have a known surface density, and can be functionalized with a variety of terminal groups, have been used as models for more difficult organic thin films. These layers are not only useful as models but are being developed as electronic devices themselves. The work in this thesis is concentrated in two areas. In the first, a variety of metals, including Ag, Au, Cu, Al, Ti, Ca, and Mg have been deposited onto a selfassembled monolayer (SAM) with a methoxy terminal group, HS(CH2)16OCH3. These metals were chosen because they are commonly used as metallic contacts in microelectronics and polymer light emitting diodes. Recent work has shown that the interaction of deposited Al with a methoxy-terminated SAM is intermediate between the ¨CCH3 case, where Al penetrates to the Au/S interface, and the -COOH, -CO2CH3 and - OH cases, where Al interacts with the terminus. Thus, a methoxy terminated SAM is an ideal monolayer in which to study how the nature of the metal¨Corganic interaction can be changed, and ultimately controlled, by the reactivity of the deposited metal atoms. In the second, the interaction of a molecular wire, 4-[4¡¯-(phenylethynyl)-phenylethynyl]- benzenethiol, which consists of three phenyl rings separated by C¡ÔC bonds, with two common electronic contacts, Ti and Au, was studied. Studies of this kind are crucial since a serious problem in molecular electronic technology is variation in device performance which is believed to be caused by issues with metal contact formation. Chapter 1 is an introductory chapter and is intended to give the reader an idea of the importance of the research preformed in later chapters. Chapters 2 through 6 in this thesis are papers that have been published or are in preparation for various scientific journals and represent continued collaborations between the Allara and Winograd groups at The Pennsylvania State University. The ToF SIMS data in these chapters was collected by Dr. Amy Walker, now of Washington University and the DFT calculations were done by Dr. Orlando Cabarcos and Mr. Michael Reinard of the Allara group.