| AVS 60th International Symposium and Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF+AS+BI+EM+SE+SS-WeA |
| Session: | Applications of Self-Assembled Monolayers and Nano-Structured Assemblies |
| Presenter: | S. Pookpanratana, National Institute of Standards and Technology (NIST) |
| Authors: | S. Pookpanratana, National Institute of Standards and Technology (NIST) H.-J. Jang, National Institute of Standards and Technology (NIST) L.K. Lydecker, National Institute of Standards and Technology (NIST) C.A. Richter, National Institute of Standards and Technology (NIST) C.A. Hacker, National Institute of Standards and Technology (NIST) |
| Correspondent: | Click to Email |
Organic-based electronics are attractive for next-generation applications because of the wide range of possibilities in tailoring the chemical structure of molecules for a desired functionality. An emerging field is to combine the flexibility of organic materials into spintronics. While the self-assembly of molecular layers onto Au is well-studied, self-assembly does not form as readily between molecules and a ferromagnetic metal due to the lack of control of the interface composition (i. e., oxide formation). Conventional approaches to fabricate hybrid organic-metal interfaces have relied on vacuum-based physical vapor deposited organic molecules since the metal-organic interface can be better controlled. However, vacuum-based deposition of organic materials limits the manufacturing and applications of such hybrid systems making solution-based processes attractive for organic-based electronics. We have explored self-assembled monolayers (SAM) on a template-stripped Co surface to understand the molecular-metal interface from a structural, chemical, and electronic point of view.
Template-stripped Co is a method to prepare consistent surfaces that can be used in ambient conditions. First, Co is evaporated onto a molecular layer-treated Si (tSi) surface, and then the Co surface is laminated to a plastic substrate. The plastic/Co surface is stripped off of the tSi and immediately placed into SAM solution. We chose octadecanethiol (ODT) and mercaptohexadecanoic acid (MHA) as “fruit fly” molecules to self-assemble onto Co. This hybrid molecule-metal interface is investigated by using microscopy, infrared spectroscopy, and photoelectron spectroscopy to provide details of the physical, chemical, and electronic structure at that interface.
The self-assembly of ODT and MHA are directly confirmed by infrared spectroscopy and X-ray photoelectron spectroscopy (XPS). The absorbance intensities of the C-H stretches of ODT and MHA on Co are comparable to those on Au, which indicates similar packing density on both surfaces. MHA has the added complexity with both the -SH and -COOH functional groups are able to bond. Moreover, the –COOH groups also affect the Co surface by reducing the native oxide as shown by XPS. Molecular electronic junctions formed on Si by flip-chip lamination [1] show that electron transport is heavily influenced by the MHA/Co interface or Co electrode when compared to a Si/MHA/Au control device. Preliminary results suggest that SAMs on Co surfaces are a promising route for controlling the organic-ferromagnet interface for next generation devices.
[1] M. Coll et al., J. Am. Chem. Soc. 2009, 131, 12451-12457.