Strain engineering of core–shell silicon carbide nanowires for mechanical and piezoresistive characterizations

Abstract

This study evaluated the mechanical properties and piezoresistivity of core–shell silicon carbide nanowires (C/S-SiCNWs) synthesized by a vapor–liquid–solid technique, which are a promising material for harsh environmental micro electromechanical systems (MEMS) applications. The C/S-SiCNWs were composed of a crystalline cubic (3C) SiC core wrapped by an amorphous silicon dioxide (SiOx) shell; however, TEM observations of the NWs showed that hexagonal polytypes (2H, 4H , and 6H) were partially induced in the core by a stacking fault owing to a Shockley partial dislocation. The stress–strain relationship of the C/S-SiCNWs and SiC cores without an SiOx shell was examined using MEMS-based nanotensile tests. The tensile strengths of the C/S-SiCNWs and SiC cores were 7.0 GPa and 22.4 GPa on average, respectively. The lower strength of the C/S-SiCNWs could be attributed to the SiOx shell with the surface roughness as the breaking point. The Young’s modulus of the C/S-SiCNWs was 247.2 GPa on average, whereas that of the SiC cores had a large value with scatter data ranging from 450 to 580 GPa. The geometrical model of the SiC core based on the transmission electron microscopy observations rationalized this scatter data by the volume content of the stacking fault in the core. The piezoresistive effects of the C/S-SiCNW and SiC core were also evaluated from the I–V characteristics under uniaxial tensile strain. The gauge factor of –30.7 at 0.008 ε for the C/S-SiCNW was approximately two-times larger than that of –15.8 at 0.01 ε for the SiC core. This could be caused by an increase of the surface state density at the SiOx/SiC interface owing to the positive fixed oxide charge of the SiOx shell.

Synthetic recovery of impulse propagation in myocardial infarction via silicon carbide semiconductive nanowires

“…It has been recently observed that similar membrane formation allows heterocellular coupling of cardiac and noncardiac cells in the scar tissue and acts as a possible substrate of heterocellular coupling 38 , and the transfer of mitochondria between stem cells and cardiomyocytes 39 . In our experiments, we compared the MNB formation as triggered by SiO 2 - and SiC-NWs; only semiconducting SiC-NWs supported coupling, because of their conductivity (i.e., ∼11.4 μS cm −1 ) 19 , and therefore impulse propagation over distances. However, SiC-NWs coupled cells had reduced junctional currents compared to physically coupled HL1 cardiomyocytes 40 , but this reduction does not impede the correct AP transfer via MNB formation.…”

“…Nevertheless, nanomaterials capable of rapidly restoring impulse propagation, with the reinstatement of “physiological cardiac conductivity” are highly desirable. Silicon carbide nanowires (SiC-NWs) have been recognized as a possible candidate for the development of a new generation of implantable nano-devices since they are chemically inert, semiconducting 19 and compatible with the biological environment 20 . In this work, we demonstrate that injectable and biophysically inspired SiC-NWs are capable of electrotonically synchronizing isolated cardiomyocytes via the formation of membrane nanobridges (MNBs) 21 .…”

Nanoarchitectonics for Wide Bandgap Semiconductor Nanowires: Toward the Next Generation of Nanoelectromechanical Systems for Environmental Monitoring

“…Recently, several methods based on both top-down and bottomup approaches have been employed to enhance the sensitivity of piezoresistive strain sensors for wider applications. [251][252][253][254] In Figure 10. a) Schematic diagram of "titration-coating" method: (i) original pad; (ii) pad with parafilm; (iii) covered with nanowires; (iv) removed parafilm.…”

“…Very recently, Nakata et al reported another interesting method for improving the sensitivity of sensing devices operating in harsh environments. [254] This method is based on the bottom-up approach in which the core-shell SiC nanowires were synthesized by a VLS technique. Figure 11j,k shows the variations of the resistance change ratio depending on an increase of the tensile strain for the core-shell SiC nanowires and SiC core, respectively.…”

“…Recently, several methods based on both top‐down and bottom‐up approaches have been employed to enhance the sensitivity of piezoresistive strain sensors for wider applications. [ 251–254 ] In this regard, our group reported a revolutionary mechanical approach to enhance the sensitivity of piezoresistive strain sensors using a 3C‐SiC nanowire‐based strain amplifying structure (namely, nanostrain‐amplifier). [ 253 ] The nanostrain‐amplifier was inspired from the dogbone structure.…”