EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Silicon nanonets are networks of randomly oriented silicon nanowires. Due to its flexibility, transparency and reproducibility, this material is highly attractive as an alternative to amorphous silicon or organic materials for various macroelectronic applications involving sensors and displays. Based on our original integration process simply relying on standard photolithography, we were already successful in demonstrating workability, reproducibility and excellent air stability along with interesting performance for device channel length ranging from the micrometer to the millimeter [1]. Rigid transistors with millimeter channel length exhibit outstanding performances with high drain current up to $10^{-7}A$, $I_{On}/I_{Off}$ ratio as large as $10^5$ and good mobility $(0.004 m^2V^{-1}s^{-1})$ as compared to a-Si and organic materials[2]. With this work focusing on flexibility, we first demonstrate the robustness of the integration process and its nice adaptation for producing flexible resistors and transistors made of nanostructured material and using only standard microelectronic technology.Second, the study of electrical performance under bending, with curvature radius in the $7-24mm$ range, evidences a crucial change in current for longer channel devices $(>200\mu m)$ but stability for the shorter ones $(<200\mu m)$. Thus, by choosing correctly the device geometry, we demonstrate that silicon nanonet is a suitable candidate for long-term electromechanical stable flexible devices (shorter devices) and for bending and pressure sensor (longer devices), allowing then to combine various geometry on one chip to produce simultaneously the sensors and the reading electronics, all based on Si nanonets. Third, with the aim to understand the interaction between electrical properties and mechanical stresses, and in particular to determine the impact of nanowire/nanowire junctions in the evolution of the properties, we have developed an original set up to study in real time the degradation of the electrical connectivity of nanonets during mechanical traction cycles carried out in-situ in a Scanning Electron Microscope.
[1]doi.org/10.1063/5.0023322
[2]doi 10.1088/2399-1984/ab1ebc