Can solids wet a surface ?


The wettability of the surfaces determines many natural phenomena and has also strong implications in many practical applications, like printing, adhesion, gluing, lubrication, etc.. Many inorganic and organic materials (like polymers) in the form of thin films, have the tendency to break in tiny droplets when heated up at temperatures well below their melting point. This instability of thin films is common to crystalline solids, such as metals and semiconductors and has been intensively studied in the last 60 years. The reason of this interest resides in the limits imposed by this spontaneous phenomenon for the further miniaturization of electronic devices (like silicon-based transistors) and of the metallic contacts. Nobody would put his mobile phone in the oven!!

Owing to their intrinsic instability the maximal temperature at which thin silicon films can be exposed does not exceed a few hundred Celsius degrees. For this reason, this natural phenomenon has been considered for long time a relevant limit for many applications.

Nonetheless, the presence of small silicon particles deeply changes the properties of the surface on which they are formed. More precisely, the formation of sub-micrometric silicon particles allows to efficiently manipulate the impinging light thus creating coloured filters, anti-reflection coatings, mirrors, polarizers and much more! Thus, the possibility of creating at will small silicon particles controlling their size, shape and density with a simple thermal process opens the new opportunity to implement special optical functions in a simple, clean and sustainable way on large scales.

A joint research from three European research groups in Como (Italy), Dresden (Germany) and Marseilles (France), showed for the first time how to precisely control the formation of complex nano-architectures based on crystalline silicon on silicon dioxide. A fundamental part of the research developed concerned the modeling of the self-assembly process of the silicon patches. Thanks to the optimization of the computational techniques (which involved a super-computer) the researchers were able to implement a code allowing to predict in a very accurate way the dynamic evolution in time of the real systems. The importance of this development resides in the new possibility to decide a priori a lithographic design and predicting its evolution in the final shape. Thus, in principle, it will be possible to choose in advance a lithographic design in order to obtain a complex nano-architecture performing a precise function. Finally, not all the materials can be easily manipulated at the nanoscale, not via dewetting nor with other techniques. Thus, exploiting a method based on “sol-gel dip-coating” and “soft nanoimprint lithography”, the silicon-based nano-architectures were exploited as “masters” and transferred to other materials, such as titania and silica. The further advantages are the possibility of choosing the substrate on which the nano-architectures are printed and also tuning the porosity of the materials in use. The low temperature employed for the calcination of these materials is relatively low (~400 oC) rendering them perfectly compatible with the modern C-MOS devices (such as transistors, cameras, etc.).

PAPER TITLE: 

Complex dewetting scenarios of ultrathin silicon films for large-scale nanoarchitectures

REFERENCE: Science Advances10 Nov 2017 : eaao1472Open Access

AUTHORS:

Meher Naffouti,1,2 Rainer Backofen,3 Marco Salvalaglio,3 * Thomas Bottein,1 Mario Lodari,4 Axel Voigt,3,5 Thomas David,1 Abdelmalek Benkouider,1 Ibtissem Fraj,2 Luc Favre,1 Antoine Ronda,1 Isabelle Berbezier,1 David Grosso,1 Marco Abbarchi,1 * Monica Bollani4 *

AFFILIATIONS

1Aix-Marseille Université, CNRS, Université de Toulon, IM2NP UMR 7334, 13397 Marseille, France.

2Laboratoire de Micro-Optoélectronique et Nanostructures, Faculté des Sciences de Monastir Université de Monastir, 5019 Monastir, Tunisia.

3Institute of Scientific Computing, Technische Universität Dresden, 01062 Dresden, Germany.

4Istituto di Fotonica e Nanotecnologie–Consiglio Nazionale delle Ricerche, Laboratory for Nanostructure Epitaxy and Spintronics on Silicon ,Via Anzani 42, 22100 Como, Italy.

5Dresden Center for Computational Materials Science, Technische Universität Dresden,01062 Dresden, Germany.

CONTACTS:

Monica Bollani, Researcher at Istituto di Fotonica e Nanotecnologie–Consiglio Nazionale delle Ricerche, Laboratory for Nanostructure Epitaxy and Spintronics on Silicon ,Via Anzani 42, 22100 Como, Italy.

(monica.bollani@ifn.cnr.it, +39 031 332 7356)


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