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A Novel Way To Tailor Organic Layers for Electronic Applications

Organic layers represent a challenging way towards improved or novel devices in classical and bioelectronics applications. Here we introduce a new in-situ method to precisely control the growth and quality of molecular layers.





In Situ Analysis of the Growth and Dielectric Properties of Organic Self-Assembled Monolayers: A Way To Tailor Organic Layers for Electronic Applications

Aleksandr Markov,Kyrylo Greben, Dirk Mayer, Andreas Offenhäusser, and Roger Wördenweber

To appeared in: ACS Applied Materials & Interfaces

DOI: 10.1021/acsami.6b04021


Sensor demonstration (A) Thickness of the molecular layer evaluated from the capacitance of the interdigital capacitive sensor, (B) schematic illustration of the partial capacitance model and (C) the capacitive structure with molecules between the electrodes.

Abstract: Organic nanoscale science and technology relies on the control of phenomena occurring at the molecular level. This is of particular importance for the self-assembly of molecular monolayers (SAM) that can be used in various applications ranging from organic electronics to bioelectronic applications. However, the understanding of the elementary nanoscopic processes in molecular film growth is still in its infancy. Here we developed a novel in-situ and extremely sensitive detection method for the analysis of the electronic properties of molecular layer during molecular layer deposition. This low frequency sensor (1 kHz) is employed to analyze the standard vapor deposition process of SAMs of molecules and, subsequently, it is used to optimize the growth process itself. By combining this method with an ex-situ determination of the effective thickness of the resulting layers via ellipsometry, we observe a large difference of the permittivity (1 kHz) of the examined aminosilanes in the liquid state (εliquid=5.5 to 8.8) and in SAMs (εSAM=22 to 52, electric field in the plane of the layer).

Permittivity of SAMsComparison or the permittivity of molecules in SAMs (upper symbols) and in the liquid state (lower symbols) as function of the thickness of the SAM layer.

We ascribe this difference to either the different orientation and order of the molecules, the different density of molecules, or a combination of both effects. Our novel in-situ analyses not only allows to monitor and optimize the deposition of organic layers. It also demonstrates the high potential of organic SAMs as organic high-k layers in electronic devices.