Nonlinear Chemical Sensitivity Enhancement of Nanowires in the Ultralow Concentration Regime

Abstract

Much recent attention has been focused on the development of field-effect transistors based on low-dimensional nanostructures for the detection and manipulation of molecules. Because of their extraordinarily high charge sensitivity, InAs nanowires present an excellent material system in which to probe and study the behavior of molecules on their surfaces and elucidate the underlying mechanisms dictating the sensor response. So far, chemical sensors have relied on slow, activated processes restricting their applicability to high temperatures and macroscopic adsorbate coverages. Here, we identify the transition into a highly sensitive regime of chemical sensing at ultralow concentrations (<1 ppm) via physisorption at room temperature using field-effect transistors with channels composed of several thousand InAs nanowires and ethanol as a simple analyte molecule. In this regime, the nanowire conductivity is dictated by a local gating effect from individual dipoles, leading to a nonlinear enhancement of the sensitivity. At higher concentrations (>1 ppm), the nanowire channel is globally gated by a uniform dipole layer at the nanowire surface. The former leads to a dramatic increase in sensitivity due to weakened screening and the one-dimensional geometry of the nanowire. In this regime, we detect concentrations of ethanol vapor as low as 10 ppb, 100 times below the lowest concentrations previously reported. Furthermore, we demonstrate electrostatic control of the sensitivity and dynamic range of the InAs nanowire-based sensor and construct a unified model that accurately describes and predicts the sensor response over the tested concentration range (10 ppb to 10 ppm).

Semiconductor Nanowire Arrays for High‐Performance Miniaturized Chemical Sensing

“…As can be noted from Figure 4d,f, the recovery time of D100P400 at low analyte concentrations (10-40 ppb) is much shorter than that at high concentrations, decreasing from 600 to 300 s, which may be due to the longer time required to equilibrate the high concentration analyte on the NW surface. [58] The selectivity of D100P400 toward NO 2 is also enhanced with an improvement in NO 2 sensing response (12.9% @1 ppm), which is more than 20 times higher than response to other gases at the same concentration of 1 ppm. To highlight the selective response toward NO 2 , sensing measurements were also performed in the presence of competing gases, such as ethanol, CO 2 , propane, and acetone, confirming that our InP NW array maintains high sensitivity toward NO 2 even with higher competing gas concentrations (Figure S10, Supporting Information).…”

“…As can be noted from Figure 4d,f, the recovery time of D100P400 at low analyte concentrations (10–40 ppb) is much shorter than that at high concentrations, decreasing from 600 to 300 s, which may be due to the longer time required to equilibrate the high concentration analyte on the NW surface. [ 58 ]…”

Recent Advances in Flexible Field‐Effect Transistors toward Wearable Sensors

“…[32,244] 1D and 2D materials were also widely used in increasing the sensitivity of (bio)chemical sensors, [245,246] such as introducing nanowires and nanotubes into the active layers to form the direct path for charge transport. [247][248][249] Pentacene/TSB3 [71] 6.3 Methanol vapor NA NA NA Nanoporous-structured semiconductor NDI3HU-DTYM2 [92] NA NH 3 NA 0.1 ppb NA Porous monolayer P3HT-azide [32] 0.32 Liquid analytes NA 1% methanol or ethanol NA (PEN) Container molecules Pentacene [34] 0.014 DNA 74 ng cm À2 650 ng ml À1 NA NA Graphene [205] NA DNA NA %1 fM NA ssDNA on Au electrodes Graphene:PDMS [204] NA DNA NA %1 nM NA Solution gated…”

“…[32,244] 1D and 2D materials were also widely used in increasing the sensitivity of (bio)chemical sensors, [245,246] such as introducing nanowires and nanotubes into the active layers to form the direct path for charge transport. [247][248][249] Table 3. Flexible FET sensors for chemical and biochemical analyte detection.…”

Sensors Based Upon Nanowires, Nanotubes, and Nanoribbons: 2016–2020

“…The most common sensor material is the Si NW, which is frequently combined with a surface modification to add a chemical or biorecognition layer to confer sensitivity and selectivity for a particular analyte molecule or class of molecules. − In addition to silicon, III–V materials, including InP, InAs, GaN, and InGaN, and IV–VI materials, including metal chalcogenides like PbS, have also been used (Table ). − Semiconductors are attractive materials for sensors because their conductivity is inherently highly sensitive to changes in the electronic environment at the surface. Particularly for 1D nanostructures, the adsorption of charged analyte species can effectively limit the conduction pathway, the resulting change in conductance leading to high sensitivity.…”