Structural and electrical properties of
alkyl/perfluoroalkyl-thiol self-assembled monolayer on
geranium as passivation layer

Mohamed-Amine Guerboukha, Virginie Gadenne, Hela Mrezguia, Younal
Ksari, Jean- Marc Themlin, Victorien Jeux, Guillaume Monier, Lionel Patrone

► To cite this version:

Mohamed-Amine Guerboukha, Virginie Gadenne, Hela Mrezguia, Younal Ksari, Jean- Marc Themlin, et al.. Structural and electrical properties of alkyl/perfluoroalkyl-thiol self-assembled monolayer on germanium as passivation layer. 2025. hal-05410104

HAL Id: hal-05410104

https://hal.science/hal-05410104v1

Preprint submitted on 10 Dec 2025

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Distributed under a Creative Commons Attribution 4.0 International License
Structural and electrical properties of alkyl/perfluoroalkyl-thiol self-assembled monolayer on germanium as passivation layer

Mohamed-Amine Guerboukhaª, Virginie Gadenneª*, Hela Mrezguiaᵇ, Younal Ksariᵇ, Jean-Marc Themlinᵇ, Victorien Jeuxᶜ,>d, Guillaume Monierᶜ, Lionel Patroneª*

Corresponding authors: virginie.gadenne@im2np.fr, lionel.patrone@im2np.fr

ABSTRACT

For several decades, germanium has been considered one of most attractive semiconductors in
various fields, in particular within the channel design of the next generation metal-oxide-
semiconductor field effect transistors (MOSFET). However, the use of germanium is
compromised by the poor quality of germanium oxide. This motivates the present study,
focused on the structural and electrical characterization of self-assembled monolayers of fluoro-

<footnote>ª Aix Marseille Univ., Université de Toulon, CNRS, IM2NP UMR 7334, Yncréa Méditerranée, ISEN Toulon, Maison du Numérique et de l'Innovation, Place G. Pompidou, 83000 Toulon, France</footnote>

<footnote>ᵇAix Marseille Univ., Université de Toulon, CNRS, IM2NP UMR 7334, Domaine de St Jérôme, Service 151, 13397, Marseille Cedex 20, France</footnote>

<footnote>ᶜ Université de Technologie de Compiègne, ESCOM, TIMR (Integrated Transformations of Renewable Matter), Centre de Recherche de Royallieu, CS60319, CEDEX, F-60203 Compiègne, France.</footnote>

<footnote>d Institut Polytechnique UniLaSalle, Université d'Artois, ULR 7519, 19 Rue Pierre Waguet, BP 30313, 60026 Beauvais, France.</footnote>

<footnote>e Université Clermont Auvergne, CNRS, Clermont Auvergne INP, Institut Pascal, F-63000 Clermont Ferrand, France</footnote>

<footnote>* Corresponding author.</footnote>
alkylthiols and variable length alkylthiols on Ge, which may be considered alternate passivation and insulating layers to replace germanium oxide. The de-oxidation/grafting technique in ethanol-water mixed solution has been adapted in this work. The results show that it provides better results than the more usual acid treatment. Indeed, such a method has allowed us to obtain smoother functionalized Ge surfaces with well-organized self-assembled monolayers (SAMs), assessed by ellipsometry, goniometry, and atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) analyses demonstrate the removal of oxide from as-functionalized Ge surface. From current-voltage measurements of the various SAMs using liquid gallium-indium eutectic contacts, it appears that fluoro-alkyl SAMs have allowed to decrease the current by more than two decades compared to bare (oxidized) Ge surfaces. Statistical analyses of the electrical characteristics are correlated with spectroscopic studies of the molecular levels, using inverse photoemission spectroscopy (IPES) for probing the unoccupied levels (LUMO), XPS for the occupied levels (HOMO), and DFT calculations.

**KEYWORDS:** Self-assembled monolayer; perfluoroalkylthiol; germanium; passivation; electrical properties, HOMO-LUMO.