Growth, Kinetics and Morphology of Multi-Layered Organic Thin Films via Low-Energy Secondary Ion Mass Spectrometry - LE-SIMS

Coordinating Institution: CRP Gabriel Lippmann
Contracting Partner(s): University of Texas, Austin
From: 01/09/2008
To: 31/08/2011
Budget: 818,000.00€
Contact(s): Wirtz Tom

Summary

The increasing sophistication of organic optoelectronic devices requires molecular-level dimensional control in the fabrication of multi-layered structures with specifically engineered interfaces. However, the effectiveness of growth and doping strategies devised to achieve the desired device structures oftentimes remains unverified due to the lack of adequate characterization techniques. In this project, we address this challenge by advancing the development of low-energy secondary ion mass spectrometry (LE-SIMS) for the analysis of organic-based optoelectronic materials systems.

The project partners at the University of Michigan are responsible for the growth of optoelectronic samples (group of Max Shtein) and the development of molecular dynamic (MD) simulations dedicated to the study of ion bombardment during low-energy dynamic SIMS (group of John Kieffer). CRP-GL is responsible for the development of low-energy SIMS for organic multi-layered samples and is also involved in the development of the MD simulations. In 2009, the optimization of the force field parameters for silicon was continued: the phonon density of states could be reproduced. Furthermore, a PhD thesis focusing on the development of low-energy SIMS for organic optoelectronic samples was started in January.

The fragmentation of thin organic films under Cs+ bombardment has been studied as a function of primary ion impact energies. For different organic compounds involved in the growth of layered structures (C60, Copper Phthalocyanine (CuPC), Tris(8 hydroxyquinolinato) aluminium (Alq3)), mass spectra of negative secondary ion intensities have been measured. Cn-, CnCs- and CxNy- secondary ion clusters have been studied in particular. The distributions of Cn- and CnNx- cluster intensities do not depend on the impact energy while the distribution of the CnCs- cluster intensities changes with the impact energy: for small impact energies oscillations are observed over the whole distribution range and for impact energies larger than 1 keV, the oscillations of the cluster intensities start only at larger cluster sizes.

Characteristic peaks obtained in the previous study have been used to begin with the characterization of a multi-layered sample containing thin films of C60, CuPC and Bathocuproine (BCP). The structure of the sample could be resolved and different impurities at interfaces could be identified. All those results led to three contributions at the international SIMS conference in Toronto. During the last 4 months of 2009, the PhD student stayed in the group of Max Shtein in order to get familiar with the growth of organic multi-layered samples and prepare samples suited for the improvement of low-energy SIMS.

Refereed Scientific Publications

• 3 submitted

Programme:

• Materials World Network, Call 2007

Foreign Funding Agency:

• National Science Foundation (USA)

Figure 1: Project Team (ltr) : Henri-Noël MIGEON, Tom WIRTZ, Khanh Quyen NGO, Catalina MANSILLA and Patrick PHILIPP (CRP Gabriel Lippmann), John KIEFFER and Max SHTEIN (University of Michigan)

Figure 2: Simulation of an impact of an oxygen atom on silicium (Energy of 100 eV, 80° angle)