Second project period 10/2010 - 03/2015

Project No.	Project Name	Responsible
G8	Characterization of molecular and nanoscaled interconnect systems	Prof. Dr. Michael HIETSCHOLD

Main Objectives

Study of molecular self-assembking monolayers on crystalline metal substrates
Cross-sectional analysis of interfaces by electron and scanning probe microscopies

Description

Interconnects from Stacked Molecules
As an approach to novel concepts well-defined supramolecular structures are a fascinating option. Based on the experience accumulated in the first period of the IRTG and the past [G8-1]-[G8-3], molecular self-assembled monolayers will be studied on crystalline metallic substrates. The crystallographic structure of the adlayers as well as their electronic structure of the molecules and their coupling to the substrate will be studied on ultrathin molecular layers deposited by OMBE by STM/STS.

Fig. 1: STM image of F₁₆CoPc on Ag (110) and structural model derived for this molecular adsorbate system [G8-1].

The main objectives are:

Extension of the investigations from one monolayer to a well defined small number of ordered layers (stacking of molecules). The number of deposited layers will be controlled by thermal desorption mass spectroscopy. First results concerning the stacking of single molecules of naphthalocyanine on a highly ordered pyrolytic graphite substrate have been described in [G8-4].
In-situ controlled deposition of metallic top electrodes (metallization) as well as metallation (the chemical reaction of suitable deposited metal atoms with the toplayer molecules) [G8-5]. To accomplish this a VT-UHV STM with in-situ deposition capabilities will be used.

Suitable molecular systems will be phthalocyanines and naphthalocyanines (at least in the starting period). The strategic aim is to control the stacking modus and to explore suitable ordered molecular aggregations for future application in molecular electronics.

Cooperation is intended with the subprojects G1 (Schulz), G3 (Streiter), G5 (Lang), and G7 (Zahn).

Cross-Sectional Analysis of Interfaces by Electron and Scanning Probe Microscopies
A detailed microscopic structural and compositional analysis of nanostructures as prepared and used in this project is very important. Based on the experience accumulated in electron microscopic investigations (mainly EBSD) within the first period of the IRTG and around [G8-6]-[G8-8], there should be now the main focus on a detailed study of interfaces which are not directly accessible on the sample. To accomplish this, especially suitable preparation techniques for cross-sections containing and opening these features (e.g. the traditional cutting-polishing-ion milling procedure for which the electron microscopy laboratory has achieved a high reputation, FIB-based cutting of TEM lamellae which have to be subsequently treated by further ion milling, slope cut face preparation and possibly ultramicrotomy) have to be applied and refined. The comparative application of different preparation approaches should allow to better understand their influence on the sample and to optmize the preparation procedures for the specific systems under consideration. Special support is expected from extensive usage of the instrumentation available in the new preparation laboratory of Leica Microsystems at the institute of physics. High-resolution Cscorrected (S)TEM will be available by a collaboration with the SuperSTEM faciltiy at the Daresbury Laboratory, UK and possibly via contacts to Portland State University [G8-9] to the unique TEAM microscopes at the Lawrence Berkeley Laboratory, USA.

Whereas in the first period basically SEM and TEM including their analytical extensions will be used, the studies should be extended to scanning probe methods later on. For this approach in-situ crystal cleavage will be added as a further preparation method for crosssections. The disjunctive information accessible by these different techniques will beanalyzed, optimized and interpreted.

Cooperation is intended with the subprojects G1 (Schulz), G2 (Otto), G5 (Lang), G6 (Albrecht), G7 (Zahn), and G9 (Schmidt).

References

[G8-1]	Toader, M.; Gopakumar, T.G.; Abdel-Hafiez, M.; Hietschold, M.: J.Phys.Chem. B submitted
[G8-2]	Ha, N.T.G.; Gopakumar, T.G.; Gutzler, R.; Lackinger, M.; Tang, H.; Hietschold. M.: J.Phys.Chem. C submitted
[G8-3]	Gopakumar, T.G.; Meiss, J.; Pouladsaz, D.; Hietschold, M.: J.Phys.Chem. C 112, 2008, 2529
[G8-4]	Gopakumar, T.G.; Müller, F.; Hietschold, M.: J.Phys.Chem. B 110, 2006, 6051
[G8-5]	Buchner, F.; Schwald, V.; Comanici, K.; Steinrück, H.-P.; Marbach, H.: ChemPhysChem. 8, 2007, 241
[G8-6]	Spange, S.; Kempe, P.; Seifert, A.; Auer, A.A.; Ecorchard, P.; Lang, H:, Falke, M.; Pohlers, A.; Hietschold, M.; Hoyer, W.; Cox, G.; Angew.Chem. (Int. Ed.) accepted
[G8-7]	Wächtler, T.; Oswald, S.; Roth, N.; Jakob, A.; Lang, H.; Ecke, R.; Schulz, S.E.; Gessner, T.; Moskvinova, A.; Schulze, S.; Hietschold, M.: J.Electrochem.Soc. 156, 2009, H453
[G8-8]	Makarov, D.; Bermudez-Urena, E.; Schmidt, O.G.; Lsicio, F.; Maret, M.; Brombacher, C.; Schulze, S.; Hietschold, M.; Albrecht, M.: Appl.Phys.Lett. 93, 2008, 153112
[G8-9]	Moeck, P.; Plachinda, P.; Moon, B.Jr.; Straton, J.; Rouvimov, S.; Toader, M.; Abdel-Hafiez, M.; Hietschold, M.: ISDRS 2009, College Park, MD, accepted.