The electromechanical response of silicon nanowires to buckling mode transitions
TL;DR: The highly flexible silicon nanowires embedded in SiO(2) microbridges exhibited unusually large fracture strength, sustaining tensile strains up to 5.6%; this will prove valuable in demanding flexible sensors.
Abstract: Here we show how the electromechanical properties of silicon nanowires (NWs) are modified when they are subjected to extreme mechanical deformations (buckling and buckling mode transitions), such as those appearing in flexible devices. Flexible devices are prone to frequent dynamic stress variations, especially buckling, while the small size of NWs could give them an advantage as ultra-sensitive electromechanical stress sensors embedded in such devices. We evaluated the NWs post-buckling behavior and the effects of buckling mode transition on their piezoresistive gauge factor (GF). Polycrystalline silicon NWs were embedded in SiO2 microbridges to facilitate concurrent monitoring of their electrical resistance without problematic interference, while an external stylus performed controlled deformations of the microbridges. At points of instability, the abrupt change in the buckling configuration of the microbridge corresponded to a sharp resistance change in the embedded NWs, without altering the NWs' GF. These results also highlight the importance of strategically positioning the NW in the devices, since electrical monitoring of buckling mode transitions is feasible when the deformations impact a region where the NW is placed. The highly flexible NWs also exhibited unusually large fracture strength, sustaining tensile strains up to 5.6%; this will prove valuable in demanding flexible sensors.
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TL;DR: Current studies indicate that conventional approaches to the bottom-up fabrication of Si NWs in nanoelectronics inevitably require complicated assembly procedures including the establishment of the accurate control of the doping level and the formation of reliable metal contacts.
Abstract: Semiconductor nanowires (NWs) have unique physical properties due to their 1D structure, which enables the more efficient transport of electrical carriers. Si NW transistors especially have attracted tremendous attention, since their interesting device performance can be utilized for integrated nanoscale electronics. These characteristics are also believed to make them useful nanoscale building blocks for electronic devices on plastic substrates that can be fabricated on a relatively large scale. To realize reliable devices with nanoscale dimensions, an assembly process with controlled orientation and density, control of the doping, and suitable contact properties of the Si NWs is required. Recent studies indicate that conventional approaches to the bottom-up fabrication of Si NWs in nanoelectronics inevitably require complicated assembly procedures including the establishment of the accurate control of the doping level and the formation of reliable metal contacts. For these reasons, most of the previous studies dealing with the bottom-up fabrication of field-effect transistors (FETs) based on Si NWs, which were grown by a deposition technique based on the vapor–liquid–solid (VLS) growth mechanism, mainly focused on homogenously doped NW devices operating mostly in accumulation or depletion mode. In the case of normally on NW FETs, the power consumption of the devices is relatively large and the flow of electric charge does not seem to be accurately modulated by the gate structure. Most recently, an n-type/intrinsic/n-type metal oxide semiconductor
17 citations
TL;DR: In this paper, a microbridge testing method for microbridge beams initially buckled by a residual compressive stress was presented, where Young's modulus, the residual stress and the yield strength of a ductile thin film were determined from the microbridge test to be 66.2? 2.9 GPa,?8.5? 1.0 MPa and 162.4? 5.9 MPa, respectively.
Abstract: In the present work, we report a microbridge testing method for microbridge beams initially buckled by a residual compressive stress. A theoretical formula is derived in closed form with the consideration of substrate deformation. Measuring the profile of a buckled microbridge beam, one can evaluate Young's modulus and the residual compressive stress of the beam. Alternatively, Young's modulus and the residual stress can also be evaluated from the microbridge test under low loads, i.e., from the elastic load?deflection curve. Moreover, we introduce a microbridge testing approach to determine the yield strength of a ductile thin film. Experimentally, microbridge samples were fabricated with a 0.48 ?m thick gold film deposited on a silicon wafer by electroplating. Young's modulus, the residual stress and the yield strength of the gold film were determined from the microbridge test to be 66.2 ? 2.9 GPa, ?8.5 ? 1.0 MPa and 162.4 ? 5.9 MPa, respectively.
17 citations