Semiconducting core / functional oxide shell nanowires – COSCOF

Molecular beam epitaxy is the main tool used in this work in order to growth core shell nanowires. However other growth methods will be investigated as hydrothermal synthesis, abblation etc. Morphological and structural caracterization will be performed via electron microscopy in order to obtain the best properties.

- Growth mechanism of the Au / Si catalyst
- Fabrication of semiconducting Ge & GaAs nanowires by molecular beam epitaxy
- Fabrication of an epitaxial shell of BaTiO3 wrapping ZnO nanowires
- Growth of SrTiO3 / GaAs nanowires

- Fabrication of core shell nanowires with abrupt interface
- Mesuring the piezotronic properties

Capping GaAs nanowires with As for preventing oxidation and subsequent shell growth
X. Guan, J. Becdelièvre, Ph. Regreny, C. Botella, G. Grenet, G. Saint-Girons, M. Gendry, X. Jaurand, J. Penuelas
Nanoscale 8, 15637 (2016)

GaAs core / SrTiO3 shell nanowires grown by molecular beam epitaxy
X. Guan, J. Becdelievre, B. Meunier, A. Benali, G. Saint-Girons, R. Bachelet, P. Regreny, C. Botella, G. Grenet, N. P. Blanchard, X. Jaurand, M. G. Silly, F. Sirotti, M. Gendry, J. Penuelas
Nano Letters 16, 2393 (2016)

Structure and morphology of Ge nanowires grown on Si (001): Importance of the Ge islands on the growth direction and twin formation
F. Boudaa, N. P. Blanchard, A. Descamp-Mandine, A. Benamrouche, M. Gendry, J. Penuelas
Journal of Applied Physics 117, 055302 (2015)

Recently much attention has been given to nanowires having semiconducting and piezoelectric properties because they can be used for developing new electronic devices and energy harvesters [1,2]. Until now most of the researches concerning these topics have focused on ZnO and GaN nanowires due to their easy preparation and their physical properties.
In this project we plan to fabricate nanowires with semiconducting core (Si) and piezoelectric functional oxide shell (BaTiO3 or PbZrTiO3). By combining both materials we expect to combine their properties in single nanostructures (such an approach has recently been validated by using a semiconducting carbon nanotube coupled with a ZnO nanowire [3]). This core / shell approach presents several advantages compared to traditional ZnO or GaN nanowires:
- Modularity: tuning the properties by choosing the material.
- Enhancement of the piezoelectric and / or semiconducting properties.
- Generic approach that could be used for various kind of coupling (not only electronic and energy harvesting but also photo-catalysis etc…).
The shell growth will be performed using molecular beam epitaxy of functional oxides on Si template nanowires but alternative methods as sol-gel growth or MBE oxide growth on ZnO template nanowires will be investigated in order to ensure the successful fabrication of core shell nanowires. A particular attention will be paid on the structure and morphology of the nanowires in order to understand the elementary growth mechanism and improve the fabrication of designed core / shell nanowires. Finally the piezoelectric, electrical and mechanical properties of core shell nanowires will be investigated in order to prove the concept developed in this project.
The results obtained by the members of the project will be reported in peer-reviewed journals and conferences.

[1] Z. L. Wang, Journal of Physical Chemistry Letters 1, 1388 (2010)
[2] Z. L. Wang, Advanced Materials in press (2011)
[3] W. Liu, M. Lee, L. Ding, J. Liu, Z. L. Wang, Nano Letters 10, 3084 (2010)