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Download fileMorphology Transition of ZnO from Thin Film to Nanowires on Silicon and its Correlated Enhanced Zinc Polarity Uniformity and Piezoelectric Responses
journal contribution
posted on 2020-06-18, 15:34 authored by Quang
Chieu Bui, Gustavo Ardila, Eirini Sarigiannidou, Hervé Roussel, Carmen Jiménez, Odette Chaix-Pluchery, Youssouf Guerfi, Franck Bassani, Fabrice Donatini, Xavier Mescot, Bassem Salem, Vincent ConsonniZnO
thin films and nanostructures have received increasing interest
in the field of piezoelectricity over the last decade, but their formation
mechanisms on silicon when using pulsed-liquid injection metal–organic
chemical vapor deposition (PLI-MOCVD) are still open to a large extent.
Also, the effects of their morphology, dimensions, polarity, and electrical
properties on their piezoelectric properties have not been completely
decoupled yet. By only tuning the growth temperature from 400 to 750
°C while fixing the other growth conditions, the morphology transition
of ZnO deposits on silicon from stacked thin films to nanowires through
columnar thin films is shown. A detailed analysis of their formation
mechanisms is further provided. The present transition is associated
with strong enhancement of their crystallinity and growth texture
along the c-axis together with a massive relaxation
of the strain in nanowires. It is also related to a prevailed zinc
polarity, for which its uniformity is strongly improved in nanowires.
The nucleation of basal-plane stacking faults of I1-type
in nanowires is also revealed and related to an emission line at about
3.326 eV in cathodoluminescence spectra, further exhibiting fairly
low phonon coupling. Interestingly, the transition is additionally
associated with a significant improvement of the piezoelectric amplitude,
as determined by piezoresponse force microscopy measurements. The
Zn-polar domains exhibit a larger piezoelectric amplitude than the
O-polar domains, showing the importance of controlling the polarity
in these deposits as a prerequisite to enhance the performances of
piezoelectric devices. The present findings demonstrate the high potential
in using the PLI-MOCVD system to form ZnO with different morphologies
and polarity uniformity on silicon. They further reveal unambiguously
the superiority of nanowires over thin films for piezoelectric devices.