Context CEA Liten has worked for over 10 years in the field of organic electronics whose objective is the realization of electronic (field effect transistors, memories) and opto-electronic (light emitting diodes, photodetectors) devices by using printable materials (semiconductor polymers). The proper operation of these devices largely depends on the quality of thin films deposited by using well-known liquid processes, on their morphologies and on the properties of the existing interfaces. Objectives of the thesis The objective of the study is to develop characterization protocols allowing a detailed analysis of the degradation mechanisms of the materials component, either in operation or after ageing protocols, as well as the evolution of interfaces that play a key role in their operation. In particular, it is proposed to develop a sputtering approach driven by argon clusters. Unlike monoatomic argon sputtering, argon clusters sputtering allows penetrating into an organic layer while limiting the degradation of its chemical structure, ensuring a much more homogeneous sputtering of organic layers without losing the chemical information. This approach facilitates the study of the so-called “soft” materials (typically organic materials); it is thus possible to characterize not only the evolution of the chemical nature of the device surface under operating conditions, but also the effects of ageing constraints on interfaces (eg diffusion) including buried interfaces. The Minatec Nanocharacterization Center (PFNC) in CEA Grenoble, within which takes place this PhD work, has recently acquired an XPS Spectrometer equipped with an argon cluster ion beam, and a ToF-SIMS spectrometer equipped with the same technology. This will allow the development of cross-analysis protocols (XPS-ToF-SIMS coupling), already successfully implemented in some other thematics in our laboratory, for this study. The work will consist in a first step, of developing protocols and optimize analysis conditions by XPS and ToF-SIMS spectroscopy in order to successfully characterize the stacks of organic and inorganic layers used in organic electronic devices, including materials and interfaces. This will be essential to understand and control Ar cluster sputtering of polymers which will be integrated into these devices. Based on this work, it will be possible to assess their evolution and degradation, as a function of the operating conditions, the nature of polymers or various surface treatments; the final objective of this work is to find the best compromises for optimizing the devices service life (choice of polymers, device structure, surface preparation etc?). Valence-band electron spectroscopy, electron microscopy and X-ray diffraction analyses will also supplement the information obtained. Study conditions The PhD student will have an excellent working environment with privileged access to various characterization techniques on state-of-the-art instruments. The study will be conducted in collaboration with CEA key industrial partners. A strong interaction with different research teams is essential, so that communication and openness will be important assets for the success of this thesis work.

This position is open until it is filled.

Département: Département des Technologies des NanoMatériaux (LITEN)
Laboratory: Laboratoire de Nanocaractérisation et Nanosécurité
Start Date: 01-10-2015
ECA Code: SL-DRT-15-0979
Contact: eric.de-vito<στο>cea.fr