Piezoresistance Characterization of Silicon Nanowires in Uniaxial and Isostatic Pressure Variation

Abstract

Silicon nanowires (SiNWs) are known to exhibit a large piezoresistance (PZR) effect, making them suitable for various sensing applications. Here, we report the results of a PZR investigation on randomly distributed and interconnected vertical silicon nanowire arrays as a pressure sensor. The samples were produced from p-type (100) Si wafers using a silver catalyzed top-down etching process. The piezoresistance response of these SiNW arrays was analyzed by measuring their I-V characteristics under applied uniaxial as well as isostatic pressure. The interconnected SiNWs exhibit increased mechanical stability in comparison with separated or periodic nanowires. The repeatability of the fabrication process and statistical distribution of measurements were also tested on several samples from different batches. A sensing resolution down to roughly 1m pressure was observed with uniaxial force application, and more than two orders of magnitude resistance variation were determined for isostatic pressure below atmospheric pressure.

Application of p and n-Type Silicon Nanowires as Human Respiratory Sensing Device

“…Resistance increments upon different humidity variations indicate that the observed response was a combined result of both pressure and humidity variation. This result was also in good agreement with our previous study on the PZR effect on SiNWs [ 17 ]. We investigated the iso-static pressure variation effect on SiNWs and observed a dramatic increase in resistance by more than two orders of magnitude when pumping the air out of the vacuum chamber and decreasing the humidity and pressure.…”

“…Our previous study showed that hydrogenation on p-type SiNWs dramatically decreased its sensitivity. As hydrogenation is known to passivate shallow and deep defects in both n and p-type Si, these results strongly indicate that surface states play a significant role in the PZR effect [ 17 ]. Surface states of the SiNWs may also play an important role in the humidity-sensing mechanism described in a review article by Akbari-Saatlu et al for metal-oxide semiconductors [ 51 ].…”

“…Gosh, et al [49] fabricated a breath 225 sensor from arrays of periodic n-type silicon nanorods [49] and attributed its function to 226 the PZR effect. According to the model of the PZR effect, any pressure applications such 227 as airflow on the SiNWs surface can impart sufficient normal pressures can deform 228 the SiNWs and cause a relative change in the resistance [17]. Controversially, a giant 229 longitudinal PZR effect was observed on p-type SiNWs and was attributed to surface states 230 [18].…”

“…Human breath is a complicated mixture of different gases including nitrogen, oxygen, carbon dioxide, and water vapor (humidity), that can cause slight temperature and pressure variation [ 14 , 15 , 16 ]. Meanwhile, SiNWs have exhibited a great piezoresistance (PZR) effect in a low-pressure range, which is critical for bio-compatible devices such as breath sensors [ 17 , 18 , 19 , 20 ]. Among the different existing approaches to synthesizing the SiNWs, the MACE method is one of the simplest methods and it offers the perspective of easy integration with microelectronics technologies at a lower cost with larger processable areas [ 21 , 22 , 23 , 24 ].…”

Effect of impurities on charge and heat transport in tubular nanowires

“…Among these nanostructures, nanowires have attracted considerable attention due to their potential applications in modern technologies. Nanowires of small size are ideal for miniaturized devices such as transistors [1], batteries [2], and sensors [3,4]. Also, their high surface area to volume ratio increases the efficiency of energy storage, and provides unique physical and chemical properties such as improved electrical conductivity, increased strength, and enhanced catalytic activity [5][6][7].…”