Thesis defence by Tabassom ARJMAND

" Silicon nanonet, a promising Percolative material for flexible and large-scale electronics "


 

Keywords:

nanowire network,percolation,transistor,mechanical behaviour,electrical behaviour,technology


cliquer pour voir la liste des membres du jury/clic here for the jury members


 

Abstract

This work focuses on the study of rigid and flexible devices composed of single silicon nanowires (SiNW) and silicon nanowire arrays, also called nanonets (SiNN). First, we report on the successful operation of a flexible single SiNW field-effect transistor where we experimentally show excellent workability, reproducibility, and air stability in the operation of the device. Then, based on the knowledge acquired during the development of flexible single nanowire devices, we address the fabrication and the functional study of the flexible SiNNs resistors. Thus, we study the electrical performance of flexible resistors under bending and tension. We then show that by engineering the geometry of the devices, different behaviors and thus functionalities appear. On the one hand, SiNN-based devices with short channel lengths (20-50 mm) are suitable candidates for electronic devices with the long-term operation even under mechanical stress. On the other hand, devices with medium or long channel lengths (100-1000 mm) have their properties impacted by mechanical stress and are therefore good candidates for bending and strain sensors. Therefore, our technology allows combining different geometries of nanonet devices on a single chip to simultaneously produce the sensors and the readout electronics. It is worth mentioning that through in-situ electrical measurements under tension combined with tensile experiments conducted directly within scanning electron microscopy, we explore the effect of tension on nanowires and their junctions. The results show that NW/NW junctions enhance the cohesion of NNs due to their good tensile strength. However, network elongation leads to the gradual elimination of percolation paths and degradation of conduction.
Moreover, in order to further explore the theory of percolation, nanonet-based transistors on rigid substrates and in the back-gate configurations are fabricated and their electrical characteristics are studied in detail. Our results show that the onset of the pre-percolation regime is related to the finite dimensions of the systems. It is observed that only nanonet devices with a square channel and sufficient size follow the percolation laws present in the literature. We also notice for the first time a phase transition in the type of percolation based on three important factors of nanonet transistors: the threshold voltage, the channel length, and the nanonet density. Finally, the observed phenomena are in good agreement with the Monte-Carlo simulations carried out during this work, which means that the percolation laws are not universal and must take into account a certain number of parameters related to the non-ideality of real systems.

Membres du jury/ Jury members :
 

Prof.

C.ZAKRI

CRPP, Université de Bordeaux, Bordeaux (France)

Rapporteur

Dr.

G.LARRIEU

LAAS 7, CNRS, Toulouse (France)

Rapporteur

Prof.

Laurent PICHON

Institut d'Électronique, Université de Rennes, Renne (France)

Examiner

Dr.

A.DENNEULIN

LGP2- Grenoble-INP- Saint Martin d'Hères (France)

Examiner

Dr.

M.Ashraful ALAM

Purdue University, Indiana (ETATS-UNIS)

Examiner

Dr.

M.Bawedin

IMEP-LAHC-Grenoble-INP- Grenoble (France)

Invité

Dr.

C.TERNON

LMGP, Grenoble INP Minatec, Grenoble (France)

Thesis Director

Dr.

B.SALEM

LTM, CNRS, CEA, Grenoble (France)

Thesis Co-director


Date infos
2 pm - Amphi M 001, Building M, ground floor
Grenoble INP Phelma-Minatec
Location infos
Grenoble INP - Phelma
3 parvis Louis Néel - 38000 Grenoble
Accès : TRAM B arrêt Cité internationale
Free entrance - No registration